Arjo-Dedessa Irrigation Project Summary

THE FEDERAL DEMOCRATIC REPUBLIC OF ETHIOPIA
MINISTRY OF WATER RESOURCES
Arjo Dedessa Irrigation Project
Feasibility Study Report
VOLUME - III
Water Resources
VOLUME - III (d)
Annexure -11           Hydraulic Design Canal Structures
Part I - Design Report
May, 2007
Addis Ababa
WATER WORKS DESIGN & SUPERVISION ENTERPRISE
IN ASSOCIATION WITH
INTERCONTINENTALCONSULTANTS ANO TECHNOCRATS INOIA PVT LTD
P.O Box 256J. Addis Ababa Ethiopia
Tcl:(25l)l 614501/631890 Fax:(1251)I 61537lE-niail w w d s.c telecom, nclciARJO-DEDESSA IRRIGATION PROJECT FEASIBILITY STUDY REPORT
CONTENTS OF THE REPORT
SERIAL
NO.
1
2
3
VOLUME NO.
PARTICULARS EXECUTIVE SUMMARY
MAIN REPORT
Part I - Report
Part II - Maps & Drawings
ANNEXURES
VOLUME-1                 SURVEY AND INVETIGATION (ANNEXURES - 1 to 3) 4               Volume -1 (a)              Topographic Survey Geomorphological Studies &
Geological & Geotechnical Investigation Part I - Report
5               Volume -1 (b)
Part II - Appendices
6                VOLUME -II               NATURAL RESOURCES (ANNEXURES - 4 to 6)
Forestry, Energy & Catchment Development Plar
VOLUME - III
WATER RESOURCES (ANNEXURES - 7 to 11)
7
Volume - III (a)
Meteorological & Hydrological & Hydrogeological Studies 
Dam & Appurtenant Works
8
Volume-III (b)
Part I - Report
9
Part II - Drawings
10
Volume - III (c)
Irrigation & Drainage
Part I - Report
11
Part II - Drawings
12
Volume - III (d)
Hydraulic Structures 
Part I - Report
13
Part II - Drawings
VOLUME IV
AGRICUTLRUE (ANNEXURES - 12 to 18)
14
Volume - IV (a)
Soil Survey & Land Evaluation
15
Volume - IV (b)
Agricultural Planning
16
Volume - IV (c)
Livestock. Fisheries, Agricultural Mechanization &
Agricultural Marketing
VOLUME - V
ENVIRONMENTAL AND SOCIO - ECONOMIC ASPECTS
(ANNEXURES-19 to 25)
17
Volume - v (a)
Environment. Health & Socio-economic Aspects
18                Volume - v (b)             Organization & Management Physical InfrastructureAnnexure -11
HYDRAULIC DESIGN OF CANAL STRUCTURESSECTION -1
PROPOSED CANAL STRUCTURESArjo-Dedessa Irrigation Project
Hydraulic Design of Canal Structure
May 2007
TABLE OF CONTENTS
TABLE OF CONTENTS.................................................................................................................................................................. •
LIST OF TABLES........................................................................................................................................................................... 11
LIST OF ANNEXURE.................................................................................................................................................................... 11
1.   REPORT FOR HYDRAULIC STRUCTURES OF CANAL.............................................................................................. 1
1.1        General........................................................................................................................................................ 1
1.2       Previous studies................................................................................................................................................ 1
1.3        The Project Proposals...................................................................................................................................1
2.      HYDRAULIC DESIGN OF CANAL SECTION................................................................................................................4
2.1        General.............................................................................................................................................................. 4
3.      HYDRAULIC DESIGN OF CANAL STRUCTURES........................................................................................................ 9
3.1        General.............................................................................................................................................................. 9
3.2        Canal Structures for Primary Canals........................................................................................................ 9
3.3        Survey and Geotechnical Investigation.......................................................................................................9
3.4        Control structures...................................................................................................................................... 10
3.4        Escape Regulator..........................................................................................................................................11
3.5        Data requirement........................................................................................................................................... 13
3.6        Data required for design............................................................................................................................. 13
3.6        Determination of flood discharge..............................................................................................................14
3.7        Selection of type of structure.................................................................................................................. 15
3.8        Head loss shalu ogcur at.............................................................................................................................17
3.9        Design............................................................................................................................................................... 22
4.   STRUCTURES UNDER DISTRIBUTION...........................................................................................................................54
4.1        General............................................................................................................................................................ 54
4.2
Canal structures...........................................................................................................................................54
4.3
Drop or fall structures.............................................................................................................................. 56
4.4
Fall on tertiary canals.................................................................................................................................56
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Hydraulic Design of Canal Structure
May 2007
LIST OF TABLES
Table 1.1         Length & command area of canal system2
Table 2.1 Duty in terms of litre/sec/ha for different component of canal4
Table 3.1 Total Number of Canal Structures25
Table 4.1 Length, Command Area. Discharge and Number of Tertiary canals proposed for secondary
CANALS OF SAMPLE AREA54
Table 4.2 Number of Tertiary Canal, their length and number of division box required55
Table 4.3         56
LIST OF ANNEXURE
ANNEXURE2-1 ANNEXURE ANNEXURE ANNEXURE ANNEXURE ANNEXURE ANNEXURE ANNEXURE ANNEXURE ANNEXURE ANNEXURE 3-6 ANNEXURE
6
2-27
2-38
2-48
3-126
3-227
3-330
3-432
3-5A34 3-5B36
3-7
ANNEXURE 3-8........................................................................................................................................................... 40
ANNEXURE ANNEXURE ANNEXURE ANNEXURE 3.10C ANNEXURE 3-11 A
3-10
3.10
3-9 A B
ANNEXURE 3-11 B.................................................................................................................................................... 49
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Hydraulic Design of Canal Structure
1. REPORT FOR HYDRAULIC STRUCTURES OF CANAL
1.1    General
May 2007
This  report  relates  to  the  Hydraulic  design  of  structures  for  Arjo-Dedessa  Irrigation  Projects  with the view to meet the requirements for the Feasibility Study.
1.2    Previous studies
In the past several studies  have been conducted for development of water resources  in Abay basin. First study  was  conducted in 1964 for "Land and water resources  of Blue Nile Basin" by United States  Bureau of Reclamation (USBR). The Second study  was  under taken for "Preliminary  water Resources  Development Master Plan for Ethiopia" by  Water and Power Consultancy  Service (India) (WAPCOS) in 1990. This  study  was  for the all three basins  of country in which Abay basin also formed a part.
Third   study   was   under   taken   by   BCEOM   in   1999   "Abbay   River   Basin   integrated   Development Master Plan".
The proposed Arjo-Dedessa Irrigation Project located on river Dedessa, which is  a major tributary of Abay  River, formed part of all studies. However all these studies  were at reconnaissance level and as such no much details are available.
1.3    The Project Proposals
The project consists of the following component:
i)  Dam
A  rock  fill  dam  of  40.6  m  height  at  selected  dam  site  on  Dedessa  River.  The  riverbed  elevation  at Dam  site  is  1320  m.  It  is  proposed  to  keep  FRL  at  1356.00  m  elevation,  to  store  water  for irrigation.  The  top  of  Dam  is  proposed  to  be  kept  at  elevation  1360.6m.  The  minimum  draw  down level  for  irrigation  purpose  is  proposed  to  be  at  1350.0  m  elevation.  The  minimum  draw  down  level has been fixed from the consideration of levels of command.
ii) Spillway
It  is  proposed  to  provide  ogee  crest  with  chute  spillway  structure  in  saddle  no-1,  for  passing  routed flood discharge. The ground elevation at saddle no.1 is approximately 1350.00 m. The spillway
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May 2007
water is  proposed to be carried into Wama River by  designing the spill channel for a length of about 500m. The crest elevation is proposed to be kept at FRL i.e. 1356.0m. The maximum water elevation is proposed to be kept at 1353.60m.
iii) Outlet for RB Primary Canal
It is proposed to locate outlet for Right bank Primary canal at saddle no.2. The ground elevation at saddle no.2 is approximately 1958 m.
iv) Outlet for LB Primary Canal
The left bank primary canal outlet is proposed to be provided on left abutment of dam itself. The topography  of left bank  is  such that downstream ground elevations  are higher than upstream ground elevation. Therefore the canal outlet for left bank canal is proposed to be located at a point where ground elevation on centre line of dam is  at about elevation of 1359.0 m. Therefore the location of outlet shall be about 10-15 m on right side from top end of left abutment.
v) Canal System
Two canals are proposed for irrigation on both flanks of dam. After the survey of command area, the FSL of canal at outlet from dam is fixed at EL 1348.0 m elevation. According to the FSL of canal and available contour map of command on 1:10,000 scale, the canal alignment of both the canals have been tentatively finalized. After finalization of alignment the total length and proposed command area for irrigation is worked out, details of which are given in table 1.1.
Table 1.1 Length & command area of canal system
Particulars of canal
Total          length proposed in km
Gross    command area in ha
Culturable   command area in ha
Right bank primary canal
44.166
6827
6215
Left bank primary canal
60.18
10998
7450
Total
102.98
17825
13665
Both the primary canals are contour canals for entire length.
For distribution of water to fields of cultivators network of distribution system is planned which consists of the following
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i) Secondary canals taking off from primary canals
May 2007
The secondary  canal are expected to act as  distributaries. But in this  canal system, since the command area is  very  small, the Primary  canals  are equivalent to distributaries. Therefore, the secondary canals are acting as minors.
ii) Tertiary canals taking off from secondary canals (minors)
These are generally  equivalent to minors. But as  the Primary  canals  are equivalent to distributaries  and secondary  canals  to minor, tertiary  canals  are working as  watercourses. Their head works have been designed as outlet.
iii) Quaternary canals taking off from Tertiary canals
These will works as field channels with the command areas of tertiary for distribution of irrigation water.
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2. HYDRAULIC DESIGN OF CANAL SECTION
2.1    General
May 2007
The estimation of canal capacity to meet water requirement for proposed cropping pattern is the most important input for irrigation in project. In the project for design of canal the cropping pattern is proposed in two phases. Phase I is proposed for 138% cropping intensity, whereas in phase II the cropping intensity  is  173%. For design of canal the requirement of water is  considered for phase II, which has maximum water requirement. The duty required per ha. of land for irrigation is evaluated and taken as per Sectoral Report of Irrigation Drainage. The duty adopted and flexibility factor considered in different canals for design of canal are as per table No. 2.1.
Table 2.1 Duty in terms of litre/sec/ha for different component of canal
Canal
Duty adopted  with
out flexibility factor
Flexibility in %
factor
Duty flexibility fa
with ctor in
in liters/sec
liters/sec
Quaternary canal
0.847
25%
1.059
Tertiary canal
0.941
20
1.129
Secondary canal
1.0175
15%
1.170
Primary canal
1.10
10%
1.21
The above figures of duty include the losses also and the efficiency for the component has also been taken into consideration. For the design, discharge for the proposed irrigated area is  first worked out with duty  without flexibility  factor and then the discharge is  calculated with flexibility factor for the canal for which design is  considered. Canal is  designed considering trapezoidal section with unlined earthen section.
Following factors are also taken into account for design of canal section.
For determination of velocity in a canal, Manning's formula is considered,
Longitudinal slope shall be considered in such a way that velocity in canal shall be non-scouring and non silting. Velocity to be non-silting and non scouring shall be decided from the ratio of — 
vo
4
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which shall be within the range of 0.90 to 1.10
Where, v = velocity calculated from formulae
vo = critical velocity calculated as
= 0.546 D064
Where, D = Depth of water considered in canal for full supply discharge
May 2007
The discharge in canal is worked out as by multiplying area of canal upto FSL and velocity 
calculated by Manning's formulae
On the basis  of above consideration, the canal discharge and canal section is  designed. The canal design discharges and design parameters for right and left bank primary canals for different sections are enclosed as Annexure -1 and 2.
• Irrigation to cultivators is provided by distribution network.
For design of distribution network number of secondary canals are planned to take off from both, right and left bank primary canals. The number of secondary canals which are proposed to take off from two canal systems are:-
Canal Systems
No. of Secondary Canal
1. Right bank canal
40
2. Left bank canal
45
From the secondary canal, tertiary canal shall take off. Further from tertiary canal quaternary canal shall be taking off. For the purpose of feasibility study sample area of two secondary canals namely RS-16 and RS-17 of right bank canal are selected for detail planning.
The secondary and tertiary canals are also designed as per the criteria given above. The design discharge and design parameter for different sections of secondary canal RS-16 and RS -17 taking off from right bank primary canal at km 21.327 and 21.788 are enclosed as Annexure 3 and 4
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ANNEXURE 2-1
Hydraulic Particulars for Right Primary Canal Rogosity coefficient (Manning's n = 0.0225)
Canal side slope (1.5:1 for cut & 2:1 for fill)
Sl.no
Cumulative Distance in km
Main canal progressive discharge of the
Bed
width
(m)
Bed
level (m)
F.S.D (m)
Velocity (m/s)
Canal bed slope
Critical velocity VQ m/S =o 546D
V/Vo
Free board (m)
0.0
0.0
7.521
6.25
1.4
0.643
0.0002
0.6772
0.950
0.70
RS-1
0.555
7.464
6.25
1.39
0.639
0.0002
0.677
0.948
0.70
RS-2
[t692
7.358
6.25
11.38
0.637
0.0002
0.674
0.949
0.70
RS-3
2.951
7.298
6.25
1.38
0.635
0.0002
0.671
0.946  0.70
RS-4
4.142
7.228
6.25
1.37
0.633
0.0002
0.671
0.948  0.70
RS-5
4.887
7.127
6.25
1.36
0.632
0.0002
0.668
0.951  0.70
RS-6    I5.750
7.087                    ,6.25
1.35
0.630        0.0002
0.665
0.952  0.70
RS-7
6.123
7.030
6.25
1.35
0.629
0.0002
0.662
0.951  0.70
RS-8
10.14
6.973
6.25
1.34
0.627
0.0002
0.662
0.952  0.70
RS-9
10.97
16/925
6.25
1.34
0.624
0.0002
0.658
0.948  0.70
RS-10
12.382
6.803
6.25
1.32
0.625
0.0002
0.658
0.958
P.70
RS-11a
15.010
6.658
6.
1.33
0.62
0.0002
0.6553
0.950
0.70
RS-11b
,15.010
,6.576
6
1.33
0.624
0.0002
0.6553
0.952
0.70
RS-12
16.393
6.447
6
1.31
0.617
0.0002
0.6490
0.951      0.70
RS-13
17.186
6.315
6
1.30
0.610
0.0002         0.6458
RS-14
17.756
6.207
6
1.28
0.610
0.0002
0.6395
0 345
0.954
RS-15
18.884
0.70
0.70
5.981
6
1.26
0.604
0.0002
0.6330
0.954
RS-16
21.327
0.70
5.523
p
1.25
0.596
0.0002
0.6298
RS-17
0.946
21.788
4.969
0.70
5
1.24
0.584
0.0002
0.6266
0.932
0.60
RS-18
22.762
4.78
5
1.21
0.578
0.00022
0.6168
RS-19
23.797
4.524
5
0.937      0.60
,1.18
0.569
0.00022
0.6070
RS-20
24.842
0.937
4.249
4.5
—
0.60
1.16
0.5852
0.00022
0.6004
RS-21
26.347
4.043
0.975
4.5
0 60
1.13
0.576
0.00022
0.5904
RS-22
28 063
3.863
4.0
0.976
1.13
.
0 60
0.603
0.00025
RS-23
0.5904
28.868
3.77
4.0
1.021
1.11
0.565
.
0 60
0.00025
RS-24
29.761
0.5837
3.683
|4,0
0.968
1.10
0.595
.
0 6w0
0.00025
RS-25
30.285
0.5803
1
3.644
4.0
1.09
.
1 028
1 025
0.593
0.00025
RS-26
0.5770
31.332
3.52
3.8
1.09
0.594
.
—_   ------- 0.60
0 60
0.00025
RS-27
31.836
3.234
0.5770
3.5
1.08
.
1 030
0.581
0 60
0.00025
RS-28
32.960
0.5736
3.188
3.5
1.08
0.578
.
1 013
0 60
0.00025
RS-29
33.818
2.99
0.5736
3.5
1.04
0.568
.
1.008
0.00025
0 60
RS-30 34.819
RS-31 35.218
2.33
0.5599
2.6
1.03
0.543
0.00025
0.5564
2.044
1 015
0 976
2.5
0.98
0 60
0.60 “
0.525
RS-32
35.922
0.00025
1.802
0.5390
,2.2
0.97
0.508
0.00025
0 974      0 50
RS-33
36.475
1.649
0.5355
2
0.96
0 949
0.501
RS-34
37.418
0.00025
1.51
0.5319
2
0.91
0.49
0 942
RS-35
38.537
1.41
2
0.00025       0.5140
0.88
0 953
n sn
050
o sn
0.481
RS-36
39.556
0.00025
1.199
1.5
0.5031
0.87
0.49
0.956
0.00025
0.50
RS-37
RS-38
40.207
0.994
0.4994
1.5
0.79
0.466
0 981
0.000285
0.50
0.4695
42.088
0.735
1.3
0.72
0.992      0 50
RS-39
0.433
43.109
0.000285
0.624
0 4425
1
0.72
0.418
.
0 979 * n rh
0.000285     0.4425
u.ou
RS-40 44.166
0.563
1
n qas
0.68
0.407
0.000285     0.4266
0.50
0 954      OJUSA
u.
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ANNEXURE 2-2
Hydraulic Particulars for Left Primary Canal
Rogosity coefficient (Manning's n = 0.0225) Canal side slope (1.5:1 for cut & 2:1 for fill)
May 2007
_
___
Sl.no
Cumulativ Main canal
_____
Velocit Canal bed Critical
PerimeterlReach
e Distance in km
progressive discharge
Bed
width
(m)
Bed
level
(m)
F.S.D
(m)
y (m/s
slope
velocity V  =
o
C.V.R
= V/Vo
0.546D064
m/s
[Free board
(m)
km)
length (m)
iDische ge
0
0.00
9.015
7.5
1.42
0.664
0.0002
,0.683
0.972
j0.70
12.62
jo.oo
LS-1
0.157
8.968
7.5
1.41
0.662
I0.0002
0.680
0.973
p.70
12.584
1200
LS-2
3.126
8.931
7.5
1.41
0.661
'0.0002
0.680
0.972
P.70
12.584
p900
LS-3
3.749
8.886
7.5
1.4
0.66
0.0002
,0.677
0.975
0.70
12.548
600
LS-4
4.638
8.863
7.5
1.4
0.659
'0.0002
I0.677
|0.973
0.70
12.548
900
LS-5
5.411
8.818
7.5
1.4
0.658
0.0002
0.677
0.972
0.70
12.548
700
LS-6
6.084
8.746
7.5
1.39
0.657
0.0002
0.674
0.975
IO.70
112.512
700
LS-7
6.553
18.701
|7.5
1.39
0.656
0.0002
0.674
0.973
0.70
I12.512
600
LS-8
9.89
8.61
7.5
1.38
0.655
0.0002
0.671
0.976
0.70
,12.476
3350
LS-9
10.486
8.455
7.5
1.36
0.649
0.0002
0.665
0.976
0.70
12.404
560
LS-10
[13.994
,8.32
7.5
1.36
0.647
0.0002
0.665
0.973
0.70
12.404
3380
LS-11
15.906
8.275
|7\5
1.35
0.645
0.0002
,0.662
0.975
0.70
112.367
1870
LS-12
20.16
,8.198
7.5
1.34
0.643
0.0002
0.658
0 976
0.70
12.331
[4410
LS-13
20.718
8.12
7.5
1.33
0.641
0.0002
0.655
0.978
0.70
12.295
600
LS-14
21.693
I8.062
7.5
1.33
0.639
0.0002
0.655
0.975
0-70
12.295
1200
LS-15
23.115
7.663
7
1.34
0.636
0.0002
0.658
0.966
Q.70
11.831
1180
LS-16
23.617
'7 587
IF-
1.33
0.634
0.0002
0.655
0.967
0.70
11.795
r440
LS-17
26.86
7.413
7
1.33
0.63
0.0002
0.655
0.961
0.70
11.795
LS-18
3060
27 653
7.334
7
1.30
0.628
0.0002
0 646
0.972
0.70
11.687
LS-19
710
28.869
7.292
7
1.30
0.627
0.0002
0.646
0.971
0.70
11.687
LS-20
1260
29 526
7.267
|7
1.30
0.627
0.0002
0.646
0.971
0.70
LS-21
11.687
680
30.333 ------ --------
7.219
7
1.29
0.625
0.0002
0.643
0.973
0.70
LS-22
11.651
31.096
7.058
830
7
1.28
0.62
0.0002
0.639
0.970
LS-23
0.70
32.44
6.378
11 615
710
6
1.27
0 636
0 000222
0.636
1.000
LS-24
6.70
33.955
10.579
6.262
1320
6
1.26
0.633
0.000222
0.633
1.000
LS-25
0.70
35.266
6.164
10.543
6
1450
1.25
0.625
0.000222
0.630
0.992
LS-26
0.70
10.507
35.673
5.322
1330
fe
1.25
0.617
0.000222
0.630
LS-27
0.980
0.60
36.718
5.286
9.5069
5
1110
1.25
0.616
0.000222
0.630
0.978
LS-28
0.60
38.076
9.5069
5.265
5
1030
1.25
0.615
0.000222
0.630
0.976
LS-29
0.60
38.912
9?5069
5.231
5
1.24
0.614
1350
0.000222
0.627               0.980
0.60
LS-30
9.4709
39.737
830
5.161
5
1.23
0.612
0.000222
0.623
0.982
LS-31
0.60
40.137
5.125
9.4348
5
1.23
0.61 0.000222
0.623
840
0.979
LS-32
0.60
40.818
5.013
9.4348
5
1.21
0.606
350
0.000222
0.617
0.982
LS-33
0.60
41.913
4.897
9.3627
5
1.20
0.602
0.000222
0.614
640
0.981 ,
LS-34 LS-35
------------
LS-36
LS-38 LS-39a
LS-40 LS-41
0.60
44.312
[4.821
9.3267
5
1.19
0.599
0.000222
0.610
1150
0.981 |
0.60
45.008
4.792
5
1.18
0.598
0.000222
9.2906
2320
0.607              IO.985 |
0.60
46.236
??617
9.2546
5
1.16
0.592
0.000222 0.600
570
LS-37
0.986
0.60
47.563
4.419
9.1824
5
1.13
0.584 0.000222
0.590
1090
0.989
0.60
48.204
4.303
5
1.11
0.549
9.0743
0.000222
0.584
1150
0.941
0.60
50.948
9.0022
760
LS-39b
51 649
3 149
0
35
1 07
0 576 I0.00025
0.570
1 010
54.124
0 60
2.778
3.5
1.0
0.556
0.00025
7 3579
0.546
1.018
54.483
0.60
2.741
3.5
0.99
0.554 |
0.00025
.
7.1056
3390
0.542
2440
LS-42
1.021
54.688
0.60
2.664
3.5
0.98
0.549
0.00025
7.0695
0.539
420
LS-43
1.019 f
-------
55.382
3 50
2.478
0.94
0.538
7.0334
3.5
0.00025
0.525
350
LS-44
57.644
1.025
3.50
1.982
3
0.89      0.512
0.00025
0.507
6 8892
530
1.010 It
LS-45     '60 159        0.899 'i
3.50
2
0.70      |0.425
0.00025
.
6 2089
0.435
2460
0.978
3.50 f
Area under 39 is dived in to two (39a&39b)
.
4.5239
2360
--------------------------------------------------------------------------------------------------------- ------------  7 Water Works Design & Supervision Enterprise
In Association with Intercontinental Consultants and Technocrats Pvt. Ltd.Arjo Dedessa Irrigation Project
Hydraulic Design of Canal Structure
May 2007
ANNEXURE 2-3
Hydraulic Particulars for Secondary Canal-RS-16.
Rogosity coefficient (Manning's n = 0.0225)
Canal side slope (1.5:1 for cut & 2:1 for fill)
SI
.n
0
Cumula tive Distanc e in m
Secondary canal progressive discharge
Bed
width
(m)
Bed
level
(m)
F.S.D
(m)
Velocity 
(V=m/s)
Canal
bed
slope
Critical velocity 
(V.)=
O.546D054 =m/s
V/Vo
Wetted perimet
er
Reach length
(m)
Dischar
ge
1
000
0 48
1
0.61
0412
0.00033
0.41
1.007
3.20
0.00
2
300
0.44
1
0 58       0403
0.00033
0.385
1.046
3.09
300
3
600
0.395
1
0.55
0.391
0.00033
0.37
1.05
2.98
300
4
900
0.341
0.8
0.55
0.379
0.00033
0.37
1.02
2.78
300
5
1200
0.283
0.6
0.55
0.364
0.00033
0.37
0.98
2.58
300
6
1500
0.221
0.5
0.51
0.342
0.00033
0.355
0.964
2.34
300
7
1800
0.16
0.50
0.44       0.315
0.00033
0.323
0.975
2.09
300
8
2100
0.11
0.5
0.35
0.307
0.0004
0.279
1.1
1.76
300
9
0.098
20.83
I 10
ANNEXURE 2-4
Hydraulic Particulars for Secondary Canal-RS-17.
Rogosity coefficient (Manning's n = 0.0225)
Canal side slope (1.5:1  tor cu  & 2:1 for fill)
SI.
no
Cumula tive Distanc e in km
Secondary canal progressive discharge
Bed widt
h
(m)
Bed leve
I
(m)
F.S.D
(m)
Velocity 
(V=m/s)
Canal bed slope
Critical velocity (Vo) =
O.546D054 =m/s
V/Vo
Wetted perimet
er
Reach length
(m)
Dischar
ge
13
0.00
0.58
1 00
0.67
0.433
0.00033
0.423
1.025
3.416
0.00
14
300
0.562
1.00
0.66
0.429
0.00033
0.419
1.025
3.380
300
15
600
0.531
1.00
0.64
0.429
0.00033
0.410             1.045
3.308      300
16
900
0.497
1.00
0.62
0.419
0.00033
0.402
1.042
3.235
300
17
1200
0.461
1.00
0.60
0.408
0.00033
0.394
1.036
3.163
300
18
1500
0.42
1.00
0.57
0.398
0.00033
0.381
1.045
3.055      300
19
1800
0.369
0.80
0.57
0.387
0.00033
0.381
1.016
2.855      300
20
2100
0.316
0.80
0.53
0.373
0.00033       0.361
1.025
2.711      300
21
2400
0.251
0.60
0.52
0.353
0.00033       0.359
0.983
2.475      300
22
2700
0.198    0.50
0.49
0.33
0.00033
0.346
0.954
2.267      300
23
3000
0.15
0.50
0.43
0.31
0.00033
0.318
0.974
2.050
300
24
0.114
0.50
0.36
0.31
0.0004
0.284
1.09
1.798
25
33.71
3
26
27
28
Water Works Design & Supervision Enterprise
In Association with Intercontinental Consultants and Technocrats Pvt. Ltd.Arjo Dedessa Irrigation Project
Hydraulic Design of Canal Structure
3. HYDRAULIC DESIGN OF CANAL STRUCTURES
3.1    General
May 2007
The p rimary c anals, I eft a nd r ight b ank P rimary c anals, o f A rjo-Dedessa p reject a re a ligned a s contour canals  thought their entire length. Canals  being contour canals  have to cross  number of drainage and streams, for which cross  drainage works  are to be designed. Besides  these structures  for existing road, access  roads  crossing the canal, road Bridges  are essential. For regulating discharges  to off taking from parent canal and for control of regulation, regulators and cross  regulators  are essential, to be provided. In Arjo-Dedessa, no drop structure in primary canals are proposed, due to topography of area and canals being contour canals.
3.2     Canal Structures for Primary Canals
For the primary canals main structures which are designed are
1 Control structures
2 Cross Drainage works
3. Bridges
i)   Head regulator
ii)  Cross regulator
iii)  Escape regulator
i)  Aqueduct
ii)  Syphon aqueduct
iii)  Canal Syphon
iv) Aqueduct with normal canal motion
v)  Super passage
i)   Road Bridges
ii)   Foot Bridges for cattle crossing
3.3    Survey and Geotechnical Investigation
For design of any  type of canal structure the detail survey  and geological investigation at every proposed site of structure, for which design is to be done, is required. The survey should provide the detail block levels of area near structure, where as geological investigation, which are required consists of either drill holes for major structure or trial pits for smaller structure,
9
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Hydraulic Design of Canal Structure
May 2007
For cross  drainage works  detail data for computation of flood level, peak  flood discharge are required. During the feasibility study of the project, no detail survey or geological investigation has been carried out. Therefore design and drawing of one structure of each type has been prepared based on available records and assumption made on the basis of available information. Therefore the drawings and designs are tentative.
Details,  which  are  considered  for  design  and  drawings  of  each  type  of  structures  are  discussed below in short.
3.4    Control structures
For providing control for required regulated discharge from primary canal to the secondary canal, from secondary canal to tertiary canal and so on, regulator are essential for each off taking canal. However regulator are combined with cross  regulators  are also proposed at places  where the discharge of secondary  canal is  large and when discharges  of primary  canal in upstream and downstream has  a difference up to 5%. The cross  regulators  shall help in maintaining the water level in upstream even when there is low discharge in parent canal. In the Arjo-Dedessa project, it is  planned to have 40 secondary canals  taking of from Right bank  canal for which 37 regulators and 3 cross regulators combined with regulators are proposed. For the left bank primary canal it is proposed to have 45 secondary canals. For left bank canal it is propose to provide 38 regulators and 7 cross regulators with regulators, for secondary canals.
The lists  of cross  regulators  proposed for right bank  canal and for left bank  are enclosed as annexure 5A, 5B. The list of regulators  is  enclosed as  annexure 6A and 6B for right bank canal left bank canal respectively.
• Hydraulic design of regulator and cross regulator shall consist of
1.   Fixation of full supply elevation of off taking canal:- For this driving head of 0.1 to 0.15 shall be considered,  and  accordingly,  the  F.S.L  of  off  taking  canal  shall  be  fixed  by  keeping  difference equal  to  driving  head  between  FSL  of  parent  canal  and  off  taking  canal.  In  case  of  cross regulator  difference  between  upstream  and  downstream  FSL  of  canal  shall  be  kept  equal  to driving head.
10
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Hydraulic Design of Canal Structure                        May 2007
2.  Fixation of water way for regulator of off taking canal and for parent canal in case of cross 
regulator
3.  Fixation of sill level and width of sill.
For  fixation  sill  level  the  depth  of  water  over  sill  up  to  upstream  FSL  is  found  out  from  the following formulas for free flow orifice or for submerged orifice, as the case may be.
The leaner length of crest in normally kept equal to bed width of down stream
canal.
4.   Energy dissipation arrangement
For the regulator or cross regulator - Down stream floor is designed for energy dissipation. In case the regulator or cross regulator is not combined with fall stilling basin with water cushion is  proposed. In this  case, cistern floor is  depressed below the down stream canal bed elevation.
In case the regulator or cross regulator if combined with fall, stilling basins with hydraulic jump with horizontal apron shall be considered. Design for energy  dissipation which shall include length of cistern, depth of floor, and basin appurtenant shall be evaluated with the help of IS codes and standard design Books.
5.   Floor thickness
Thickness of downstream floor shall be worked out for uplift pressure. Uplift pressure shall be calculated from the maximum creep length of seepage and creep length up to the point of floor under consideration. The maximum uplift pressure on down stream shall be exerted when canal on upstream is  at FSL and downstream canal is  dry. The head of water shall be calculated from water elevation of canal in upstream to the bottom elevation of floor.
3.4     Escape Regulator
Escape is a safety structure to pass the excess water from canal to adjoining drains and there by avoiding the breaching of canal down stream of structure or for repair of canal in case breach has occurred. The increase of discharge in canal may be due to sudden closure of out lets
11
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Hydraulic Design of Canal Structure
May 2007
The escape has to have necessarily cross regulator and regulator head for escape for discharging excess  water. Therefore design of escape is  similar to regulator and cross  regulator structure. The difference being that, for the escape a fall is generally required to be provided to negotiate the drop due difference between the elevation of bed of canal and bed of stream. The fall shall be designed either as  a vertical fall, chute fall or ogee fall deepening on the height of fall and discharging capacity of escape.
The  design  shall  be  based  on  formula's and procedure  as laid down in standard IS codes and books.
In addition there shall be escape channel in down stream of fall of escape which shall carry spilled discharge of canal safely to stream. The escape channel shall be designed as per channel design with trapezoidal section. One escape for each primary  canal has  been provided for feasibility study. The escape has been proposed in the head reach of primary canal.
The escape location and details are listed along with list of structures for cross regulator.
Cross Drainage Works
In the project both the primary canals right and left are contour canals. The canal alignment has tentatively  been finalized on the basic  of contour map on 1: 10,000 scale. From study  of canal alignment, canal has to cross many streams, and river like WAMA. The right bank canal crosses several streams, and Major Rivers like WAMA.
The right bank canal has to cross 27 streams with catchment area ranging from 0.8 sq km to 33 sq km. Besides these streams right bank canal crosses a major river Wama having catchment area of approximately 3542.sq km. Thus there are 28 C.D. works for right bank primary canal.
The left bank primary canal has to cross 37 streams or river having minimum catchment area of 0.45 sq km to maximum of 300 sq km.
The list of streams on which cross drainage works are to be constructed is enclosed as annexure 7A and 7B for right and left bank primary canal respectively.
There are many type of structures which are considered for cross drainage works
_________________________________________________ ________________________________ 12 Water Works Design & Supervision Enterprise
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Hydraulic Design of Canal Structure
May 2007
Selection of type of structure depends largely on the discharge of canal, flood discharge of stream, highest flood elevation, lowest bed elevation of stream or river and canal bed elevation.
The type of structures are
i)
Canal is taken over the stream or river
A)  Aqueduct
B)  Siphon aqueduct
C) Aqueduct with canal in normal section
ii)
Drainage discharge is passed over canals
A)  Super passage
B)  Canal siphon
3.5    Data requirement
When the canal is aligned as a contour canal, for disposal of natural drainage discharge across canal, construction of cross  drainage structures  are necessary. Cross  drainage works  are thus unavoidable on any contour canal system.
3.6    Data required for design
For design of any type of cross drainage works following data is taken into account.
(A) For Canal
i)   Full supply discharge
ii)  Bed width and bed elevation of canal
iii)  Full supply depth and elevation
iv) Water surface slope
v)  Top elevation of bank
v i) Cross section of canal showing Natural surface elevation etc.
vii) Nature of earth material and value of coefficient of rugocity (n), adopted.
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(B) For Stream /Drain/ River
i)   Maximum observed flood discharge and flood elevation at the canal crossing Site
ii)   Peak flood value for 25-year return period for C.D. works other than Box aqueduct is considered. For larger catchment area more than 50 km peak 
May 2007
flood value for 50 years or 100 year return period is considered. For aqueduct
on major river or streams peak flood value for 100-year return period shall be
taken into account.
iii)  Water surface slope for observed or evaluated highest flood condition
iv)  Longitudinal section of stream or drain to a suitable distance upstream and
downstream of canal crossing.
v)   For calculating maximum flood elevation for peak discharge value, in case it is 
more than observed maximum flood value, then cross section of stream or drain
at canal crossing site and at least 100 m upstream and downstream of crossing
site.
vi) Site plain of proposed crossing including counter at suitable interval preferably 
at 0.5m contour interval
vii) Catchment area of stream or drain up to canal crossing.
viii) Log of borehole or trail pit data
ix) n: coefficient of rugosity is considered according to nature of bed materials of
river or stream.
3.6     Determination of flood discharge
HFL of stream or drain, bed elevation of stream and bed level of canal and their relative discharges  are primarily  considered in selection of most suitable type of structure for a particular location.
The canal data is  made available on the basis  of tentatively  finalised design and alignment of canal. For stream data neither detail survey  nor geological investigations  are available, therefore the designs are based on some assumption made and available records.
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Water Works Design & Supervision Enterprise
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Hydraulic Design of Canal Structure
May 2007
For design of C.D work calculation of peak flood discharge from catchment area and computation of HFL is important. For peak flood discharge computation, catchment area of stream or drain is obtained from 1 in 50,000 available maps. For computation of peak  flood discharge from small catchment, rational formula as given in draft final report of hydrology is considered copy of which is an closed as annexure 8. On the basis of rational formula a computer programme is prepared in which following variables  are required, which are worked out and entered in the program for obtaining the peak flood discharge
1.  Catchment area obtained from in 50,000 map
2.  Length of stream from origin to crossing point:- obtained from 1 in 50,000 map
3.  Maximum elevation -obtained from 1 in 50,000 map
4.  Bed elevation of stream = Approximate values are assumed from contour map for canal of
scale 1 in 10,000
5.  Return period = 25 years, 50 years or 100 years is considered depending upon the
catchment area of stream or drain
6.  24 hour mean rainfall: - The value of rainfall for different period of return years is given in
the report of hydrology. Copy of which is enclosed as annexure 9
7.   CV factor:- Given in hydrology report. On the above basis the peak flood discharge for each drain or stream is evaluated and the values are enclosed in Annexure - 7A and 7B for right bank and left bank canal respectively.
For Wama River crossing the peak flood discharge values for 100 and 500 year return period are computed in hydrology  repot, copy  of which is  enclosed an annexure 10. Hydrologist also intimated peak flood discharge values for 50 and 100 year return period, for drain or stream which has catchment area more than 20 sq. km. The flood values are shown in Annexure 7A and 7B
3.7 Selection of type of structure
The s election of t ype o f s tructure for p articular I ocation s hall d epend o n t he h igh f lood I evel o f stream or drain, bed elevation of canal, bed elevation of stream and relative discharge of drain and canal.
Following are the broad consideration for deciding type of structure.
15
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Hydraulic Design of Canal Structure
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1)  Box aqueduct /aqueduct/: - When HFL with afflux of stream or drain is considerably below the canal bed elevation then aqueduct structure is suitable. In this case canal is passed in trough or duct.
2)  Syphon aqueducts: - When difference between HFL of stream or drain and bed elevation of canal  is  minimum  or  when  canal  bed  elevation  is  just  below  HFL  of  stream  or  drain,  Syphon aqueduct structure is most suitable. In this case the stream discharge is passed below the canal. The stream or drain discharged is syphoned under pressure by depressing the bed of stream or drains at the structure.
3) Aqueduct, with canal in full section
When HFL of stream or drain is  below the canal bed elevation, and when catchment area and discharge of drain is not very large, canal is taken over the drainage in normal canal section with out reducing the area, there by avoiding the head loss
4)          Super     passage:-     When     FSL     of     canal     is     sufficiently     below     the     bed level  of  stream  on  drain,  then  super  passage  structure  is  suitable.  In  this  type  of  structure  the drainage or stream discharge is carried over the canal.
5) Canal syphon:- When canal FSL is below , or near the bed elevation of stream or drain, and canal  discharge  is  comparatively  less  compared  to  flood  discharge  of  stream  or  drain,  canal syphon  structure  can  be  considered  suitable.  The  discharge  of  drainage  or  stream  is  taken  over the canal and canal discharge is passed under pressure by depressing canal bed at the structure.
On the above broad basis  after computation of flood values and bed elevation, type of structure which are proposed are tabulated as per annexure 7A and 7B for right bank canal and left bank canal respectively.
• The design of structure shall consists of following components
Determination  of  high  flood  elevation  after  assessing  peak  flood  value.  Fixation  of  high  flood elevation shall be done by trial and error method
16
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The discharge passing through the stream at the crossing point is  evaluated for the assumed flood elevation by  multiplying the area up to assumed flood elevation by  velocity  calculated for flow by Manning's formula.
In case discharge of stream at assumed flood elevation is  much more, then lower flood elevation shall be assumed. If discharge calculation provides  less  discharge at assumed HFL then calculation for higher flood elevation shall be carried out.
Afflux calculation
Due to proposed CD work  if the waterway  of stream is  reduced in structure, there shall be increase in upstream water level, which is  termed as  Afflux. Afflux  shall he evaluated by  Mole worth's formulae
Calculation for Head loss
When  canal  or  stream  discharge  is  proposed  to  be  passed  through  a  duct  or  barrel  there  shall  be head loss.
Entry and exit of trough or barrel
X- Friction loss in the barrel or trough
Loss of head in bends, generally no bends are provided in trough or barrel in irrigation
structure.
The loss  of head is  depended on velocity  at entry  and exit, velocity  in barrel length of barrel and the material of trough or barrel used. The calculation for lead loss  in done as  per procedure and formula given in Indian standard codes  and standard book. The head loss  shall be accounted for, in case of canal by  lowering the FSL of canal on downstream by  equal amount of head loss. In case of stream either allowing increase in the upstream HFL or lowering the down stream HFL of stream, by lowering stream bed i.e. re-sectioning the stream down stream of structure
Scour depth calculation
Due   to   obstruction   in   water   way   of   stream   there   shall   be   scour   in   stream.   The   foundation   of structure in taken below the recommended scour depth zone for abutment wings and piers.
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Hydraulic Design of Canal Structure
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The scour depth is  calculated by  standard formula, i e. either by  Lacey's  formula or by  unwins formula available in standard IS codes  and books. The foundation of structure is  taken 2, 1.5 or 1.33 times  the scour depth calculated from above formula, depending upon the position of component and flow direction of stream.
The scour depth is measured below the H.F.L of stream.
Scour depth calculation is  important for determining foundation elevation of different component of structures. The foundation elevation shall be taken below the scour depth and shall rest on firm strata. If hard rock is met earlier foundations shall be taken 0.6m inside hard rock.
Determination of water way
The waterway determination for trough or barrel of canal or stream shall be fixed on the basis of velocity  that can be allowed in trough so as  to have minimum head loss  of canal. The waterway  for stream shall be decided from consideration of submergence of area in upstream and availability of safe free board for canal, to avoid any head loss in canal.
Free board
Free board in the vertical clearance is necessary for the safety of canal or structure.
In canal free board is measured from F.S. elevation of canal to top bank elevation
In  structure  the  free  board  is  considered  between  the  Afflux  HFL  of  stream  or  FSL  canal  to  the bottom of slab of structure or between Afflux HFL and top of bank of canal.
For canal the free board varies according to the discharge of canal and generally ranges from 1.00 to 0.3 m.
For  structure  the  free board is generally kept from 1.0m  to 0.5 m minimum for structure of major canal. For structures on minor and micro minor canals the minimum free board is kept as 0.30 m.
Design for floor thickness for uplift
The floor D/S of structure is generally subjected to uplift pressure, when there is no head of water on floor, but in upstream of floor there is water at maximum elevation.
There shall be two types of uplift head
___________________________ _ _________ ___________________________________________ 18 Water Works Design & Supervision Enterprise
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I.          Static  head  due  to  sub  soil  water  below  the  down  streambed  up  to  the  foundation elevation of floor. This head is constant through out the length of the floor.
II.         Seepage pressure:- seepage pressure is due to water head created due to difference in elevation  of  water  level  in  upstream  and  downstream  bed  elevation.  This  pressures  is varying  from  downstream  to  upstream  end  of  floor.  It  is  minimum  at  downstream  end and  maximum  at  upstream  end.  To  find  out  the  uplift  pressure  at  particular  point  first total creep length from u/s to D/s cut off is calculated. This length shall include u/s cutoff depth, u pstream i mpervious f loor I ength, and d epth o f o ther c utoff, d ownstream floor length and downstream cut off. Then the creep length up to the point where pressure is to be calculated is considered. Uplift seepage pressure at the point under consideration shall be:
= Seepage head x 1
°f creep upto the point in consideration' Total creep length
7
The sum of the static pressure and seepage pressure shall be counteracted by weight of concrete floor. Therefore to calculate thickness of floor, total uplift pressure shall be divided by unit weight of concrete, normally  plain CC floor shall be provided. Incase the thickness  of floor calculated is more, R.C.C floor can also be provided.
The  concrete  or  impervious  floor  upstream  or  downstream  shall  be  protected  from  scouring  by providing a cut off wall at the end of floor
Upstream down stream protection
Upstream and downstream impervious  floor shall be protected by  providing pervious  protection beyond the impervious floor, consisting of CC block or stone pitching laid over gravel or filter layer. Thickness  of impervious  floor shall depend upon the discharge and velocity  of water flowing through structure.
A toe wall shall be provided at the end of impervious floor to protect it from scouring
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Water stops
Besides this for all structures where there is a joint between two bays or span's, PVC water stops
or copper plate water stops shall be provided
Bearings
Any slab or Super structure, which is to carry a moving load of traffic over it, and transferring load to sub structure, suitable bearings between superstructure and substructure shall be provided (e.g. neoprene bearing).
Weep holes
For irrigation structure weep holes  are generally  provided in retaining walls, wings  walls  etc. But these weep holes shall be provided above the hydraulic gradient line. For proper drainage and to avoid earth particles to be carried through these weep holes graded filter shall be provided in back of hole. Spacing of weep holes  shall be normally  kept 2 to 3 m apart. The list of structures  for each type of CD works proposed to be provided, enclosed as following annexure.
1  List of aqueducts
2  List of syphon aqueducts
3 List of C.C work with earthen section
4  List of canal syphon
Drop structure or fall
Annexure - 8 A & B
Annexure - 9 A & B
Annexure - 10 A & B
Annexure - 11 A & B
In Arjo - Dedessa project both the primary  canal, left and right, are counter canals  for entire length. The topography of command is such that no fall or drop structure are proposed on primary canals.
However for secondary  and tertiary  canals  the ground slope is  steeper than the proposed bed slopes of canal. Therefore there shall be fall (drop) structures for these canals. Since the discharge of secondary and tertiary canals are small, and drop height is kept maximum up to 1.5 m, therefore
vertical  type  falls  and  well  type  falls  (for  very  small  discharge  around  0.03  m3/sec)  are  proposed the main consideration in design of falls are
1.  Selection of type of fall, depending upon discharge and drop height.
2.  Length of crest. - normally kept equal to the downstream width of canal or channel
3.  Determination of crest elevation.
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The  formula  used  is  to  determine  depth  of  water  over  crest,  shall  be  for  free  flow  weir  or submerged weir depending on the D/s F.S. elevation and crest elevation
The crest elevation is evaluated by deducting depth of water calculated by formula from upstream
F.S.L or T.E.L.
Energy dissipation
For  small  height  of  drop,  energy  dissipation  is  done  by  water  cushion  floor.  This  is  done  by depressing the downstream floor below down stream bed elevation of canal.
For Escape structure and bigger drop height, the energy dissipation shall be provided by providing hydraulic jump with horizontal stilling basin. Horizontal stilling basins are of two types, type I and type II depending upon Froude number. For Froude number up to 4.5 type I basin shall be considered. For Froude number more than 4.5 basin type II shall be selected. The design shall be d one as per the design procedure provided i n I ndian codes, books a nd U .S.BR Book. F or energy dissipation following calculation shall be carried out
1.  Calculation of floor length
2.  Depth of depression of floor below downstream bed elevation
3.  Thickness of floor
4.   Protection works
5.  Cut off
Design and calculations shall be carried out as explained earlier and with the help of cods design books etc.
Road Bridges and footbridges
Whenever  canal  crosses  existing  roads,  having  communication  links  between  two  places  a  road Bridge shall be provided
In Arjo - Dedessa project no existing major road like national high way or major road of standard DSi, to DS6 as  per Ethiopian Roads  authority, is  crossing any  of the canals. There is  only  one existing road Keketo hot spring to Wama Adere, of DS7 standard, is  crossing right bank  primary canal. Some access roads connecting the people residing in groups at different places are
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crossing  the  canals.  For  these  road  bridges  are  proposed  to  be  provided.  List  of  road  Bridges proposed is enclosed as Annexure 12 - I A & B
The distance between two existing access roads that are crossing the canal is generally more than
5  km, therefore it is proposed to provide foot bridges 2 m wide for crossing of canal by cattles and human beings. These footbridges are proposed in between the existing roads.
For the cross  regulator a footbridge across  canal is  already  provided, therefore at such places separable footbridges  are not provided. In some places  the foot bridge are combined with head regulators. The list of foot bridges provided is enclosed as Annexure 12 - II A & B.
3.9 Design
For design of road bridge, following consideration are there
Water way
Generally the water way under the bridge shall be provided nearly equal to the waterway of canal. For this the length of bridge is taken either equal to the linear waterway at FSL of canal. The length can be split up into two or more spans, if the width is more In this case one or more piers and abutments or buried piers at both end shall be provided.
Alternatively the linear water way can be restricted to bed width of canal. Due to restriction of water way (area) in this the afflux or head loss shall be more than in case of provision of linear water way equal to width of canal at FSL.
For canals with minor discharge RCC Hume pipe crossings can be considered
Afflux calculation
Due to obstruction in waterway due to either reduction of linear water way or due to provision of pier, area of water way is reduced. Due to reduction in area, there shall be afflux, which shall be calculated by Mole worth's formula
The  afflux  calculated  shall  be  accomated  by  keeping  difference  between  upstream  and  down stream FSL of canal equal to afflux
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Scour depth
May 2007
Due to reduction of the area of waterway, velocity  under the bridge shall increase. Increase in velocity shall have effect of scour in bed. The scour depth shall be calculated by Lacey's formula for normal scour depth. The maximum score depth shall be taken as 1.33, 1.5 and 2 times the normal scour depth for piers  and abutment. This  scour depth is  measured below the F.S.L of canal. Foundation of structure shall be kept below the maximum scour depth.
General for all structures for width of abutments piers and wing walls, side walls and return walls
Generally the top width of abutment is kept from 1.0 m to 2.0 m depending upon the structure, its type and size.
The top width of other walls shall be kept as 0.5 m for major structure of primary canal and 0.30 m for structures on canals of smaller discharge.
The bottom width at foundation elevation for abutment and walls is proposed to be kept as 0.5 to
0.55 times the height of abutment and walls, measured from top elevation to foundation elevation.
• All the structures are generally proposed to be constructed of cement concrete of different mix and strength. In place of concrete, stone masonry in cement mortar col. 1.4 can also be used in construction, depending upon availability of size and good quality masonry stones or rubble.
A list of all structure proposed on Right and left bank primary canals is enclosed as Annexure 13A and 13B respectively.
Drawing and design prepared
For feasibility study type designs and drawing of following type of structures have been prepared and are in separate volumes.
1. Control structure
1.1      Escape on Right bank primary canal (RB.P.C) at km. 2.0
1.2     Head regulator for secondary canal RS-16 of RPC at km 21.327
1.3     Head regulator for secondary canal RS-17 of RPC and cross regulator at km 21.788
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2.  C.D works
2.1      Aqueduct across WAMA river for RPC at km 8.40
2.2      Syphon aqueduct for RPC at km 22.00
2.3      Canal siphon for RPC at km 2.00
May 2007
2.4      Aqueduct with normal canal in earthen section for left bank primary canal at km 25.54.
3.  Bridges
3.1      Road bridge (without pier) for Keketo hot spring to WAMA Adere for right bank primary canal at 15.00 km
3.2      Road bridge (with pier) for access Road of left bank primary canal at 41.5 km
3.3      Foot Bridge (cattle crossing) for RPC at km 19.00
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As per details given in ANNEXURES 5 the total number of structures on primary Canals are given in Table 3.3.
Table 3.1 Total Number of Canal Structures
S.No
Structure details
Number of
RBPC.
Structures
LBPC Total
Total
Grand
Total
1.0
Control structures
1.1
Head    regulators    for    secondary canal
37
39
76
1.2
Head regulators and                cross regulators with foot bridge
3
7
11
1.3
Escape
1
1
2
Total 1
41
47
88
88
2.0
Cross Drainage works
2.1
Aqueducts
2
4
6
2.2
Siphon Aqueducts
17
16
33
2.3
Canal syphons
4
2
6
2.4
C.D  works  with  canal  in  earthen embankment
5
15
20
Total 2
28
37
65
65
3
Bridges
3.1
Road Bridge
4
6
10
3.2
Foot bridge
3
0
3
13
Total ■
7
6
13
*13
Grand total 1to3
76
90
166
166
4.0
Bridge combined with cross regulator or Head regulator not counted for total no for structures
4.1
Road Bridge
1
0
1
4.2
Foot Bridge
5
8
13
Total
6
8
14
14
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ANNEXURE 3-1
List of Proposed head and cross Regulators /Escape A) F o r Right b ank prim a r y c ain a I
s.
No
Name of structure
Distance from head of canal in km
Discharge of primary canal in m3/sec
Upstream = u/ s
Dwonstream = d / s
Discharge        of secondary 
canal in m3/sec
Remark
1
H.   Regulator   for   secondary canal      RS-17      and      cross regulator  and  foot  Bridge  No.
5
20.95
u/s = 5.523
d/s = 4.969
0.58
Designed
2
H. Regulator for secondary canal RS-27, cross  regulator with Road Bridge No. 4 for Access Road
30.8
u/s = 3.52
d/s = 3.234
0.30
3
H. Regulator for secondary canal RS-38, cross  regulator and foot Bridge No. 8
40.65
u Is 0.994 
d/s 0.735
0.272
4
Escape   with   cross   regulator and Foot Bridge
1.80
u/s = 7.028
d/s = 7.028
Escape discharge 7.00
B = For left Bank Primary Canal
1
H.  Regulator  for  secondary  canal  LS-9,  cross regulator and Foot Bridge (Cattle crossing)
10.51
u/s 8.61
d/s 8.455
0.162
2
H. Regulator for secondary  canal LS -15, crossing Regulator Foot Bridge No. 3 (Cattle crossing)
23.15
u/s 8.062 
d/s 7.663
0.417
3
H.  Regulator  for  secondary  canal  LS  -23,  cross Regulator and Foot Bridge No. 4
32.16
u/s 7.058 
d/s 6.378
0.711
4
H.  Regulator  for  secondary  canal  LS  -26,  cross regulator, Foot Bridge 5
36.05
u/s 6.164 
d/s 5.332
0.881
5
H.   Regulator   for   Secondary   canal   LS   -   33 crossing Regulator with Foot Bridge No. 6
42.24
u/s 5.013 
d/s 4.897
0.12
6
H.   Regulator   for   secondary   canal   LS   -   39, cross Regulator, Foot Bridge No. 7
50.94
u/s 4.303 
d/s 3.149
1.206
7
H.  Regulator  for  secondary  canal  LS  -44,  cross regulator Foot Bridge No. 8
55.36
u/s 2.478
d/s 1.982
0.519
8
Escape with cross regulator and foot Bridge
3.25
8.931
8.00
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ARJOO- DEDESSA PROJECT
LIST OF HEAD REGULATOR STRUCTURES
Distance Discharge of Primary Discharge of
i              Name of structure from origin canal in m3/sec in Secondary canal Remarks
ANNEXURE 3-2
No
-
in KM                     m3/sec 
A = RIGHT BANK PRIMARY CANAL
1   Head Regulator for
0.555
u/s=7.521
in m3/sec
0.0.057
Secondary canal RS-1
d/s=7.464
2
Head Regulator for
1.692
u /s=7.464
0.106
Secondary canal RS-2
d/s=7.358
3
Head Regulator for
2.951
u/s=7.358
0.06
Secondary canal RS-3
d/s=7.298
4
Head Regulator for
4.142
u/s=7.298
0.07
Secondary canal RS-4
d/s=7.228
5
Head Regulator for
4.887
u/s=7.228
d/s=7.127
0.101
Secondary canal RS-5
6
Head Regulator for
5.750
u/s=7.127
0.04
Secondary canal RS-6
d/s=7.087
7
Head Regulator for
6.123
u/s=7.087
0.057
Secondary canal RS-7
d/s=7.030
8
Head Regulator for
10.14
u/s=7.030
0.077
Secondary canal RS-8
d/s=6.973
9
Head Regulator for
10.97
Secondary canal RS-9
u/s=6.973
d/s=6.925
0.028
10
Head Regulator for
12.382
Secondary canal RS-10
u/s=6.925
d/s=6.803
0.122
11
Head Regulator for
15.010
u/s=6.803
Secondary canal RS-11
0.086
d/s=6.576
12
Head Regulator for
16.393
Secondary canal RS-12
u/s=6.576
d/s=6.447
0.135
13   Head Regulator for Secondary canal RS-13
17.186
u/s=6.447
d/s=6.315
0.132
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14   Head Regulator for
17.756
u/s=6.315
0.120
Secondary canal RS-14
d/s=6.207
15   Head Regulator for
18.884
u/s=6.207
d/s=5.981
0.237
Secondary canal RS-15
16   Head Regulator for
21.327
u/s=5.981
0.478
Secondary canal RS-16
d/s=5.523
18   Head Regulator for
22.762
u/s=4.969
d/s=4.78
0.198
Secondary canal RS-18
19   Head Regulator for
23.797
u/s=4.78
0.266
Secondary canal RS-19
d/s=4.524
20   Head Regulator for
24.842
u/s=4.524
d/s=4.249
0.288
Secondary canal RS-20
21   Head Regulator for
26.347
u/s=4.249
0.216
Secondary canal-DR-21
d/s=4.043
22   Head Regulator for
28.063
u/s=4.043
d/s=3.863
0.187
Secondary canal- RS -22
and foot bridge no. 6
23   Head Regulator for
28.868
u/s=3.863
d/s=3.77
0.098
Secondary canal- RS -23
24   Head Regulator for
29.761
u/s=3.77
0.090
Secondary canal- RS -24
d/s=3.683
25   Head Regulator for
30.285
u/s=3.683
Secondary canal- RS -25
0.040
d/s=3.664
26   Head Regulator for
31.332
Secondary canal- RS -26
u/s=3.664
d/s=3.52
0.130
28   Head Regulator for
32.96
u/s=3.234
Secondary canal- RS -28
0.048
d/s=3.188
29   Head Regulator for
33.818
Secondary canal- RS -29
u/s=3.188
d/s=2.99
0.207
30   Head Regulator for
34.819
u/s=2.99
Secondary canal- RS -30
0.690
d/s=2.33
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31   Head Regulator for Secondary canal- RS -31 and foot bridge no.7
32   Head Regulator for Secondary canal RS-32
33   Head Regulator for Secondary canal RS-33
34   Head Regulator for Secondary canal RS-34
35   Head Regulator for Secondary canal RS-35
36   Head Regulator for Secondary canal RS-36
37   Head Regulator for Secondary canal RS-37
39   Head Regulator for Secondary canal RS-39
40   Head Regulator for Secondary canal RS-40
34.218
u/s=2.33
d/s=2.044
u/s=2.044
d/s=1.802
u/s=1.802
d/s=1.649
u/s=1.649
d/s=1.51
u/s=1.51
d/s=1.41
u/s=1.41
d/s=1.199
u/s=1.199
d/s=0.994
u/s=0.735
d/s=0.624
u/s=0.624
d/s=0.563
May 2007
0.296
35.922
36.475
37.418
38.537
39.556
40.207
43.109
44.166
0.253
0.160
0.145
0.104
0.220
0.214
0.116
0.063
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ANNEXURE 3-3
LIST OF HEAD REGULATOR STRUCTURES B- LEFT BANK PRIMARY CANAL
S.No
•
Name of structure
Distance
Discharge of
Discharge of
Remarks
from origin
Primary canal
Secondary canal
1       Head Regulator for
0.157
u/s=9.015
d/s=8.968
0.048
Secondary canal-LS-1
2       Head Regulator for
3.126
u/s=8.968
0.039
Secondary canal- LS -2
d/s=8.931
3       Head Regulator for
3.749
u/s=8.931
d/s=8.886
0.047
Secondary canal- LS -3
4       Head Regulator for
4.638
u/s=8.886
0.029
Secondary canal-DL-4
d/s=8.863
5       Head Regulator for
5.411
u/s=8.863
0.042
Secondary canal-DL-5
d/s=8.818
6       Head Regulator for
6.084
u/s=8.818
0.075
Secondary canal- LS -6
d/s=8.746
and foot bridge no1
7      Head Regulator for
6.553
u/s=8.746
d/s=8.701
0.047
Secondary canal- LS -7
8       Head Regulator for
9.89
Secondary canal- LS -8
u/s=8.701
d/s=8.61
0.095
9       Head Regulator for
13.994
Secondary canal- LS -10
u/s=8.455
d/s=8.32
0.141
10     Head Regulator for
15.906
Secondary canal- LS -11
u/s=8.32
d/s=8.275
0.047
and foot bridge no.2
11     Head Regulator for
20.16
u/s=8.275
Secondary canal- LS -12
0.081
d/s=8.198
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12     Head Regulator for
20.718
u/s=8.198
d/s=8.12
0.081
Secondary canal- LS -13
13     Head Regulator for
21.693
u/s=8.12
0.061
Secondary canal- LS -14
d/s=8.062
14     Head Regulator for
23.617
u/s=7.663
d/s=7.587
0.08
Secondary canal- LS -16
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ANNEXURE 3-4
LEFT BANK
B- PRIMARY CANAL
Name of structure       Distance in KM
Discharge of in
m3/sec
Discharge of Remarks in m3/sec
15     Head Regulator for
26.86
u/s=7.587
0.181
Secondary canal- LS -17
d/s=7.413
16     Head Regulator for
27.653
u/s=7.413
0.083
Secondary canal- LS -18
d/s=7.334
17     Head Regulator for
28.869
u/s=7.334
0.044
Secondary canal- LS -19
d/s=7.292
18     Head Regulator for
29.526
u/s=7.292
0.027
Secondary canal- LS -20
d/s=7.267
19     Head Regulator for
30.333
u/s=7.267
0.05
Secondary canal- LS -21
d/s= 7.219
20     Head Regulator for
31.096
u/s=7.219
0.169
Secondary canal- LS -22
d/s=7.058
21     Head Regulator for
33.955
u/s=6.378
0.121
Secondary canal- LS -24
d/s=6.262
22     Head Regulator for
35.266
u/s=6.262
0.103
Secondary canal- LS -25
d/s=6.164
23     Head Regulator for Secondary canal- LS -27
24     Head Regulator for Secondary canal- LS -28
25     Head Regulator for Secondary canal- LS -29
26     Head Regulator for Secondary canal- LS -30
27     Head Regulator for
36.718
38.076
38.912
39.737
40.137
u/s=5.322
d/s=5.286
u/s=5.286
d/s=5.265
u/s=5.265
d/s=5.231
u/s=5.231
d/s=5.161
u/s=5.161
0.038
0.022
0.036
0.073
0.038
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28     Head Regulator for Secondary canal- LS -32
29     Head Regulator for Secondary canal- LS -34
30     Head Regulator for Secondary canal- LS -35
31     Head Regulator for Secondary canal- LS -36
40.818
44.312
45.008
d/s=5.125
u/s=5.125
d/s=5.013
u/s=4.897
d/s=4.821
u/s=4.821
d/s=4.792
0.118
0.08
0.033
46.236           u/s=4.792
d/s=4.617
0.18
32     Head Regulator for Secondary canal- LS -37
33     Head Regulator for Secondary canal LS -38
34     Head Regulator for Secondary canal- LS -40
35     Head Regulator for Secondary canal- LS -41
36     Head Regulator for Secondary canal- LS -42
37     Head Regulator for Secondary canal- LS -43
39     Head Regulator for Secondary canal- LS -45 and end structure
47.563
48.203
54.124
54.483
54.688
55.382
60.18
u/s=4.617
d/s=4.419
u/s=4.419
d/s=4.303
u/s=3.149
d/s=2.778
u/s=2.778
d/s=2.741
u/s=2.741
d/s=2.664
u/s= 2.664
d/s=2.478
u/s= 1.982
d/s=0.915
0.207
0.12
0.388
0.037
0.081
0.194
1.067
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ANNEXURE 3.5A
ARJO-DEDESSA PROJECT
A Right bank primary canal
Catchment Stream
Details for selection of type of structures
Max
Min
Retur Rainfall n
Coeff. Of Peak
Discharge Bed
discharge
elevation
Length
Elevation Elevation Perio n
Variation
of canal
of canal
Name structure
and Area
and
or zm i  ni
S.No.
distance
Qt=
2
(km )
1
2
3
(m)
4
(m asl) 5
(m asl) 6
R24 (year (mm)
78
RF
CV
9
MA3/S
10
m3/s 11
of canal (m)
12
1
2
CDR-1 2.00
CDR-2 2 9
10.00
4.75 5.52
3
4
5
CDR-3 3.95
2.5
0.875 2.65
0 306
0.306
0 306
CDR-4 6.00
CDR-5 7.6
1.625 5.84
5.11
10.75
6       CDR-6 Wama river 3542
7
8
9
10
CDR-7 9 15
CDR-8 10.4
CDR-9 11.5
CDR-10 13.38
11     CDR-11 172
12
13
14
CDR-12 19.55
CDR-13 22.45
CDR-14 24.65
1.2 14 9.6 4.825 3.275 3.75 57.6
10.13
3.61 3.26 11.21 8.90
7.028 1346.14 7.028 1345.71
7.028         1345.5
7.028         1345.09
7.028         1344.77
7.028 1344.38
7.028 1344.23
6.658
1344.00
6.658
1343.78
6 658
1343.41
.306
.306
.306
5.61 9.65 74.00
6.32
1342.56
5 981
1342.13
4.780
1341 49
4.249
1341.1
15
16
17
CDR-15 26.0
4.043
1340.79
CDR-16 26.5
10.67
22
CDR-17 27.65
27 15
18      CDR-18 29.7
19
20
CDR-19 32.1
CDR-20 33.0
13.87 40.25 08
1400      1565       1348 5   25     88.00
1000      1540       1346      25     88 00
2500      1520       1346      25     88.00       .
1600      1520       1344       25     88.00     0 306
3000      1540       1345       25     88 00     0 306
1332
1200      1440       1344       25     88.00     0.306
1000      1380       1343.5    25     88.00     0.306
6500      1640       1343       25      88.00     0.306
3200      1560       1342       25     88.00     0.306
2800      1480       1342       25     88.00     0
1700      1480       1341 5    25      88 00     0
19500    2300       1339.5    50      98.00     0
13500    1880       1337       25     88.00     0.306        8.51
11500    1740       1340 5    25      88.00     0 306        9.04 1900      1380       1336.8    25      88.00     0.306        3.40 15500    2460        1336       50      98.00     0.306        35.5/40.1 11000    2280       1338.2    50     98.00     0.306        18.90 13500    2360       1338.5    50     98.00     0.306        55.3/62.4 1200      1360       1336       25      88.00     0 306        1.45
Water Works Design & Supervision Enterprise
4.043
1340.68
3.863
1340.42
3.644
1339.94
3 188
1339 26
2 990
1339.1
Type of Structure
Proposed
13
Canal Syphon
Syphon Aqueduct
Syphon Aqueduct
Syphon Aqueduct
Syphon Aqueduct
Aqueduct
Syphon Aqueduct
Syphon Aqueduct
Syphon Aqueduct
Syphon Aqueduct
Syphon Aqueduct
Syphon Aqueduct
Syphon Aqueduct
CDWork.canal in earthen sectior Syphon Aqueduct
CDWork.canal in earthen sectior CDWork.canal in earthen sectior Syphon Aqueduct
Aqueduct
CDWork.canal in earthen sectior
34
In Association with Intercontinental Consultants and Technocrats Pvt. Ltd.Arjo-Dedessa Irrigation Project
Hydraulic Design of Canal Structure
May 2007
21
CDR-21 33.45
1.38
2000      1400
1338.5
25     88.00     0.306
2.32
2.990
1338.96
Syphon Aqueduct
22
CDR-22 34.4
7.53
6000      1600
1335
25     88.00     0 306
9.02
2.044
1338.6
CDWork.canal in earthen sectioi
23
CDR-23 36.5
1.05
1200      1380
1341
25     88.00     0.306
220
1.510
1338.13
Canal Syphon
24
CDR-24 37.0
2.4
1500      1410
1337.5
25     88.00     0.306
5.24
1.510
1338
Syphon Aqueduct
25
CDR-25 38.21
15.4
13500    2200
1337.7
50     98.00     0.306
16.90
1.410
1337.74
Syphon Aqueduct
26
CDR-26 39.9
8
6400      1740
1337
25     88.00     0.306
10.76
0.994
1337.37
Syphon Aqueduct
27
CDR-27 41.4
3.3
4300      1620
1338
25     88 00     0.306
539
0.735
136.92
Canal Syphon
28
CDR-28 42.4
33
17400    2480
1338
30     98.00     0.306
39.1/44.1
0 624
1336.73
Canal Syphon
Water Works Design & Supervision Enterprise
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ANNEXURE 3-5b
ARJO-DEDESSA project
B-Left bank primary canal
Catchment Stream Max
Details for selection of type of structures
Min         Return Rainfall Coeff. Of Peak discharge
Name
structure distance
and Area
and
Length Elevation Elevation Perion
R24
Variation
of 24 Hr
RF Qt=
Discharge Bed
of canal elevation of canal
of canal
S.No.
1             z                            3                                                                                          90 306        5.50
2                (m)        (m asl)    (m asl)    (years]I (mm)        CV            MA3/S (km )
10
(m)
4
5
6
7
8
12
1
z
43/48 5
CDL 4 5 28 1 2 1300 1420 1344 25 88.00 0 306 4.92 8.863
CDL-1 0 60 1.95
CDL-2 3.95 5.6
CDL-3 4.7 29.6
1800
1400
1345
25
88 00
1345.75
6000
1680
1345
25
88.00
9000
1780
1340
50
98 00
0.306        12.05 0 306
m3/s 11 8.968 8.931 8.931
1345.79
1345.74
3
4-
-.
6             CDL 6 7 99            0 55           1000      1430       1345       25          88.00     0.306        1.85               8.701
-.
.
5             CDL 5 6 53            1 15           1400      1425       1345.5    25          88 00     0.306        4.54               8.746
.
1345.54
1345.20
.
1344.90
1344.88
8             CDL-8 8.51             1.85           1800      1460       1344       25          88.00     0.306        4.26               8.701
7             CDL-7 8.14            1.85          1900      1480       1338       25          88.00     0 306        4.46               8.701
1344.81
9             CDL-9 9.23            0.45           1100      1460       1344       25          88 00     0.306        1.64               8.701
1344.66
10           CDL-10 12 36        9.65           4000      1640       1344       25          88.00     0.306        16.56             8.455
1344.07
11           CDL-11 15.35        3.75           2000      1400       1340       25          88.00     0.306        6.12               8.32
1343.60
12           CDL-12 20.09        1.7            2000      1440       1341       25          88.00     0.306        3.37                8.275
1342.53
13           CDL-13 20.65        4.3            3500      1480       1341       25          88.00     0.306        6.19                8.198
1342.43
14           CDL-14 24.14         11.5          4500      1540       1338.8    25          88.00      0.306        15 22              7.587
1341.64
15           CDL-15 25.54         1.8            1900      1430       1339.5    25          88.00      0.306        3.58                7.587
1341.36
16           CDL-16 25.88         1.45          1600      1420       1339       25          88.00      0.306        3.18                7.587
1341.30
17 CDL-17 27.93 0.94
18           CDL18 28.84         0.9
19           CDL-19 34.10        7.0
1300
1387
1340
25
88.00
0.306
1.98
1340.92
1300
1360
1339
25
88.00
0.306
1.49
1340.74
3000
1400
1337
25
88.00
0 306        8.61
20           CDL-20 36.66        0.53           1400      1440       1337       25           88.00      0 306        1.46                5.322
7.334
7.292
6.261
1339.53
1338.86
Water Works Design & Supervision Enterprise
In Association with Intercontinental Consultants and Technocrats Pvt. Ltd.
Type of Structure Proposed
13
Syphon Aqueduct Syphon Aqueduct
Aqueduct
Syphon Aqueduct Syphon Aqueduct Syphon Aqueduct CDWork.canal in earthen Syphon Aqueduct Syphon Aqueduct Syphon Aqueduct CDWork.canal in earthen CDWork.canal in earthen Syphon Aqueduct CDWork.canal in earthen CDWork.canal in earthen CDWork.canal in earthen Syphon Aqueduct
Syphon Aqueduct CDWork.canal in earthen CDWork.canal in earthen
36Arjo-Dedessa Irrigation Project
Hydraulic Design of Canal Structure
May 2007
21
CDL-21 38.25
0.5
1000      1440       1338       25
88 00
0.306
1.85
5.286
1338.51
Syphon Aqueduct
22
CDL-22 38.59
0.48
1000      1440       1338       25
88.00
0.306
1.78
5.265
1338.43
Syphon Aqueduct
23
CDL-23 38.73
0.6
1100      1341       1337       25
88 00
0.306
0.99
5.265
1338.40
CDWork,canal in earthen
24
CDL-24 39.48
2.54
2500      1400       1336       25
88.00
0.306
3.65
5 231
1338.25
CDWork,canal in earthen
25
CDL-25 40.28
300
44000    2480       1334.5    100
108.00
0.306
147.5/166.5
5.161
1338.08
Aqueduct
26
CDL-26 40.59
1.23
1750      1440       1337       25
88.00
0.306
2.78
5.161
1338
Syphon Aqueduct
27
CDL-27 41.84
1.48
2000      1440       1334.5    25
88.00
0.306
3.02
5013
1337.75
CDWork.canal in earthen
28
CDL-28 44.81
61
27000    1900       1335       50
98 00
0 306
40.8/46 0
4.821
1337
Aqueduct
29
CDL-29 48.53
3.98
1800      1380       1334       25
88.00
0.306
6.42
4.303
1336.24
CDWork.canal in earthen
30
CDL-30 50 01
1.43
1800      1380       1332.5    25
88 00
0.306
2.38
4.303
1335.87
CDWork.canal in earthen
31
CDL-31 52.52
2.1
2000      1380       1335       25
88.00
0.306
3.17
2.778
1335.26
Canal Syphon
32
CDL-32 54.13
7.05
3500      1480       1333 5    25
88.00
0.306
10.20
2.741
1334.87
Syphon Aqueduct
33
CDL-33 54 48
70.0
17500    1990       1330       50
98.00
0.306
66.8/75.5
2.664
1334.79
Aqueduct
34
CDL-34 55.04
2.45
2100      1460       1335       25
88.00
0.306
5.10
2.478
1334.68
Canal Syphon
35
CDL-35 56 76
2.65
2200      1460       1333.5    25
88.00
0.306
5.33
1 982
1334.15
Syphon Aqueduct
36
CDL-36 58.48
8.7
6700      1920       1329       25
88.00
0.306
13.40
1.961
1338.78
CDWork.canal in earthen
37
CDL-37 59.00
2.3
2400      1440       1332       25
88.00
0.306
4.07
1.961
1333.65
CDWork.canal in earthen
Water Works Design & Supervision Enterprise
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May 2007
ANNEXURE 3-6
List of Aqueduct Structures
A= For Right Bank Primary Canal
s.
No
Details      of Structure
Distance of structure from origin in km
Catchment area  in  sq. km
Maximum flood discharge in m3/sec
Discharge of        canal m3/sec
1
Across
Wama River CDR-
6
8.4
3542
100 year = 584
500 year = 776
7.028
2
CDR-19
32.1
40.25
50 Year = 55.30
100 year = 62.40
3.128
B = For Left Bank Primary Canal
1
CDL-3
4.7
29.6
50 Year = 43.0 100 year = 48.5
8.931
2
CDL-25
40.28
300
50 Year = 147.5 100 year = 166.5
5.161
3
CDL-28
44.81
61.0
50 Year = 40.8
100 year = 46.0
4.821
4
CDL-33
54.48
70.00
50 Year = 43.0
100 year = 48.5
2.664
38
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May 2007
ANNEXURE 3-7
List  of  Syphon  Aqueduct  Structures A = Right Bank Primary Canal
s.
No
Details of
CD work
Distance from origin in km
Catchment Area  in  sq. km
Peak  flood discharge in m3/sec
Canal discharge in m3/sec
1
CDR- 2
2.90
0.875
4.75
7.028
2
CDR- 3
3.95
2.65
5.62
7.028
3
CDR- 4
6.00
1.625
5.11
7.028
4
CDR- 5
7.60
5.84
10.75
7.028
5
CDR- 7
9.15
1.2
3.61
7.028
6
CDR- 8
10.40
1.4
3.26
6.658
7
CDR- 9
11.50
9.6
11.21
6.658
8
CDR-10
13.38
4.825
8.90
6.658
9
CDR-11
17.20
3.275
5.61
6.315
10
CDR-12
19.55
3.75
9.65
5.981
11
CDR-13
22.45
57.6
74.00
4.78
12
CDR-15
26.00
10.67
9.04
4.043
13
CDR-18
29.70
13.87
18.90
3.644
14
CDR-21
33.45
1.38
2.32
2.99
15
CDR-24
37.00
2.4
5.24
1.51
16
CDR-25
38.21
15.4
16.90
1.45
17
CDR-26
39.90
8.0
10.76
0.994
B= Left Bank Primary Canal
s.
No
Details  of CD work
Distance from o rigin in km
Catchment Area in sq.
km
Peak flood discharge in m3/sec
Canal
discharge in m3/sec
1
CDR- 1
0.60
1.95
5.50
8.968
2
CDR- 2
3.95
5.6
12.05
8.931
3
CDR- 4
5.28
1.2
4.92
8.863
4
CDR- 5
6.53
1.15
4.54
8.746
5
CDR- 6
7.99
0.55
1.85
8.701
6
CDR- 8
8.51
1.85
4.26
8.701
7
CDR- 9
9.23
0.45
1.64
8.701
8
CDR-10
12.36
'9.65
16.56
8.455
9
CDR-13
20.65
4.3
6.19
8.198
10
CDR-17
27.93
0.94
1.98
7.334
11
CDR-18
28.84
0.90
1.49
7.292
12
CDR-21
38.25
0.5
1.85
5.286
13
CDR-22
38.59
0.48
1.78
5.265
14
CDR-26
40.84
1.23
2.78
5.161
15
CDR-32
54.13
7.05
10.20
2.741
16
CDR-35
56.78
2 65
5.33
*—- 1.9--8-2------------
39
Water Works Design & Supervision Enterprise
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May 2007 ANNEXURE 3-8
List of Cross Drainage Works, with canal in earthen section A = Right Bank Primary Canal
s.
No
Detail of CC Work
Distance of Structure from origin in km
Catchment area in sq.
km
Peak  flood discharge in m3/sec
Discharge of canal in m3/sec
1
CDR- 14
24.65
10.13
25 year = 8.51
4.249
2
CDR-16
26.5
2.2
25 year = 3.40
4.043
3
CDR - 17
27.65
27.15
50 year = 35.5 / year = 40.1
3.863
4
CDR - 20
33.0
0.8
25 year =1.45
2.99
5
jCDR - 22
34.4
7.53
25 year = 9.02
2.044
B = Left Bank Primary Canal
1
ICDL- 7
8.14
1.85
25 year = 4.26
8.701
2
CDL-11
15.35
3.75
25 year = 6.12
8.32
3
CDL-12
20 09
1.7
25 year = 3.37
8.275
4
CDL-14
24.40
11.5
25 year = 15.22
7.587
5
CDL-15
25.54
1.8
25 year = 3.58
7.587
6
CDL-16
25.88
1.45
25 year = 3.18
7.587
7
CDL-19
34.10
7.0
25 year = 8.16
6.261
8
CDL-20
36.66
0.53
25 year = 1 46
5.322
fzz
CDL-23
38.73
0.6
25 year = 0.99
5.265
10
CDL-24
39.48
2.54
25 year = 3.65
5.231
11
CDL-27
41.84
1.48
25 year = 3.02
5.161
12
CDL-29
48.53
3.98
25 year = 6.42
4.303
13
CDL-30
50.01
1.43
25 year = 2.38
14
CDL-36
4.303
58.48
8.7
25 year = 13.40
1.961
15 |
DDL-37
59.00
2.3
25 year = 4.07
1.961
40
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May 2007 ANNEXURE 3-9
List of Canal Syphon Structures
A = Riqht Bank Pr imary Canal
S.
No
Location
Distance from o rigin
km
Catchment area is sq.
km
Peak    flood    discharge in m3/sec
Canal
discharge in m3/sec
1
CDR-1
2.00 km
2.50
25 Year = 10.0
7.028
2
CDR-23
36.50 km
1.05
25 Year = 2.20
1.51
3
CDR-27
41.4
3.3
25 Year = 5.39
0.735
4
CDR-28
42.4
33
50 year = 39.10 100 year = 44.10
0.624
___________
B = Left bank Primary Canal
1
CDL-31
52.52
2.1
25 year = 3.17
2.778
2
CDL-34
55.04
2.45
25 year = 5.10
2.478
41
Water Works Design & Supervision Enterprise
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May 2007 ANNEXURE 3-10 A
List of Road Bridges
A = Right Bank Primary Canal
s.
No
Details of Bridge
Distance from
origin in
km
Discharge of canal in m3/sec
Bed  width in m
Depth of water in m
Width of canal at FSL
1
Road Bridge No.1 for Access Road
5.50
7.028
6.25
1.35
10.30
2
Road   Bridge   for   Katketo Hol spring to Wama-Adere
15.00
6.576
6.00
1.33
10.00
3
Road   Bridge   No.   3   for Access Road
24.50
4.249
4.5
1.16
7.88
4
Road Bridge No. 4 for access road combined with head Regulator for RS-27 and cross regulator
30.8
3.234
3.5
1.08
6.74
5
Road   Bridge   No.   5   for Access Road
35.75
1.649
2
0.96
4.88
B = Left Bank Primary Canal
1
Road Bridge No.1 for Access Road
11.00
8455
7.5
1.36
11.58
2
Road Bridge No.2 for Access Road
18.50
8.275
7.5
1.35
T155
3
Road Bridge No.3 for Access Road
41.50
5.013
5
1.21
8.65
4
Road Bridge No.4 for Access Road
46.50
4.617
5
1.16
8.50
5
Road  Bridge  No.5  for Access Road
53.00
2.778
3.5
1.0
6.50
6
Road Bridge No.6 for Access Road
59.50
1.961
3.0
0.89
5.70
42
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May 2007
ANNEXURE 3.10 B
List of Foot Bridges (Cattle Crossings) Provided
A = Right Bank Primary Canal
(i) Independent - foot Bridges (cattle crossings)
S. No
Detail
Distance from origin in km
Canal discharge in m3/sec
Bed
width m
Depth of water in
m
Width of
canal
FSL
1
Foot Bridge No.1
2.5
7.028
6.25
1.35
10.30
2
Foot bridge No 3
12.00
6.658
6.00
1.33
10.00
3
Foot Bridge No. 4
19.00
5.981
6.00
1.26
9.78
B= Left Bank Primary Canal No independent foot Bridges are proposed for Left Bank 
Primary Canal
(ii) Foot Bridge combined with other structures
A Right bank Primary Canal
1
Head regulator for RS-17 cross  regulator A foot Bridge No.5
21.788
D/s 4.969
5.00
1.24
8.72
I2
Head regulator for RS-22 and Foot Bridge No.6
28.063
D/s 3.863
4.00
1.13
740
3
Head regulator for RS-31 and Foot Bridge No. 7
35.218
D/s 2.044
2.5
0.98
5.44
4
Head Regulator for RS-38, cross  Regulator and Foot Bridge No. 8
42.088
D/s 0.735
1.3
0.72
3.46
43
Water Works Design & Supervision Enterprise
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Hydraulic Design of Canal Structure
May 2007
ANNEXURE 3.10 C
B = Left Bank Primary Canal
1           Head regulator for LS-6 and Foot Bridge No.1
2           Head regulator for LS -9 Cross regulator and
Foot Bridge
3           Head regulator for LS -11
6.084 D/s 8.746 7.5
10.486 D/s 8.455 7.5
1.39 11.70
1.36 11.60
and Foot Bridge No. 2             15.906      D/s 8.275        7.5 4           Head regulator for LS -15,
cross regulator & Foot
1.35              11.55
Bridge No. 3
5           Head regulator for LS -23, cross regulator,
Foot Bridge No. 4
6           Head regulator for LS -26. cross regulator,
Foot Bridge No. 5
7           Head Regulator for LS       - 33, cross Regulator,
Foot bridge No. 6
8          Head Regulator for LS       - 39, cross regulator and Foot Bridge No. 7
23.115      D/s 7 .663       7.0
1.34              11.00
32.44         D/s 6.378        6.00              1.27              9.80
35.673      D/s 5.322        5
1.25              8.75
41.913      D/s 4 897       5
51.649      D/s 3.149       3.5
9           Head Regulator for LS      - 44 cross regulator and Foot bridge No. 8
57.644 D/s 1.982       3
1.20              8.60
1.07              6.70
0.89             5.70
44
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ANNEXURE 3-11 A
ARJOO- DEDESSA PROJECT
LIST OF ALL STRUCTURES
A-         RIGHT BANK PRIMARY CANAL
S. No         Name of structure            Distance          Discharge of             Discharge of              Flood Discharge of        Remarks
from origin
Primary canal
Secondary canal
Stream or River
in KM
in m3/sec
in m3/sec
in M3/ sec
1          Head Regulator for
0.555              u/s=7.521
0.057
0
Secondary canal-RS-1
d/s=7.464
2
Escape Structure
1 80
7.358
Escape Discharge
7.00
3
CD Work CDR-1
2.00
7.358
10
4
Foot Bridge no-1
2.50
7.358
0
NSL(m)
1347
5
CD Work CDR-2
2.90
7.358
4.75
6
CD Work CDR-3
3.95
7.298
5.52
7
Road Bridge no1
5.50
7.298
0
NSL(m)
1347
8
CD Work CDR-4
6.00
7.087
5.11
9          CD Work CDR-5
7.60                   7.030
10.75
10
CD Work CDR-6
8.40
7.030
100 year= 584
Aqueduct Wama River
500 year = 776
11
CD Work CDR-7
9.15
7.030
3.61
12
Head Regulator for
10.14
u/s=7.030
0.077
Secondary canal-RS-8
d/s=6.953
0
and Foot Bridge no-2
13
CD Work CDR-8
10.4
6.953
14
3.26
CD Work CDR-9
11.5
6 925
11 21
15
Foot Bridge no-3
12.00
6.925
0
0
NSL(m)
16
CD Work CDR-10
13.38
6.803
1345
8.9
17
Head Regulator for
15.010
u/s=6.803
0.227
Secondary canal-RS-11
d/s=6 576
18
Road Bridge for Kaketo
154
6.576
Spnngs to village
o
NSL(m)
Wamw Adere
0
1345
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19        Head Regulator for Secondary canal-RS-12
20        Head Regulator for Secondary canal- RS -13
16.393             u/s=6.576 d/s=6.447
17.186             u/s=6.447 d/s=6.315
0.135
0.132
21        CD Work CDR-11                       172                   6.315                           0
5.61
22        Head Regulator for
17.756
u/s=6.315
0.12
Secondary canal- RS -14
d/s=6.207
23        Head Regulator for
18 884
u/s=6.207
0.237
Secondary canal- RS -15
d/s=5.981
24        Foot Bridge no-4
19 00
5.981
0
NSL(m)
1343
25        CD Work CDR-12
26        Head Regulator for Secondary canal- RS -16
19.55
5.981
9.65
21.327             u/s=5.981 d/s=5.523
0.478
27        Head Regulator for
21.788
u/s=5.523
0.58
Secondary canal- RS -17
d/s=4.969
and Cross Regulator
and Foot Bridge no-5
28        Head Regulator for
22.762
u/s=4.969
0 198
Secondary canal- RS -18
d/s=4.78
29        CD Work CDR-13                     22.45
46.43
30        Head Regulator for Secondary canal- RS -19
31        Head Regulator for Secondary canal- RS -20
23.797              u/s=4.78
d/s=4.524
24.842             u/s=4.524
d/s=4.249
0.266
0.288
32        Road Bridge no3
25.390
4.249
0
NSL(m)
33        CDWorkCDR-14
25.526
4.249
1341.5
8.51
34        Head Regulator for
u/s=4.249
Secondary canal- RS -21
26.347
d/s=4.043
0.216
35        CD Work CDR-15
26912
d/s=4 043
9.04
36        CD Work CDR-16
27.40
d/s=4.043
3.4
37        Head Regulator for
27.65
u/s=4.043
Secondary canal- RS -22
d/s=3.863
0.187
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and Foot Bridge no-6
38        CD Work CDR-17                     28 60              d/s-3 363
39        Head Regulator for                  28 868             u/s=3 863
50 year = 35 5
100 year= 40
Secondary canal-DR-23
d/s=3 77
0098
40        CD Work CDR-18                      29 7                   3.77                                                                 189 41        Head Regulator for                  29 761              u/s=3.77
Secondary canal- RS -24
d/s=3.683
42        Head Regulator for                  30 285             u/s=3 683
Secondary canal- RS -25
d/s=3.664
0.09
0 04
43        CD Work CDR-19                    30 656                3.664
44 Head Regulator for 31 332 u/s=3.664 0.13
50 year =55 3 100 year = 62.4
Secondary canal- RS -26
d/s=3 52
45        Head Regulator for                  31 836              u/s=3.52
0.3
Secondary canal- RS -27 and Cross Regulator and Road Bridge no4
d/s=3.234
46        CD Work CDR-20                     32.75                  3234
1.45
47        Head Regulator for Secondary canal- RS -28
32.960             u/s=3.234 d/s=3.188
0.048
48        CD Work CDR-21                     33.13                 3.188
2.32
49        Head Regulator for Secondary canal- RS -29
33.818             u/s=3.188 d/s=2 99
0.207
50        CD Work CDR-22
34.151
2 99
9 02
51        CD Work CDR-23
34 532
2.99
2.2
52        Head Regulator for                  34 819              U/s=2 99
Secondary canal- RS -30
d/s=2.33
069
53        Head Regulator for                   35218              u/s=2.33
Secondary canal- RS -31 and Fool Bridge no-7
d/s=2.044
0 296
54        CD Work CDR-24                     35 523                2 044 55        Head Regulator for                   35 922             u/s=2 044
5 24
Secondary can3l- RS -32
d/s=1 802
0 253
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56        Head Regulator for
36.475            u/s=1 802
Secondary canal- RS -33
d/s= 1.649
0.16
57        Road Bridge no5
36.975
1.649
0
NSL(m) 1339
58        Head Regulator for
37.418
u/s= 1.649
Secondary canal- RS -34
d/s=1.51
0.145
59        CD Work CDR-25
37 63
1.51
169
60        CD Work CDR-26
38.16
1.51
10.76
61        Head Regulator for
38 537
Secondary canal-DR-35
u/s=1.51
d/S=1.41
0 104
62        CD Work CDR-27
39.289
1.41
5 39
63        Head Regulator for Secondary canal- RS -36
64        Head Regulator for Secondary canal- RS -37
39.556            U/S=1.41
d/s=1 199
40.207            u/s= 1 199
d/s=0.994
0.22
0.214
65        CD Work CDR-28                   41 207                0 994
50 year =39.1
100 year= 44.1
66        Head Regulator for Secondary canal- RS -38 and Cross Regulator and Foot Bridge no-8
67        Head Regulator for Secondary canal- RS -39
40.088             u/s=0.994 d/s=0 735
0 272
43.109             u/s=0.735 d/s=0 624
68        Head Regulator for                  44 166             u/s=0 624
Secondary canal-RS-40 and End Structure
d/s=0.563
0 116
0063
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ANNEXURE 3-11 B
ARJOO- DEDESSA PROJECT
LIST OF ALL STRUCTURES
B- LEFT BANK PRIMARY CANAL
S.No.         Name of structure            Distance         Discharge of            Discharge of            Flood Discharge of Remarks 
from origin
Primary canal
Secondary canal
Stream or River
in KM
m m3/sec
in m3/sec
in M3/ sec
1          Head Regulator for Secondary canal-LS-1
2          CD Work CDL-1
3          Head Regulator for Secondary canal- LS -2
4          Escape Structure
0.157              u/s=9.015
d/s=8 968
0.60                  8 968
3.126              u/s=8.968
d/s=8.931
0.048
0
0.039
5.5
0
3.25 8.931 0 Escape Discharge
8
5
CD Work CDL-2
3.45
8.931
0
12.05
6
Head Regulator for
3.749
u/s=8.931
0.047
0
Secondary canal- LS -3
d/s=8.886
7
CD Work CDL-3
4.30
8.886
0
50 year =43.0
100 year = 48 5
8
Head Regulator for
4.638
u/s=8 886
0.029
0
Secondary canal- LS -4
d/s=8.863
9
CD Work CDL-4
5.28
8 863
0
4.93
10
Head Regulator for
5411
u/s=8.863
0.042
0
Secondary canal- LS -5
d/s=8.818
11
Head Regulator for
6.084
u/s=8.818
0.075
0
Secondary canal- LS -6
d/s=8.746
and Foot Bridge no-1
12
CD Work CDL-5
6 53
8 746
0
4 54
13
Head Regulator for
6.553
u/s=8.746
d/s=8.701
0.047
0
Secondary canal- LS -7
14
CD Work CDL-6
7.99
8 701
0
1 85
15
CD Work CDL-7
8.14
8 071
0
4 46
16
CD Work CDL-8
8.51
8.071
0
4 26
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17        CD Work CDL-9
18        Head Regulator for Secondary canal- LS -8.
9.23                 8.071                          0 9.89              u/s=8.071                   0.095
May 2007 1.64
19        Head Regulator for
10.486
u/s=8.61
0.162
Secondary canal- LS -9.
d/s=8.455
cross regulator
20        Road Bridge no.1
11.00
8.455
0
0
NSL(m)
1346
21        CD Work CDL-10
12.36
8.455
0
16.56
22        Head Regulator for
13 994
u/s=8455
0.141
Secondary canal- LS -10
d/s=8.32
23        CD Work CDL-11
15.34
8.32
0
6.12
24        Head Regulator for
15.906
u/s=8.32
0047
Secondary canal- LS -11
d/s=8.275
and Foot Bridge no-2
25        Road Bridge no.2
18.5
8.275
0
0
NSL(m)
1345
26        CD Work CDL-12
20.09
8.275
0
3.37
27        Head Regulator for
20.16
u/s=8.275
0.081
Secondary canal- LS -12
d/s=8.198
28        CD Work CDL-13
20.65
8.198
0
6.19
30        Head Regulator for
20.718
u/s=8.198
0.081
Secondary canal- LS -13
d/s=8.12
31        Head Regulator for
21.693
u/s=8.12
0.061
Secondary canal-DL-14
d/s=8.062
32        Head Regulator for
23.115
u/s=8.062
0.417
Secondary canal- LS -15
d/s=7 663
and Cross Regulator
and Foot Bridge no-3
33        Head Regulator for
23.17
u/s=7.663
0 08
Secondary canal- LS -16
d/s=7.587
34        CD Work CDL-14
24.14
7.587
0
15 22
35        CD Work CDL-15
25.54
7 587
0
3.58
36        CD Work CDL-16
25.88
7.587
0
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37        Head Regulator for
26.86
u/s=7.587
0.181
Secondary canal- LS -17
d/ =7.413
s
38        Head Regulator for
27 653
u/s=7.413
d/s=7.334
0.083
Secondary canal- LS -18
39        Head Regulator for
28.869
u/s=7.334
0.044
Secondary canal- LS -19
d/s=7.292
40        CD Work CDL-17
29.090
7.292
0
1.49
41        Head Regulator for
29 526
u/s=7.292
d/s=7.267
0.027
Secondary canal- LS -20
42        Head Regulator for
30.333
u/s=7.267
0.05
Secondary canal- LS -21
d/s=7.219
43        Head Regulator for Secondary canal- LS -22
44        Head Regulator for Secondary canal LS -23 and cross regulator
and Foot Bridge no-4
31096 u/s=7.219
d/s=7.058
32.44              u/s=7.058
d/s=6.378
0.169
0.711
45        Head Regulator for
33.61
u/s=6.378
d/s=6.262
0.121
Secondary canal- LS -24
46        CD Work CDL-19
34.1
6262
0
8.61
47        Head Regulator for
u/s=6.262
Secondary canal- LS -25
35.266
d/s=6 164
0.103
48        Head Regulator for
35.673
u/s=6.164
d/s=5.322
0881
Secondary canal- LS -26
and Cross Regulator
and Foot Bridge no-5
49        CD Work CDL-20
3666
5.322
0
1.46
50        Head Regulator for
u/s=5.322
Secondary canal- LS -27
36 718
d/s=5.286
0.038
51        CD Work CDL-21
37.90
5.286
0
1 85
52        Head Regulator for
38.076
u/s=5.286
Secondary canal- LS -28
d/s=5.265
0.022
53        CD Work CDL-22
38.59
5265
0
1.78
54        CD Work CDL-23
38.73
5265
0
0.75
55        Head Regulator lor
38.912
u/s=5.265
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Secondary canal- LS -29
May 2007
56         CD Work CDL-24
39.48
d/s=5.231
5.231
0.036
0
3 65
57         Head Regulator for
39.737
u/s=5.231
d/s=5.161
0.073
Secondary canal- LS -30
58         CD Work CDL-25
40.033
5.161
0
50year= 147.5
100 year =166 5
59         Head Regulator for
40 137
u/s=5 161
0.038
Secondary canal- LS -31
d/s=5.125
60         CD Work CDL-26
61         Head Regulator for Secondary canal- LS -32
62         Road Bridge no.3
40.59
5.125
40.818             u/s=5.125 d/s=5.013
0
0.118
2.78
41.5 5.013 0 0 NSL(m)
1337
63
CD Work CDL-27
41.84
5.013
0
3.02
64
Secondary canal- LS -33
41 913
u/s= 5.013
0.12
and Cross Regulator
d/s=4 897
and Fool Bridge no-6
65
Head Regulator for
41.312
u/s=4.897
d/s=4.821
0 08
Secondary canal- LS -34
66
CD Work CDL-28
44.81
4.821
0
50 year =40.8
100 year = 46 0
67
Head Regulator for
45 008
u/s=4.82l
0.033
Secondary canal- LS -35
d/s=4.792
68
Head Regulator for
46.236
u/s=4.792
d/s=4.617
0.18
Secondary canal- LS -36
69
Road Bridge no.4
46.5
4.617
0
0
70
Head Regulator for
NSL(m)
1337
47.563
u/s= 4.617
0.207
Secondary canal- LS -37
d/s=4.419
71
Head Regulator for
48 204
u/s=4.419
d/s=4.303
0.12
Secondary canal- LS 38
72
CD Work CDL-29
48.53
4.303
0
6.42
73
CD Work CDL-30
50 01
4.303
0
2 38
Head Regulator for LS -
74
39
51 649
u/s=4.303
1.206
and Cross Regulator
d/s =3.149
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and Foot Bridge no-7
May 2007
75
CD Work CDL-31
52.52
3.148
0
3.17
76
Head Regulator for
54.124
u/s=3.149
0.388
Secondary canal- LS -40
d/s=2.778
77
Road Bridge no.5
53.00
2.778
0
0
NSL(m)
1336
78
CD Work CDL-32
54.13
2.778
0
10.2
79
Head Regulator for
54 483
u/s=2 778
0.037
Secondary canal- LS -41
d/s=2.741
81
CD Work CDL-33
54 580
2.741
0
50 year = 66 8
100 year = 75 5
80         Head Regulator for Secondary canal- LS -42
83         CD Work CDL-34
82         Head Regulator for Secondary canal- LS -43
54.668              u/s=2.741 d/s=2 664
55.04
2.664
55.382              u/s=2.664 d/s=2.478
0.081
0
0.194
5.1
85
CD Work CDL-35
56.76
2.478
0
5.33
84
Head Regulator for
57.644
u/s=2.478
0.519
Secondary canal-LS -44
d/s= 1.982
and Cross Regulator
and Foot Bridge no-8
86
CD Work CDL-36
58.48
1.982
134
88
CD Work CDL-37
59
1.982
4.07
89
Road Bridge no.6
59.5
1.982
0
NSL(m)
90
Head Regulator for
60.18
1334
u/s= 1.982
Secondary canal- LS -45
d/s=0.915
1.067
and End Structure
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4. STRUCTURES UNDER DISTRIBUTION 4.1 General
May 2007
For feasibility study two secondary canal systems are selected for detail planning and design. The selected secondary canals are RS-16 and RS-17 of Right Bank primary canal, taking off from primary canal at km 21.327 and km 21.788 respectively.
In detail planning and design, the planning and design has been done for tertiary canals taking off from secondary canal and quaternary canals taking from tertiary canals, and drainage for command. The details of the area proposed in each secondary canal, its discharge at head, number of tertiary canals taking off are given in Table 4.4.
Table 4.1 Length, Command Area, Discharge and Number of Tertiary canals proposed
for secondary canals of sample area
s.
No
Secondary 
canal
Area proposed
in Ha
Discharge
in m3/sec
Length,
in km
No of tertiary 
canal left /Right
Total
1
RS-16
339.9
0.48
2.1
8/7
15
2
RS-17
414.75
0.58
3.00
11/11
22
3
The tertiary canals are planned to take off approximate at every 300 m distance of secondary canal.
The maximum discharge for tertiary canal 0.042 m /sec is for RT-17-15 of the secondary canal RS -17. The minimum discharge is  of the order 0.007m3/sec  for tertiary  canal RS-17-1 of secondary canal RT -17.
The maximum length of tertiary  canal is  1.321 km for RT-17-15 of secondary  canal RS-17. whereas the minimum length is only 179m (0.179km) for tertiary canal RT-17-1 of secondary canal RS-17.
4.2 Canal structures
For the secondary canal, tertiary canal the topography is such that the ground slope is steeper than designed canal bed slope. Therefore there shall be number of drop (fall) structures along these canals. Besides the falls, following canal structures are planned in distribution system.
1. There are no streams, which are crossing these canals there fore there shall be no CD work structure designed for sample area.
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2.    The  control  structures  for  every  Tertiary  canal  taking  off  from  secondary  canal  shall  be provided
3.    For control of water level in secondary canal, at tail of secondary canal a duckbill weir is proposed.
4  For  flow  measurement  flow  measurement,  structure  for  every  secondary  canal  at  head shall be provided. (Parshall flume)
5.    There   are   no   access   or   existing   roads   are  crossing  the  canal   distribution   system. However   for   movement   of   food   grains   cattle   or   human   beings,   a   road   Bridges   or footbridges  shall  be  combined  with  fall  structures.  No  separate  bridge  structures  are proposed in the sample area
6.    The  quaternary  canals  are  proposed  to  take  off  from  tertiary  canal  generally  at  50m intervals For every quaternary canal, turnout structure is proposed.
For  feasibility  report  following  structures  are  proposed  and  type  design  and  drawing  of  each type of structure are prepared and attached in design and drawing volume.
1.
Control structure
1.1
Adjustable proportional module (A.P.M) for tertiary canal RT-16-9 taking off from RS-
16 secondary canal at 1.20km.
Total structures required in sample area are 37 numbers.
1.2
Division Box or turn out structure for quaternary canal taking off from tertiary canal
RT-16-9 of secondary canal RS-16
Total number required in sample area are as per table 4.2
Table 4.2 Number of Tertiary Canal, their length and number of division box required
—
s.    Secondary        Total no of tertiary No         Canal                       canal
Left    Right     Total
Total length of Tertiary cana  in km
Left Right Total
Total no of division
box required
1
RS-16 8 7
RS-17 11 11
15
7.729
3.841
r2
11.570
22
7.323
225
7.747
Total                         19       18
37
15.070
281
—
26.64         506
Therefore total 506 division box structures are required in sample area
1.3Duck bill weir:-At the tail of every secondary canal, d uck bill weir is proposed to control the water level. For sample area there shall be two structure of duckbill weir.
For whole project, the number of secondary canals proposed are:
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For RBPC
=40
For L.B.M.C
z_45
Total
85
Therefore total number of duckbill weir in project shall be 85
1.4     For measurement of flow in canal it is proposed to provide Par shall flume at the
head of every secondary canal.
So far sample area number of structures shall be           =             2
For project area number of structures shall be                =          85
4.3 Drop or fall structures
For secondary canals in sample area, drop structure as per L-Section prepared for RS-16 and RS-17 are 15 and 17 respectively. Total 32 numbers of falls shall be there in secondary canal of sample area.
4.4 Fall on tertiary canals
Discharge of tertiary canal is very small. From tertiary canal quaternary canals are proposed to off take generally at every 50m interval. For efficient, supply of water for irrigation, the FSL in tertiary canal is required to be kept above ground level, so those quaternary canals are capable to supply water to field at ground level The drop in ground level in 50 m or even 100m interval is very less say 0.2 to 0.3 m. Therefore fall drops in tertiary canal shall also be small. As such a rapid fall or cascade type fall is designed and drawing prepared for Gumera irrigation project, which shall be used for Arjo Project.
In the sample area 37 tertiary canals are planned and provided. Out of 37 tertiary canals, 'L'- Section, the length and number of falls structures required are given in table 4.3 below:
Table 4.3
S. No Tertial canal
Length  of
canal in km
tertiary  Number  off proposed
alls
1
RT-17-16
130
16
2
RT-17-8
0.55
8
3
RT-16-3
0.85
7
4
RT-16-1
0.65
7
Total
3.35
38
56
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For 3.35 km there are 38 No. of falls for sample area length of tertiary canal as per table no. 1
11.57 and 15.07 km for Rs-16 and RS-17. So total number of falls on tertiary canals in sample
area shall be for RS -16
= 131 RS-17 =
15.07
3.35
x 38 = 171
Total 3Q2
It  is  proposed  in  tertiary  canal  where  fall  is  provided  Division  Boxes  shall  not  be  provided Therefore net division box required shall be
RS-16 - 225 - 131 = 94
RS-17 -281 - 171 = 110
204
So net 204 Division Box shall be provided.
57
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Hydraulic Design of Canal Structure
List of reference books, and   codes
1      Design of small dams by USBR
2      Standard Books
3      Indian Standard Codes
i)      Is code   No 12331 - 1988 - General requirements for canal outlet
May 2007
ii)      Is - code No. 5186-1994 - Design of chute and side channel spillways - criteria
iii)      Is code     No. 11527-1985 - criteria for structural design of Energy Dissipators
iv)      Is code     No. 4997 - 1968 - Criteria for design of hydraulic jump with stilling basin
with horizontal and sloping appron
v)        Is code No 7114 - 1995 - criteria for Hydraulic design of cross regulators for canals
vi)       Is code No. 6531 - 1994 - canal Head regulators criteria for design
vii)        Is  code  No.  6936  -  1992  -  Guide  for  location  selection  and  hydraulic  design  of canal escapes.
viii)        Is  code  No  7784  part-l  -  1993  -  Design  of  cross  drainage  works  code  of  practice, (General features)
ix)         Is  code  no.  7784  part  2  sect.  -  1995  -  Design  of  cross  drainage  works  code  of practise aqueducts
x)       Is code no. 7784 Part. 2 sect. 2 - 2000 - code of practise for design of cross 
drainage work super passage
xi)        Is  code  No.  7784  Part.  2,  sect.  3.  1996  -  code  of  practise  for  design  of  cross drainage works canal syphon.
xii)        Is  code  No.  7784  Part  2  -  sec.  4  -  1999  -  Design  of  cross  drainage  works  code  of practice
xiii)      Is code No. 7784 part 2 sec. 5 - 200 code of precise for design of cross drainage works syphon aqueducts
xv) Indian Road congress code - 78 - 2000
xiv)     Is code No 1233.-1998 - General requirement for canal outlets
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HYDRAULIC DESIGN OF CANAL
STRUCTURESArjo-Dedessa Irrigation Project
Hydraulic Design of Canal Structure
TABLE OF CONTENT
1. CONTROL STRUCTURES
1.1      design of Regulator for RS-16
1.2      DESIGN OF HEAD REGULATOR FOR SECONDARY CANAL RS-171
1.3      DESIGN OF ESCAPE REGULATOR ON RIGHT - PRIMARY CANAL
May 2007
2. CROSS DRAINAGE WORKS........................................................................................................ 4
2.1      Design of Aqueduct on Right Primary Canal4
2.2      DESIGN OF SYPHON AQUEDUCT FOR JEJEBA RIVER CROSSING WITH RIGHT PRIMARY CANAL AT 22.0 KM63
2.3   Design of Canal Syphon For Right Bank Canal At Km 2.00
.......... 77
2 4 Design of Aqueduct (With Normal Canal Section) at Km 25.54 of Left Primary Canal
3.      ROAD BRIDGES/FOOT BRIGE97
3.1      Design of Road Bridge at Km -15 Of Right Primary Canal97
3.2      Design of Road Bridge at 41.50 Km of Left Primary Canal102
3.3      Design of Foot Bridge for Cattle Crossing at Km 19.00 of108
4.         STRUCTURES UNDER DISTRIBUTION SYSTEM
4.1      Design of APM-Out Let for Tertiary Canal Rt-1 6-9 Of Dr - 16 of Right Primary Canal .114
4.2      Design of Duck Bill Weir for Secondary Canal RS-17 of Right Primary Canal ] ] 8
4.3      Details for Turn out Structure (Division Box) For Quaternary Canal (Field Channel) .125
89
114
4.4      Design of Vertical Fall 1.5m and Road Bridge at KM 1.05 of Secondary Canal RS-16         .127
4.5       1.0M WELL TYPE FALL ON TERTIARY CANAL RT-16-9
4.6      DESIGN OF PARSHALL FLUME FOR SECONDARY CANAL RS-17143
LIST OF TABLE
Table 3.1 Total Pressure along length of Floor
Table 3.2 Balance Pressure along length of Floor
LIST OF ANNEXURE
137
ANNEXURE - 1.
ANNEXURE - 2
ANNEXURE-3
ANNEXURE- 4
ANNEXURE - 5.
ANNEXURE-6
ANNEXURE- 7
ANNEXURE- 8
ANNEXURE - 9. ANNEXURE -10
...    . 45 61 122
.    I23 124
.148 149
150
151
•   152 I
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1. CONTROL STRUCTURES
1.1 Design of Regulator for RS-16
Taking Off At Km 21.327 of Right Primary Canal
May 2007
Arjo-Dedessa Irrigation Project is planned to provide irrigation facility to 13665 ha land. The project consists of constructing an earthen and rock fill dam across Dedessa River at latitude
80-3T12" N and longitude 36’-40'-04” E.
The maximum light of dam is proposed to be 40.6m from river bed elevation. The surplusing arrangement i.e. spill way is proposed in saddle No. 1 on right flank. For purpose of irrigation two canal systems are proposed to takeoff the left bank primary canal, is proposed to takeoff from abutment of dam, at a distance of about 10m from the end of dam. Another canal right bank primary canal is proposed to takeoff from saddle No. 2 on right bank. Both the primary canals are canals. The FSL of both the canals at off take point is proposed to be kept at EL 1348.00.
The lengths of left and right bank canal and number or secondary canals taking off from them are given below:-
Primary canals
Length in km
No. of secondary canal
Right bank canal
Left bank canal
42.80
60.18
40
45
From the right bank  primary  canal, a secondary  canal RS-16 takeoff from km 21.327. For providing regulated release of water in secondary canal RS-16, a head regulator is proposed to be provided. Since at km 21.788 km a cross regulator, along with head regulator for RS-17 is proposed, cross regulator is not proposed at km 21.327.
The details of canals are as below
A Right Bank Primary - Canal
1)  Full Supply discharge =      ' $ =  5.981 D/S      5.523
6 
= — ni
D/S     5.5
2)  Bed width                    =            ■
3)  Full supply depth        = -      - -
D/S      1.25
1.26 
: ------ ni
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4)  Velocity
5)  Canal bed slope
Side slopes
6)
7) Full supply elevation =
8)  Canal bed elevation Ground elevation
9)
U/S 0.604           , ------ =-------- m / sec D/S 0.596
= 0.0002
D/S
U/S
D/S
U/S
D/S
U/S
D/S
= 1.5:1(H:K)
1343.23             calculation 1343.23
1341.97
,,
---------- as per calculation
1341.98
= 1343.50
B Details of RS-16 secondary canal
1) Full supply discharge    = 0.48 m3/sec
2)  Bed width
3) Full supply depth
4)  Velocity
5)  Bed slope
6)  Side slope
= 1.00 m
= 0.62 m
= 0.398 m/sec = 0.0003 = 1.5:1 (H:V)
7)  Full supply elevation     = 1343.08 as per calculation
8)  Canal bed elevation
= 1342.46 as per calculation
Fixation of FSL of primary and secondary canal
A) Primary canal
The  FSL  of  right  bank  primary  canal  at  off  take  point  from  dam  is  proposed  to  be  kept  at 1348.00 m.
From head to 21.327 km the slope proposed is 0.0002
Therefore FSL at regulator i.e. at 21.327 km
= FSL at off take - 0.00020 x 20350
= 1348.00-4.07 = 1343.93
From 0 km of canal to 21.327 km anticipated head loss in structures is considered as 0 70 m
Therefore FSL at regulator point i.e. 21.327km
= 1343.93- 0.70 = 1343.23
2
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Hydraulic Design of Canal Structure
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Since cross regulator is not proposed on primary canal the upstream and downstream FSL of primary canal shall remain same
U/s Bed elevation = FSL - u/s depth of water
= 1343.23- 1.26 = 1341.97
D/s Bed elevation = FSL - D/s depth of water
= 1343.28- 1.25 = 1341.98
It is proposed to provide 0.15 m elevation difference between FSL of primary and secondary canal.
FSL of secondary canal
= FSL of primary canal - 0.15
= 1343.23-0.15 = 1343.08
Canal bed elevation of secondary canal
= FSL - Full supply depth
= 1343.08-0.62 = 1342.46m
Design for waterway of Regulator for secondary canal
The details of secondary canal are as below
1)  Bed width = 1.0 m
2)  Full supply depth = 0.62
3)  Area = 1.21 m2
4)  Wetted perimeter = 3.25 m
5)  Hydraulic mean depth = 0.37
6)  Slope of canal = 0.0003
7)  Velocity = 0.398 m/sec
It is proposed to keep crest elevation of regulator 0.15 m. above bed elevation of secondary canal.
Crest elevation = canal bed elevation + 0.15
= 1342.46 + 0.15 = 1342.61
The waterway for regulator is determined from the formulae
Q = C Be H,
s
3'2
Where, Q = discharge of secondary canal
Cs = modified coefficient of discharge for submerged weir
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Be = Effective waterway
He = u/s depth of water above crest elevation
C = shall depend on degree or submergence which is given by = ——
s
where, H  = Difference between u/s and D/s FSL of canal = 0.15 m
May 2007
3
d
He = U/S FSL - crest elevation
= 1343.23- 1342.61 = 0.62
Degree of submergence =           = 0.242
From   the   graph   between   degree   of   submergence   and   ratio   of   modified   coefficients   of discharge, coefficient (Cs/c), for value of degree of submergence of 0.242 is 0.90
— =0.90 C = value of c = 1.82
C
Cs = 0.92 c = 0.90 x 1.82 = 1.64
In the formulae
Q = Cs Be He372
Substituting values Q = 0.48 m /sec
Cs = 1.64 and He = 0.62
0.48= 1.64 x Be (0.62)3'2
= 1.64 x 49 x Be
= 0.80 Be
Be =          = 0.60m
0.80
Height between FSL of secondary canal and crest elevation
1343.08- 1342.61 =0.47
Provide linear waterway of canal = 0.80 m
Provide vertical lift gate of size 0.90 x 0.60 m
The width of crest shall be kept as 1.00 m with upstream slope as 1:1 downstream slope as 2:1
• Level and length of downstream impervious floor for secondary canal
Q = 0 48 m3/sec and Length L = 0.8 m
Q 0.48
Discharge intensity = “ =              = 0.6 m /sec
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. Length of Cistern = 5 x (D  - Di)
2
= 5 x (0.66 - 0.25) = 5 x 0.41
= 2.05 m
Provide 3 m length of cistern
Depth of u/s and D/s cut off is proposed to be kept as 1.5m below u/s bed elevation and bed elevation of secondary canal.
Elevation of u/s cut off for primary canal
= 1341.97 - 1.5 = 1340.47 m say 1340.50 m.
D/s cut off elevation for secondary canal
1342.46- 1 5 = 1340.96 say 1341.00 m
• Floor length and floor thickness
U/s floor - u/s impervious floor of cement concrete shall be provided in primary canal for entire bed width of 6.00 m and for 3 m length on either side of centerline of Regulator
Cutoff on all the three side of impervious  floor shall be provided Since u/s  floor is  not subjected to any uplift pressure provide floor thickness of 0.45 m consisting of top 0 15 m thick cc M-20 laid over 0.30 m thick cc M-15.
For negotiating difference between upstream canal bed and crest elevation provide slope of 1 1 (H:V)
. . Length for slope
-    Crest elevation - u/s bed elevation)
-    (1342.61 - 1341.97) = 0.64 = 0.64
Provide 0.70 length
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Head loss HL = U/s FSL - D/s FSL
= 0.15
From blench curve for above Ef2 is 0.52
. Floor elevation = D/s FSL - Ef2
= 1343.08-0.52 = 1342.56 Since canal bed elevation is 1342.46 cm Provide floor elevation at 1342.40 m
Ef, = Ef2 + HL
D.52 + 0.15 = 0.67 From graph for Efi = 0.67 Di = 0.25 and D  = 0.66
May 2007Arjo Dedessa Irrigation Project
Hydraulic Design of Canal Structure
May 2007
For  negotiating  difference  between  downstream  bed  elevation  and  crest  elevation,  it  is proposed to provide 2:1 slope
So length for slope = 2 (crest elevation - Bed elevation of secondary canal)
= 2 (1342.61 - 1342.46)
= 2 x 0.15 = 0.30 m
• Thickness of downstream floor.
Downstream floor is subjected to maximum uplift pressure when the primary canal is at FSL and secondary canal is dry
There shall be two heads acting on cistern floor
1. Static head
2 Seepage head
1.  Static head - It is a constant head acting on entire floor.
Assuming the sub soil water shall be at downstream bed elevation.
And assuming thickness of floor 0.45m
/.static head on cistern floor shall be
= D/s canal bed elevation - Bottom elevation of floor
Bottom elevation of floor = cistern floor elevation - 0.45
= 1342.40-0.45= 1341.95
= 1342.46- 1341.95 = 0.51m = 0.51 Vsq.m
2.   Pressure due to seepage head
Pressure due to seepage head.
Pressure due to seepage shall be variable with minimum pressure at the end of cistern floor and increasing on the upstream end of floor with maximum pressure being at the upstream end just below the gate of regulator.
Seepage head = u/s FSL - Downstream bed elevation of canal
= 1343.32 - 142.55 = 0.77m = 0.77 t/m2
To  find  out  pressure  on  different  points  of  floor  first  total  path  length  shall  be  worked  out (Sketch for path length is enclosed).
Total path length = 1.5+1 5+8.6+1+0.3+3+1.5+1.5
= 18.90m
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The seepage pressure at any point is found out by the equation
May 2007
Seepage head = (1-
seepage Path length upto the po int
Total seepage path length
Total seepage path length upto end of floor i.e. before cut off wall = 18.9-(1.5+1.5) = 15.9 m
Uplift pressure due to seepage head
= 0.77(1-15.9/18.9)
= 0.77 (1-0.84)
= 0.77 x 0.16 = 0.12m = 0.12 t/m2 Total uplift = static pressure + seepage pressure
= 0.51 + 0.12 = 0.63 t/m2
Thickness required = ^^ = 0.28m
2.25
Thickness considered 0.45m is sufficient at the end of floor Thickness of floor just below the gate
.. Length = 1.5 + 1.5 + 8.6 + 0.5 = 12.1m
Seepage pressure = 0.77
12 1
= 0.77(1-0.64)
= 0.77 x 0.36
= 0.27m y 0.27 t/m2
Total uplift pressure = static pressure + seepage pressure
= 0.51 + 0.27 = 0.78
0 78
Thickness required = —— = 0.34m
2.25
Actually thickness provided is 0.45
So provide 0.45m thickness of cistern floor for entire length
• Upstream and downstream protection
Previous protection of cc. block or stone pitching over gravel shall be provided beyond impervious cc. floor to upstream floor on both ends. It is proposed to provide 0.45 thick pervious protection consisting of 0.30 cc. block or stone pitching laid over 0.15 thick gravel. The length of upstream protection shall be
depth of u! s cut off  1.5  ? $
thickness of floor 0.6
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May 2007
Provide pervious protection for 3m length.
A toe wall at the end of pervious floor shall be provided with top width of 0.5m and 0.8m at foundation elevation. Foundation elevation shall be kept 1.0 m below upstream canal bed elevation.
The length of downstream protection for head regulator
= 2 x depth of cut off
= 2x 1.5 = 3.0m
Provide 3.00 meter length beyond cistern floor. A toe wall at the end of protection shall be provided with top width 0.5m and 1 00m at foundation elevation. The depth of Toe wall shall be kept 1.5m below the downstream canal bed elevation.
• Fixation of elevation of operating plateform and road Bridge.
It is proposed to provide one lift gate of 0.9m x 0.6m
Therefore the bottom elevation of operating plate form for gate shall be
= Crest elevation + 2 x height or gate + 1.0m
= 1842.61 + 2x0.6 + 1.00
= 1842.61 + 1.20 + 1.00 = 1844.81m keep at 1844.80
Considering thickness of RCC slab of platform as 0.20m
Top of operating plate form = 1844.8 + 0.20 = 1845.00m
For Road Bridge
For Right bank canal a service road of 5.0m width is proposed on left bank. The secondary canal also takes  off on left side of primary  canal. Therefore a road slab shall be provided across D/S abutments of regulator
The Bottom elevation of Road slab shall be kept 0.5m above FSL of secondary canal
Bottom elevation of slab should be above
= 1343.08 + 0.5= 1343.58
Considering 0.30m as thickness of road slab.
Elevation of Road slab = 1343.67 + 0.30 = 1343.97m
The ground elevation at regulator = 1343 50
So service Road elevation shall be 0.60m above Ground elevation
= 1343.50 + 0.60 = 1344.10
So provide Road slab elevation at 1344.10m
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Bottom elevation = 1344.10 - 0.30 - 1343.80
So free board above FSL of secondary canal
= 1343.80- 1343.08 = 0.72 m
Which, is more than 0.5 m.
• Top and Bottom width of Abutments wing and return walls.
May 2007
For abutment:- Abutments shall be provided below operating platform, Road slab; and any load bearing slabs which shall be supported on abutments.
The top width of abutment shall be 1.00m. The bottom width shall not be less than 0.50 times the height measured from top elevation of abutment to foundation elevation. The face on water side shall be vertical and width shall be increased on other side of abutment.
• Wing, Side and return walls
The top width of all walls that are not supporting any slabs for load shall be kept as 0.50m. Bottom width shall be kept not less  than 0.50 times  the height of wall measured from top elevation of wall to the foundation elevation. The face of wall shall be dept vertical on waterside and width is increased on other side of wall.
The  foundation  of  Abutment  and  wing  wall  shall  be  kept  1.5  m  below  primary  canal  bed elevation
Foundation elevation = 1341.97 - 1.5 = 1340.47 keep at 1340.40 m.
The drawing for this structure is available at drawing no. AD-F-Canal-D-01 to 03.
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F$L
1342 4GQSlm
OS CBL of secondaiy
'canal I 342 46
1340 50Arjo-Dedessa Irrigation Project
Hydraulic Design of Canal Structure
May 2007
1.2 DESIGN OF HEAD REGULATOR FOR SECONDARY CANAL RS-17
AND CROSS REGULATOR ON RIGHT BANK PRIMARY CANAL AT KM
21.788
1. Arjo-Dedessa project consists of providing irrigation facility to a command area of 13,665 ha (approximately).
The project proposal consists of constructing a Earthen and rock fill dam across Dedessa river at location Latitude 8°-3T-12"N and longitude 36°-40'-04" E the height of dam is proposed to be
40.6 m from the river bed. Different elevation proposed for dam are:
River bed elevation 1320.0m
TBL 1360.0m
FRL 1356.00m
The spillway is proposed to be located in saddle no1 in right flank. The minimum draw down elevation for Irrigation purpose is proposed as 1350.0m.
Two canal systems are proposed to take off from Dam, one from left flank and other from right flank. The right bank canal is proposed to take off from saddle No 2 in right flank. Where as left bank canal is proposed to take off from left abutment of main dam at a distance of 10.0 m from the end point of left bank of Dam.
The full supply elevation for both the canal systems at off take point is proposed to be kept at 1348.00 m at off take point of canal.
The left and right bank primary canals are contour canals for their entire length. The total
length of left bank primary canal is 60.18km and that of right bank primary canal is 42.80 km
For irrigation to command area secondary canals are proposed to take off from Primary canals From left bank primary canal, 45 no of secondary canals are proposed to take off, whereas 
from right bank primary canal 40 secondary canals are proposed to take off
From the Right Bank primary canal at km 21.788 secondary canal RS-17 is proposed to take off. For release of regulated water from primary  canal to secondary  canal Head regulator is required to be constructed. To maintain required supply  level in secondary  canal even when there is  low supply  in primary  canal full supply  elevation in primary  canal is  required to be maintained. For maintaining full supply  level in primary  canal, it is  proposed to provide cross regulator on primary canal.
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The details or primary and secondary canals are as below -
Right bank primary canal km 21.788.
U/S          5.523 m / sec
May 2007
1   Design discharge
2.  Full supply elevation 3   Bed width
4.  Full supply depth 5. Canal bed elevation 6.  Bed slope
D/S 4.969 m’ / sec
U.S         1343.11 m DS            1343.01 u/s           5.5 m
= -------- Di S          5.0 m
u/s
D/S
1.25
= ----- Hl
1.24
u/s 1341.86
DIS 1341.77
U/S 0.0002
D/S
= -----------m
0.00022
7.  Side slopes or canal (H:V)            = 1.5:1
8. Velocity
9. Ground elevation
U/S 0.596 m / sec
D/S 0.584 m/ sec
= 1343.70
Details of secondary canal RS-17
1. Design discharge           = 0.58 m3/sec 2. Full supply elevation      = 1343.01m 3. Bed width                     = 1.0m
4.  Full supply depth        = 0 68m
5.  Bed elevation
= 1342.33 m
6. Bed slope
= 1 in 0.0003
7. Side slopes of canal
H: V (1.5:1)
8 Velocity
= 0 418/sec
■ Calculation of FSL at Regulator site.
The FSL of Right bank primary canal at off take point from Dam is kept as 1348 00m
From head to 21.788 km the slope proposed is 0 0002. Therefore FSL at regulator i.e 21 788 km
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= FSL at off take point - 0.0002 x 20950
= 1348 00-4 .19 = 1343 81
From 0 km of canal to 21.788 km anticipated head loss in structures is considered as 0 70 m. Therefore FSL at Regulator point
= 1343 81 -0.70 = 1343.11
BED elevation u/s = full supply elevation - Full supply depth
= 1343.11 - 1.25 = 1341.86
It is proposed to provide difference of 0.1m between u/s and D/s FSL of Primary canal for cross regulator.
Therefore D/S FSL of canal
= U/s FSL-0.1 = 1343.11 -0.1 = 1343.01
D/S bed elevation = DS FSL - Full supply depth
= 1343.01 - 1.24 = 1341.77
• Design of Head regulator for secondary canal RS-17 fixation of crest level and water way.
It is proposed to keep width of opening equal to bed width of secondary canal, i.e. 1 0m
The details of secondary canal are
Area = A = 1.39 m2
Wetted perimeter = p = 3.47 m
Hydraulic depth R = 0.4
S = 0.0003
Velocity in canal 0.418 m/sec
It is proposed to provide difference between u/s FSL of canal and FSL of secondary canal as 0.10m.
Therefore FSL of secondary canal = FSL of primary canal - 0.10
= 1343.11 - 0.1 = 1343.01
Bed level of secondary canal = FSL - Full supply depth of secondary canal
= 1343.01 - 0 68 = 1342.33
It is proposed to keep crest elevation 0.15 meter above downstream bed elevation Crest elevation = 1342.33 + 0 15 = 1342 48m
The waterway is determined by formula (for secondary canal) Q=C.BeHei‘ Q = Discharge of secondary canal
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May 2007
C= Coefficient of discharge for submerged weir Be = effective bed width
He = Depth of u/s water above crest.
Q = 0.58 m3/s
yy
C= shall depend on degree of submergence, which is given by = —~
Where, Hd = difference between u/s and D/S FSL.
= 1343.11 - 1343.01 = 0.10
He = u/s FSL - crest elevation
= 1343.11 - 1342.48 = 0.63 m
Degree of submergence = — =            = 0.158 day 0.16
H  0.63
e
For value of degree of submergence 0.16 from graph between ratio of modified coefficient of discharge is = 0.82 c =0.82
For broad crested weir cd is taken as 1.82
. C  = 0.82x 1 82 = 1.47
s
From formula
Q = C  x Be x (He)
s
3/2
Where, Q = 0.58m3, C =1.47, He = 0.63
s
0.58 = 1.47 (O.esy^xBe
= 1.47x0.50xBe
= 0.74 Be
Be = — = 0.78 m
0.74
So provide 0.90 width and height = 0.60 m of opening
Provide vehicle sluice gate of size 1.00m x 0.75 m (Height) for Head regulator.
■ Level and length of down stream floor
Q = 0.58 m3/sec L = 1.00 m
Discharge intensity q = —             = 0.58     / sec
L1
Head loss = u/s FSL - D/s FSL
H2 = 1343.20 - 1343.10 = 0.10 m
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From blench curve
EF2 for above value's of q = 0.58 and HL = 0.10m is 0.5 Floor elevation = D/s FSL - Ef2
= 1343.01 - 0.50 = 1342.51 m Since canal bed elevation is 1342.33
Keep down stream floor level as 1342.30 m
Efi = Ef2 + H2
= 0.5 + 0.1 = 0.6
From graph for Ef1=0.6
D^O.25 and D  = 0.60
2
Length of cistern = 5(D -Di)
2
= 5(0.6-0.25) = 1.75
May 2007
Provide 3m length of cistern
U/S cut off depth of 1.5m is proposed to be provided from u/s bed elevation
So U/S cut off elevation = 1341.86 - 1.50 = 1340.36
D/s cut off depth in proposed 1.00m below D/s cistern elevation = 1342.33-1.00 = 1341 33. so keep at 1341.30
Design of Cross Regulator water way
■ Fixation of crest - elevation and waterway
The crest elevation of the cross regulator shall be kept at upstream bed elevation of primary canal i.e. at elevation 1341 86 m
The water way for cross regulator shall be worked out from formula Q = CBe (He)372
Where,
Q = Discharge downstream
C = Coefficient of discharge a constant worked out from degree yy
of submergence = ~
Be = Effective length
He = Head over crest
Hd = Difference between u/s and D/s FSL = 0.10m Here Hd= 0.10m
He = u/s FSL - crest elevation = 1343.11 - 1341.86 = 1.25
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Degree of submergence =
— = 0.0806 say 0.08 1.25
3
Cs = 1.125
He = 1.25
4.969 = 1.183 x Be (1.25J372
= 1.65 x Be
«       4.969
„
Be =-------- = 3.01 say 3m
1 65
So provide two bays of 1.80 each with peir of 1.00 m width
Total length Bt = Be +2 (Nx kp+ ka) x He
Where, N = No of peirs
Kp = for peirs with a rounded nose i.e. ease and cut water = 0.01
Ka = for square abutment with head walls at 90° to direction of
flow = 0.20
Bt = 3.00 + 2 (1x0.01+0.2) x1.25
= 3.00 + 2x0.21 x1.25
= 3.00 x0.525 = 3.525
So assumed width of 3.6 m with two bays of 1.8 m each is sufficient to pass discharge Total width = 2x18 + peir width = 3.6 + 1 = 4.60 m
Provide vertical lift gates two No of size 2.00 m x 1.5 m each
• Level and length of downstream floor
3
Q = 4 969 m /sec and length is 3.6 m
4 969
.-. Discharge per m length q = —------ = 1 38 m /sec
3.6
Water Works Design & Supervision Enterprise
From the curve between degree of submergence and ratio of modified coefficient to free fall coefficient for value 0.081 is 0.65.
— = 0.65 , Cs = c x cd
Cd
Value of cd for broad crested weir = 1.82 /.Cs = 0.65 x 1.82 = 1.183
The water way from formulae
Q = Cs Be (He)3/2 where, Q = 4.969m /sec
3
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Hydraulic Design of Canal Structure
Head loss = U/s FSL - D/s FSL
HL= 1343.00- 1342.90 = 0.10
From the blench curve for discharge per meter length of 1.38m3/sec and
May 2007
HL = 0.10 the depth Ef2 below Downstream water level = 0.80 m. Therefore, cistern elevation
= D/s FSL - 0 80
= 1343.01 -0.80 = 1342.21
Down stream canal bed elevation is 1341.77, Therefore cistern elevation shall be kept at 1341.75 m.
Ef, = Ef2 + HL = 0.80 + 0.10 = 0.90 for value of Ef, = 0.90 D, = 0.40 & D  = 0.9
2
Cistern length = 5(02-0,) = 5(0.90 - 0.4)
= 5 x 0.5 = 2.5 m
Provide length of 3 m impervious floor of cement concrete
■ Floor length and floor thickness
It is proposed to provide upstream floor for 8m length from consideration of secondary canal and downstream floor for 3.00 m length. For drop in u/s and D/s bed elevation provide slope of 5:1, Therefore length of drop portion shall be
= 5 (u/s bed elevation-cistern elevation)
= 5(1341.86 - 1341.75)
= 5x0.11 = 0.55 say 0.50
Total floor length = u/s floor length + length for drop + D/s floor length
= 8 ♦ 0.50 ♦ 3 = 11.50 m
Provide u/s impervious floor thickness of 0.45 m. out of which top 0 15m thick floor shall be of cc M-20 laid over 0.30 m of cc M-15.
Total creep length (As per enclosed sketch).
= 1.5 + 1.5 ♦ 8 + 0.50 + 3+1.5 + 1.51
= 17.51 m
So Total creep length of flow of path is = 17.51 m
Downs  stream  floor  shall  be  subjected  to  maximum  uplift  pressure  when  in  upstream  canal water is at FSL and downstream is dry.
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.. Maximum seepage head = u/s FSL - Downstream bed elevation of canal = 1343.11- 1341.77 = 1.34 m
Assume thickness of cistern floor as 0.60 m
. Bottom elevation of cistern floor = 1341.75 - 0.60 = 1341.15 There shall be two heads acting on cistern floor
1. Static head
2.  Seepage head
May 2007
1. Static head:- Assuming the sub soil water shall be at the elevation of downstream canal bed elevation.
Therefore static head on cistern floor shall be
= D/s canal bed elevation - Bottom elevation of floor
= 1341.77 -1341.15 = 0.62m = 0.62 tons/m2
The seepage pressure shall be variable with minimum pressure at the end of D/s floor a nd increasing on the upstream end of cistern floor with maximum pressure being at the upstream and just below the gates of cross regulator.
Maximum seepage head = 1.34m
The uplift pressure at D/s end of floor shall be
Total creep length
Seepage length upto down stream end of floor = 1.5 + 1.5 + 8 + 0.50 + 3 = 14.50
e
Seepage pressure = 1.34 (1---------
4             /4 14-50
17.51
= 1.34 (1-0.83) = 1.34x0.17
= 0.23 = 0.23 t/sq.m
Total uplift pressure = Static pressure + seepage pressure = 0.62 + 0.23 = 0.85
Thickness of floor required = —ota^ up W pressure
unit weight or collegete
So thickness of 0.60m considered is sufficient at end of floor seepage pressure at u/s end of floor
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Seepage path length upto the point
= 1.5 + 1.5 + 8 = 11.00
So seepage uplift pressure
= 1.34 (1--*M) = 1.34 (1-0.63) 17.51
May 2007
= 1.34 x 0.37 = 0 50 m = 0.50 t/m2
Total uplift pressure = static pressure + seepage pressure
= 0.62 + 0.50 = 1.12 t/m2
.. Thickness required at u/s end of floor
= 1^1 =0.50
2.25
So assumed thickness of 0.60 m for entire length of 3.50 m for downstream floor is sufficient. Provide top 0.15 cc. of M-20 laid over 0.45 in thick cc. M-15
■   Vertical cut offs.
The minimum depth of upstream and down stream cut off shall be kept as 1.5 m below canal bed elevation at the end of impervious cc. floor. Foundation elevation of upstream cutoff
= Upstream canal bed elevation - 1.5
= 1341.86 - 1.5 = 1340.36 keep at 1340.30
Foundation elevation of downstream cutoff
= Downstream canal bed elevation - 1.5
= 1341.77- 1.5 = 1340.27 keep at 1340.20
■   Upstream and Downstream protection
The upstream and downstream pervious  protection shall be provided beyond impervious  cc floor. The pervious  protection for upstream shall consist of 0 .45m thick  cc  blocks  or stone pitching laid over 0.15m thick  gravel with total thickness  of 0.60m. Downstream pervious protection shall consists of 0.60m thick cc. block or stone pitching laid over 0.30m thick gravel layer, thus total depth is 0.90 m.
This  pervious  protection  shall  be  provided  beyond  upstream  and  downstream  impervious  cc floor.
Length of upstream pervious protection
Depth of upstream cut off
thickness or imperious floor
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— = 2.5 m, provide pervious protection for 3m. Length beyond upstream
0.6
cc. floor.
A toe wall at the end of pervious floor shall be provided with top width as 0.5 m and width at foundation 0.8 m and the foundation elevation shall be 1.00m below upstream canal bed elevation.
Downs  stream pervious  protection for protection of downstream scour and cistern floor. The
length of downstream protection shall be provided for twice the depth of downstream cut off = 2
x 1.5 = 3.02
Provide 3 m length of 0.9 m depth out of which depth of cc block or stone pitching shall be 0.6
m laid over 0.30 m gravel.
A toe wall at the end of protection shall be provided with top width = 0.5 m, bottom width at foundation elevation 0.8 m and foundation of toe wall shall be taken 1.00 m below the downstream canal bed elevation.
Thickness of Downstream floor for Head Regulator
The u/s impervious floor length is same as that of cross regulator with cut off 1.5 m depth.
Canal bed elevation of primary  canal is  1341 86 and that of crest of secondary  canal is 1342.48, a slope of 1:1 is  proposed to negotiate difference in elevation. Similarly  for negotiating difference between crest elevation and D/s cistern elevation of regulator a slope of 5:1 is considered.
So sloping length
U/s = 1 x (crest elevation - u/s bed elevation)
= 1 x (1342.48- 1341.86)
= 0.62
D/s = 5 x (crest elevation - D/s cistern elevation
= 5 (1342.48 - 1342.30) = 5 x 0.18 = 0.90m
The u/s floor is not subjected to any uplift pressure in any condition. Therefore the u/s Floor is proposed to be of 0.45 m thickness with Top 0.15 m with cc. M-20 laid over 0.30 with cc M-15
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Hydraulic Design of Canal Structure
May 2007
Downstream floor is subjected to uplift pressure, and maximum uplift pressure is exerted when water level in u/s is at FSL and downstream is dry
In this condition two types of pressure are exerted
i) Static 
ii) seepage head
Static pressure is constant head. Seepage pressure is variable, minimum at down stream end of floor and maximum at upstream end. This pressure is applicable on bottom of floor
Assuming thickness of down stream floor as 0.45 m
Bottom elevation of floor = cistern elevation - 0 45 m
= 1342.30-0.45 = 1341.85
Seepage head = upstream FSL - Downstream bed elevation of canal
= 1343.11 - 1342.33 = 0.78 m
Static head:-
Assume sub soil water elevation at downstream canal bed elevation, therefore Static head = D/s canal bed elevation - Bottom elevation of cistern floor
= 1342.33 - 1341.85 = 0.48 m = 0.48 t/m2
Seepage pressure
Total seepage path creep length = 5.5+0.62+1.0+1.90+3+1+ 1 07 = 14 09 m
(As per sketch enclosed) Seepage pressure at any point
= Seepage head x (1 - L  P S  P
ee   a   e
ath                  upto the po int
Total seepage path length Seepage pressure at the end of floor
Seepage path length upto end of floor
= 5.50 +1+0.62 +1.00+1.90 + 3.00
= 11.52m
Seepage pressure = 0.78 (1-—— )
14.09
= 0.78 (1-0.82) = 0.78 x 0 18 = 0.14m = 0.14 t/m2
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Total uplift pressure = static head + seepage head = 0.48 + 0.14 = 0.62 t/m2
total uplift Thickness of floor required =-----------------—-----------
unit weigth of concrete
225
May 2007
Thickness of floor considered as 0.45m is sufficient to meet the requirement at end of floor
Seepage pressure at u/s i.e. below gate
Seepage path length = 5.5 + 0.62+0.5
= 6.62 m
«      /x 6.62 .
Seepage pressure = 0.78 1--------- )
_
14.09
= 0.78 (1-0.47) = 0.78 x0.53
= 0.41m say 0.41 t/m2
Total uplift pressure = static head + seepage head
= 0.48 + 0.41 = 0.89 m = 0.89 t/m2 , Total uplift presure
_L. ,
Thickness required =------------ — - -------------
unit weigth or concrete
So assumed thickness of 0 45m is considered suitable
Provide cc. m-20for top 0.15m thickness rest 0.30 shall be cc M-15
Upstream and downstream protection
Pervious protection of cc. block or stone pitching over gravel shall be provided beyond
upstream and downstream impervious cc floor. Upstream protection for head regulator shall be same as already proposed to be provided for cross regulator downstream protection.
Downstream protection is proposed to the provided for twice the length of downstream cut off depth = 2x1.07 x 2.14
Provide 3.00 length of pervious protection, consisting of 0.45 m thick cc block or stone pitching laid over 0.15 thick gravel.
At the end of protection a toe wall 0.5m wide at top, 1.0m deep with 0 8m width at foundation shall be provided
----------------------------------------------------------------------------------------------------------------------------- 22 Water Works Design & Supervision Enterprise '
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Hydraulic Design of Canal Structure
Fixation of elevations of operating platform
A. Cross Regulator
May 2007
It is already proposed to provide 2 lift gates of size 2.00 m x 1.5 m for cross regulator
Bottom elevation of operating platform is  proposed to be kept at upstream Bed elevation of canal i.e. at EL.1341.75. The bottom elevation of operating platform shall be fixed in such a way  that, after lifting the gate fully, there shall be a clear difference of 1 Om between bottom elevation of operating platform and in condition when gate is lifted fully.
Bottom elevation of slab of operating platform = crest elevation + 2 x height of gate + 1.00
= 1341.86 + 2x 1.5 + 1.00
= 1341.86 + 4.00 = 1345 86 m
Considering 0.45 m thickness of RCC. Slab for platform
Top elevation of operating platform shall be
= 1345.86 4- 0.45 = 1346.31 m provided at 1346.3 m
Width of operating platform shall be 2.5 m.
Foot Bridge
A foot bridge is proposed across main canal for crossing from one side to another and also for easy approach for operation and maintenance of gates.
This foot bridge shall also serve as crossing for cattle’s and residents of area.
The width or foot bridge shall be 2.00 m clear.
The Bottom elevation of Foot Bridge shall be
= D/s canal FSL + 1.00
= 1343.01 4- 1 = 1344 01 m
Top elevation of Bridge slab shall be
Bottom elevation + thickness of RCC slab
Assume thickness of slab as 0.40 m.
Elevation of service road slab Top elevation = 1344 01 4- 0.4 = 1344.41
The ground elevation considered as 1343.70 Upstream FSL of canal is 1343.00
Free board is 0.60 m. Top or bank RL = 1343.60 m
Since  ground  elevation  is  1343.70,  embankment  of  0.6m  height  above  ground  elevation  shall be provided for service road.
.. Service Road elevation = 1343 70 4- 0.6 = 1344.30
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So top of foot bridge slab shall be at kept at same elevation as that of service road.
B = For Head Regulator
The gate size proposed for head regulator is = 1.0 m x 0.75 m
Bottom elevation of operating platform is fixed as
= Crest elevation + 2 x height gate + 1.0 m
= 1342.48 + 2 x 0.75 + 1.00
= 1342.48 + 2.5 = 1344.98 m say 1345.00
Considering 0.30 m as slab thickness
Top elevation of operating platform
= 1345.0 + 0.30 = 1345.30 m
There is a service road 5.0m wide on left bank of canal. The secondary canal is also taking off on left side. Therefore a bridge slab shall be required to be provided across secondary canal near head regulator. The elevation of Road is 1344.30 keeping elevation of top of Road slab
as 1344.30 and considering slab thickness as 0.45 m
Bottom elevation of slab = 1344.30 - 0.45 = 1343.85 m
The FSL of secondary canal is 1343.01 m
The clearance between FSL and bottom of Road slab
= 1343.01 -1343.01 = 0.84 m
For secondary canal, free board required is 0 50 m. Since clearance is 0.84 m, which is more than required.
Top & bottom width of Abutment, wing and return walls.
For Abutment: Abutments shall be provided below, operating platform, Road slab, foot bridge slab, i.e. where the walls has to bear loads. The top width shall be kept as 1.00m the bottom
width shall be 0.50 times the height from elevation of top of abutment to foundation elevation
The face on water side shall be vertical and width shall be increased on other side
Wing wall: All walls which are not supporting any load, top width shall be kept as 0.50 m
Bottom  width  calculation  and  face  on  water  side  shall  be  in  the  same  manner  as  that  of abutment.
Based  on  the  above  design,  a  detailed  drawing  has  been  prepared  which  is  available  at Drawing no AD-F-Canal-D-D04 to 06.
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In Association with Intercontinental Consultants and Technocrats Pvt. LtdU/SFSL 1343 11 „
r Gates for cross regulator D/S FSL 1343 01
U/S floor
U/S canal bed EL
D/S floor 1341 75
IQ
IT
(i) FLOOR LENGTH FOR PRIMARY CANAL
d1341 36
! 1341 25
(u) FLOOR LENGTH FOR HEAD REGULATORArjo-Dedessa Irrigation Project
Hydraulic Design of Canal Structure
May 2007
1.3 DESIGN OF ESCAPE REGULATOR ON RIGHT - PRIMARY CANAL
AT Km 2.00
Arjo-Dedessa Irrigation Project envisages  construction of earth and rock  fill dam at lat 8°-31'-12” N and long. 36°-40,-04”E. The site has been selected after reconnaissance visit to alternative sites identified earlier in past studies. The height of dam is proposed to be 40.6m. Two canal systems are proposed to takeoff from dam for irrigating command area downstream of dam. One canal is  proposed from left flank  and another from right flank. The right bank canal is proposed to take off from saddle No 2 located in right flank. The minimum draw down level is proposed to be at 1350m elevation. The FSL of canal at off take point in proposed to be 1348.0m elevation.
The right bank canal is proposed to be a contour canal The canal crosses the river Wama at about 8.00 km from off take point. Near WAMA RIVER canal shall be in heavy filling in both the flanks of proposed aqueduct. An escape is essential on main canal to release water suddenly for safety of canal, when canal in downstream is breached or canal is required to be closed for maintenance or due to sudden closure of outlets by cultivators.
Therefore Escape structure is to be located in Initial reach and subsequently in other reaches at intervals depending upon the importance of the channel and vicinity of suitable drain
It is proposed to provide an escape for Right bank main canal about 2.00 km downstream from off-take point of canal. Near escape site at km 2.00 there is drain having catchment area or about 2.5 km . This drain joins WAMA River after about 500m downstream from the crossing point of drain and canal. Canal near the drain is in cutting.
The escape shall have following components
1         Sluice  for Escape  from left bank  of canal
2         Fall of about 6 to 8m with sluice and   lift gates
3         Cross   regulator
4         Escape channel
Canal FSL and bed elevation at location of structure canal data. Right Bank -
2
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Hydraulic Design of Canal Structure
1        Canal full supply discharge
May 2007
including 10% flexibility factor
7.52 m3/s
2
Bed width
6.25 m
3
Full supply depth
1.40 m
4
Longitudinal slope of canal
1 in 5000
5
Side slope
1.5: 1
6
Location or Escape
2 km from off take point
7
Velocity in canal
0.643 m/sec
8
Ground elevation
1949.00m
Stream details
1
Catchment area
=
2.50 sq. km
2
a) 100 year peak flood discharge
As per hydrology report
=
10.00 m3/sec
b) Add 30 % extra for design
=
3.00 m3/sec
c) Total design discharge
=
13.00 m3/sec
3
Slope of river 20 m in 1000 m length
from 1350 to 1330 m
=
1 in 50
4
River bed elevation at canal crossing
=
1347.00 m
Calculation of FSL and Canal Bed Elevation.
FSL of canal at offtake points is 1348.0 m. The slope of canal is 1 in 5000, therefore drop in 2
km (2000 m) shall be
= 0.4 m 5000
FSL of canal at Escape is                 = 1348.0 - 0.4 m
= 1347.6 m
Canal bed elevation = 1347.6 - 1.4 = 1346.2 m
Discharge for escape can be considered upto 60% of the discharge of main canal. However since the escape is located in the initial reach the discharge in the escape is considered nearer to the full supply discharge The full supply discharge of canal is 7.52 m /sec. So escape shall be designed for 7.00 m /sec only
3
3
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Design of cross regulator
May 2007
The cross regulator is required for diverting the discharge through escape structure to escape channel. There shall be difference of 0.15 m between upstream and downstream FSL of primary right bank canal. Bed width, discharge, full supply depth shall remain same for u/s & d/s canal.
1
FSL elevation
C//5/
/D/S
\W.6/
/1347.45
2
Canal bed elevation
U %is
1346.2/
7\ 346.05
• Fixation of crest elevation and waterway.
The crest elevation of the cross regulator shall be kept at the upstream canal bed elevation. The crest elevation = 1346.2 m. The bed width i.e. linear waterway shall be calculated from formulae
Q = C.Be He3'2
C is modified coefficient, depending upon degree of submergence. Degree of submergence is given as —
He
Where. h  = Difference between u/s and D/s FSL of canal 0.15
d
He= Head = u/s FSL - crest elevation
= 1347.6 - 1346.2 = 1.4m
Degree of submergence =           =0.107
From graph between degree of submergence and ratio of modified coefficient to free coefficient is 0.70
So modified coefficient = 0.70 x 1.705 = 1.19
Where, 1.707 is coefficient for broad crested weir Substituting values of Q = 7.52 He = 1.4 and Cd = 1.19
7.52 = 1.19 Be (l^)3'2
Be -          7 52
_
7 -52
6          1.19x(l.4)3'2 ~ 1.19x1.66 = 3.81
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Assumed 2 bays of 2.25m each with one peir of 1.50m width
Total length Bt = Be + 2 (N x Kp + Ka) He
= 3.81 + 2 (1 x 0.01 + 0.20) 1.40
= 3.81 + 0.29
= 4.10
N = No. of Peirs
Kp = for rounded ease water = 0.01
Ka = for square abutment with head walls at 90° = 0.20
Thus assumed width for water way is suitable
Total water way 4.5 + peir width = 4.5 + 1.5 = 6.00m
• Level and length of downstream floor
Q = 7.52
7 52                a
Discharge per meter length = yy = 1.67 m /sec
Head loss HL = u/s FSL - D/s FSL 1347.6 - 1347.45
= 0.15m
Ef2 from blench curve = 0.90m
Downstream floor level = D/S FSL - Ef2
= 1347.45-0.90= 1346.55
But the canal bed elevation is 1346.05 so adopt cistern level = 1346.00 Ef, = Ef2 + HL = 0.90 + 0.15 = 1.05 from graph
Di = 0.4 D  = 1.1 m
2
Cistern floor length required = 5 (D -D,) = 5(1 1-0.4) = 3.5 m
2
May 2007
Provide 5 m = length of cistern
Gate size and Elevation of operating platform
For operation of cross Regulator, 2 gates of 2.25 m x 1.5 m shall be provided. Gates shall be vertical lift gates with side roller and hoisting arrangements. For hoisting arrangement a operating platform shall be provided. Top elevation shall be fixed as such that when gate is fully opened there shall be clearance of 1.0 m between top of gates and bottom of operating platform.
Top elevation = crest elevation + 2 x height of gate platform + 1.00 +
thickness of slab
Assuming depth of slab as 0.60 m
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Hydraulic Design of Canal Structure
Top elevation = 1346.2 + 2 x 1.50 + 1+ 0.6 = 1346.2 + 4.6 = 1350.8
Keep top elevation at 1351.00 m
Vertical cut offs
May 2007
The minimum depth of u/s and downstream cut off shall be provided 1.5 m below bed elevation.
Bottom elevation of upstream cutoff = upstream bed elevation -1.5 = 1346.2 - 1.5 = 1344 7 m Bottom elevation of downstream cutoff
= D/S bed elevation -1.5
= 1346.05- 1.5 = 1344.55 m
Top width 0.50m Bottom width 1.00 m
Total floor length and floor thickness
It is proposed to provide upstream and downstream floor for 10 m length.
For difference in floor elevation a slope of 5:1 is proposed
Length for drop = 5 x 0.15 = 0.75 m
The  thickness  of  upstream  floor  is  considered  as  0.6  m.  On  the  upstream  there  shall  be  no uplift pressure, as the column of water shall balance the uplift.
For downstream floor minimum thickness of 0.6 m shall be provided The floor thickness shall be kept as 0.60 at the end of cistern floor and 0.8m at the beginning of cistern floor.
Total creep length (As per enclosed sketch)
= 1.5 + 1.5 + 5 + 0.75+5.00+1.5+1.5
= 16.75m
The maximum uplift pressure on downstream floor shall be there when the upstream canal is at full supply elevation and downstream canal is dry.
There shall be two type of pressure working on bottom of floor pressure duct
1) Static head and
2) Seepage head
1) Static head = D/S canal bed elevation - Bottom elevation of floor
(i.e floor thickness considered)
= 0.80 m = 0.80 t/m2
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Hydraulic Design of Canal Structure Seepage head shall vary from point to point.
May 2007
The minimum seepage uplift head shall be at end of cistern floor and it shall increase in the upstream with maximum seepage uplift at upstream end of floor. Maximum seepage head = u/s FSL - Downstream bed elevation
= 1347.60 - 1346.05 = 1.55 m
Calculation of uplift pressure at different points and thickness Uplift pressure at end of downstream floor
Total creep length upto the point
= 16.75 - 3 = 13.75 m
Uplift pressure = 1.55 (1-
) 16.75
= 1.55(1 082) = 0.28 m
Total head = static head + uplift
= 0.80 ♦ 0.28 = 1.08 m = 1 08 t/m2
.. Thickness required = -------- = 0.48 m
TL. .
‘   -4    1-08
2.25
Therefore 0.60 thickness of floor at end of floor shall be sufficient
Total uplift at 2 m from downstream
= Total creep length upto the point = 13.75- 5 = 11.75 m
Seepage uplift = 1.55 (1 -
) 16.75
= 1.55 (1-0.70)
= 0.465
Total head = static head + 0.465
= 0.8 + 0.465 = 1.265 m = 1.265 t/m2 1.265
Floor thickness = - — = 0.56 m
So thickness of 0.6m is sufficient upto 2 m from end.
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At 3.5 m from D/S end of floor
Total creep length = 16.75 - 6.5 = 10.25 m.
May 2007
Seepage uplift =1.55(1 -
) 16.75
= 0.72 m
So 0 8 thickness considered shall be sufficient So provide 0 6 thick floor for 3 00m length from downstream end and provide 0 8m thick floor for length from 3 0m downstream end to 7 00 m from downstream end or floor
Upstream floor shall be 0 6 m thick
The floor shall consists of cement concrete of following mix (strength)
For 0.60 m thick floor - Top 0 15m thick of cc M-20 and 0 45 m thick cc M15
For 0 80 m thick floor - Top 0.15 m thick cc M-20 and 0 65m thick cc M15
Upstream protection
Upstream protection shall be provided to protect the floor It is proposed to provide 0 6m thick cc block or stone pitching over 0.3 m thick gravel
= 1.55 (1-0.61)
= 0 60 m
Total head = 0.60 + 0.80 = 1.4 m = 1.4 t/m2 14
Thickness required = ------ = 0 62
2.25
So thickness of 0.8 m shall be provided
At 5 m from D/S end of floor
Total creep length = 16 75 - 8 75 = 8m Seepage pressure = 1 55 (1 -    y, )
= 1.55 (1-0 48) = 081
Total head = 0.8 * 0 81 = 1.61
4  > 61
Thickness required = ------ 2.25
The length of protection required =
. Scour depth of cut off I 5
—-
=         =1.67
thick ness proposed 0.9
So provide length of 2.00 m of loose protection beyond upstream floor
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Launching apron
It is proposed to provide boulder 0.6 m thick over 0.3 m filter or gravel. The total cubic contents of the appron shall be = 2.25 times depth of cut off
D = depth of downstream cut off = 1.5 m
Volume = 2.25 x 1.5 = 3.37 cm
Thickness of appron provided is 1 00 m.
3 37
Length required shall be —— = 3.37m
Total length of protection and launching apron required = 1.67 + 3.37 = 5.04 m. In upstream it is proposed to provide protection of 2m length so provide launching appron = 5.04 - 2 = 3.04m; provide 3 m.
Downstream protection
To  protect  down  cistern  floor  and  scour  of  1.5m  depth  of  cut  off,  down  stream  floor  shall  be provided for a length
= 2 x depth of cut off
= 2 x 1.5 = 3.00 m
Provide 3.00m protection of 0.60m thick cc block or stone pitching over 0.3 m graded filter.
• Toe wall
Toe wall at the end of upstream and downstream protection work shall be provided. The top
elevation of toe wall shall be at upstream and downstream canal bed elevation respectively 
The toe wall shall have following dimensions.
Top width o.5 m foundation width 0.8 m and depth of 1.0 m.
Design for Escape sluice and Escape channel
The escape sluice shall be located on left bank of canal near Maribo stream, catchment area of which is 2.5 sq. km and peak flood discharge for 25 year return period is 10 m /sec and design
discharge considering with 3 0% extra discharge is  1 3.0 m3/sec. The peak  flood has  been computed based on rational formula given in hydrological report. The bed elevation of stream at 200m downstream of the crossing is 1335.0 m. This stream joins Wama River at a distance of about 500 m downstream of crossing. The discharge through escape sluice and escape
3
3
channel is proposed to be 7.00 m /sec. Therefore
the Maribo stream  is quite suitable to take
discharge. The stream bed elevation at canal crossing point is 1345 m. where as the river bed
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elevation 100 m downstream of crossing is 1340.0 m. The bed elevation of canal upstream of structure is at elevation 1346.2 m. So escape sluice shall be combined with approximate 7.25 m fall.
Design of Escape channel and determination of tail water level
The escape channel is proposed to be earthen channel with cc block of stone piching for 15m length near junction of channel with stream C.C blocks or stone pitching is also proposed for 10m length after the downstream appron.
It is proposed to provide 0.8 m/sec velocity in escape channel.
Discharge to pass = 7.00 m /sec
Velocity proposed = 0.8 m/sec
Area of channel required = — = 8.75 sq. m
0.8
Assume bed width of escape channel as 5m, water depth as 1.30 m a nd side s lopes 1 .5:1 (H:V) then area = (B + nd)d Where, B = bed width of channel
3
= (5 + 1.50 x 1.3) 1.3
n = Horizontal component of side slope
2
= 6.95 x 1.3 = 9.035 m2                       d = Depth of water in channel
Required area is 8.74 m  so section adopted is appropriate and is considered suitable Actual velocity = — = —-— = 0.78 m/sec
A 9.035
P = 5 + 1.80 x 1.3 = 7.34
R= — =
P
=          = 1.23 R-'1 = 1.15
9.035
, where n = 0.025
0.78 = 46 S1'2
.-.s1'2 = — =0.017
46
S = 0.00029 1 in 3500 Appox.
Bed elevation of Escape channel at junction with stream about 100 m downstream of crossing point of canal is proposed as 1339 m (1.00 m below stream river bed elevation) of 1340 0
Water elevation shall be 1339.0 + 1.30 m = 1340.30 m
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The  length  of  escape  channel  is  proposed  to  be  200  m.  Water  elevation  at  downstream  of appron of fall shall be
1340.30 + 200 x slope = 1340.30 + 200 x 0.00029 = 1340.30 + 0.058 = 1340.358 say 1340.36
Tail water level at junction of Escape channel and appron of
escape fall shall be
1340.36 m.
Bed elevation = 1340.36 - 1.30 = 1339.06 m.
Design of escape sluice
3
Escape sluice has to pass discharge of 7.00 m /sec. The FSL of canal is 1347.6 m. Where as canal bed is  1346.2 m. The Tail water level is  1340.36m. Therefore there shall be a fall of 1347 6 - 1340.36 = 7.24 m. Therefore escape sluice is proposed to be combined with 7.24 m fall. It is proposed to provide glacis fall with gate.
Water way and crest elevation
The upstream canal bed elevation is 1346.2 m and FSL elevation is 1347.6 m. Normally crest elevation of Escape channel is  kept at canal bed elevation. Since Escape structure is combined with fall, therefore for better flow condition it is proposed to keep crest elevation 0.15 m above canal bed elevation. The width of crest proposed is  1.00m, from consideration of providing vertical lift gate at crest elevation
= 1346.2 + 0.15 = 1346.35.
Linear water way required is calculated from formulae Q = 1 84 Le D3'2
Where,
3
Le = linear water way
Q = Discharge considered = 7.0 m /sec D = Depth of water over the crest
= u/s FSL - crest elevation = 1347.6- 1346.35 = 1.25 m
Q = 1.84 Le D3'2 7 = 1.84 x Le (1.25)3'2
= 1.84 x 1 40 x Le
Le =--------------- = 2.71 m 1.84 .r 1.40
So, provide opening of 2.80 m
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Gate and Elevation of Operating Platform
May 2007
•  For  control  of  discharge  from  escape  sluice  a  vertical  lift  gate  of  3.00m  x  1.5  shall  be provided. Gate shall be vertical lift gate with side roller and hoisting arrangement. For fixing hoisting  arrangement  a  operating  platform  shall  be  provided.  Top  elevation  of  operating platform  shall  be  fixed  in such a way that when the gate is fully opened, there shall be clearance of 1.00 m between top of gate and bottom elevation of slab for operating platform.
Top elevation of operating platform
= Crest elevation + 2 x height of gate + 1.00 m + thickness of slab
Assuming thickness of slab as 0.60 m.
Top elevation = 1346.35 + 2 x 1.5 + 1.0 + 0.60
= 1346.35 + 4.60 = 1350.95
So keep elevation at 1351.00 m
• D/S Glacies
It is proposed to provide 2:1 slope in downstream glacies to be joined tangentially to the cistern floor with radius equal to 0.8D
0.8x1.25 = 1.00m.
Approach:-
Upstream glacies:- upstream slope of glacies is proposed to be kept as 1/2:1 joined tangentially to the crest with a radius equal to
D/2     = — = 0.62 Say 0.6 m.
2
Side walls:- the side walls shall be splayed at an angle of 45° from the end of upstream end to be extended by 1.0 m into the earthen banks from the line of FSL. The top elevation shall be 1.00 m above upstream FSL.
Calculation for depth downstream for energy dissipation.
It is proposed to provide a glacies fall with slope of downstream glacies as 21
TWL:  1340.36  and  the  bed  elevation  of  downstream  Escape  channel  is  1339.06.  Considering Datum elevation at 1339.06 (Reffer enclosed sketch)
U/s TEL above 1339.06 shall be = AZ + d + ha
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Where, AZ = crest elevation - D/S canal bed elevation d = depth of water above crest elevation
ha = velocity head of approach AZ = 1346.35- 1339.06
= 7.29
d =1.25
V2 ha = head due to velocity of approach = —
V = ~ = considering rectangular section
= —-— = 1.87m/sec 3x1.25
May 2007
ha =
 r =(iw
2g 19.62
3.50  = 0.18 19.62
u/s TEL = 7.29 + 1.25 + 0.18 = 8.69
Down steam TEL at jump neglecting all other losses
= di + head due to velocity at junction of Glacies and D/S floor = ha Where, di = depth at jump and
Vi = velocity at jump „ Q           7        2.33        , .
= — = — = —— replacing value of Vi
Ad
}
u  (K,)2                 (2.33)2                    5.43       0.277 2g      19.62 rf,2 19.62J,'           d2
Equating U/s TEL = D/S TEL
8.69 d* = d* + 0.277 solving this equation = 0.181m
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—-— = 12.88 m / sec 0.181
Froud No.=   A               12.88 12.88
79.81x0.181 ” 1-32
= 9.76
Energy dissipation
It  is  proposed  to  provide  hydraulic  jump  with  horizontal  appon.  Since  Froude  number  is  more than 4.50 stilling basin Type II shall be adopted
D2 = the depth of water adjacent to Dt is calculated as per formula
D,
=0.5(l + 8/2 -l)
V>            7
= 0.5^1+ 8x(9.76)2 -l) =0.5(27 62-1) = 13.31
D, = 13.31 x 0.181 = 0.72m = 2.41m
Another formula
 0,181 
D.g 4
2x5.43     + 0.1812
2     + ^0.181x9.81 +             4
V6.11 + 0.0082
V6.1182
= 0.09 + 2.473 = 2.363
Therefore adopt D = maximum of two values i.e 2.41 m
2
Cistern elevation = D/S TEL - 2.41
= 1340.36-2.41 = 1337.95
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So cistern shall be depressed by
= D/S bed elevation of escape channel - cistern elevation = 1339.06- 1337.95 = 1.11 m
May 2007
The difference between cistern elevation and bed elevation of escape channel shall be joined by slope of 2:1 (H:V)
Length of Cirstern required is  determined from Graph between Froude number and ratio of length of cistern (Lb) and downstream depth of water (d2) (copy  of graph is  enclosed as Annexure -1)
The value of — for Froude No 9.76 is 3.95
d2
^- = 3.9 Say 4
d2
L„ = 4x2.41 =9.46
Length of cistern can be determined from another formula Length = 5 (d -d-i)
2
Where, d2 = Depth of water adjacent to jump
d1 = depth of water at jump
= 5(2.41 -0.18)
= 5 x2.229 = 11.15m
Since maximum length out of two formulas is 11.15 m
So provide length of stilling basing as 12.0m
Basin Appurtenants: -
As  per  Froude  No.  9.76,  Hydraulic  jump  with  horizontal  appron  basin  Type  II  is  selected accordingly the basin appurtenant are designed (Refer Annexure - 1)
i)
Chute blocks:- Height width and spacing of the chute block shall be equal to J, =
0.181m Say 0.2 m. The chute block shall be provided at junction of glacing and
horizontal appron. The chute near side walls shall be at 0.1m from wall.
ii)
Basin block
Shall be provided at a distance of 0.8 D  from edge or chute blocks
2
= 0.8 x 2.41 = 1.928 Provide at 2 m.
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Height = h , the height shall be calculated from graph between Froude no and — For
b
t/i
Froude number 9.76 value of — is 2.25
— =2.25
h b = 2.25x0.181 =0.40
Provide height of 0.40 m
Width at bottom and spacing = 0.75 Hb
= 0.75 x 0.40 = 0.30 Top width shall be = 0.02 h  = 0.02 x 0.4 = 0.08
b
iii)  End sill
At  the  end  of  floor,  dented  sill  shall  be  provided.  Upstream  face  shall  be  vertical,  downstream face shall be with slope of 2:1
Height = 0.20 d  = 0 2 x 2.41 = 0.482
b
Provide 0.1 m.
Upstream face shall be vertical and downstream face shall be with slope of 1:1 Spacing from side walls shall be kept = 0.375 H  = 0.375 x 0.4 = 0.15 m
2
Provide 0.5 m
Top width = 0.02d  = 0.048 provide 0.1 m
2
Spacing and bottom width = 0.15D2 = 0.15 x 2.41 = 0.36 m
Provide 0.4m
The  end  dent  is  proposed  to  be  adjacent  to  side  wall  and  shall  have  no gap  between end  dent and sidewall.
Upstream protection and cut off
In u/s impervious floor of cc for 5m length is proposed to be provided At the end of floor a
curtain wall to act as cut off to a depth of 1.5m below the u/s canal bed elevation shall be
provided. The cut off wall shall be of 0.5 width at top and 10m at foundation elevation
Though there shall have no uplift pressure on upstream floor, however thickness of upstream
floor shall be kept as 0.60m. The bottom of upstream cut off = u/s canal bed elevation -
depth of cut off
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= 1346.2 - 1 5
= 1344.7
Beyond impervious floor, for a length of 5m pervious protection of 0.6m thick cc block of stone pitching over 0.3 m gravel shall be provided in bed and side slopes of canal. A toe wall 1.0m deep shall be provided at the end of pervious protection with 0.5 top width at top and 0.8m at bottom.
Down stream cut off and protection
Provide  cutoff  wall  2.0m  below  the  cistern  level  with  top  width  of  0  5m  a nd bottom  width of 1.00m at foundation.
Foundation elevation of curtain wall = cistern elevation - 2.00
= 1337.95-2 = 1335.95
Downstream protection
Impervious  floor beyond downstream floor shall be provided for 6m length, consisting of cc block or stone pitching 0.6m thick laid over 0.3m thick gravel. A toe wall at end of impervious floor of 1.0m depth with 0.5m top width and 0.8m width at bottom shall be provided
Thickness of Downstream floor
The maximum uplift pressure on downstream floor shall be when in the upstream Canal water is at FSL and downstream is dry. Considering floor thickness of 1 00 m and assuming subsoil water level at D/s bed elevation
The static head = D/S bed elevation - Bottom elevation of cistern
= 1339.06- 1336.95
= 2 11 m
Total seepage head = u/s water elevation - d/s bed elevation
= 1347.6 - 1339.96 = 8.54 m
Creep length for sloping appron = 2.24 (1346.2 - 1337.95)
= 2.24 x 8 25 = 18.48
Total creep length from U/S to D/S (Refer sketch No.2)
= 3+3+5+1.075+18.48+12+2+3.11 =47.665
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The uplift pressure at different points of floor shall be
May 2007
= 8.54(1
creep length upto point
Total creep length
The weight of concrete shall counteract uplift pressure.
Total uplift head = Static head + seepage head at that point.
The floor shall be designed as RCC. The floor shall be designed for uplift pressure as balance head i.e. = Total uplift pressure - 2.25
Uplift pressure and balance head for which design is to be done is given in following Table
Static head 2.11 m Total creep length = 47.665 m Seepage head= 8 54
Table 3.1 Total Pressure along length of Floor
1s
No
Point considered
Creep length
upto point
Uplift pressure
head
COk3
8.54(1-        )
47.665'
Static
head
Total
head
m/t
Total
pressure
in t/m2
1
2
3
4
5
6
7
1
At end or floor
42.665
0.854
2.11
2.964
2.964
2
2m from end of floor
40.665
1.28
2 11
3.39
3
4m
38.665
3.39
1.62
2.11
3.73
3.73
4
6m
36.665
1.96
2.11
4.07
4.07
5
8m
34.665
2.31
2.11
4.42
10m     ”
32.665
4.42
6
2.65
2.11
4.76
4.76
7
12m     "
30.665
3.07
2.11
5.18
5 18
Provide 1 .m RCC floor upto 2m length, 125 RCC floor from 2 to 6m and 1.5m thick floor from 6 to 12 m from end or floor. So balance pressure for design of RCC. floor shall be
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Table 3.2 Balance Pressure along length of Floor
s.
No
Point
Total uplift pressure
t/sq.m
Thickness of          slab proposed
pressure due to self weight of floor 2.25 x thickness  of floor
Balance pressure for which RCC floor is to be designed
1
At end of floor
2.964
1.0
2.25
0.714
2
2m from end
3.39
1.0
2.25
1.14
3
4m from end
3.73
1.25
2.81
0.92
4
6m from end
4.07
1.25
2.81
1.26
5
8m from end
4.42
1.5
3.375
1.045
6
10 m "
4.76
1.5
3.375
1.385
7
12 m ”
5.18
1.5
3.375
1.805
The width of fall is 3.00 m and bed width of Escape channel is 5 m The transition length shall be provided with splay of 1 in 5.
Length required = x 5 = 5m
Provide d/S previous protection for 6m length
D/S sidewalls of cistern shall be for length of 12*2 - 14 m with top elevation equal to 1.5m above downstream Tail water level
= 1340.36 + 1.5 = 1341.86, provide upto 1342.00 m
Return walls shall be at right angle to sidewall at the end with top elevation at 1342.00 m
Length shall be 1.5 (Top elevation - D/S bed elevation) + 1.5
= 1.5 (1342- 1339.06) + 1.5
= 1.5 x 3 + 1.5
= 4.5 + 1.5 = 6 m
The foundation elevation is proposed to be kept 1.5 m below cistern elevation i.e. 1337.95 - 1.5 = 1336.45, keep at 1336.50 m.
Top width of sidewall and return wall shall be 0.5 m
Bottom width = 0.55 x height up to foundation
= 0.55 x 5.50 = 3.025 m
Provide 3.00 bottom width front face shall be kept vertical.
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Road
May 2007
Provision of service road of 5.00 m width on canal is made on left bank of Right bank primary canal. The escape structure is also proposed on left bank of canal, therefore a slab for road bridge across escape structure is necessary.
It is proposed to provide 5.00 m wide road slab adjacent to tower for lift gate of escape.
It is assumed that thickness of RCC slab shall be 0.6 m and top road slab elevation shall be same as that of service road i.e. at EL 1349.60 m.
The Detailed drawings of the structure, based on above design calculations, are available at Drawing no. AD-F-Canal-D-07 to 10.
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Dimension Sketch for Basin III
I
I
I
I
I
I
U/S FSL 1347.60
Gates for cross regulator
'D/S FSL 1347.45
W canal ted £L1345.20
U/S floor
D/S floor                                —i
50
.
i 0 75
5.0
U/S Cut-off
D/S Cut -off
1) FLOOR LENGTH FOR CROSS REGULATOR
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Hydraulic Design of Canal Structure
2. CROSS DRAINAGE WORKS
2.1 Design of Aqueduct on Right Primary Canal ACROSS WAMA At Km. 8.00 RIVER
General
May 2007
For development of i rrigation in Ethiopia, Blue Nile River basin is considered as one of the potential area In Blue Nile river basin Dedessa river is one of the important river. Yield from the catchment of river is considered suitable for harnessing for irrigation purpose.
In the past, studies were conducted by different agencies USBR, WAPCOS, and BCEOM for locating different dam sites on river Dedessa for the feasibility study. After reconnaissance visit to site and studies of alternative proposal, the dam site location at lat 8°-3T-12"N and longitude 36°-40'-04"E is tentatively selected. The dam site is approximately 1.5km upstream of junction of Dedessa and Wama River.
The Project Proposal
In the project proposal it is proposed to irrigate 13665 ha (approximate) of land on both flanks of dam. The dam is proposed to be earth and rock fill dam The maximum height of dam is proposed to be 40 6 m from riverbed elevation of 1320.00 m.
Canal Proposal
For irrigating area on both flanks, two canals are proposed to takeoff from dam, one on the left bank and other on right bank Left bank canal is proposed to take off from left bank abutment of dam. In the right flank, there are two saddles adjacent to each other, saddle No-I and saddle No.2. In saddle No. 1 spillway  structure is  proposed to be located, where as  outlet for right bank canal is proposed to be provided in saddle no. 2.
From  the  consideration  of  elevation  of  command  area,  the  elevation  at  outlet  from  dam  with minimum draw down elevation is tentatively fixed at elevation of 1350 m-
The elevation in saddle is  approximately  1357.5 m, where as  the elevation of out let is proposed to be kept at 1350 m elevation. The FSL in canal down stream of outlet is accordingly fixed at 1348 m elevation.
The area is proposed to be irrigated by two canal systems, left and right bank canals taking off from the dam and saddle no. 2 of right flank. The lengths and discharge of canals at out let point for two canal systems are as below:
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s.
No
Canal
Area of
irrigation
in ha
Approximate
length of Primary
canal in km
Discharge at
Head in m3/sec
1
Left bank canal
7450
60.18
9.015
2
Right bank canal
6215
42.80
7.521
Total
13665
102.98                       16.536
Topography
The topography of command area is very undulating, as such the primary canals for left and right bank  are to be aligned as  contour canals. Since canals  are contour canals, number of drainage channels or streams shall be required to be crossed, for which cross drainage works are to be constructed. In right bank  there is  major river Wama, which is  a major tributary  of Dedessa river and is  running very  near to dam area. Wama river joins  Dedessa river approximately 1.5 km downstream of proposed dam. The right bank primary canal has to cross Wama river in its initial reach.
The right primary canal is aligned to cross Wama river at about 8km from outlet. The location of crossing at Wama river with canal is at location 251325N, 946000E, with river bed elevation at1332.0 m. The crossing point is  about 8.5 km upstream of junction of Wama river and Dedessa river.
Hydrological Detail of Wama-River
- Data for Wama River at crossing point.
Since WAMA River has very large catchment and structure across river shall be very important therefore flood value for 100 years return period is considered for design.
The hydrological data for Wama river is obtained from 1 in 50000 maps, available survey maps in scale1:10, 000 and hydrology draft report.
i)  Catchment area approximately
3542 km2
ii) 100 year peak flood discharge
584 m3/sec
iii) 500 year peak flood discharge
776 mJ/sec
iv) River bed elevation
1332.00m
v) Average river slope
1 in 800. (0.00125)
- Hydrological data for canal
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Hydraulic Design of Canal Structure
May 2007
Hydrological data are based on canal design carried out for command area of right bank canal computed from survey maps.
i) Full supply discharge (inclusive of 10% flexibility factor)
ii) Canal bed width
iii) Full supply depth
iv) Longitudinal slope of canal
v) Length of canal from origin upto crossing
vi) Velocity in canal
vii) Side slopes of canal
~~       7.52 m3/sec
=        6.25 m
=        1.40m
= 1 in 5000 (0.0002)
=        8.00 km
=        0.643 m/sec =         1.5:1 (H:V)
2:1 (H:V) in filling
Since FSL of canal at head is proposed to be 1348.00m. The FSL at crossing shall be
FSL at head - loss of head due to slope upto crossing point
- Loss of head in structures upstream of crossing
= 1348 - 0.0002 x 8000 - 0.10 m (assumed head loss in structures) = 1348- 1.6 -0.1
= 1346.3 m
vii) FSL of canal at crossing
=         1346.3 m
viii) Bed elevation of canal at crossing        =         1346.3 - 1 4
=         1344.9 m
Calculation for high flood elevation
For evaluating high flood elevation in river, value of peak flood discharge of 100 year return period shall be considered. For free board purpose peak flood value of 500 year return period shall be considered.
As per hydrology report the peak flood discharge values are:-
i) For 100 year return period
ii) For 500 year return period
=         584    m3/sec =         775 m3/sec
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Hydraulic Design of Canal Structure
May 2007
For evaluating high flood elevation of river following topographical details are considered.
i. Cross section of river at crossing point
ii. Longitudinal slope of river
iii. River bed material
Detail topography survey and geological investigation are yet to be completed. In absence of detail survey  and investigation, which may  take some time, data available from different available records are considered for design.
Cross section of river has been computed from contour survey map of command. The river slope computation is carried out from 1:50,000 map. It is reported that exposed rock out crops are available at crossing point.
On the basis of above information, highest flood elevation has been computed
For calculating highest food elevation following formula has been used.
Q = A x V Where Q = Peak flood discharge in my / sec
A = Area of river below flood level elevation considered
in m2
V = Velocity of river during flood in m /sec
The velocity is calculated by Manning's formula
K = l/?2'35''2
n
Where, n = Coefficient of rugosity depending on river bed material
R = Hydraulic mean depth = A/P
A = Area of river below flood elevation
P = Wetted perimeter of river below flood elevation
S = Longitudinal slope of river
As reported, exposed rock out crops and boulders are available at crossing site, therefore value of n is  considered as  0.03. The longitudinal slope of river upstream and downstream of crossing is  obtained from 1:50000 Map. The slope is  evaluated by  considering two contour points crossing the river and the distance between them. The slopes worked out are
Up stream of crossing = 1.700 (0.00143)
Down stream of crossing = 1:800 (0.00125)
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Hydraulic Design of Canal Structure
May 2007
For computation of high flood elevation slope of 1: 800 has been considered. Based on above data and cross section of river, values for area, wetted perimeter, discharge and velocity for different elevation from 1336m to 1338m a re computed for every 0.25 m interval. From the computed values a rating curve for discharge and flood elevation is drawn. The detail values and rating curve is enclosed as annexure 2. From the rating curve the highest flood elevations are worked out for flood values of 100 and 500 years return period.
i.  For 100 year peak flood of 584 m' / sec flood elevation is = 1336.66 m
ii. For 500 year peak flood of 776 m' / sec flood elevation is = 1337.08 m
iii Width of river at 1366 6 m elevation is = 155.90 m = 156.00 m
Area at high flood elevation of 1336.66 m = 318.79 m2
Wetted perimeter = 163.57 m and velocity = 1.83 m/sec
•  Selection of type of structure
The canal discharge is  only  7.52 m3/sec  and bed elevation at crossing is  1344.9 m. The
3
discharge in Wama river is 584 m /sec and highest flood elevation is 1336.66 for 100 year flood and 1337 08 for 500 year flood. Clear difference of more than 7.5 m is available between HFL of river and canal bed, therefore box type aqueduct structure is most suitable for crossing.
•  Water way of drainage
The width of river at HFL is 156 m, and there is difference of approximately 7 5m between H.FL and canal bed elevation, therefore the river water way can be restricted at crossing point.
The width of river for regime condition is given by Lacey's equation P = 4 83< 2
r
Where,
Q = Total Peak discharge in m3/sec = 584 m3/sec
P = 4.83 V584 = 4.83x24.17 m3/sec = 116.72m say 117.0m
It is  proposed to provide peirs  at 10 m c/c  interval. Peirs  shall be of reinforced cement concrete 1.0 m thick, with peir cap of 2.0 m wide and for 1.5m height. The peir cap shall be provided to accommodate the bearings between super structure and peir, necessary for moving ___ __________________________________________________________________________ 5]
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3
vehicular load. The cap shall also provide the support for superstructure trough of canal. The cut and case water of peir shall also be provided 2.0 m wide with semi circular shape.
Length of river at HFL elevation of 1336.66 is 156.0 m if the length of structure is reduced from 156 m, canal in flanks  of river shall be in heavy  filling. Heavy  filling section shall be uneconomical and when the canal is flowing there shall be always danger of heavy losses and breaching of canal any time during running of canal.
To avoid such occurrence, it is proposed to provide 200 m length of aqueduct structure with 20 bays of 10 m each center to center. So there shall be 21 peirs at 10m center to center. Peirs at entry and exit end shall be burned peirs. Due to provision of more length, of structure, there shall be reduction in length of heavy filling reach, and reduction of waterway of river at HFL shall be also minimum.
• Canal Water way
The full supply discharge of canal is 7.52 m /sec with bed width of 6.25 m. water depth 1.4m, and velocity 0.643 m/sec.
Assuming velocity of 1.35 m/sec in trough, Area of trough required for passing the discharge,
Q                          7 S?
Velocity in trough
Assuming depth of water in barrel same as that of canal i.e 1.4 m
A 5 57
Waterway required shall be = — =             = 3.98 Say = 4.0 m
1.4     1.4
Assuming free board of 0.5 over water depth for trough
Height of trough required is = 1 4 + 0.5 = 1.9 m provide 2.0 m.
Therefore required size of barrel is 4.0m x 2.0 m. Provide twin ducts of 2.0 m x 2.0m. with a vertical divide wall of 0.30 m thickness.
The twin ducts shall be of reinforced cement concrete with, top. bottom slab and middle wall shall have thickness of 0.3 m. The outer side walls shall be 0.45 m thick. It is proposed to take road over the duct. For easy entry and exit of vehicles from canal to road over duct the earth work of canal shall be provided to cover the end peir for about 6 m length of duct on both side of structure. Inside width of duct shall be 4.3 m and outer width 5.2 m.
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•    Transitions
May 2007
It is proposed to provide 4:1 splay in contraction at entry and 5:1 splay in expansion at exit.
Canal bed with - Width of barrel
Length of contraction transition =------------------------ - ---------------------- x 4
=
43= —“”x4=3-90
Provide 4 m
I
I
I
I
I
I
I
I
I
Length of expansion transitions =             — x5 = 4.875
Provide length of 5.00 m
Shape at entry and exit points shall be bell mouth type
•    Head loss and bed levels at different section
■ Head loss is calculated for different sections (Refer sketch enclosed)
Sections considered are:-
1-1 At the entry point from canal to structure
2-          2 At the entry point of duct
3-3 At the exit point of duct
4-          4 At the exit point of downstream of canal Considering section at 1-1
Canal bed width 6.25 m, Water depth 1.4, side slopes 1:5:1
Area at FSL = (B + nd)d
Where, B = Bottom width in m
d = depth of water in m
n = side slopes of canal
Q=Discharge in m /sec
A=Area in m2
V= velocity in m/sec
A = (6.25 + 1.5 x 1.4) 1.4= 11.69 m2
Q = AxV, ..V = Q/A
Velocity = 7.52 / 11.69 = 0.643 m/sec
3
.. Velocity head = V2 / 2g = —
2x9.81      19.62
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= 0.021 m
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Canal bed elevation = 1344.9 m
Canal FSL = 1346.3 m
TEL = FSL + velocity head = 1346.3 + 0.021 = 1346.321
At Section 2-2
Area of trough = 2x2x14 = 5.6
V2 = Velocity = Q/A = 7.52/5.6 = 1.34 m/sec
Velocity lead = = 1 342/19.62 = 1.80 / 19.62 = 0.092 m
May 2007
0.2 (k22
-^ )
2
Loss of Lead in contraction =
0.2 0 8^0.413)^^
=
Elevation of water surface = TEL at section 1 -1 - 0.014
= 1346.321 -0.014 = 1346.307
Elevation of water surface = TEL- Velocity head
= 1346.321 - 0.0902 = 1346.217
Bed elevation = 1346.217 - 1.40
= 1344.817m
Bottom elevation of trough slab and top elevation of peir
= 1344.817 - 0.30 = 1344.517 m
At section -3-3
Head loss from section 2-2 to 3-3
In this section the RCC trough barrel shall continue from section 2-2 to 3-3, therefore area, velocity, wetted perimeter, and velocity head shall remain constant at both sections.
The head loss in this reach shall be calculated from Manning formula
V3 = 1/n R S
V3= velocity between section 2-2 to 3-3
Where n = Coefficient of rugosity depending on surface material, taken as 0.016 for concrete surface
R = Hydraulic mean depth = A/P
A = Area of trough upto water elevation in trough P = Wetted perimeter of trough
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S = Slope in trough
R = AlP = ——— = 5.6/96 = 0.58 4+ 4x1.4
R2'3 =0.70
V3 = 1.34 = 1/0.016 x 0 70 S *
May 2007
I I 4
4
I
9
I
I
I
I
I
I I
I
4
Loss of head in expansion between section 3-3 and 4-4 is
2
0.3 (r< -r/) = o,3 [(1,34)2 -(0.634) ]
■■■ S = .00094
Head loss in trough = Length of trough x slope
= 200 x 0.00094
= 0.188
Elevation of TEL = TEL elevation at 2-2 -0.188 = 1346.307 - 0.188= 1346.119
Elevation of water surface = 1346.119 -velocity head
= 1346.119 - 0.092 = 1346.027
Bed elevation = water surface elevation - water depth
= 1346.027-1.4 = 1344 627
Bottom elevation of duct slab and top of of peir No. 21 (downstream peir)
= 1344 627 - 0.30 (thickness of bottom slab of trough)
= 1344.327 m
Section at 4 - 4
The section from 3-3 to 4-4 is expansion transition portion. The canal section at 4-4 is same as at section 1-1, therefore velocity, velocity head shall remain same as that of section 1-1.
‘ V  = 0 643 m/sec and velocity head 0.021 m
2g
0.3(1.80-0.413)
= 19.62 = o.O21
19.62
Elevation of TEL at 4-4 = TEL of section 3-3 - head loss 
= 1346.119-0.021 =1346.098
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Elevation or water surface TEL at 4-4 -Velocity head = 1346.098 - 0.021 = 1346.077 m
Bed elevation = water surface elevation - water depth = 1346.077-1.40 = 1344.677
Total head loss in structure
Ma y 2007
= Upstream FSL at section 1-1 - Downstream FSL at section 4-4
= 1346.30- 1346.077 = 0.223 m
Foundation elevation
Foundation  elevation  determination  is  dependent  on  the  scour  depth  measured from  Highest flood level.
Scour depth is calculated by two formulae. One by Lacey's formula and another by Unwin's formula
Lacey's formula
Scour depth Di = 1.35 ^2//
q = discharge per unit length
f = sill factor depending upon bed material
_ Q (Total dis ch arg e)
Effective linear waterway
Proposed length of structure is 200m between entry and exit peir, but effective length at HFL is only 156m.
There shall be 15 peir of 1 m thickness at H.FL
So effective water way =156-1x15 = 141
Q = 584 m3/sec
Therefore discharge per meter length q = ------- = 4.14 /sec
141
Since  it  is  reported  that  exposed  rock  outcrop  and  boulders  are  seen  in  river  bed  for  which value of silt factor is not given assuming maximum value of 1.00 for heavy sand
584
2    1/3
D, = 1.35 (q /f)
2      1/3
= 1.35 (4.14 /1)
= 1.35 x 2.58 = 3.48m
Foundation of peirs are to be kept 1.50 D, Below highest flood elevation.
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The H.FL of river is 1336.66 m. Scour depth for peirs should be 1.5 x 3.48 = 5.22 m below HFL
• Scour depth by Unwin formula
According to Unwin formula = normal scour depth = £>' = R(W/L)
Where R = Hydraulic mean depth of river below H.FL
W = Lacey's regime width = 4.73 Jo
Q = Maximum flood value
L = Obstructed width of water way of river
R = For River when H.FL at 1366.66 m from Table available at Annexure - 2
= 1.85 + 0.09 of (difference between 1366.50 and 1366 66)
= 1.94
W = 4.73 V584 = 114.31m
L = Obstructed width = 141.0 m
D' = 1.94 (114.31 / 141)067
=1.94 x 0.87 = 1.69m say 1.70 m
The maximum scour depth for peir is taken as = 2 x D'
= 2 x 1.70 = 3.40m below H.FL.
For   determination   of   foundation   elevation,   maximum   scour   depth   calculated   shall   be considered.
The scours depths are :
Scour depth as per Lacey's formula As per Unwim formula
5.22
3.40
Scour  depth  values  by  Lacey's  formula  being  higher  is  adopted  for  fixation  of  foundation elevation.
The H.F. Elevation is 1336.66m
River bed elevation is 1332.00m
Foundation elevation for peirs = 1336.66 - 5.22 = 1331.44m
Depth below river bed is only 0.56m
Therefore, Keep minimum depth of 2.0m below river bed i.e 1330.00m
Foundation level of peirs located in river portion below H.FL shall be 1330.00m
Peirs  located  above  H.FL  elevation  foundation  elevation  shall  be  kept  2.0  m  below  ground elevation at peir location.
Foundation elevation of wings & transition walls shall be kept 2.00m below ground level
• Afflux in drainage
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2
2
Due to contraction of river flow area at structure site, there shall be rise in High flood water elevation which is Afflux, which is calculated by formula
Afflux = h = (v /17.85 + 0.0152) (A /a - 1)
Where, v = is velocity in unobstructed stream in m/sec
A = Area of unobstructed stream in m2
A = Area of obstructed area of stream in m2
Where, V = 1.83 m/sec
A = 318.50 sq.
Area of obstructed stream = Area of stream unobstructed upto HFL - Area of peirs
There shall be 15 peirs in entire length of waterway at HFL
The average area of peirs shall be for 3 peirs only in river portion (for height between elevation 1332 to 1336.66) i.e. 4.66 m
The remaining 12 peirs shall have average height between elevation 1332 to 133.66 i.e. 4.66 m and 1.0 m.
Therefore area of peir
= 3x 1 x 4.66 + 12x1 x -4 66 + 1
2
= 13.98 + 33.6 = 47.58 sq. m
Obstructed water way 318.50 - 47.58 sq. m = 270.92 m2
Afflux = (1 83 /17 85 + 0.0152) {(318.50/270.92) -1}
= (0.188 + 0.0152) (1.38- 1)
= 0.1628 x 0.38     = 0.062 m
Afflux HFL = 1336.66 + 0.062 = 1336.722
Free board
Free board in drainage is the difference between lowest bottom elevation of slab of trouqh and afflux HFL of river
Free board = 1344.327 - 1336.722
= 7.605 m
Minimum free board required is 1.0m
Therefore there is sufficient tree board of 7.6m a.aifable, which is much more than rena free board of 1.00m.
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2Arjo Dedessa Irrigation Project
Hydraulic Design of Canal Structure
Loads and forces to be considered for design of box
Loads and forces to be considered for different components of trough are:- Top slab:- (i). Self weight
May 2007
(ii). Combination of Moving load of vehicle on road which shall create
maximum moments
Bottom slab:- (i). Self weight
(ii) Weight of water
Middle wall (i). Self weight
Side walls (i) Water pressure from inside (ii) self weight
The whole structure shall be monolithic structure and shall have fixed (rigid) joints.
The  stresses  acting  on  each  member  due  to  load  and  forces  acting  shall  be  obtained  by moment distribution method.
Length of Peirs
The total outer width of duct is  5.2 m. Adding for cut water and ease water of semi circular type, which shall continue up to the ground elevation. The radius of cut and ease water shall be taken as per dimension of peir cap i.e. 1.0 m.
Therefore total length of peirs shall be 5.2+1.0+1.0 = 7.2m
Water seals or stops
There shall be joints at every junction of trough between two consecutive bays. The joints shall be located at the center of peir. For preventing leakages from joints, either copper metal water seals  made of copper plate or corrugated synthetic  sheets  shall be provided The shape and width or corrugated synthetic Rubber water stops shall be as below (Refer sketch enclosed)
Bearings
It is proposed to provide road on top or trough. Therefore, suitable bearing shall be provided for transferring movements  of moving load from Superstructure to substructure. Bearings  shall be fixed between the bottom level of trough slab and top of peir. Separate bearings  shall be provided for each trough of bay.
Lining:-Canal adjacent to aqueduct is  in filling of about 7 m from bed elevation To reduce heavy  seepage from heavy  filling reach of canal, cement concrete lining shall be provided^ canal. The lining shall be 100mm thick C.C M15 casl in situ and work of lining shall be done
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with paver lining machines. Concrete lining shall be laid over 150 mm thick compacted sub grade. The sub grade material shall be semi pervious and non-swelling.
The detailed drawings for this structure are available at Drawing no-Ad-F-canal-F-11 to 14.
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Hydraulic Design of Canal Structure
Arjo Dectessa Irrigation project
Flood Level Computation for Aqueduct Crossing over Warra River
May 2007
Annexure - 2
Manning's n
0.03
Average Bed Slope, s      0.00125 1 in 800
Elev (m)
Area (Sq.m
)Perimeter (m
)R(m)
Q(m3/s
) Vel (rrV
s)Width (m
)
1338.00 1337.75 1337.50 1337.25 1337.00 1336.75 1336.50
1336.25 1336.00
556.78
508.01
461.22
416.39
373.53
332.72
294.02
257.44
222.97
203.19
199.35
191.46
183.57
175.67
167.33
158.85
150.37
141.88
2.74
2.55
2.41
2.27
2.13
1.99
1.85
1.71
1.57
1284.8
1117.0
976.78
847.18
727.90
62002
522.36
434.19
355.19
7  2.31 0  2.20
2.12 2.03
1.95
1.86
1.78
1.69
1.59
186.89
191.12
183.24
175.37
167.50
159.03
150.56
142.09
133.62
For Design Flood
Q=               584 m3/s Elev=     1336.66 m Width=   155.905 m
Rating Curve at Wama Crossing
1335 50 •
000                    20000                 40000                  60000
800 00                 1000 00
1200 00                1400 00
Discharge (m3/s)
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61OX Thk bottom slab of trough
♦
ELi34Wfi__
tL 1343 01U
T
------- WATER LEVEL LTTJF
Two dud 4 x 2m
US BudEL 1341 74
D2S BED 1341.649
0.30 Thk.bottom slab of (rough
TE10
■itrituf
Contraction Transition
5D____________
Expansion
Transition 4
SKETCH FOR HEAD LOSS IN CANAL TROUGH & DIFFERENT ELEVATION OF CANALArjo Dedessa Irrigation Project Hydraulic Design of Canal Structure
May 2007
2.2 DESIGN OF SYPHON AQUEDUCT FOR JEJEBA RIVER CROSSING WITH RIGHT PRIMARY CANAL AT 22.0 KM
The  Arjo-Dedessa  project  consists  of  providing  irrigation  facility  to  a  command  area  of  13665
ha (appox). A Dam is  proposed to be constructed on Dedessa river at Latitude 8°-31'-12" N and longitude 36°-40’-04”E. The dam site is  located about 1.5 km upstream of junction of Dedessa and Wama river. The height of dam is proposed to be 40.6 from the river bed. River bed elevation at Dam site is 1320m. The minimum draw down elevation proposed is 1350 m. Full Reservoir Level is  1356 m. Two-canal systems  are proposed to takeoff from dam, one from left flank  and other from right flank. The right bank  canal system is  proposed to takeoff from saddle No 2 in right flank of dam. Spill way is proposed to be located in saddle No 1 in right flank. The full supply  elevation of right bank  canal takeoff from right saddle No 2 is proposed to be 1348.00 m at takeoff point.
The primary canal is a contour canal, and has to cross many river, major and minor streams. The canal crosses the Wama River in its initial reach. Major command area of canal lies after crossing of Wama river The canal crosses at km 22 (appox) Jejeba tributary, which is a major tributary  to Wama river The catchment area of Jejeba tributary  at crossing point is  appox  60 sq. km. The hydraulic data of canal and Jejeba tributary are as follows.
CANAL DATA:-
1.  Distance of canal from origin up to crossing    point             22km
2. Full supply discharge of canal
3.  Bed width
4.  Full supply depth
5.  Longitudinal slope
6.66m3/sec 6.00 m
1.35 m
1 m 5000 (0.0002)
6.  Side slope
1.5:1 (H:V)
7.  Velocity in canal
0.623  m/sec 
8.  Free board
0.90m
Fixation of FSL at crossing point
The distance of canal up to crossing point from origin is 22 km. The canal longitudinal slope is 1 in 5000. There is head loss of 0.21 m for Wama aqueduct and cons.denng 0.30 Head loss of other structures up to JeJeba crossing, FSL of canal is worked out as follows.
FSL at crossing point = FSL at off take point - head loss due to slope in canal -
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head loss in other structures up to crossing points.
= 1348 - 22000 x 0.0002 - 0.21 - 0.30
= 1348-4.4-0.51
= 1348-4.91
= 1343. 09
Bed elevation of canal = FSL at crossing point - water depth of canal = 1343.09- 1.35 = 1341.74
Stream data
May 2007
1.  Catchment area
= 60 sq.km
3
2.  Peak flood discharge for 50 years return period = 74.00 m /sec
The discharge is computed as per rational formula given in hydrological report, depending upon the intensity of rainfall, time period and slope of river etc.
3.  River bed elevation =1339.50 (assumed)
4.  River longitudinal slope at crossing point
Calculation of slope is done from 1 in 50,000 map. Slope of 40 m is there in 3.8 km (Difference between contour upstream and downstream of crossing site)
Slope = 3800/40 = 1 in 95 say 1 in 100 (0.01)
Determination of HFL
The  value  of  peak  flood  by  rational  formula  is  74  m3/sec  Add  10%  for  safety  purpose Therefore the discharge considered for design shall be
3
= 74 + 7.4 = 81.4 = say 82 m /sec Determination of HFL is worked out from the formula
Q = AxV
3
Where, Q = maximum flood discharge in m /sec
A = Area of stream below HFL in m2 V = Velocity in m/sec for design flood V is determined by Manning's formula
1Vu r = - ,v r
n
3  s^3
Where, n = coefficient of rugocity = 0.030
R = for assumed value of HFL
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Hydraulic Design of Canal Structure
A = area of stream upto HFL
P = wetted perimeter and S = river bed slope = 0.01 River bed is assumed as 1339.50 m
Assume HFL of 1341.10 m Area = 36 x 1.6 12 =28.8
P =36.5
May 2007
/?
=
 2H=o.79           =0.85
36.5
3
Therefore, V = 1/0.030 x 0.85 (0.01 )2
= 33.33 x 0.85 x 0.1 = 2.83 m/sec
Q = A x V = 28.8 x 2.83 = 81.50 m3/sec
Required design discharge is 82 m /sec, therefore the assumed HFL of 1341 1 is adopted for design.
The HFL of Jejeba tributary is 1341.1 and canal bed elevation at crossing point is 1341.74 m, and there will be very  small free board between HFL and invert level of slab for canal. Therefore, it is proposed to provide syphon aqueduct at crossing point.
Proposal of - Canal for structure
The earthen banks of canals are discontinued and the canal water is proposed to be taken in concrete (RCC) trough. Canal is proposed to be flumed, service road shall be taken on top slab of trough.
Drainage water way
Lacey's regime perimeter width = 4.83^0
= 4.83-782
= 4.83x9.055
= 43.74 m
The velocity of unobstructed stream is 2 83 m/sec
Allowing velocity of 3m/sec through duct, area of opening required
J = — = 27.33 m2
3
Providing 3 duct of 4 m x 2.25 m
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Total area = 3 x 4 x 2.25 m =27 m2
Two peirs of 1.25 width and abutments of 2m width are proposed to be provided.
Total water way = 4 x 3 + 1.25 x 2 = 12+2.5
= 14.5 m Canal Waterway
May 2007
Bed width of canal is 6.00 m, water depth is 1.35 m, velocity is 0.623 m/sec. Allowing velocity of 1.20 m/sec through trough area required to pass canal discharge will be as follows:
Allowing water depth same as that of canal of 1.35 m, width of trough required
5 53
W=— = 4.11m
1.35
So provide duct width = 4.00 m
Allowing 0.60 m free board in canal the depth of duct shall be = 1.35 + 0.60 = 1.95 m = provide 2m
Provide duct of 4.0 m x 2.00 m size
Velocity in duct = — 66 = 1.23 m/sec.
4 x 1.35
Provide splay of 4 in 1 in contraction and 5:1 in expansion
6-4
Length of contraction transition = ------- x 4 = 4m
2
_?l
Length of expansion transition = --------- x 5 = 5m
In contraction and expansion transitions CC. floor of 600 mm thick, shall be provided with top 150 mm thick CC M-20 laid over 450 mm thick CC M-15.
Length of duct of flumed portion
~
14-5 +                   = 14 5 + - = 16.5 (50 % of abutment width)
= 16.5 m + 9 m for Road
= 25.5 say 26.0 m
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Head loss and bed levels at different section (Refer enclosed sketch)
At section 1-1
Area of canal = (B + nd )d = (6.00 + 1.5 x 1.35) 1.35 =10.83 m2 V = 0.623 m/sec
./ - .. .           . V2 0.6232
Velocity head = — =------------= 0.02m
_ __
2g 19.62
FSL elevation of canal = 1343.09
TEL = 1343.09 + 0.02 = 1343.11
Bed elevation = 1343.09 - 1.35 = 1341.74 m
At section 2-2
Area of trough = 4 x 1.35 = 5.4 m2
Velocity =1.23m/s
,    1.232       1.52
.. , ...
Velocity head =--------=-------- = 0.08
2g 19.62
Loss of head at contraction transition from section 1-1 to 2-2 Loss of head    _ Q 2 (1.232 - 0.623 )
2
2g
(1.52 -0.39)     0.2 x 1.13
May 2007
= 02------
i =-----------------------  = 0.012, n 1:9.62            19.62
TEL elevation at 2.2 = TEL at section 1-1- head loss in contraction transition = 1343.11 -0.012
= 1343.098 m
Water elevation at section 2.2 Bed elevation at section 2.2
= 1.43.098 - velocity head
= 1343.098 - 0.08 = 1343 .018m = 1343.018- 1.35 = 1341 668
Bottom elevation of trough slab = 1341.668 - 0.30 =
----- = 1341.368 (assuming Slab thickness of
0.30m)
At section 3-3
Section  of  trough  between  2-2  and  3-3  is  the  same.  Therefore  velocity  of  1.23  m/sec  and velocity head of 0.08 m shall remain the same.
Area of section is 5 4 m2.
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Wetted perimeter = 4+2x1.35 = 4+2.70 = 6.70m Hydraulic mean depth = 7? = -^ =      = 0.81
. . R % =0 87
Velocity is given by Manning formula
K = -7?^S^ n = 0 018 for concrete surface
n
^^Jl.23/(0.018)2 J-52 *0 0003 = q 00065
May 2007
7?^
(0.81)^
076
Hence head loss = 0.00065 x length of canal trough
= 0.00065 x 26
= 0 017 m
TEL elevation at sec 3-3 = TEL at sect 2-2 - Head loss between section
2-2 & 3-3 = 1343.098 - 0.017 = 1343.081
Water surface elevation at section 3.3
= TEL at section 3.3 - velocity head
=1343.081 - 0.08 = 1343.001
Bed elevation = water elevation - water depth
= 1343.01 - 1.35 = 1341.654
Bottom level of slab = 1341.654 - 0.30 = 1341.354
Section 4-4
Canal section at section 4-4 is same as that of section 1-1 Therefore velocity of 0 623 m/sec and velocity head = 0.02m shall remain same The trough velocity and velocity head of section 3.3 is 1.23 m/sec and 0.08 m
y 3  y 4 Head loss in expansion = 0.3 —------ —
((1.23)~ - (0.623)2) 19.62
(1.52-0,39) 19.62
TEL elevation at section 4-4
= TEL at section 3-3 - Head loss in expansion
= 1343.081-0.017 = 1343.064
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Water elevation at section 4-4 (FSL in canal)
= TEL at 4.4 - velocity head
= 1343.064 - 0.02 = 1343.044
Bed elevation at section 4-4
= Water surface elevation - water depth = 1343.044 - 1.35 = 1341.694m
Total head loss from U/s canal FSL to D/S canal FSL =1343.09 - 1343.044 = 0.046 m.
May 2007
The canal trough shall be having bottom and top slab of 0.30m thickness and side wall, of 0.45 m thickness. Road of DS7 standard as per Ethiopian Roads Authority shall be considered and design for moving loads as per bridge design manual 2 002 being used in Ethiopia shall be considered.
Total width of trough = 4 + 2 x 0.45 = 4.9 m
So peir length shall be = 4.9 + cut water + ease water
= 4.9 + 2x0.75 = 4 9 + 1.5 = 6.4 m
Road on Top shall have width
= 4.9-2 times width for railing wall of 0.20 m
= 4.9-2 x 0.2
= 4.9-0.4
= 4.5 m
Loss of head through siphon Barrel
Head loss through siphon Barrel is calculated by Unwin's formula
L V2
+ + />-) —
2g
Where, f, = Coefficient of loss of head at entry = 0.505
f 2 = a (1 + b/R) Where value of a and b are taken as 0.00316 and 0.030 for cement plaster of concrete surface
L - length or barrel in meter = width of trough = 4.9 m
R = hydraulic mean depth = — -     4x2.25 P 2(4 + 2.25)
V = 3 m/sec
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h = (1 + 0.505 + 0.00316 (1 + 0.030/0.72) 4.9/0.72) = (1+0.505 +0.022) ^962
19.62
HFL of stream as calculated earlier is 1341.1m
Keeping downstream HFL of stream as 1341.1
Upstream HFL with afflux shall be = D/S HFL + Head loss = 1341.1 + 0.70 = 1341.8m
• Up lift pressure on roof of trough slab
V2 32
Loss of head at entry = 0.505 — =----------= 0.505 = 0.23m 2g 19.62
Level difference of effective head at the entry
U/S HFL - head loss at entry = 1341.8-0.23
= 1341.57 m
May 2007
Minimum bottom level of slab (as calculated) for down stream end
= 1341.357
Hence uplift on trough slab
= 1341.57 - 1341.357
= 0.213 m or 0.213 tons/m2
In empty trough condition,
Only self-weight of the slab 0.3m thick which is 0.3 x 2.40 = 0.72 t/m shall counter balance the uplift pressure. Self-weight of trough itself is more than uplift pressure, hence no additional provision is required for design of slab for uplift pressure
The canal trough is proposed to be of rigid (fixed) joint type. T herefore. stresses s hall be calculated in each member of trough by moment distribution. Uplift pressure of 0 213 t/m shall also be considered in calculating stress  distribution and reinforcement shall be pToXed accordingly.
2
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Uplift pressure on floor of drainage
The size of drainage is proposed as 3 ducts of 4.0 m x 2.25 m.
May 2007
Top elevation of bed floor of drain = Bottom elevation of trough slab = 1341.357 - 2.25 =
1339.10
The lowest stream bed elevation level is 1339 50m
So stream bed shall be depressed by 1339.50 - 1339.10 = 0.40 m
Assume thickness of Bottom of RCC Slab = 1.00 m
The Bottom elevation or floor slab            = 1339.10 -1.0 = 1338 10 m
Since the floor of drain is to be depressed a sloping floor of CC in bed for upstream and down stream for 5 m length shall be provided with a cut off wall at the end of cc floor. The cut off wall shall be taken up to scour depth elevation.
Uplift
Calculation of pressure on floor slab of stream
The maximum uplift pressure on floor of stream shall be when the stream is dry and canal is at full supply elevation.
a) Static uplift Head on the barrel floor
= Bottom level of trough slab - 2.25
= 1341 354-2.25
= 1339.104 say 1339.10m
Bottom RL of floor considering 1.00 thick RCC. Slab = 1338.10 m
Assuming the sub soil water level up to the bed elevation of stream, the static uplift on floor
Bed elevation or stream - Bottom elevation
= 1339 50 - 1338.10 = 1.40 m = 1.40 Vm2
b) Seepage head:- Seepage head shall be maximum when canal is running at FSL and stream is dry.
The total seepage head = FSL or canal - bed level of stream
= 1343.09 - 1339.50       = 3.59 m say 3.60 m
Residual seepage head at center of first span of barrel is  calculated by  considering the seepage flow shall be along x-a-y. Neglecting floor depression (Refer enclosed sketch) The total length of seepage flow shall be as follows
1 Upstream C.C floor length in canal
from centre of abutment
4 nn ™
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2.  Abutment half width
3.  Half of barrel span
4.   End of drainage floor from Centre of floor % length ♦ 5.0 m
May 2007
1.00 m 2.00 m 7.50
Total length
14.50 m
Creep length up to centre of barrel = 7.00 m
.. Residual seepage head at centre point of floor
= 3.60(1-0.48)
= 3.60 x 0.52 = 1.87 m = 1 87 t/m2
Thus total uplift = Residual seepage head + static head
= 1.87 m + 1.40 m = 3.27 m, i.e. 3.27 tons/sq. m
3?7
If only CC floor is provided then required thickness shall be =      = 1.45m
2.25
But it is proposed to provide 1.0 m thick RCC. Floor, and structural design shall be done according to uplift pressure.
The uplift pressure that is exerted on floor shall be
= Total uplift pressure - self weight of slab
= 3.27 -2.25 = 1.12 t/m2
So floor shall be designed for residual pressure of 1 12 t/m2
Design of gravity floor
RCC raft for drainage floor off 1.00 m thick for length of 6.5 m shall be provided. After that length of gravity floor is proposed as 5.00 m. the residual seepage head at the end of RCC Floor and start of gravity floor shall be
Total creep length = 14.50 m and creep length up to end of RCC floor is
4 + 1 + 2 + 2.5 = 9.5 m
.. Residual seepage head = 3.60 (1 - 9.5 /14.5)
3.60(1 — 0.66) = 3.60x0.34
= 1.224 m
Since 1.0 m thick CC gravity floor is proposed static head from
stream bed elevation shall be
same as that or RCC floor i.e. 1 40 m
Total uplift pressure at junction
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= Static pressure + residual seepage floor = 1.40 + 1.224 = 2.624 t/sq m
Thickness of floor required = 2.624/2.25 = 1.16 m
May 2007
3
Provide 1.25 m CC gravity floor at junction of RCC floor, which shall be reduced to 1.00 m at end. A cutoff wall shall be provided at the end of gravity floor
Scour depth
Scour depth is calculated by Unwin's formula
Scour depth by formula
R = 1.35 (q/f)V3
q = discharge per unit length and f = sill factor as per bed material
Total clear length = 4 x 3 = 12 m
q = 82/12 = 6.83m /m length
Take f = 2 for heavy sand
R= 1.35 x (6.83/2)1/3
= 1.35 x 1.51
= 2.03 m
Scour depth for pier shall be two times the scour depth calculated above
= 2x2.03
= 4 06 m from HFL
Foundation elevation for pier
= HFL-4.06
=1341.1 -4.06 = 1337.04 m - provide 1337.0m
For abutment foundation shall be taken as 1.5 times scour depth
= 1.5x2.03
= 3.045
= 3.05 m, say
Foundation elevation of abutment =1341.1 - 3.05
= 1338.05
Provide 1338.00 m
The foundation elevation of (loot slat, Is 1338.10 and that of gtavlt, Hoot is 1339 ,n , „ 1337.85
So keep foundation of abutment at 1337.85m
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May 2007
Upstream and downstream cut off wall shall also be kept at 1337.85 m. elevation
Normal scour depth by Lacey's formula
D'=0.79 (43.74/12)°67
R = Scour depth D' - R(W/L) 0.67
R = Hydraulic mean depth
W = Lacey's width
L = actual width provided
R = 0.79 (for HFL)
W= 43.74 L=12
= 0.79x2.38
= 1.88 m
Since  this  depth  is  less  than  scour  depth  calculated  by  previous  formula  the  scour  depth considered and foundation elevation fixed earlier shall be provided
Free board
In canal free board of 0.7 m is provided
Top bank elevation in down steam of structure shall be
FSL of canal + 0.70 m
=1343.05 + 0.70
=1343.75
In the stream the upstream HFL with afflux is 1341.8 m
So the difference between top of canal banks and afflux HFL
= 1343.75 - 1341.8 = 1.95
Minimum free board required is one meter. Available free board is 1.95 m. which is more than required.
The canal trough shall be structurally designed for following loading and pressure
Top slab = Self weight
= load of moving traffic vehicle load as per bridge design manual 2002 to create maximum bending moment
Side walls = Self weight
= Water pressure from inside for height of 1.35 m
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Bottom slab
i) Condition when canal full and drainage dry
- Self weight
- Water pressure of 1 35m column
ii)  Condition when canal is dry and drainage at HFL
- Self weight - acting down stream
- Uplift pressure on bottom of slab
For Drain barrel
Bottom slab
i) When drain is full and canal dry
-    self weight
-    weight of water up to afflux HFL.
ii. When drain dry and canal is full
i. Self weight acting down ward ii. Uplift pressure acting upwards
May 2007
For Piers Self-weight * max weight of trough when canal is running full ♦ load of one span for max vehicular load.
For Abutment
-self weight
- Earth pressure horizontal from back (when drainage is dry)
- Load of 1/2 span for max. vehicular road.
• Upstream and downstream pervious protection for canal
Previous protection consisting of 0.45 m thick CC block or stone pitching laid over 0.15, thick gravel for 4.0m length shall be provided in upstream and downstream after impervious concrete floor in transitions. The protection shall be provided in canal bed and side slopes. A Toe wall shall be provided at the end of pervious protection for a depth of 1.0 m. Top width of toe wall shall be kept as 0.5 m and bottom width as 1.00 m for 0.30 m he.ght from foundation. The detailed drawings for this structure are available at Drawing No. AD-F-Canal-F-15 to 16
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75U5CBL '>46.20 5.0
urafatriav-gQ—
Daplh q! Jump
SKETCH FOR DETERMINING DEPTH AT JUMP
US TEL. 134Q06
I'SflgdEl, ol 9§cap» 1339 06ArJo Dedessa Irrigation Project
Hydraulic Design of Canal Structure
2.3 Design of Canal Syphon For Right Bank Canal At Km 2.00
May 2007
The Arjo-Dedessa Irrigation project is one of the identified projects for development of Irrigation area in Ethiopia. In the past studies were conducted for identification of dam site location and command area. After studies for different proposal are examined and reconnaissance visit to different sites, dam site at location Latitude. 8°-31’-12” and Longitude 36°-40,-04” E on Dedessa river is considered suitable. The height of dam is proposed to be 40.6 m from river bed elevation 1920 m. The proposed MDDL is 1350 m for canal outlets The project proposal consists of providing irrigation facility on both flanks of Dedessa river. For irrigation two canals are proposed, one on the left bank and another on right bank. The right bank canal is proposed to take off from a saddle No2 situated on right flank about 2.5km from main dam In the saddle No. 1 on right flank, it is proposed to provide spillway structure.
The right bank canal is a contour canal having about 40 secondary canals takeoff from primary canal. The main structure on right bank canal is Wama River aqueduct about 8 km from takeoff point of canal from dam. A Number of small tributaries are crossing the canal before Wama river for which suitable structures are to be designed.
A very small drain crosses Right bank canal at about 2 km from takeoff point. The catchment area of small tributary or drain is about 2.5 sq km. The FSL of canal at off take point below dam is fixed as 1348.0m.
The hydrological data of canal and stream are as below.
Canal Data
1
Full Supply discharge
=
7.52 m3/sec
2
Full supply depth
=
1.40 m
3
Bed width
=
6.25 m
4
Longitudinal Slope
=
1 in 5000 (0.0002)
5
Side slope
=
1.5: 1 (H:V)
6
Velocity
=
0.643 m/sec
7
FSL at offtake points below dam
=
1348.0
8
Bed elevation at off take point
=
1346 6
9
Distance of crossing of drain
from offtake
=
2.2 km
10
Ground elevation on bank (av)
=
1948.5 m (Assumed)
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Drainage details
1         Catchment area
May 2007
2.5 sq. km
22
Peak flood value for 25 year flood
10.0 m3/sec
33
River slope from 1350 to 1330 m
1 in 50 (0 02) in 1000 m
44
lowest stream bed assumed elevation
1346.00 m
55
Bank elevation
1348.00 m
H.F.L. of Drains
The peak flood discharge of drainage for 25 year return flood is computed as10 00 m3/sec. The flood computation has  been done from the rational formulas  and procedure is  given in hydrological report of the Project.
The discharge of drain
The discharge as per rational formula is = 10.00 m /sec
Since the discharge computation is as per Rotational formula, and catchment area is small add extra discharge of 30% (3.0 m /sec) for computation of HFL for safety 3.0 m /sec
3
3
3
3
Therefore Total discharge = 13.00 m /sec
The cross section of drain is such that in 10m distance elevation of 1347.00m is available Assuming HFL at 1347 0 m.
Area at HFL = — = 5 m2 2
/?2,3=0.59
Velocity in drain = V = -R2,iS''2 Consider n = 0.03
n
K =------ x0.59(0 02)1'2
0.03
= 2.78 m/sec
Q = A x V = 5 x 2.78 = 13.90 m3/sec
3
The peak design discharge considered is 13.00 m /sec.
Therefore H FL of 1347.0m elevations considered is adopted for design Canal FSL and bed elevation at crossing point.
The canal FSL. at off take point
= 1348.00
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The longitudinal slope of canal is               =  1 in 5000 (0.0002) The distance of canal from off take point = 2.00 km 2000
May 2007
FSL at crossing point
=  FSL at off take - 2000 x 0.0002
(Head loss in structure considered as 0.04 m)
= 1348.0-0 40-0.04= 1347.56
Canal bed elevation at crossing point = FSL - Full supply depth
= 1347.56- 1.40
= 1346.16
Since discharge of drain is  very  small and also bed elevation of canal and river bed are practically at same level and distance of drain is not more than 25 m at ground elevation, therefore canal syphon structure is proposed at this crossing point.
Section of drainage channel
As per Lacey’s formula the width of water way = 4.73 y[Q
= 4.73 Vl3 = 4.73 x 3.63 = 17 41 m
But the bed width at HFL of drainage is only 10 m Therefore drain section shall be kept as per natural water way.
Canal Waterway
The discharge of canal is =
Bed width is Velocity Normal area
=
=
=
7.52 m3/sec
6.25 m
0.643 m/sec
(B + nd)d = (6.25 + 1.5 x 1.4) 14 11.69 m2/sec
In the barrel velocity proposed is 2 x 0.643 = 1 286 m/sec Provide velocity of 1.35 m/sec in barrel for canal
Area of barrel required          =          n? "557 m2 Depth of water in trough is proposed to be 1.6 m
So width of barrel required =
Provide barrel width 3.25 m Provide barrel size
557 o
—- = 3.48 m
1.6
= 3.25m x 1.6m = 5.2 m2
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7.52
Actual velocity in barrel = —;-------- = 1-45 m/sec
May 2007
7
3.25x1.6
This velocity shall be checked for s ub critical flow condition. For sub critical flow condition Froude number should be less than one. Froude number is calculated as
F = v _
145
y[gd >/9.81xl.6
v = 1.45
d = 1.6
= Lil=o.37
3.96
Since value of F is less than one. the flow in barrel shall be sub critical.
Head loss and bed levels at different section of canal barrel Width of canal syphon barrel is 3.25 m and width of canal is 6.25 m Provide splay of 3: 1 in contraction and 4:1 in expansion.
Length of contraction transition =
3 = 4.5m , Say 5 m.
Length of expansion transition =------- ------- x 4 = 6 m
Since the width of drainage at elevation 1348.0m is 25 m, the length of syphon barrel of canal below drainage is proposed to be of 25m. Losses at different - Section are calculated as given below. (Refer enclosed sketch)
At section 1-1
The FSL elevation at section 1-1 = 1347.56
Area of normal canal section Velocity in canal
Velocity head TEL at section 1-1
= 11.69 m2
= 0.643 m/sec
v 2 0.6432
= — = ----------- = 0.02 2g 19.62
= FSL + 0.02
1347.56 + 0.02 = 1347.58
Bed elevation of canal
At section 2-2
- 1346.16 m
,1 is proposed .hat at enir, and exit the depth ot water be increased to 1.9m trom 1 6 m keeninn the top ot barrel 0.1m beiow FSL at .bis  point. The ieeei barrel at entry  and exit sbail be
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May 2007
higher than that at centre portion. This shall help in keeping ends of barrel submerged and barrel shall run full for better syphoning.
Area of section at entry and exit = 3.25 x 1.9 = 6.175 m‘ Velocity = — = -1.22 m/sec
i        i nr
A 6.175
Velocity head = — =
2g 19.62          19.62 Loss of head between sections 1-1 to 2-2
- — = 1,35 = 0.07 m
19.62
Say                0.01
TEL at section 2-2
TEL at section 1-1 - head loss =1347.58 - 0.01 = 1347.57m
RL of water surface = TEL - Velocity head = 1347.57 - 0.07 = 1347.50 m
Elevation of bed (Invert Elevation) = Water surface - water depth - thickness of upper slab = 1347.57 - 1.9 - 0.10 - 0.3 (assuming thickness of slab as 0.30 m)
= 1345.20 m
Bottom elevation of Bottom slab of trough = 1345.20 - 0.30 = 1344.90 m
Head loss through barrel
Head loss through barrel is given by formula
/ y1
h = (i+fl+f2 -) — 
/? 2g
f, = 0 08 for Bell mouth entry
Where, a and b are constants depending upon the surface of flow, and R = hydraulic mean depth of trough
For concrete and cement plaster surface a = 0.00316 and b = 0 10
= 0.2 x 148 °
41
- = 0.2 x 0 048 = 0.01
Therefore f2 = 0.00316 (1 + -^-
0.54
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= 0.00316(1+0.19) = 0.00316 x 1.19
= 0.0038
Length of barrel considered is 25 m Velocity in barrel = 1.45 m/sec Substituting values in formula
May 2007
1.2^a2._10 = o 12
19.62
At section 3-3
Elevation of TEL
Elevation of TEL at sec 2-2 - head loss through barrel
= 1347.50-0.12 = 1347.38 m
Elevation of water surface
= TEL of sec. 3-3 - velocity head
= 1347.38-0.07        =         1347.31 m
Bed elevation of floor = Water surface elevation - Water depth at exit - 0.3 thicken of slab
= 1347.31 - 1.9 - 0.10 - 0.30
= 1345.01m
Bottom elevation of bottom slab = 1345.01 - 0.3
= 1344.71m
The sections at 3-3 and 4-A are similar to section at 2-2 and 1-1, therefore velocities at section 3-3 and 4-4 and velocity head shall be same as per section 2-2 and 1-1 respectively
Velocity at 3-3         =1.16 m/sec Velocity at 4-4         = 0.643 m/sec Velocity head at 4-4 = 0.02
Loss of head in expansion transition
= 03 (<-V^ xn^ -
1 162 0
-^)
2
2g = 0-3d.35-0.41)
19.62
19.62
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TEL at section 4-4 =TEL at section 3-3 - 0.014
= 1347.38-0.014 = 1347.366
Elevation of water level = TEL - velocity head
= 1347.366 - 0.02 = 1347.346 m Bed elevation of canal = 1347.346 -1.40
= 1345.946 m
Total loss of head in structure from upstream to downstream = U/S FSL - D/S FSL
= 1347.56 - 1347.346 = 0.214 m
Barrel details
May 2007
The barrel of syphon is proposed to be of size 3.25 mx 1.60 m, the top and bottom slab are proposed to be of RCC, 0.30 m thick and side wall 0.45 m thick. The slabs and side wall of barrel shall be designed for stresses  calculated by  moment distribution. As  the velocity  in drainage channel is  comparatively  high and drainage is  proposed to be carried in earthen section, therefore to avoid damage due to abrasion to slab of syphon duct an over burden of earth of minimum 0.6 m thickness shall be provided below the drainage channel bed elevation.
The top of barrel elevation in central portion = Drainage bed elevation - 0.6
= 1346.00 - 0.6 = 1345.4 m
Bottom elevation of top slab =1345.4 - 0.30 = 1345.1
Invert elevation of bottom slab of barrel = Bottom elevation of top slab - water depth
= 1345.1 - 1.6 = 1343.5
Bottom elevation of Bottom slab = 1343.5 - 0.3
= 1343.2 m
It is proposed to provide 0.20 thick base lean concrete of M-10 below bottom slab of barrel. The foundation elevation shall then be
= 1343.2-0.2 = 1343.00 m
Bed elevations of slab at different points in barrel are:-
1        At entry         1345.2 m
2         At exit           1345.01 m
3         In barrel at length of 14m =1343.50m under base of drain.
The invert elevation under drain shall be joined by slope of aDDox      1  in i   tk       , r     v. appux. i   in o. The
length of sloDe
belween entry to barrel and to center portion sbalt be   6   nt and that of center podion to exit end
of barrel the length shall be 5.0 m.
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Impervious Floor
May 2007
2
Impervious concrete floor shall be provided for entire length of contraction and expansion transitions.
Length of impervious floor on upstream = 5.00m
Length of impervious floor on downstream = 6.00m
Uplift Pressure on barrel floor and impervious floor
The maximum uplift pressure on barrel floor and impervious floor shall act when the canal is dry and drainage at HFL.
The HFL of drain = 1347.00 m
The bottom elevation of foundation at center portion = 1343.00 m
Total uplift pressure = 4.00m = 4 t/m2
Bottom Slab shall be designed for uplift pressure of 4 t/m  for 14 m length For slab at entry the uplift pressure shall be of two types, static pressure and seepage uplift pressure
Static head at point B, assuming sub soil water level upto bed elevation of canal = Bed elevation of canal - foundation elevation at points B.
= 1346.16-(1343.50-0.50)
= 1346.16- 1343.00 = 3.16m
Seepage head at B = HFL - 1343.50 = 1347 - 1343.50 = 3.50 m Total creep length = 9.10 + 6 + 5      = 20.10 m (Refer enclosed sketch) Length upto B = 6 + 4.10 = 10.10 m
Seepage pressure = 3.50 (1               = 3.50 (1 - 0.67)
= 1.16m
So total head = static head + seepage head = 3.16+1.16 = 4.32 m = 4.32 t/m2
2
2
So uplift at B=4.32 t/m  and at C the up lift shall be 4 t/m
C.c Floor at B. shall also be subjected to same uplift pressure as that of Barrel trough = 4 32 Thickness of floor required at point B shall be =      - =
2.25
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Hydraulic Design of Canal Structure
May 2007
Provide thickness  1.00m at B reduce to 0.6m at A. As  there shall be no uplift pressure, therefore, minimum thickness  of 0.6m is  proposed. However floor shall be designed as 
2
reinforced cement concrete for uplift pressure of 1.92 - 1.00 = 0.92 m = 0.92 t/m .
For exit end and down stream floor concrete at point D, E, F. the uplift pressure at D shall be same as for barrel slab i.e 4 t/m2
Static head
= D/S canal bed elevation - foundation elevation at point F
= 1345.936-(1342.51 - 0.50) where 0.50 is thickness floor and base concrete = 1345.936 - 1343.00 = 2.936 say 2.95m = 2.95 t/m2
Seepage head = HFL - 1343.50
= 1347- 1342.9 = 3.50 m
Total creep length = 41+5+6 =15.10m
Length upto point E = 4.5 + 5 = 9.1m
91
Uplift due to seepage = 3.5 (1-——) = 3.5 x (1-0.60)
= 3.5 x 0.40 = 1.40 m Total uplift at E = 2.95 + 1.40 = 4.35m = 4.35 Vsq. m
For Barrel Slab
2
2
So uplift pressure at D shall be 4 t/m  and for floor at E = 4.35 t/m The floor at E shall have same uplift pressure of 4.35 t/m2 Thickness of C.C floor required at E
Provide floor thickness of 1.00m at point E to reduce to minimum thickness of 0 6m at F. At F there shall be no uplift pressure, therefore, minimum thickness is provided. The floor shall be designed as reinforced cement concrete.
The floor shall be designed for uplift pressure of 1.93 - 1 00 = 0 93 say 1 t/m2 There shall be 0.20m thick foundation concrete of M10 below RCC floor
85Arjo Dedessa Irrigation Project
Hydraulic Design of Canal Structure Upstream and downstream protection
May 2007
Upstream and downstream pervious protection for 5m lengths in upstream and 6.0 m length is downstream shall be provided beyond c.c  floor. The protection shall be given in bed and slopes of canal 0.6m above FSL of canal. The protection shall consists of 0.6m thick c.c block or stone pitching laid over 0.3m gravel or well graded filter.
Load and Stresses on trough
The  slabs  of  barrel  shall  be  subjected  to  following  loads  and  pressure,  which  shall  be considered for design
1        Top slab
i)  Self weight
ii) Earth load
iii) Weight of water below saturation level
2         Bottom slab
i) Self weight
ii) Uplift pressure
iii) Reaction of soil resulting due to load of structure on foundation.
3         Side walls shall be tested for two conditions
i)  High flood in the drain and canal empty.
In this case earth pressure of soil and water shall act from out
side on Barrel walls.
ii) When no water in drain while barrel is full
In this case water pressure shall act from inside and saturated
earth from out side.
The barrel shall be of RCC. monolithic with rigid ends and shall bedes.gned as continuous Structure. The stresses in members shall be obtained by moment distribution method.
The thickness of barrel slab and side walls shall be 0.30 thick The barrel size in center is 3 25 mx 1.6 m. Therefore lengths of horizontal slab shall be 3.25 + 2x0 3 = 3 85m
Length of vertical side walls shall be 1.60 + 2 x 0.30 = 2 20m
At entty and exit ends ot battel the size ot battel Is 3.25 n x 1 90 m so >ength  o< tnembets a, entry and exit end shall be as follows:                                                                                          rs a
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For horizontal slab 3.25 + 0.6 = 3.85 m Vertical members 1.9 + 0.6             = 2.5 m
May 2007
The detailed drawings for this structure is available at Drawing  no. AD-F-Canal-F-17 & 18.
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May 2007
2.4 Design of Aqueduct (With N ormal C anal Section) at K m 2 5.54 of Left Primary Canal
Canal data
1.  Canal discharge                    =         7.587m3/sec 2.  Full supply depth                  =         1.33 m
3. Canal bed width                    =         7.0 m
4.  Canal bed slop                      =         0.0002
5. Side slopes
=           1.5H:1V
6.  Full supply elevation
=
1342.69 m
7.  Canal bed elevation
=
1341.36 m
8.  Free board
=
0.5 m
Stream data
1
Catchments area
=
1.8 km2
2.
Maximum flood discharge
=
3.59 m3/sec
3.
Stream bed elevation
=
1339.5m
4.
Average river slope
=
from (1:10,000 map)
A
Stream elevations 300 m u/s and 300 m D/s starting from crossing location are At, 300 m u/s elevation = 1349.0 m
300m D/s elevation = 1329.5m
,           1349.0-1329.5
Average - slope =----------------------= 0.0325
300 + 300
The peak flood discharge as per rational formula for 25 year return
Period flood
=         3.59 m3/sec
For design purposes Add 20% extra           =         0.72 m2/sec
Total flood discharge for design       =         4.31 m3/sec
Stream high flood level determination
The  HFL  elevation  is  determined,  after  assuming  an  elevation  for  HFL.  Using  Design formulae: - Q = A x V
Where, Q = Design Discharge of stream considered A = Area of stream below HFL in m2
V = Velocity in m/sec for design flood V = velocity is calculated by Manning's formula
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V = -R2 3S1'2 where, n = coefficient of rugocity assumed as 0.03
n
R=Hydraulic mean depth = —
P=wetted perimeter
S= Average slope of stream
May 2007
Assume HFL at 1339.8 - from the cross section of the stream on the graph sheet
2
P= 7o.32+l.82 + Vo.32+22 P= 18 + 2.02
P = 20.02
V = -R2I3S'12
n
V = — x(O.15)2,3x(O.O325)1'2
0.03
\l - 1.696 m/sec
'
3
Q - A x V = 3m2 x 1.696 m3/s = 5.088 m3/sec.
Design discharge = 4.31 m /sec
So design discharge is little more than required design flood
The assumed HFL of 1339.8 m for flood discharge is adopted for design
Drainage waterway
According to Lacey's formula perimeter
W = 4.7370
W = 4.73 74.308
= 9.82 m
Provide 2 duct of width 4.5 m and assume pier thickness as1m
Total clear water way =2x4.5 =9m
Pier thickness = 1_m
Total waterway between abutments = 10 m
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Canal water way
It is proposed to carry canal across stream in earthen section
May 2007
It is proposed to pass stream discharge through twin duct of 4.5 m width with water depth of
0.30 m i.e. depth of water upto HFL above stream - bed elevation.
The width of stream at HFL is 20 m, where as the width provided is 9.00 m
Original area of steam is 3.00 m2
Area of stream provided in duct = 9 x 0.3 = 2.7 m2
Due to reduction of area from 3.0 m2  to 2.7 m2. there shall be afflux, which is calculated by Moleworth's formula
(V
------ + 0.0152
2
<17.85             J
UJ
....
• i a. •                < Q Total design discharge
Where, V = is velocity in duct = — =-------------- -------------- —
a 
Area of duct
A = Area of waterway unobstructed
a = Area of water way provided in duct
V = — = 1.60m/sec
2.7
A = 3.0 m and a = 2.7 m2
Substituting values
= (0.1424*0.0152) (1.23-1)
= 0.1586 x0.23
= 0.04 m
So upstream HFL with afflux shall be
= 1339.8 *0.04 = 1339.84
It is proposed to provide abutment over which 0.50 m thick R r r  k.ii u
e
micK k.c.C shall be provided The earth
cushion of 0.5m shall be provided between (op of slab elevadon and canal bed ele.af.on
Therefore bottom elevation of slab and top elevation of peir shall be
= Canal bed elevation - earth cushion depth - thickness of slab
= 1341.36-0.5-0.50 =1340.36
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May 2007
Free board above afflux HFL = Bottom elevation of slab - Afflux HFL of stream
= 1340.36- 1339.84
= 0.52 m
The free board is just enough to accommodate the required discharge with afflux HFL and is more than required free board of 0.5 m.
Scour depth calculation and determination of foundation elevation
The determination of foundation elevation of abutments, wings and pier is dependent on the scour depth, which is measured below the highest flood elevation.
Calculation of scour depth by two formulas (Lacey's & Unwin's formula)
• Using Lacey's formula       -R =
f - silt factor
Q(total discharge)
effective linear waterway
4.31 m2 / sec
= 0.48 m/sec Assuming light sand is available is bed stream, value of f = 1.00
So, R = 1.35    48/[/1         = 0.83 m say 1.00 m
• Using Unwin’s formula
D' = R( /  )
w
067
l
Where,                R = hydraulic mean depth corresponding HFL
W = Lacey’s regum width = 4.73 y]Q
= 4.73 V43T= 9.82 m
L = obstructed width of water way of river = 9.00 m
D'-0.15 (9.8%)“’
D' =0.16 m
Scour depth by Lacey's formula is more therefore safe. So R= 1.00 m is considered for fixation of foundation elevation
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Foundation elevation of abutments & wing wall
Max scour depth = 1.5 x normal scour depth
= 1.5 x 1.00
= 1.50 m
So foundation level for abutments and wing walls
= HFL-1.50 m
= 1339.8- 1.50 m
= 1338.30 m
Foundation elevation of pier
Max scour depth = 2 * normal scour depth
= 2*1.00 m
= 2.0 m
So foundation level for pier = 1339.8-2.00
= 1337,8 m
Length of duct shall be worked out from the enclosed sketch Total length =           1+2.50+13.10+5.00+1 = 22.60 m Design for floor of stream
May 2007
It is proposed to provide C.C floor in the duct and in u/s and D/s approach and exit between wings.
The ground elevation near stream where canal slope joins NSL is 1340.0 and top bank level is 1343.39
Then the sloping length of canal with 2.1 slopes
= 2*(1343.39 -1340.0)-1
= 2*3.39-1
= 6.78-1 = 5.78 say 6.0 m
So provide cc floor in approach and exit end for 6.0 m lengths and for width varying between wings.
Provide thickness of floor as 0.5m in duct
So, bottom elevation of floor
= Stream bed level - 0.5
= 1339.5-0.5 = 1339.0 m
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May 2007
On t he f loor maximum u plift is e xerted when t he c anal r uns full and d rain is d ry. T herefore maximum uplift will be
= FSL of canal- floor slab level
= 1342.69- 13639.0
= 3.69m = 3.69 t/m2
It is proposed to provide cc lining in canal for filling portion adjacent to structure the lining shall be 100 mm thick CC M-20 cost in situ, laid over 150 mm thick compacted sub grade. The sub grade material shall be pervious and non-swelling. Due to provision of lining the uplift pressure is considered as 50 % of total Lead
2
2
So, uplift becomes = 50% * 3.69 t/m  = 1.845 t/m
Residual uplift pressure on the slab will be:
= 1.845-0.5* 2.25
= 0.720 t/m2
So, floor shall be RCC and shall be designed for uplift pressure of 0.72 t/m2
Upstream and down stream protection and cut off
Pervious protection of 0.45 thickness consisting of 0.3m thick cc blocks or stone pitching laid over 0.15m thick gravel shall be provided beyond RCC floor. The length of pervious protection on u/s and D/s of stream shall be for 5.0m
•  A  cut  wall  of  0.5m  top  width  to  a  depth  of  1.5m  below  the  steam  bed  level  is proposed to be provided. The cut off shall be provided at the end of u/s and D/s RCC floor. The bottom width shall be 1.00 m
A toe wall at the end of pervious protection shall be provided in upstream and down stream The top width of toe wall shall be 0.5m, depth 1.00m below bed elevation of stream and bottom width 0.8m
Top and bottom width of abutments wings and return walls
For abutments: The top width of abutment shall be kept as 1.00 m the top elevation shall be at elevation of slab i.e at EL. 1340.86 m
The width at foundation teuet (1338.30) shatt be 0.5 times difference between top eleuabon and foundation elevation
Bottom width = (1340-86 - 1338.30) x 0.5
= 1.28 m provide 1.5m at foundation elevation and 1 25 m at
0.3 above foundation elevation i.e.1338.60 m.
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Wing wall and return wall
The top width of wing wall and return wall shall be kept as 0.5 m The bottom width shall be kept as.
0.5 x (top elevation - foundation elevation)
May 2007
The wing wall shall have maximum top elevation as that of top of canal bank i.e 1343.39 and minimum top elevation as 1341.00. Return wall shall also have top elevation as 1341.0 m
Maximum bottom width
= 0.5 (1343.39 - 1338.30) = 0.5 x 5.09
=  2.545  m  provide  2.75  m  at  foundation  elevation  and  2.5  m  at  0.3  above foundation elevation i.e. 1338.60 m
Minimum bottom width = 0.5 (1341.0 1338.30) = 1.35 m provide 1.50 m at foundation elevation and 1.25 m at 0.3 above foundation elevation i.e. 1338.60
The f ace o n w ater s ide shall be v ertical u p t o 0.5 mb elow g round level a nd w idth s hall b e increased on other side, from 0.5 m below ground elevation width shall increase on both sides.
The detailed drawings for this structure are available at Drawing no. Ad-F-canal-F-19 & 20
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3. ROAD BRIDGES/FOOT BRIGE
3.1 Design of Road Bridge at Km -15 Of Right Primary Canal
May 2007
In Arjo - Dedessa Project Right Primary  canal after crossing Wama River, crosses  a road connecting Ketketo hot spring to Wama Adere town. The Ketketo hot spring is  an important tourist spot. Right Primary  canal at 15 km crosses  the road at 15 km. A road Bridge is proposed to be constructed at this crossing.
The details of canal are:-
1
Full supply discharge
6.66 me/sec
2
Bed width
6.00 m
3
Full supply depth
1.35 m
4
Velocity
0.623 m/sec
5
Canal longitudinal slope
1 in 5000 (0.0002)
6
Side slopes
1.5:1 (H: V)
7
Free board
0.8 m
The FSL at offtake point of canal is 1348.00 m so canal FSL at crossing point of bridge shall be
=    1348.0 -
’ Head ,oss at Wama crossing - Head loss at other
structures = 1348.00 - 3 - 0.21 - 0.24 = 1348 - 3.45 = 1344.55 m
FSL at crossing is 1344.55 m
Canal Bed level at crossing point = 1344.55 - 1.35 = 1343 20 m
The Road elevation at crossing point is assumed as 1345.50 m. General ground elevation is 1345.00 m.
Canal Water way
The existing canal water way 
= (B+nd)d
= (6+ 1.5 x 1.35) 1.35= 10.83 m2
Water Way for Bridge
Providing width of structure between abutments equal to bed width of canal
proposed to provide waterway of single span of 6m with watAr do .k 303
cans, or 1.35 m.
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Then velocity in bridge portion shall be:- Velocity = —         = 0.82 m/sec
6x1.35
May 2007
If velocity is increased to two times the velocity in canal, then velocity shall be 2 x 0.623 =
1.246 m/sec
Assuming velocity of 1.20m/sec and water depth of 1.35 m then linear water way required shall be
5.55 sq.m
The linear waterway of Bridge shall not be less than 70% of canal bed width.
70% of canal bed width = 6x0.7 = 4.2 m
Since water way of 4.11 m as calculated above is less than 4.2 m (70% or bed width of canal), therefore provide waterway of 5.0 m with single span and water depth of 1.35m. Therefore with waterway width of 5 m and water depth of velocity under bridge shall be
Area = 5 x 1.35 = 6.75 m2
V = — = —— =0.987 m/sec
A 5.0x1.35
So provide width of 5 m and water depth of 1.35 m
Afflux
Due to contraction of area from 10.83 to 6.75 m2  there shall be an afflux. Afflux is calculated by Mole worth's formulae.
A=
{17.85 J
(0.987) +qq|52
yl +0.015} 17.85
f- 1’
-'
16.75 J
= f22Zl +0.01521 {2.57-1} [17.85              J
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= {0.055 + 0.0152} x 1.57 = (0.0702) x 1.57 = 0.11m
May 2007
The difference between FSL upstream and downstream of canal shall be kept equal to afflux.
Upstream FSL = 1344.55 m
Downstream FSL = 1344.55- 0.11 = 1344.44 m
Bed elevation downstream = 1344.44 - 1.35 = 1343.09 m
• Scour depth
Scour depth is calculated by formula
where f = is silt factor and q is discharge per running meter
Here f is taken as 1.00
q = Discharge per running meter = yy = 1.33 m
Substituting values
fl 33Y/J
Scour depth R = 1.35 I —y I      = 1.35 x (1.33),/J = 1.35 x 1 09
- 1.48 m, say 1.50 m
Foundation shall be taken 1.5 times scour depth below D/s FSL of canal therefore foundation depth of abutment shall be
= 1.48x1.50 = 2.22 m
Foundation depth for abutment shall be = Downstream FSL of canal - scour depth Therefore foundation elevation = 1344.44 - 2.22 = 1342.22 m
Keep foundation at 1342.20 m
Upstream canal bed elevation is at 1343.20
Therefore depth of foundation below canal bed shall be 1.00 m
Free board
The free board of 0.6 m shall be provided between u/s FSL of r^i u
Road slab.
So Bottom elevation of Road slab = Upstream FSL + free board
= 1344.55 + 0.6
= 1345.15 m
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The thickness of road is assumed as 0.6 m
So top of road elevation shall be = 1345.15 + 0.60 = 1345.75 m
May 2007
In  the  upstream  the  canal  bed  shall  be  flumed  from  6.00  m  to  5.00  m  in  5  m  length  and  in downstream expansion of canal bed from 5.00 m to 6.00 m in 5 m length.
Road Width
It is proposed to provide 4.0 m clear width of road, curb 0.3 high 0.65 m wide and parapet wall of 0.5 m thickness  and 0.5 m high above curb. Total height of parapet wall shall be 0.8 m above road elevation including height of curb. So total width of slab shall be: = 4 0 + 2 x 0.65 = 5.3 m
Abutments
Abutments  shall be of 1 m width at top and shall be of CC M15. Bottom width at foundation elevation level shall be 0.5 times  height, height measured from foundation elevation = 0.5 x (1345.75 - 1342.20) = 0.5 x 3.55 = 1.775 m
Provide width of 2.0 m at EL 1342.50 and 2.25 m at foundation elevation -1342.20.
Wing and parapet walls shall be provided with top width of 0.5 m, and height of wing wall shall be 0.8 m above road elevation.
Therefore the top elevation of wing wall and parapet wall shall be
= 1345.75 ♦ 0.80 m = 1346.55 m
Wing walls shall be aligned curved upto 1m inside top of canal bank elevation Wheel guards 0.30 m x 0.30 m (0.75 m height) shall be provided at 2.0 m c/c interval
Foundation of wing wall shall be kept as that of abutment i.e. at 1342 20m Bottom width of wing wall = 0.5 x height of wing wall upto foundation Height of wing wall = Top elevation - foundation elevation
= 1346.55 - 1342.20 = 4 35
So width of wig wall at foundation elevation shall be = 0 5 x 4 Upstream and downstream protection
-oi
~ m. provide 2.25 m
Upstream and downstream protection in transition for a lenoth of s m k
a jin snail be provided in canal bed. The protection shall consist of 0.30 m thick CC blocks or stone pitching laid over 0 15 thick gravel.
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Toe wall
May 2007
A toe wall with 0.5 m top width shall be provided at the end of upstream and downstream protection. Toe wall shall be taken to 0.8 m depth below canal bed elevation. The bottom width shall be 0.8 m at foundation elevation.
Elevation of toe walls
Top elevation
Foundation
Proposed
in m
elevation in m
elevation in m
Upstream
1343.20
Downstream
1343 09
1342.40
1342.29
1342.30
1342.30
Structural design of Road Slab:-
Road of DS-7 standard as per Ethiopian Roads Authority shall be considered. Design of road slab shall be done for moving loads as per bridge design Manual 2002 being used in Ethiopia. The slab shall be designed for moving loads. Spacing of moving load shall be considered in such a way that it shall create maximum bending moments. The clear width of Road shall be kept as 4.5 m.
The drawings for this structure are available at Drawing no. Ad-F-Canal-G-21 & 22
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3.2 Design of Road Bridge at 41.50 Km of Left Primary Canal Left Primary canal
May 2007
An access road connecting the people residing in the upstream of canal is crossing by Left primary canal at 41.5 km. For communication and access from one side of canal to another side a Road Bridge is  proposed at 41.50 km. After the project is  completed traffic  shall increase for transportation of crop from command area to the residence of c ultivators or. for other purpose. As such the road bridges is most essential.
The details of canal at crossing point are as follows: 1. Full supply discharge      =         5.013 m3/sec
2. Bed width
=         5.0 m
3. Full supply depth
=
1.21 m
4. Velocity
=
0.606 m/sec
5. Longitudinal slope
=
0.000222
6. Side slopes                    =         1.5:1(H.V)
7. Free board
=
0.60 m
8. Full supply elevation
=
1339.04 m
9. Canal bed elevation
=
1337.83 m
10 Natural surface level     =        1339.00 m
With side slopes of canal of 1.5:1, the width of water way at FSL
= Bed width+2 x horizontal component of slope of canal x water depth
= 5+2x1.5x1.21 = 5+3.36 = 8.63 m
Say = 8.65 m
The bridge can be designed keeping width of structure equal to bed width of canal and de th equal to F.S.L. In this case flow area for canal is being restricted there shall be more head lo^ equal to afflux, as such FSL and bed level elevation of canal shall be required to be lowered contour canal head loss for structure is to be kept minimum. Therefore, it is proposedT^
Bridge in such a way that the waterway at FSL is not reduced.
Since waterway at FSL is 8.63 m, it is proposed to provide waterway of 9 m The 9 m span shall be much thicker therefore it is proposed to provide two soahc J
° Pr°Vlde
— ,o 5Pa„ „ ,0 m) rtth one w :
dau
; ,z“xwi“oi
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The top width of peir is proposed to be kept as 1.00 m with ease water and cut water semicircular in shape. The faces of peir shall be kept vertical faces up to 0.2 m below the canal bed elevation. Width of peir in foundation shall be increased as per design
• Height or peir
It is proposed to provide 0.6 m free Board above FSL of canal
Top elevation of peir = canal FSL + 0.60
- 13390.04 +0.6 = 1339.64 say 1339.65 m
Canal bed elevation = 1337.83 m
Height of peir above canal bed = 1.81 m
• Road slab elevation & width
It is proposed that the thickness of road slab be kept as 0.6 m. Therefore elevation of road shall be = peir elevation + thickness of slab = 1339.65 + 0.60 = 1340.25 m
It shall correspond to road classification of DS , standard as per Ethiopian Roads Authority as 
7
this is an unpaved access road.
As per standards the road width required shall be 4 00 m. Therefore Road bridge slab shall be of 4.0 m clear width between the curb. Curb of 0.3 m height and 0.65 m wide at road level shall be provided. Above curb a parapet wall 0.5 m high and 0.5 m wide shall be provided.
Therefore total height of parapet wall with curb shall be 0.80 m above Road elevation Total width of slab = clear width proposed +2 x width of curb
= 4+2x0.65 = 5.3 m
Elevation of parapet wall = Road elevation + total height of parapet wall = 1340.25 + 0.80 = 1341.05 m
• Abutments
Abutment shall be of 1.0 m width at top. The top elevation elevation i.e. 1340.25 m
The road slab shall rest on abutment for 0.5 widths
Of abutment shall be
at Road
Wing walls and parapet walls shall be provided with top width of 0.5 r ' ’ ‘
m and height shall be 0.8 m above road elevation i.e. at 1341.05 m. The wing walls shall have width of 0.5 for
.       0.5 m height from top. It shall have curb for 0.30 m height with width as 0.65 m at road elevation.
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The total height of abutments, peir and canal wing walls shall be based on scour depth
Wing walls shall be aligned straight to road direction road slab and shall be taken 1 0 m inside canal banks
• Canal waler way
The existing canal water way (area) provided is (A) = (B * nd) d
Where B = canal bed width= 5 00m
n = side slopes = 1.5
d = water depth = 1.21 m
Substituting values
A = (5 ♦ 1.5 x 1.21)x 1.21
(5 ♦ 1.815) x 1.21 = 7 48 sq m2
Water way under bridge
It is p roposed t o p rovide two c lear span o r 4 m w idth e ach with o ne p eir o f 1 .0 m width i n between
So width of structure between abutments = 2x4.0*10 = 9.00 m
The width of waterway at FSL is 8.65 m; therefore there shall be obstruction by peir area only in waterway area. The waterway area shall he reduced by area of peir
• Area for flow of water under bridge = Area of unobstructed canal - Area of peir up to
FSL above bed elevation of canal = 7.48 - 1.21 x1 = 7.48 -1 21
= 6.27 m2
Due  to  reduction  of  area  of  flow  from  7  48  to  6.27  m2   there  shall  be  an  afflux,  which  is calculated by Moleworth's formulae
A = Afflux =
(V
------- + 0.0152
1
1
(J7.85               J
Pm? 1 - -1
Id J
Where v = velocity under bridge = — =--------------- Total discharge
a Observation area under Bridge A = Area unobstructed = 7.48 m2
a = Area obstructed = 6.27 m2 V = ^^=0.80 m/sec
6.27
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’(hS+00152)"42-1’
= (0.0359 + 0.0152)0.42
= 0.0511 x 0.42 = 0.02m
For the flow condition under the bridge the difference between upstream and downstream FSL shall be kept equal to afflux
• Down stream FSL of canal = upstream FSL - Afflux
= 1339.04-0.02 = 1339.02 m Downstream bed elevation = downstream FSL - water depth
= 1339.02-1.21= 1337.81 m
• Scour depth
Scour depth is calculated for deciding the foundation elevation The scour depth is calculated by the following formula
Scour depth R = 1.35
Where,       f = silt factor
q = discharge per running meter Q = Total discharge
f = is taken as 1
Q
A var age waterway
5.013       5.013 ^5 + 8.63^ ~ 6.81
Substituting values of q = 0.74 and f = 1
f0 74 V,J
Substituting Value R = 1.35 -—
= 1.23 m
The maximum scour depth is taken as 1.5 times normal scour depth for abutments and w wall below FSL elevation of canal. For peir the depth is taken as 2 times normal scour depth^9
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Maximum scour depth for abutment and wing walls
= 1.5x1.23 = 1.85 m
Foundation elevation for abutment and wing wall = FSL - 1.85
= 1339.04 - 185 =1337.19 m Keep foundation at 1337.15 m
For peir the maximum scour depth = 2 x 1.23 = 2.46 m below FSL Foundation elevation = FSL - 2.46 = 1339.04 - 2.46 = 1336.58 m
Keep at 1336.50 m
Width of abutment and wing walls
Abutment: - Top width proposed is 1.00 m at elevation 1340.25 Foundation elevation = 1337.15m
Total height = 1340.25 - 1337.15 = 3.10 m
The bottom width shall be kept as 0.5 times height = 0.5 x 3.10 = 1 55
May 2007
So provide 2.0 m width at foundation and 1.5 m width at 0.30 m above foundation elevation
Wing wall
The top elevation of wing wall = 1341.05 m
Foundation elevation = 1337.15 m
Total height = 1341.05 - 1337.15 = 3.90 m
The bottom width shall be kept 0.5 time height.
Bottom width = 0.5 x 3.90 = 1.95 m
Provide bottom width = 2.25 m at foundation elevation and 2.0 m at 0.30 m above foundation elevation.
The  face  of  abutments  and  wing  walls  on  waterside  shall  be increased on other side.
Peir
Top elevation of peir is 1339.64 m
Foundation elevation is 1336.50 m
Total height = 1339.64 - 1336.50 = 3.15 m
Bottom width = 0.5 x 3.15 = 1.575 m
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Provide 2.0 m width at foundation elevation 1.5 m width at 0.3 m above foundation elevation up to 0.25 m below canal bed elevation.
Upstream and downstream protection
Canal section under bridge is not reduced, but due to provision of peir area of water way is restricted. Due is reduced waterway velocity in canal under bridge is increased. Therefore it is proposed to provide protection of only pervious nature i.e. CC block or stone pitching 0.30 m thick over 0.15 m thick gravel for width of bridge of 5.3 m . In addition for 3.0 m length on upstream and downstream pervious protection in bed and canal slopes up to 0.5 m above FSL shall be provided. Total length of protection shall be 11.3 m.
Toe wall
A toe wall of 0.5 m width at top shall be provided at the end of upstream a nd d ownstream protection. Toe wall shall be 0.8 m deep below canal bed elevation and bottom width at foundation shall be 0.80 m
For elevation of Toe wall             U/s
Top elevation
= 1337.83
Foundation elevation            = 1337.83-0.80 = 1337.03
foundation elevation
Structural design of road slab
1337.00
D/S
1337.81 1337.81-0.80 1337.01 1337.00
As  already  mentioned,  the  access  road  being  unpaved,  the  road  is  considered  as  of  DS standard as laid by Ethiopian Roads Authority. Design of road slab shall be done for moving loads as per bridge design Manual 2002 of Ethiopian Road Authority being used in Ethiopia
The slab shall be designed for spacing of moving loads in such a manner, that it shall create maximum bending moment.
The drawings for this structure are available at Drawing no. AD-F-Canal-G-23 & 24
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3.3 Design of Foot Bridge for Cattle Crossing at Km 19.00 of Right Primary 
Canal
In the Arjo-Dedessa irrigation project two primary canals system i.e. Right and Left Primary canals proposed. Both the primary canals are contour canals. There are practically no well- established roads in the command for communication from one end to other. However there are some access  roads  (unpaved), which are for communication between citizens  living at different places. Such access roads are very few in numbers and are being crossed by canal, for which road bridges have been proposed These access roads are very far off from each other, generally more than 5 km. away. Presently cattle's and citizens can move in open fields from one place to another, but after construction of canal it shall be difficult for cattle and human being to cross canal from one side to another side from any place except over proposed Road Bridges, which are far away  from each other. In such case, cattle and citizens  are required to travel very long distances for crossing the canal. Also after canal is in operation, they shall be required to carry their agriculture produces from command area to their residence or from residence to market places. Therefore some (cattle crossings) foot bridges  are proposed to be provided in between the proposed road bridges.
In some cases, the footbridges  are combined with regulator or cross  regulator structure. However in case, structures are not in the vicinity of proposed footbridge site, independent foot bridges (cattle crossings) are proposed. One such footbridge (cattle crossing) is proposed at km 19.00 of Right Primary canal.
The detail hydrological data of canal at proposed crossing point are as given below:
1. Full supply discharge
= 5.981 m3/sec 
2. Bed width
= 6.00 m
3. Full supply depth
= 1.26 m
4. Velocity
= 0.604 m/sec 
5. Side slopes
= 1.5:1
6. Free board
= 0.70 m
7. Full supply elevation
= 1343.50
8. Canal bed elevation
= 1342.24
9. Natural ground elevation
= 1343.50 m
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•    Water way at FSL with canal side slopes of 1.5:1
= Bed width + 2 x horizontal component of slope x water depth = 6.00 + 2x1 5x1.26
= 6.00 + 3.78 = 9.78 m
May 2007
To keep head loss in canal to minimum, it is proposed not to constrain waterway area of canal. There fore it is proposed to provide two span of clear width 4.5 m (centre to centre span = 5.5 m) each with one peir and abutments at both ends. The top width of peir is proposed to be 1.0 m, with ease water and cut water semicircular in shape. Both the faces of peir are proposed to be kept vertical up to 0.24 m below the canal bed elevation
•    Height of peir
It is proposed to provide 0.6 m free board above F.S.L of canal
Top elevation of peir shall be = Canal FSL + 0.60
= 1343.50 + 0.60
= 1344.10 m
• Height of peir above canal bed = top elevation of peir-canal bed elevation
= 1344 10-1342.24 = 1.86 m.
Foot bridge slab top elevation
It is proposed that the thickness of slab shall be 0.30 m
• Elevation of top of slab = peir top elevation + 0.30 m
= 1344.10 + 0.30= 1344.40 m
H is proposed to Keep the width of footbridge as 2.0 m with parapet wal, 0( 0.50 m widlh on bo h ,
side of road and shall be of 0.8 height
Total width of slab shall be = 2+2 x 0.5 = 3.0 m
Abutments
Abutments at both ends shall be of 1.00 m width at top. The top elevation of abutment shaii h same as that of top elevation of road slab. The siab of badge shall rest on abutment (or 0 5
width.
The wing walls along with parapet walls at the both end of abutment shall h
0m
angle  to  abutment  with  top  width  of  0.5  m  and  shall  be  kept  0  8m  abov  6   P™'^  at   "9ht
and shall extend for 1.00 m length inside canal bank                     01 3
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• Top elevation of parapet wall and wing wall shall be = Top elevation of slab + 0.8 m = 1344.40 + 0.8 = 1345.20 m.
May 2007
The total height and width at foundation elevation will be fixed with reference to scour depth.
Canal waterway
The existing unobstructed water way (area) of canal = (B + nd) d
Where B = bed width of canal = 6.0 m
n = horizontal component of slope 1.5
d = water depth = 1.26 m
Substituting values
A = (6+1:5 x 1.26
= 6 + 1.89)1.26
= 7.89x 1.26 = 9.94 m2
Water way under bridge
As proposed there shall be two spans of clear width of 4.5 m with one peir of 1.0 m thickness. So width between abutment = 2 x 4.5 + 1.0 = 9.0 +1.0 = 10.0 m
Where as the linear waterway in canal at FSL is 9.78 m.
Therefore there shall be obstruction due to peir only in waterway of canal. Due to obstruction of peir there shall be reduction in waterway under the bridge.
Area  of  waterway  under  bridge  =  unobstructed  area  of  canal-  area  of  peir  up  to  FSL above canal bed elevation
= 9.94 - 1 x 1.26 = 9.94 - 1.26 = 8.68 m2.
Due  to  obstruction  of  area  of  »aten»a,  from  9.94  f„  868  m>.  lhere  shall  be  afflux  which  „ calculated by Moleworth's formula
( v2                           WA\2
A = Afflux = ------- + 0.0152    -      -1 1
37.85         J I a J
Where, v = velocity under bridge = — = Total d,scfl^ge
A Area under Bridge A = unobstructed area = 9.94 m2
a = obstructed area = 8.68 m2
O 5.981 ncn ,
■ V = — = -------- = 0.69 m/sec a 8.68
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Afflux =
(°
69 2
17 85              J = (0476+0.0152] {
U7.85               r
)  +0.0152]
W-.}
\ 8.68 J 1.31-1}
= (0.0267 + 0.0152) 0.31
= 0.042x0.31 = 0.013 m
For the flow condition, under the bridge, the difference between upstream and downstream F.S.L shall be kept equal to afflux = 0.013 m
Downstream FSL of canal = upstream FSL- afflux
= 1343.50-0.013 = 1343.487 m Downstream bed elevation = D/s FSL - water depth
= 1343.487 - 1.26 = 1342.227 m
Scour depth calculation
Scour depth is calculated for deciding the foundation elevation The scour depth is calculated by the following formula
R=
Where, f = silt factor taken as 1
q = discharge per running meter
Q = total discharge
5 981    5 981
= g -        -        =0 76
q Av. waerway (leaner) 6 + 9.78
15.78
2
2
Scour depth - 1.35
1.35x0.91
= 1.23 m
The maximum scour depth Is considered as 1.5 times normal scour depth (or abutments and wing wall and 2 times (or par The maximum scour deplh is measured below lhe FSL of canal Maximum scour depth for abutments & wings = 1.5x1.23 = 1 85 m
Foundation elevation = FSL - scour depth
= 1343.50- 1.85
= 1341.65 m
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Hydraulic Design of Canal Structure Width of abutments and wing wall
May 2007
Abutment: - Top width proposed is 1.00 m at slab elevation of Road Bridge i.e. 13344.40 m.
Foundation elevation = 1341.65 keep foundation 0.8 m below canal bed elevation i.e
1342.24 - 0.80 = 1341.44 say 1341.40 m.
Total height = 1344.40 - 1341 40 = 3.00 m.
The bottom width at foundation elevation shall be kept = 0.5 x height of abutment
= 0.5 x 3.00 = 1.50 m
Keep foundation width of abutment at foundation elevation = 1.75 m a nd 1 .50 m a t 0.30 m above foundation elevation
Wing wall
Top width proposed as 0.5 m at elevation 1345.20 m
Foundation elevation=1341.40 m
Total height = 1345.20 - 1341.40 = 3.80 m
Bottom width = 0.50 x 3.80 = 1.90 m
Provide width of wing wall = 2.25 m at foundation elevation and 2.00 m at 0.30 m above foundation elevation. The face of abutments and wing walls on waterside shall be kept vertical and width shall be increased on other side.
• Peir
Top elevation of peir = 1344.10
For peir maximum scour depth below FSL = 2 x 1.23 = 2.46 m Foundation elevation = FSL - 2.46
= 1343.50 — 2.46 - 1341.04 m
Keep at 1341.00 m
Total height of peir = 1344.10 -1341.0 = 3.10 m
Bottom width = 0.50 x 3.10 = 1.55 m
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Length of Peir
May 2007
It is proposed to provide cutwater and ease water semi circular in shape Peir width proposed is 1.0 m.
Length of peir = foot bridge width + 2 x parapet width ♦ 2 time radius of ease and cut water
Length = 2 + 0.5 x 2 + 2 x 0.5 = 4.00 m
Length at elevation 1342.0 shall be kept as 4.50 m and at foundation elevation for 0.30m height = 5.0 m
Upstream and down stream protection
It is proposed that canal section under bridge shall remain same as that of canal, but due to provision of peir, water way is reduced from original waterway of canal, as such velocity under bridge shall increase. Therefore it is proposed to provide protection of only pervious nature i.e CC blocks or stone pitching 0.30 m thick laid over 0.15 m thick gravel for 4.0 m width of canal under bridge and 2.0 m length on both side of bridge. The protection shall be given in canal bed and slopes up to 0.3 m above FSL i.e. up to elevation of 1343.80 m
Total length of protection shall be 7.0 m:
Toe wall
A toe wall of 0.5 m width at top shall be provided protection. Toe wall shall be of 0.8 depth below foundation shall be 0.80 m.
Elevation of toe wall
U/s Toe wall
Top elevation
1342.24
Foundation elevation
1342.24-0.80
1341.44
Keep at
1341.40
a 11 he end o f upstream a nd d ownstream canal bed elevation and bottom width at
D/s Toe wall 1342.227 1342.227-0.80 1341.427 1341.40
Structural design of foot bridge slab
The slab is subjected to live load of animal and human shall b e considered as per live load consideration for dead load of slab.
being  moving  over  slab  The  live  load slabs of residential h ouses along with
The drawing for this structure are available at Drawing no. Ad-F-Canal-G-25 &26
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4. STRUCTURES UNDER DISTRIBUTION SYSTEM
May 2007
4.1   Design of APM - Out Let for Tertiary Canal Rt-16-9 Of Dr - 16 of Right Primary Canal
In Arjo-Dedessa Project, it is  proposed that for finalization of feasibility  study, a sample area for distribution system be designed for estimation. For the purpose, of study  area of two secondary  canal systems  RS-16 and RS-17 taking off from Right-bank  primary  canal are selected. The details  of area proposed for irrigation from these two secondary  canals  and number of tertiary canals, are as below:
Secondary Canal
No. of Tertiary canal
Area proposed in Ha
Left
Right
Total
Left
Right
Total
RS-16
8
7
15
217.9
122.2
340.1
RS-17
11
11
22
213.46
201.29
414.75
Total
19
15
37
431.36
323 49
854.85
The maximum discharge of tertiary  canal is  0.040 m3/sec  for RT-16-9 of RS-16 secondary canal with 20% flexibility  factor. This  tertiary  canal takes  of from 1.20 km of secondary  canal RS-16. As  the maximum discharge of tertiary  canal is  0.040 m3/sec, which is  equivalent to discharge of water course. Therefore for regulating flow from secondary  canal to tertiary  canal it is proposed to provide Adjustable Proportional Modular (APM) outlet
Design of Tertiary canal
The discharge of tertiary  canal is  0.040 m3/sec  considering earthen canal section with 0.30 m bed width and 0.20 m water depth with side slopes  of 1.5:1. Area of canal = (B + nd)d where B = bed width
n = side slope
d = water depth
= (0.30* 1.5 x 0.2) 0.2 = (0.3 + 0.3) x 0.2
= 0.6 x 0.2 = 0.12 sq. m P = wetted perimeter = B + 2 (Vn *l) d
r
2
= 0.30 + 2 (Vl.5  +l)o.2O
= 0.3 + 0.4 V3.25
= 0.3 + 0.72 = 1.02 m
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Hydraulic mean depth R = — =
P 1.02
= 0.1176
R273 = 0.24
It is proposed to provide slope of 1 in 1000 = 0.001 Velocity by Manning’s formula:
V= 1/?2'3(S)*'2
n
Where, Substituting values
n = coefficient of Rugocity = 0.0225 R = Hydraulic mean depth
S = Slope
V = —!— x 0.24 (0.001)1/2
0.0225
V = 10.66 x 0.0316 = 0.338 m/sec Q = AxV = 0.12x 0.338 = 0.4056 m3/sec So assumed section of canal is alright Details of secondary and tertiary canal
s.
No
Description
Secondary canal
at 1.20 km
Tertiary
Canal RT
1
Full supply discharge Q in m3/sec
0.283
0.040
2
Full supply depth in m
0.55
0.20
3
Canal bed width in m
0.60
0.30
4
Bed slope
0.00033
0.001
5
Full supply elevation
1334.10 (u/s)
1333.95
6
Bed elevation
1333.55
1333.75
7
Ground elevation
1333.70
1333.70
8
Velocity m/sec
0.73
0.338
For safe and suitable design of APM outlet following three conditions shall have to be
I 151 Condition Where: H'm
Hs
I          H'm > Hm
= modular head = (1 -E) Hs
= Depression head = 0.3D
D = Depth of water in supply channel and
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II
E R
Y Hm
2 nd Condition Where WH
H’m
= Efficiency = — (Vi + 16/? - 3) 27?
= Depression Ratio = —
_ 
or
= Depth of orifice.
= minimum modular head = (0.82Hs - 0.5 Bt)
WH > H’m
= Working head
= FSL of supply channel - FSL of off taking canal and = (1-E) Hs
III 3rd Condition H/2 > Y
Where H = Depth of FSL upto crest of APM
= (H  <• Y)
s
and Y = Depth of orifice
For the APM of RT-16-9
1. Available working head WH
WH = FSL of secondary canal - FSL of tertiary canal = 1334.10-1333.95 = 0.15 m
2.  Depression head of APM
H$ = 0.30 = 0.3x0.55 = 0.165 m
3.  Discharge through orifice
q = 4.03 x Bt x Y JTh , Assume Bt = 0.20 m /sec
3
■Y=               V
_
0.04
4.03 x Bt x jHs 4.03 x 0.20 /o. 165 0 04             _ 0.04
_
4.03 x 0.20 x 0.406 " 0328 = °-122 m I.   Depth of FSL to crest of APM
H = (Hs + Y)
= 0.165+ 0.122 = 0.287 m Hs 0.165
j. Depression ratio R = — =                  1.35
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6.  Efficiency E            = —(Vl + 16/? -3) 2/T
May 2007
’
-       1 Pl+ 16+ 1.35 3) 2x1.35'
= 0.370(4.75 -3) = 0.370 x 1.75 = 0.650 m
= H'm = H  (1-E)
'
7   Modular Ratio
s
H’m    = 0.165 (1-0 65)
= 0.058 m
8.  Minimum Modular Head = Hm
= (0.82 Hs -0.5 Bt) = 0.82x0.165-0.5x0.20 = 0.1353-0.10
= 0.0353 m
Now for above design
i)  For condition I = H'm = 0.058
Hm = 0.0353
As H'm is greater than Hm design is safe ii)   For condition II WH > Hm
WH =
0.15 m
Hm
=
0.0353 m
As WH is greater than Hm Hence design is safe
iii) For Condition III H/2 > Y
Y = 0.122 m
Since H/2 is greater than Y. Hence design is safe
In this design all three conditions are satisfied, hence design is safe Different elevation of APM
Crest Elevation of APM = u/s FSL - H = 1334.10-0.287 = 1333 813 m Top of APM orifice
= Crest EL + Y = 1333.813 * 0.122 = 1333.935 m
The drawing for this structure is available at Drawing No. Ad-F-Canal-DlS-27
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4.2    Design of Duck Bill Weir for Secondary Canal RS-17 of Right Primary Canal
For regulation water level in canal and control on the quantity  of water passing through it to dissipate energy  and enable water to be delivered as  per requirement safely, control structures are essential. The control structure can be
1.  Cross regulators
2.  Check structures (orifices etc)
3.  Weirs etc.
Weir
A fixed over fall crest or weir controls the water level at a given height within relatively narrow limits. The height and the crest length are determined in relation to the discharge to be passed over the weir crest and to control requirements e.g maximum permissible level fluctuations etc.
Greater crest length is required for precise control. In canals at the tail end, particularly in
distribution channels, the width available is generally insufficient to accommodate a transversal
weir with crest length enough to pass the full supply discharge within.
For such conditions following type of weirs have been developed
(1) Diagonal weir
(2) Duckbill weir
(3) Z type or specially shaped weir.
Out of the above weirs, duckbill weir is  most commonly  used, as  it is  economical, providing optimum discharge capacity  in relation to length of structure. The advantage of this  type of structure is  the simplicity  in construction and maintenance and reliability  in operation The weir is  suitable for irrigation water when silt Ioad is  less  such as  canals  of reservoir project. For removal of silt a flush opening can be provided in the weir at the floor of structure
Proposal
It is proposed to provide a Duckbill weir at the tail of every secondary canal For th
sample design the secondary canal RS-17 is selected for which detail m & P^ ^ °
0
f
haves been done.
The details of secondary canal
1. Full supply discharge
2. Full supply depth
3. Bed width
anning and design
RS-17 at the tail i.e. at 3.00 km. = 0.15 m3/sec =150 litres/sec = 0.43 m
= 0.50 m
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4. Slope
= 0.00033 or 1 in 3000
5. Side slopes
= 1.5:1
6. Velocity
= 0.31 m/sec 
7. Full supply elevation
= 1326.15 m
8. Canal bed elevation
= 1325.72 m
9. Ground elevation
= 1326.20 m
10. Top of bank elevation
= 1326.45 m
• Hydraulic design of Duckbill weir
The discharge over a duckbill weir is based on the formula
Q =
Where m = discharge coefficient
Bt = length of crest
H(Crt)= water depth i.e. head on the crest
The value of m depends on shape and the angle x. In case if angle x is larger than 45° the values for m, i.e. coefficient of discharge are
For unrounded shape         = 0.32
For rounded shape             = 0.36
The duckbill weir is s uitable a nd preferable when x is m ore than 4 5° and up t o 7 0° 11 is recommended that, at the end of duckbill weir crest width is fixed at 40 cm. independent of the bottom width of canal.
For the purpose of determining the discharge per meter length the graph is available t Annexure 3. From this graph total length of crest required shall be worked out Fi
available at annexure 4 is used to determine the angle x from the required crest length '9Ure
For the canal RS-17 at km 3.00
Canal discharge
= 0.15 m3/sec = 150 liter/s 
Side slope
= 1.5:1
Bottom width
= 0.50 m
Water depth
= 0.43 m
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It is assumed that maximum water level variation shall be 0.15 m
i.e. H(crt) = 0.15 m
• Crest height = 0.43-0.15 = 0.28 m
From Annexure-5, part -1 for value of Bed width of 0.5 and height S=0.28 Available transversal length L=B(t) = 1.34m
May 2007
Form figure - at Annexure 3 graph between H(crt) in cm's and discharge J/ per meter of crest length.
For H(crt) = 0.15 m = 15 cm and m= 0.32 Discharge per meter length of weir = 81.5^/ = q Therefore total length of weir required
Bt = ^- = Q
A I II
Total dischzi^e discharge permeter
1.84-0.40
-^    =    1.84. 81.5
A = slant length =------- -------
^=0.72 2
1.34-0.40     0.94
a = -------------- =------- = 0.47
22
From above value of A and a from figure - at Annexure - 4 the angel is 50° The angel being more than 45° the selection of Duckbill weir is justified. Check for discharge from the following formula
Q = m x Bt x V29
M= 0.32 for un rounded crest Bt = 1.84 H
(crt)
= 0.32 x 1.84 Vi 9.62 x (0.15)J,: = 0.1515 m /sec
The discharge of canal is 0.15 m /sec Therefore the dimensions used are correct.
= 0.15
3
3
The recommended dimensions for standard Duckbill weir are shown in fioure
yuie - iii  available at Annexure 5. In the case of RS-17 the dimensions are as given hereunder
B = bed width = 0.50 m
f = Assumed 0.50m (upstream floor) Y, = upstream water depth = 0.43
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•. IU1
= 0.5+1.29 = 1.79 say 1.80 m
L = Total length of crest = 0.40+2A = 1.84 m
a - 50° between weir crest and cross section of channel
M = 1.5 f- 1.5s + 0.20
= 1.5*0.5-1.5*0.28+0.20
= 0.45-0.42+0.20 = 0.53 say 0.60 m
K = Asina = 0.72 sin50° = 0.72x0.766=0.552
Distance up to crest end from cross section of channel
= 0. 552 = say 0.55
P = Downstream floor length
= 2.5 f = 2 5x0.5 = 1.25 m
f = 0.5m
With  these  dimensions  the  drawing  of  duckbill  weir  has  been  prepared,  which  is  available  at Drawing no AD-F-canal-DIS - 28.
Arjo-Dedessa Irrigation Project
Hydraulic Design of Canal Structure
H(crt) = Difference between upstream water elevation and crest elevation =0.15m
S = Height of crest = 0.28 m
C = Thickness of weir = 0.15 m
f. - Width of available upstream water surface = (B+2ny ) = 0.5+2*1.5*0.43
May 2007
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Annexure - 3
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Annexure - 4
FIGURE b-A Delo rrruzution of (. Ircirn known B
and al «             <M).
S
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Annexure - 5
Section Bfi
Std'or £-<•
Rohh of k/iTo6lt dinensiefti
cotoci’iti
uo to lOOO t/t
9 • C 20 »o i 00
f « 0 20 t   i on
O
1
/ (  OO to 0 70 l.apMreom
aeptn)
05 'o 0 5 K>’’»r»nct oefwter xa'/toa
•W on« cret* we*}
• • OiO to 0 60
C  »  0  15  (tn<kn««»  of
/ 1 <*iatn o» dvdMOCi* uOlirsstr L « (fofof *nqtn of cr«M ' 0 40 ♦ 2 4)
luttooj
•< « (ongfe bttwsen wee c'tal and cron Ifc'ten
of chonnell
*• • K5/-I 5f > 0 20
>  ■  4  im«<
/ • *JZ
/■f
FIGURE 6-11.  - Standard duckbill weir design
for capacities up to 1000 l/g.
F) p« “Giraudet ‘
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4.3   Details for Turn out Structure (Division Box) For Quaternary Canal
(Field Channel)
Under the distribution network  system, the water for irrigation is  provided to farmers  field through quaternary canals (field channels). The quaternary canal receives water from tertiary canal. For distribution of water from tertiary  canal to quaternary  canal a turn out structure (Diversion Box) is proposed to be provided
In Arjo-Dedesa Project a sample area of secondary canal RS-16 and RS-17 is considered for planning and design of distribution network system. In this area detail planning is carried out for tertiary  canals  takingoff from secondary  canal and quaternary  canals  takingoff from tertiary canals. In detail planning the quaternary  canals  are planned to takeoff only  on one side of tertiary canals.
Therefore turn out structure (Division Box) shall be designed to have out let for water on one side only.
It is proposed that these turns out structure shall be constructed from hollow, concrete blocks of size 40cm x 20 cm and 20cm. high. The hollow block structure shall be placed at least 30 cm below t he s urface of t he ground o r canal bed elevation which ever i s less, on 1 0 t o 1 5 c m concrete foundation. The top of concrete foundation shall form the floor of structure. The first course of 40 x 20 x 20 cm block shall be laid in the fresh concrete of the foundation. The blocks shall be leveled at every course. The procedure of laying block shall be the same as done in case of brick masonry.
The size of opening shall be kept equal to bed width of tertiary  canal for upstream and downstream end. Where as openings for quaternary canal the size shall be kept as 30 cm The hollow blocks at both ends of opening shall have a groove 6 cm in the centre of width (20cm) of block. The water flow is controlled by removable gates 5 cm thick either made of timber or steel.
When the blocks have been laid, a coping of CC M-20 7.5 cm thick shall be placed on the top course and on the crest of the openings. Copying can also be done by providing pre-fabricated blocks of 7.5 cm 20 cm wide and 80 cm or 60 cm long blocks. The cores (holes) of the block shall be filled with lean concrete CC M-10.
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The  tertiary  canal  at
both  ends  of
structure  and  quaternary  canal  downstream  of  openings 
shall
be protected by CC
block or rubble
lining 0.225 m thick land over 0.075 m thick gravel for
1.00
m length.
Drawing for turn-out
For typical drawing of the turnout structure has  been prepared for Tertiary  canal RT-16-9 under secondary  canal RS-16 of Right Primary  canal The tertiary  canal takes-off at 1.20 km from secondary  canal RS-16. The length of tertiary  canal is  1.186 km and about 22 quaternary canals are proposed to takeoff from tertiary canal on right side
The detail data of Tertiary canal RS-16-9 is as follows 1. Full supply discharge         =        0.04 m3/sec
2. Full supply depth                =        0.20 m
3. Bed width
=        0.30 m
4. Full supply ele3vation = 1333.95
5. bed elevation = 1333.75
6. Slope of canal
=
1 in 1500 i.e 0.00 67
7. Side slope of canal
=
1.5:1
8. Ground elevation
=
1333.70
9. Free board
=
0.3.0 m
Top of bank elevation shall be
FSL ♦ 0.30 = 1333.95+0.30= 1334.25
The  foundation  of  structure  shall  be  taken  0.5  m  (50  cm)  below  canal  bed  elevation  or  ground level which ever is lower
In this case the ground level is at lower elevation of 1333.70 m. Therefore foundation shall be The detailed drawings are available at Drawing no. AD-F-Canal-DIS-29 & 30
126Arjo Dedessa Irrigation Project Hydraulic Design of Canal Structure
May 2007
4.4   Design of Vertical Fall 1.5m and Road Bridge at KM 1.05 of Secondary Canal RS-16
In Arjo-Dedessa Project there are two Primary canals, left and right canals, taking off from dam. Both these primary  canals  are contour canals  for their entire length. There are secondary canals taking off from these primary canals. Details of length and head discharge of Primary 
canal and number of secondary canals taking off from the primary canals are given below:
S. No
Canal
Length           Discharge at              No. of in km                 head in              secondary
m3/sec                  canals
1
Left Primary canal                        60.18                   9.015                    45
2             Right Primary canal                     44.166                 7.521                    40
For the purpose of detail planning of distribution system, with tertiary, quaternary  canals, command area of secondary canals RS-16 and RS-17 of Right canal has been selected as sample area. The secondary canal, RS-16 takes off at km 21.327 and RS-17 at km 21.788 from right primary canal. The discharges at head for these secondary canals are as follows
RS-16 = 0.48 m3/sec
RS-17 = 0.58 m3/sec
These secondary canals are aligned practically on ridge. The slope of the ground is steep and therefore a number of falls (drop structures) are proposed for secondary canal. Out of total falls one of the fall of 1.5 m depth is proposed at km 1.05 of RS-16 secondary canal
In the secondary canal service road Is proposed on left bank, which is proposed to be 5 0 wide. Tertiary canals are taking of on both sides i.e. on left and right side of seconda ""
tn the command of RS-16, no established or access road is crossing the canal p
canal only footpath of 2.0 m wide is proposed for movement of cade's and hcman bLngs Z
approach to their fields.
ror
Therefore for tertiary canals which are taking off on right side, for communication of h uman beings (cultivators) and cattle's from field to service road of secondary canal for movement of irrigations activities and movement of agricultural product across the secondary canal a foot bridge is most essential. Therefore it is proposed to combine Foot Bridge with proposed fall.
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The details of secondary canal at km 1.05 are as follows 1.  Full supply discharge        =          0.283 m3/sec
2.  Full supply depth              =          0.55 m
May 2007
3.  Bed width 4.  Velocity
=          0.60 m
= 0.364 m/sec
5. Full supply elevation =
6. Canal bed elevation =
u/s _ 1335.65 D/s 1334.15
u/s _ 1335.10 D/s 1333.60
7.  Ground elevation              =          1335.40
8.  Drop
=          1.5 m
The  discharge  of  canal  at  km  1.050  is  0.283  m3/sec.  and  drop  is  1.5  m.  Therefore,  it  is proposed to provide a vertical type of fall, with 2.00 m wide footbridge
The following design procedure is followed.
Calculation for crest elevation
Throat width of crest is considered equal to u/s bed width = 0.60 m
Assume (length) breadth of crest = 0.8 m
For vertical falls Q = discharge is given by formula Q = C x Bt x D3/2
Where, Q = Discharge of canal
C = Coefficient of discharge
Bt = Throat width
D = Depth of crest below u/s TEL
= 0.283 m3/sec = 1.82
Lt = Length of (Breadth) crest, assumed as 0.80 m
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Substituting values, and D can be found out as follows
0.283   = 1.82x0.6 £>3'2
1.82x0.6
0.89
= 1.14 Z)5'3
May 2007
0.283
1.14
= 0.248
D = (0.248)3/5 = 0.43m
This depth is proposed below U/s TEL
U/s TEL = U/s FSL of canal - velocity head due to approach
V 2
Velocity head =          = Va velocity of approach 2g
Velocity of approach =
Q
A
Since  rectangular  section  is  proposed  above  crest  it  is  assumed  that  rectangular  section  of canal is effective.
i.e. b x d = bed width of canal i.e. 0.6 m and x depth of canal 0.55 m A = 0.6 x 0.55 = 0.33 sq. m
Head due to velocity of approach - — -
Va1 (0.86)2  0.74
n nj-| y^’004
U/s TEL = 1335.65 + 0 04    =         1335.69
Crest elevation
=              u/s TEL ’ O-4^
= 1335.69-0.43 = 1335.26
. U/s Protection: - No protection is required. But provide CC floor for 1.5 m  length of 0 30 m thickness, consisting of 0.10m CC M-20 laid over 0.20 CC M-10
At the end of u/s floor a curtain wall of 0.8 m depth with 0.3 m width at tnn a
ai “jp ana 0.5 m width at bottom shall be provided at upstream canal bed elevation.
c
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•    D/s Expansion:
May 2007
D/s sidewalls shall be straight and parallel upto the end of downstream floor, and shall have return at right angles to sidewall. Face on waterside of sidewalls shall be kept - vertical.
•    Energy dissipation
It is proposed to provide water cushion at the toe of drop for energy dissipation by means of impact and sudden deflection of velocity from vertical to horizontal direction. The water cushion is formed by suitably depressing the floor below the downstream bed of canal.
The dimension i e. length and depth of cistern shall be found out by following formula Length = 5(H xD) f
L
Depth =
Where, D = Depth of crest below upstream TEL = 0 43 m HL = Height of drop in meter = 1.5 m
Substituting values
.. Length of cistern = 5 (1.5 x 0.43)1,2 = 5 x 0.78 = 3.90 m So provide 4.00 m length
Depth of cistern = -(1.5 x 0.43)       = -x0.72 = 0.18 m. Say 0 20 m
1 
on 1
4
4
So floor elevation of cistern = D/s canal bed elevation - depth required for cistern
Foundation elevation = Elevation of cistern - 0.80
= 1333.40-0.80 = 1332.60 m
• Bed protection
Length of bed protection = 3 x d/s F.S depth
3 x 0.55 = 1.65 m, Provide 2.00 m
Bed protection shall consist of CC blocks or stone pitching 0.30 m thick laid over 0.15 m thick gravel. At the end. it shall be protected by a Toe wall 0.3 m width at top 0 80m deep and 0 50m wide at foundation elevation. This  protection shall be given in bed and side <=i
and side slopes of canal.
130Arjo Dedessa Irrigation Project
Hydraulic Design of Canal Structure
• Length (Breadth) of crest
Length of crest Lt is calculated from formula
= 0.55 y] Elevation of crest - elevation of cistern = 0.55 Vl335.26-1333.40
= 0.55 VL86
= 0.55 x 1.36 = 0.75 m
So assumed length 0.80m is sufficient.
•    Crest wall
May 2007
Thickness of crest wall at base shall be provided 0.5 times height between elevation of crest and elevation of cistern.
elevation ofcrest - elevation of cistern = 0 50 (1335.26 - 1333.40)
= 0.50 x 1 86 = 0.93 m
Provide 1.00 m at cistern elevation and 1.50 m at foundation elevation, which shall be taken 1.00 m below cistern elevation i.e. 1333.40 - 1.00 = 1332.40 m
•    Uplift pressure and thickness of d/s floor
1 st Condition for exit gradient
When upstream water level is at crest and downstream is dry
H = Elevation of crest - d/s bed elevation = 1335.26 - 1333.60 = 1.66 m
Depth of d/s curtain wall = 0.80 m with bottom width = 0.8 m
Creep length from u/s to d/s end (Refer enclosed sketch)
= 0.80 + 0.65 + 1.55 * 1.25 + 4.00+ 0.65 + 0.80 = 9.7 m
Two types of uplift pressure will act.
1.  Static pressure
2.  Seepage pressure
It is assumed that at the end of floor, thickness of floor shall be 0.50 m and at toe of f ||
1 Static head: For static head assuming that sub-soil water i«t hi
io ai a/s canal bed
Then static head = d/s canal bed elevation - Bottom elevation of floor
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ulic Design of Canal Structure
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Bottom elevation of floor = Cistern elevation - thickness of floor
= 1333.40 - 0.60 = 1332.80 m
Static head = 1333.60 - 1332.80 = 0.8 m = 0.8 t/sqm
2.
Seepage pressure
This pressure shall be maximum when in u/s water is at crest elevation and in d/s canal is dry.
.. Seepage head = crest elevation - Dds canal bed
= 1335.26- 1333.60 = 1.66 m
So seepage pressure at the end of floor cistern
= Seepage head I I - ^ngth from u ! s  upto ‘hat point
Total creep length
Length of creep upto the end for cistern floor = 9.7 - 0.8 - 0.65 = 8.25 m
Seepage pressure = 1.66
= 1.66 (1-0.85) = 0.25 m = 0.25 t/m2
Total uplift pressure = 0.80 + 0.25 = 1.05 t/m2
Thickness    required    =    uP^fi    pressure
wt of concrete
So thickness provided of 0.50 m in sufficient at end Thickness at toe of crest:
Length upto toe = 8.25 - 4 = 4.25 m
So seepage pressure = 1.66
= 1.66 (1-0.44) = 0.73 m = 0.73 t/m2 Total uplift = 0.8 + 0.73 = 1.53 t/m2
Thickness required =             = 0 68
m
2.25
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So provide thickness of 0.8 m at the toe of crest and 0.5 m at the end of floor Top 0.15 m shall be CC M-20 and rest CC M-15.
U/s and D/s Protection
Provide for 2.0 m -length pervious protection of cc block or stone pitching 0.30m thick laid over
0.15  m  thick  gravel.  The  above  protection  shall  be  provided  beyond  concrete  floor  in  upstream and cistern floor in downstream.
The protection shall be provided in canal bed and slopes. At the end of previous  protection a toe wall shall be provided for 0.8 m depth with width of 0.5m at top i.e at canal bed elevation and bottom width of 0.80 m at foundation elevation.
• Foundation elevation and width of wing walls
The ground elevation = 1335.40 m
D/s cistern elevation = 1333.40 m
Downstream  wing  wall  shall  be  taken  1.00  m  below  cistern  elevation.  Upstream  wing  shall  be taken 1.00 m below upstream bed elevation.
.-. The top elevation of wing walls shall be kept 0.3 m above FSL of canal
Top elevation of u/s wing wall = u/s Full supply elevation + 0.30 m
= 1335.65 + 0.30 = 1335.95 m
Since the upstream bank elevation is at 1336.15 m
The top elevation shall be kept at 1336.15 m
Foundation elevation of u/s wing wall = u/s canal bed elevation -10m = 1335.10 -1.0 = 1334.10
Total height of u/s wing wall = 1336.15- 1334.10 = 2.05 m
Top width of wing wall = 0.30 m
Bottom width = 0.50 x height = 0.5 x 2 05 = 1.025
Provide 1.00m width at 0.3 m above foundation elevation and 1
<
, m at foundation elevation
• D/s wing walls and return
Top elevation = d/s full supply elevation + 0.3
= 1334.15 + 0.30 = 1334.45 m. keep at 1334.50
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..n „
n   uu
Te ^ «
n
itsArjo-Dedessa Irrigation Project
Hydraulic Design of Canal Structure
May 2007
Since  the  ground  elevation  is  at  1335.40  m  and  service  Road  elevation  in  d/s  is  kept  0.50  m above ground elevation, the top of d/S wings shall be kept at 1335.90 m.
Foundation elevation = cistern elevation - 1.00 m = 1333.40 - 1.00 = 1332.40
Total height of d/s wing wall = 1335.90 - 1332.40 = 3.50
Top width shall be kept as 0.30 m
Bottom width = 0.5 x height = 0.5 x 3 50 = 1.75 m
Keep width of 1.75 m at 0.3 m above foundation elevation and 2.0 m at foundation elevation.
Foot Bridge
It is proposed to provide footbridge of 2.0 m width. The bridge shall be located over the cistern
floor at the end of cistern floor, measuring 2.0 m towards fall The top elevation of slab shall be
kept at the downstream service road elevation of 1335.90 m. The thickness of RCC slab shall
be kept as 0.30 m. So bottom elevation of slab will be at 1335.90 - 0.30 = 1335.60 m
D/S FSL is 1334.15 m. So difference between D/S FSL and Bottom of slab i.e. free board =
1335.60- 1334.15= 1.45 m.
So free board of 1.45 m is sufficient than required 0.50 m The slab of foot bridge shall rest on abutments at both ends. The top elevation of abutment shall be top elevation of slab i e
1335.90 m.
Foundation elevation of abutment shall be taken 1.00 m below cistern elevation Foundation elevation = Cistern elevation - 1.00
= 1333.40 -1.00 = 1332.40
Top width of abutment shall be kept as 0.80 m
Bottom width = 0.5 height of abutment
= 0.5 (Top elevation - foundation elevation) = 0.5(1335.90-1332.40)
= 0.5x 3.50 = 1 75 m
So  keep  width  of  1.75  m  at  0.30  above  foundation  elevation  i.e foundation elevation
D/S Return wall
Return wall shall be kept 0.8 m above footbndge slab elevation i.e. 1335.90 + 0.8 = 1336.70
1332.70 m and 2.0 m at
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Foundation shall be kept at 1.00 m below cistern elevation i.e. 1332.40 m
Top width shall be 0.30 m and bottom width = 0.5 times height
= 0.5 (Top elevation - foundation elevation) = 0.5 (1336.70 - 1332.40) =2.15 m
May 2007
Keep  width  of  2.25  m  at  0.30  m  above  foundation  elevation  i.e.  1332.70  and  2.50  m  at foundation elevation.
The  detailed  drawing  of  the  structure  based  on  above  detailed  design  is  available  at  Drawing no. AD-F-Canal-DIS-31& 32.
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4.5 1.0M WELL TYPE FALL ON TERTIARY CANAL RT-16-9
May 2007
In the Arjo - Dedessa project there are two Primary  canals, left and Right Primary  canals, takingoff from the dam. The Left and Right) primary  canals  are contour canals. Secondary (Distributory) canals are takingoff from these primary canals.
For the purpose of detail planning of distribution network  system the command area of the secondary  canals  RS-16 and RS-17 under Right Primary  canal has  been selected. In above sample area secondary  canals, tertiary  and quaternary  canals  along with the proposed drainage arrangements  have been planned in details. The number of tertiary  canals  that are takingoff from these two secondary canals along with their length and discharge at head are as under
S. No
Secondary canal
Length  in km
Head    Discharge in m3/sec
No of Tertiary canals
Left
Right
Total
1
RS-16
2.10
0.48
8
7
15
2
RS-17
3.00
0.58
11
11
^22
3
The maximum discharge of tertiary canal RT-16-9 is 0 04 m /sec with 20% flexibility factor This tertiary canal is takingoff from 1.20 km of secondary canal RS-16 on left side The discharge of tertiary  canal  is  very  small  and  it  is  equivalent  to  watercourse.  Therefore  the  dischar  e  of tertiary  canal  is  kept  same  as  0.04  m’/sec  for  entire  length  of  tertiary  canal.  T  he  length  o^ tertiary  canal  RT-16-9  is  proposed  to  be  1186m.  The  ground  level  along  the  canal  is  stee  I falling and difference between the ground elevation in the length of 1186 m is from S
1327.00  (-  6.7  m)  l.e.  slope  is  1  in  177  The  F.S.L  of  secondary  canai  RS  ,6^  '“"'J0
1334.10 m (up stream).
Design of Tertiary canal
The tertiary canal section is required to be designed first
The discharge of tertiary canal is 0.040 m3/sec considering earthen bed width and 0.20 water depths and side slopes of 1 51
Area of canal = (B+nd) d
Where :
B = bed width
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n = side slope
d = water depth
= (0.30+1.5x0.2)0.2 = (0.3 + 0.3) x 0.2
= 0.6 x 0.2 = 0.12 sq m
P = wetted perimeter = B + 2(Vn2 + I) d
= 0.30 + 2(Vl.5  + l )o.2O = 0.3 + 0.4 V3.25
= 0.3x0.72 = 1.02 Hydraulic mean depth R = — =
May 2007
z
= 0.1176
P 1.02
R273 = 0.24
It is proposed to provide slope of 1 in 1000 = 0.001
Velocity by Manning's formula:
V = -«2/}(5),/2
n
Where, n = coefficient or Rugocity = 0.0225
R = Hydraulic mean depth
S = Slope
Substituting values
V= —!—x 0.24 (0.001)1/2
0.0225
V = 10.66 x 0.0316 = 0.338 m/sec
Q = A x V = 0.12 x 0.338 = 0.4056 m3/sec
So assumed section is alright.
The slope of canal is 1 in 1000 where as ground slope in 1 in 177 The     neretore there shall number of falls on tertiary canal. It is proposed to provide 1 00 m 'wlYePll er „tall just down
say at a distance of 10 m of tertiary canal
The u/s full supply elevation of secondary canal at off take of tertiary canal is 1334 driving head 0.15m proposed for tertiary canal, the full supply elevation of n- 1 ° m W'th
«eam
1334.10-0.15 = 1333.95 m
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With slope of 1 in 1000 in canal the FSL of canal at 10 m shall be
FSL elevation at head - 10/1000 = 1333.95-0.01 = 1333.94m
The ground elevation at 10 m is assumed same as that at head i.e. 1333.70 m Therefore Details of tertiary canal at 10m distance are as follows
May 2007
1. Full supply discharge —
2. Full supply depth —
3.  Canal bed width
4. Full supply elevation =
5. Canal bed elevation =
3
.
u/ s     0.04
=------ m / sec u/s     0.04
u / s     0.20 m
D/s 0 20 m
D/s 0.30 m
u/s _ 1333.94 D/s " 1332.94 U/s _ 1333.74
D/s ~ 1332.74
6.  Canal slope
=
0.001, 1 in 1000
7.  Side slopes of canal
=
1.5 : 1
8.  Ground elevation
=
1333.70
Design of fall
Since well type fall is proposed, first determination of crest elevation is required. For crest it is assumed that rectangular notch shall be provided at upstream end of well. Width of the notch is proposed to be equal to bed width of canal i.e 0.30 m
Determination of crest elevation.
Discharge through rectangular notch is give by formulae
Q^xcdxBjlg dyl
3
Where Q = discharge of canal = 0.04 m /sec
cd = coefficient of discharge = 0.62
B = Horizontal length (width) of notch = 0.30 m
d = Depth of crest below upstream F.S.L elevation
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Substituting values in formula, d can be evaluated
0.04 = | x0.62 x 0.30 x 72x9.81 x d3'2
= 121=0.073
0.53
3                     2/5=0.17
d  =(0.073)
Neglecting the velocity head due to velocity of approach
Crest elevation of notch = U/s FSL of canal- d = 1333.94 - 0.17 = 1333.77 m. U/s protection
May 2007
No protection on upstream is required. However, provide for 1.00 m length protection of CC blocks or stone pitching for 0.30 m depth laid over 0.15 m thick gravel. At end of protection a toe wall of 0.30 m width at top at u/s canal bed elevation for 0.90 m depth shall be provided. Bottom width at foundation shall be 0.60 m
Energy dissipation: -
It is proposed to provide water cushion in well for energy dissipation by means of impact and deflection of velocity  from vertical to horizontal direction. The water cushion is  formed by suitably depressing the floor below the down stream canal bed elevation. The length and depth of water cushion required shall be determined by following formula
Length = 5 x (H xD)''
2
l
Depth = -(H,xD)2'j
4
Where, D = Depth of crest below upstream FSL = 0.17
HL = Height of drop in meter = 1.00 m
Substituting values
Length of cushion required = 5 (1 xO. 17)1/2
= 5x0.41 = 2.05 m
Provide well of RCC pressure pipe of 1.0 m diameter.
Rest of cushion length required shall be provided by fixing H
downstream of well before the water is released in canal section 3 P'Pe for 2 m |ength
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4 £ x/)) 2' 1                4
Depth = -(//
= -x 0.31 = 0.08 m
4
Provide depth of 0.15 m below the bottom elevation of proposed Hume pipe
May 2007
= -(lx0.17)2'3
In downstream of well provide RCC Hume pipe of 0.30 m diameter for 2.5 m length
The velocity in pipe shall be given by
Q = 0.04
A nd2
4
22 0 32
Area of pipe = —x——= 0.0707 m2
74
V =             = 0.57 m/sec
0.0707
The velocity in canal is 0.338 m/sec
To pass the discharge of canal through pipe it is essential that pipe should run full. For pipe to run full the top of pipe shall be kept 0.10 m below down streams FSL of canal
Assuming the thickness of pipe 0.08 m
• Different elevation for pipes are as follows
Top elevation = d/s FSL - 0.1 = 1332.94-0.1 = 1332.84
Bottom elevation of pipe = top elevation of pipe - 0.30-2 thickness of pipe
= 1332.84-0.30-2x0.08
= 1332.84-0.46 = 1332.38m.
Provide the floor for water cushion in well, 0.15 m below d/s invert elevation of pipe Invert elevation of pipe
= Bottom elevation + thickness of pipe
= 1332.38 + 0.08 = 1332.46 m
So water cushion floor elevation = Invert elevation of pipe - 0 15 = 1332.46 - 0.15 = 1332.31
Water cushion floor shall be 0.50m thick, Top 0.15 with cc. M-20 lain
. ora over 0.35 m thick CC M
10.
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Bottom elevation of cushion floor = Top floor elevation- 0.50m
= 1332.31-0.50=1331-81. Keep 1331.80 Length of pipe in downstream of well is 2.5 m
The top elevation of pipe of well is kept-0.30m above upstream elevation Top elevation = u/s FSL +0.30 = 1333.94 + 0.30 = 1334.24 m
May 2007
The Bottom elevation of pipe is proposed to be kept 0.25 m inside water cushion floor
Bottom elevation of pipe = water cushion floor elevation 0.25
= 1332.31-0.25 = 1322.06 m
Length of pipe of well of 1.0 m diameter = Top elevation - Bottom elevation
= 1334.24-1322.06 = 2.18 m
If the pipe is available in 2 25 m length it shall be used other wise 2.5 m length pipe shall be used.
D/S Protection
The invert elevation of D/S outlet pipe is = 1332.46
The D/S canal bed elevation is = 1332.74m
Therefore to negotiate the difference in level, sloping floor from 1332.46 to 1332.74 m shall be provided for 2.00 m length.
The floor i.e. protection shall consists of 0.30 m CC block or stone pitching laid over 0 15 m
thick gravel for 3.0 m length in bed and slope of canal. The pitching in slope shall be 0^30 m
above down stream F.S.L of canal i.e. up to 1332.94+0.3 = 1333 24 m
A toe wall at the end of down stream protection shall be provided with 0.20 m top width at D/S canal bed elevation and 0.8 m deep, with bottom width of 0.50 m at foundation
The detailed drawing for the structure is available at Drawing No. AD-F-Canal DIS 33
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4.6 DESIGN OF PARSHALL FLUME FOR SECONDARY CANAL RS-17
For  measuring  the  rate  of  flow  of  canal  or  channel  there  are  number  of  methods  and  de some of them are
—
1     By   measuring   velocity   by   float   or   current   meter   for   known   sections   (useful   for   large discharge)
2   By weirs
3   By Venturi flume device or structure
4   By Parshall flume device or structure
Out of the above for smaller discharge, like for secondary  canal of Arjo-Dedessa Project, Parshall flume appears  to be more suitable structure that can be used for the flow measurement. It is  proposed to provide flow measurement structures  i .e. Parshall flume at head of every secondary canal in the project.
The  parshall  flume  is  a  critical  depth  measuring  device.  The  parshall  flume  is  inline  open channel measuring structure.
The flume consists of three principal sections
a)         Converging  or  contracting  section  at  its  upstream  end,  which  is  broad  and  flat  and  floor is level, both longitudinally and transversely.
b)        Constricted section or throat, which is narrow and floor inclines downward
c)        Diverging or expanding section in the downstream.
The floor of diverging sections  slopes  upward. The floor of converging section is  the crest of flume. The walls  of converging section to throat are kept vertical. Throat section has  parallel walls, and floor inclining downwards  generally  at a slope of 3:8 (H: V). Diverging section has  a floor inclined upward generally  at a slope 1:6 (V: H) and wall diverging towards  the outlet A graduated scale is fixed in a stilling well constructed in the converging section to measure head of water over the floor of this  section. Another scale is  fixed in the other stilling well at the beginning of the divergent section to measure the head at that section for submerged flow
These flumes are built either of wood, steel sheets, concrete blocks, concrete or bricks
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Hydraulic Properties
Mayj?oo7___________________________
Discharge through the Parshall flume can occur under free flow or submerged flow condition. To determine the rate of flow or discharge, two depth gauge, are provided in the wells as explained above. Both gauges are set with zero points at the mean elevation of the crest of the flume.
When the correct relation between throat width and discharge is  chosen, the velocity  of approach is automatically controlled. This control is accomplished by selecting a throat, wide enough to accommodate the maximum flow to be measured yet, narrow enough to cause an increase in the depth of flow upstream. The result is  a larger cross-sectional area of the approaching stream and hence a reduction in velocity.
For the feasibility study, type design of one parshall flume structure for secondary canal RS-17 of Right Primary canal has been done. The hydraulic data for secondary canal RS-17 at 300 m below the Regulator are as given below:-
The secondary canal RS-17 takes off at km 21.788 from Right Bank Primary Canal.
1
Design discharge
=
0.58 m3/sec
2
Full supply elevation
=
1343.01 m
3
Bed width
=
1.0 m
4
Full Supply depth
=
0.68 m
5
Bed elevation
=
1342.33 m
6
Bed slope
=
1 in 300
7
Side slopes
=
1.5:1 (H: V)
8
Velocity
=
0.418 m/sec
9
Ground elevation
=
1343.20 m
The design of Parshall flume is based on FAO Manual 26-1
For the design of Parshall flume, quantity of flow can be measured through several sizes flume, but for the sake of economy the practical size should be selected from consideration
j) First assume that a submergence shall not exceed 70% for non submergence flow.
jj) Flume size, waterway dimension W shall be selected from one third to one half th
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iii)  Flume  water  way  shall  not  be  too-narrow,  due  to  which
high  and  long  upstream
embankment might be required.
In case of RS-17 secondary canal bed width is 1.0 m, so width and flume size shall be between
0.33m <W< 0.50m
From the table available in Annexure - 6, the only standard size flume available in above range is 45.72 cm say 46.0 cm.
3
For discharge of 0.58 m /sec i.e. 580 Its/sec, the Ha is 68 cm i.e. 0.68 m.
For submergence of 70% ratio of — = 0.70
Ha
Hb = 0.70 x 68 = 47.6 = 48 cm
At 70% submergence, the water surface in throat at the second gauge (Hb) shall be kept level with that of the lower end of the flume Therefore for this condition of flow, the depth of water below the structure shall be same as before the flume is installed i.e. 0 68 m.
By subtracting Hb from D, the value for x i.e. depth of D/s floor below crest is obtained x = 68- 48 = 20 cm
.. Crest elevation shall be 20 cm above the bottom elevation of D/s channel.
The actual loss of head for discharge of 580 It/sec with 70% submergences, crest 20 cm above and for the flume size of 46 cm, the loss of head between upstream and downstream FSL from graph available as Annexure - 7, shall be 28 cm.
Since this loss of head is loo large .hereto, either increase the submergence ratio to 85-/ increase the Home size. From to graph I, can be seen thai by increasing only width s, " flume the loss can be reduced but not to major extent Therefore it is 
submergence ratio to 80% in addition to increase width size of flume to 60 96. Tei 0 cm^86 Therefore it is proposed to select 60.96 (61cm) throat width and 60 cm « u
submergence ratio. The free flow discharge for above flume  o
fr  m t„e
Annexure-6, is 0.667 It/sec or 667 It/sec.
., For 80% submergence ratio
Hb = 0.8 x Ha = 0.8x60 = 48.00 cm
X = D - Hb = 68-48 = 20cm
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Crest elevation shall be 20cm higher than D/s bed elevation. Head loss for 647 flow and 80% submergence for 61 cm throat of flume shall be 14.00 cm. So difference between upstream and downstream FSL shall be 14.00.
The depth of water upstream from the structure shall be equal to
= Water depth in canal downstream + 0.14
= 0.68 + 0.14 = 0.82 m
•    Different elevation of structure
Keeping U/s FSL 1343.01
•    U/s canal bed elevation = 1343.01 - 0.82 = 1342.19 m
D/s FSL = 1343.01 - 0.14 (Head loss) = 1342.87 m
D/s canal bed elevation = 1342.87-0.68(D) = 1342 19 m
Crest elevation shall be 1342.19+0.20
= 1342.39 m
Discharge for submerged flow
For submergence of 80% negative correction shall be applied of evaluation for elevation of submerged discharge to the free flow discharge. This submerged discharge is determined by using a correction factor as per diagram available at Annexure - 8. The diagram is a graph between correction of flow to upper head Ha, and percentage submergence.
The (graph) diagram Is (or throat width o( 30.54 cm 6ume for other throat size, multiplying (actor Is given. For 60.96 (61) cm throat width multiplying (actor is 1.6. The correction for discharoe (or submerged condillon shall be obtamed by subtracting correction of flow multiphed b
multiplication factor from discharge of free flow condition
For Ha = 60cm and throat width 61.00 cm, Free flow discharge = 647 lit sec
From the diagram for computing rate of flow for submerged condition for 30 5 width Ha = 60 cm and 80% submergence, the subtracting discharge is about 33 lt/sec F throat width multiplying factor is 1.8 so Total discharge to be deducted shall -
y
61
59.4 say 60 lite/sec 
S 3         6 = 33 x 18 =
Submerged flow discharge = Free flows discharageuu- 60 =0644r7- 60 - 587 lit/sec or 0 5R7 against the required discharge of 0.58 lit/sec 
m /sec
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Therefore selection of throat width of 61 cm & Ha - 60 cm is alright.
May 2007
Standard   dimensions   and   capabilities   of   the   parshall   flume   are   given   in   enclosed   table annexure - 9 and 10 for various throat widths for free flow.
The dimensions for the design under consideration are as follows:- For 61 cm throat width (All dimensions are in cm).
i) A= 102
ii) B = 150
iii) C = 92
iv) D = 122                  v) E = 92                      Vi) F = 61
Vii) G = 92
Viii) K = 7.6
IX) N = 23
X) X = 5.1                   XI) Y = 7.6
Minimum flow that can be measured = 11.89 It/s i.e. 0.0119 m3/sec 
Maximum flow that can be measured = 936.7 It/s i.e. 0.937 m3/sec
With  the  dimensions  as  given  above  a  detailed  drawing  for  parshall  flume  has  been  prepared which is available at Drawing no. AD-F-Canal-DIS-34.
147Arjo-Dedessa Irrigation Project Hydraulic Design of Canal Structure
May 2007
Annexure - 6
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Annexure 7
DUgrAjm       for       d<t<       rtninlnB          the       head       iota       throu-h
luring Gum* (82)
*
I
I
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Annexure - 8
Throat   arid   th
H                  cm
1 JO. 5
1.5                45.7
Multiplying factor (M)
2
61.0
1.  H
>
91.5
2.  4
4
122.0
3.  I
5
152.5
3. 7
6
121 0
4I
Hum. (11).
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150Arjo Dedessa Irrigation Project
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Annexure - 9
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Summery

Project Overview

The Arjo-Dedessa Irrigation Project is a major water resources development in Ethiopia, featuring:

A 40.6m high rock-fill dam on the Dedessa River (tributary of Abay River)
Two primary canal systems (Right Bank and Left Bank) totaling 102.98km
Irrigation command area of 13,665 hectares
Comprehensive hydraulic structures including regulators, cross-drainage works, and bridges

        Key Components
        Dam: FRL at 1356.0m, minimum drawdown at 1350.0m
Spillway: Ogee crest with chute spillway structure
Canal Systems: Right Bank (44.166km) and Left Bank (60.18km) primary canals

    

Canal System Details

Canal	Length (km)	Gross Area (ha)	Culturable Area (ha)	Secondary Canals
Right Bank Primary	44.166	6,827	6,215	40
Left Bank Primary	60.18	10,998	7,450	45

Hydraulic Structures

Control Structures

Head regulators (76 total)
Cross regulators (11 total)
Escape regulators (2 total)

Cross Drainage Works

Type	Right Bank	Left Bank	Total
Aqueducts	2	4	6
Siphon Aqueducts	17	16	33
Canal Siphons	4	2	6

Bridges

Road Bridges: 10 total
Foot Bridges: 3 independent + 14 combined with other structures

Design Parameters

        Hydraulic Design Criteria
        Manning's roughness coefficient (n) = 0.0225
Canal side slopes: 1.5:1 (cut), 2:1 (fill)
Velocity ratio (V/V₀) maintained between 0.90-1.10
Critical velocity formula: V₀ = 0.546D⁰·⁶⁴

    

Sample Secondary Canal System

Detailed planning for sample secondary canals RS-16 and RS-17 includes:

Canal	Length (km)	Command Area (ha)	Discharge (m³/s)	Tertiary Canals
RS-16	2.1	339.9	0.48	15
RS-17	3.0	414.75	0.58	22

Key Design Features

Contour alignment for primary canals
Flexibility factors incorporated in duty calculations (10-25%)
Non-scouring, non-silting velocities maintained
Comprehensive energy dissipation measures
Detailed scour protection design