FEDERAL  DEMOCRATIC  REPUBLIC  OF  ETHIOPIA MINISTRY OF WATER RESOURCES
ERER DAM & IRRIGATION DEVELOPMENT PROJECT
Final Detail Design Report
Annex E: Irrigation & Drainage Design May. 2009
CONCER1 ENGINEERING AND
CONSULTING ENTERPRISE P.L.C. (CECE)
ENGINEERS WATER RESOURCES A AGRICULTURAL
DEVELOPMENT PLANNERS
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Executive Summary
Volume I :            Dam & Appurtenant Structure Annex A: Dam Design
Annex B: Dam Appurtenant Structures Annex C: Geotechnical Study
Annex D: Hydrolog}'
Volume II:           Irrigation & Drainage
Annex E: Irrigation & Drainage Design Annex F: Road Infrastructure
Annex G: Project Control Centers
Annex H: Operation & Maintenance Manual Volume III:          Project Worth AnalysisTable of Contents
1.0 Introduction
1.1 Aim of Project
1.2 Location of Project
1.3 Access to the Project Area
2. About the Project
2.1 Source of Irrigation Water
2.2 Climatic Conditions
2.3 Topography of Command Area.1
2.4 Population'
2.5 Land Use
2.6    Project Components .
3.1 Physical Characteristics8
3.0 Soil Suitability
3.1.1 Texture.................................................................................................................................................... 8
3.12 Drainage Class8
3.1.3  Soil Depth8
3.1.4  Soil Type9
3.1.5 Infiltration Rates9
3.2 Chemical Characteristics10 
4.0 Crop Water Requirement11
4.1 Cropping Pattern11
4.2 Proposed Cropping Pattern11
4 3 Crop Water Requirement12 
4.4 Irrigation Scheduling13 
5.0 Irrigation Water Quality
6.0 Field Irrigation
6.1 Depth of Watering
6.2 Field Irrigation Efficiency
6.3 Field Channel Discharge
6.4  Field Size
6.5 Furrow Spacing
7.0 Irrigation System
7.1 Canal System
7.1.1 Primary Canal
7.1.2  Secondary Canals. 7.1.3 Tertiary Canals 7.1.4 Quaternary Canals
7.2 GCA AND CCA
7.3 Irrigation Intensity
7.4    Night Irrigation
16
17
17
18
18
19
19
19
19
20
20
21
22
237.5 Irrigation Efficiencies
7.5.1  Storage Efficiency
7.5.2  Conveyance Efficiency
7.5.3 Field Application Efficiency 
8.0 Planning and Design of Canal Network
8.1 Canal Alignment
8.2 Canal Design
8.3 Design Criteria
8.3.1 Limiting Velocities
8.3.2 Working Head
8.3.3 Longitudinal Slope
8.3.4 Critical Velocity Ratio (CVR)
8.3.5 Free Board
8 3.6 Bank Width
8 3.7 Saturation Gradient
8.3.8 Inspection Roads
8.3.9 Canal Embankment Material
8.3.10 BERM
8.3.11  Catch Water Drain 
8 4 Command Area And Design Discharges For Quaternary Canals 8.5 Calculations of Design Capacities
8.5.1 Quaternary Canals
8.5.2 Tertiary Canals
8.5.3  Secondary Canals
8.5.4 Primary Canal
8.5.5 Capacity Statements for Different Reaches 8 6 Procedure Adopted for Design
9.0 Irrigation Structures
9.1 ESCAPE Structures45
9.1.1  Choice of Types of Escape45
9.1.2  Criteria for Location46
24
25
25
25 
.26
26
27
28
29
29
29
30
31 
31
31 
32
33 
33
.34 
36
36
37 
.37 
.38 
.39 
.44 
.45
32
9.1.3  Criteria for Escapes Capacity47
9.1.4  Design Considerations.....................................................................................................................................................48
9.2 
Canal
Head 
and 
Cross
Regulators49 
9 3 Outlet Structures: 50
9 4 Drop Structures
9.5    Tertiary canal Head Regulator
9.6    Duck Bill Weir Structure
9.7 Tail Escape Structures
10.0 Cross Drainage Structures............................................................................................................  gg
10.1 Aqueducts...............................................................................................................................  56
10.2 
11.0 Field Drainage System
11,1  Excess Rain Water
Culverts
6011.2 Excess Irrigation Water......................................................................................................................... 67
11.3  Field Drain Capacity.............................................................................................................................67
11.4 Tertiary Drains.......................................................................................................................................68
11.5 Drain Layout..........................................................................................................................................69
12.0 Flood Protection Embankments.............................................................................................................. 71
12.1 Design Criteria...................................................................................................................................... 71
12.2 Design ofEmbankments........................................................................................................................ 73
13.0 Construction Materials............................................................................................................................75
13.1       Earth Works..................................................................................................................................... 75
13 .2 Masonry and Concrete Works............................................................................................................... 75
14.0 Operation and Maintenance of Irrigation           System..................................................................... 76
14 1 Dam Structure........................................................................................................................................76
14 2 Regulatory Structures............................................................................................................................. 76
14.3 Operation Of Reservoir And Conyeyance           System :..................................................................... 77
14.4 Field Irrigation....................................................................................................................................... 78
14.5 Maintenance........................................................................................................................................... 78
14.5.1 Canal Network........................................................................................................................... 78
14.5.2 Field System.............................................................................................................................. 78
14.5.3 Drains.........................................................................................................................................78
14.5.4 Roads......................................................................................................................................... 78
15. Land Grading............................................................................................................................................. 79Erer Dam & Irrigation Project ZCECE & CES
1.0 Introduction
1.1 Genesis of the project
Ethiopia is confronted  with  food  scarcity  problem.  Rain  fed  agriculture is being  practised  with  age old  agricultural technology  which  has resulted  in  low production.  Imgated  agriculture is recognised  as one of the major means to  solve the food  deficit problem and  alleviate the poverty  of rural people,  besides ensuring  increased  production  of raw materials for agro-industry,  reduced food import, savings in foreign exchange and creating employment opportunities.
Considering  the importance of irrigated  agriculture in  all round  development,  the government of Ethiopia had  initiated  action  to  bring  more and  more area under irrigated  agriculture In  1998, Wabe Shebelle River Integrated  Master Plan  was drawn  up  and  Erer irrigation  project was identified  as one of the potential scheme for development of irrigated  agriculture.  Consequently Pre- Feasibility  and  Feasibility  studies were carried  out by  Water Works Design  and  Supervision Enterprise ( WWDSE  ) in  association  with  WAPCOS and  Synergies India Pvt,Ltd  respectively  in 2002-05  and  2006-07  This project was found  technically  feasible,  economically  viable, environmentally  sound  and  socially  equitable and  therefore recommended  for implementation.  The detailed  designs are now being  prepared  to  enable the government to  implement the project with promptitude.
Table 1.1 Salient Features of The Project
Description
Figures
Latitude and Longitude (Command
area)
UTM 1009300 N to 1028300 N (9°07 17 Nto9°1740’ N)
and
UTM 193375 E to 199650 E (42°12 24 E to 42°16 03 E)
Catchment area
•
419.00 Sq. Km
Annual rainfall
650 mm to 800 mm
Net CCA
•
3722 Ha
River Bed (deepest)
'1348.00 m
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Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES___________________________________________________
Dead Storage Level
/ New Zero Elevation (50 years)
1369.85 m
MDDL
1371.OOM
FRL
1379.00 M
MWL
1382.60 M
Dam Type
Zoned Earth fill
Top of Dam
1384.60 m
Maximum height of dam
36 60 m
Gross storage
5067.50 Ha-m
Live storage
2303.40 Ha-m
Spillway Type
Ogee weir with inclined chute
Waterway of spillway
30 m
Inflow design flood (greater of 0.5 PMF and 10,000 year return period)
641.90 Cumec
Spillway routed flood
•
440 50 Cumec
Area to be irrigated (CEA)
3370hectares
FIRR
11.16(%)
E/RR
14.56 (%)
B/C ratio
1.50
NPV (financial)
204* 106 birr
NPU (economical)
122* IO6 birr
Financial & economic viability
verified
1.2  Location of Project
The Erer Irrigation  Project proposes to  draw irrigation  supplies from Erer River which  is a tributary  of Wabe Shebelle River.  The project is located  at about 530  km from Addis Ababa and 
19 km from Harar town. The command area is situated on both sides of Harar-Jijiga road which is
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Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009
iErcr Dam & Irrigation Project ZCECE & CES
11  km  from  Babile  town  towards  Harar.  The  proposed  dam  site  is  situated  about  6  km  on  left  side of Harar-Jijiga road (see figure 1.1).
Erer Irrigation  Project is located  in  two  Regional States,  namely  Regional State of Harari and Regional State of Oromia.  In  Oromia,  project area is situated  in  Babile of the East Hararge
Zone   In   Harari   it   is   situated   in   Erer   and   Soft   Woredas.   The   command   area   is   situated   in   2 
Kebeles ( Kile and  Erer Dodota) of the Harari Region  and  in  about 7  Kebeles ( Erer Ibada,  Ifadin, Gamachu,  Erer Guda,  Tula,  Berkele and  Tofiq  ) of Oromia region  Major part of command  lies in Erer Ibada and Efadin Kebeles.
The command  area starts from some distance downstream of the dam and  extends only  on  right bank  of Erer river.  The command  area is narrower and  smaller near the dam site and  becomes wider in  the downstream side The irrigable area is mainly  situated  below the bridge on  Harar Jijiga road  and  extends beyond  confluence of Erer River and  Bidisimo  stream covering  only  the right bank  of the river.  Although  suitable areas are available on  left side of the river also,  due to limitation  of water availability  for irrigation  only  the command  on  the right bank  of Erer River is chosen for this project.
The  command  area  is  located  between  UTM  1009300  N  to  1028300  N  (  9°  07*  17”  to  9°  17’ 40”Latitude ) and UTM 193375 E to 199650 E (42°12’24”to 42° 16’ 03”Longitude).
1.3 Access to the Project Area
The project area can  be accessed  by  an  asphalt road  (511  km) from Addis Ababa to  Harar town and  further 19  km by  all weather gravel road  which  connects Harar with  Jijiga town.  Harar town can  also  be accessed  partly  by  air up  to  Dire Dawa and  remaining  about54  km.  by  road  from Dire Dawa to Harar.Babile is the nearest town which is 11 km from project area.
The proposed  dam site which  is about 6  km from Harar- Jijiga road,  is connected  by  fair weather road.  The entire proposed  command  area from head  to  tail is connected  by  fair weather road  and therefore,  the area can  be accessed  for carrying  construction  materials and  equipment without making special arrangement of approach roads
---------------------------------------------------------------------- --- --------------------------------------------  3 Annex E Irrigation & Drainage Design /Final Detail Design Report /2009ERRER DAM IRRIGATION PROJECT ROAD NETWORK
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PRIMARY CANAL SECONDARY CANAL ROAD
INDEX CONTOUR INTERVAL CONTOUR
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RIVER
NATURAL DRAIN UN SUITABLE LAND
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2. About the Project
2.1  Source of Irrigation Water
The source of irrigation  water for the proposed  command  area is the flows of Erer River Errer is a tributary  of Wabe Shebelle River which  is situated  in  the semi arid  area of Wabe Shebelle basin.  Wabe Shebelle river basin  is located  between  0° N to  9° 30’ latitude and 38° 30’ E  to  46° E  longitude .  It originates from the Bale mountains at an  approximate elevation  of 4000  m above mean  sea level and  drains in  to  Indian  Ocean,  after crossing Somalia.  The total basin  of Wabe Shabelle is approximately  280,000  km2,  of which  72  % lies in  Ethiopia Large part of Somalia,  part of Oromia,  part of Southern  Nations, Nationalities and  People (SNNP),  part of Dire Dawa and  the entire Harari,  are located  in Wabe Shebelle Basin
Erer River and  its tributaries originate from the highlands close to  kombolcha town  where general elevation  is about 2500  m above mean  sea level.  The Erer catchment up  to  the proposed  dam site is about 419  km2  The water shed  has dense network  of tributaries.  The major tributaries are samte,  Gadi,  Ulan-ula,  kombolcha,  Bosensa,  Hida and  Daka.  The topography  of the catchment is dominantly  mountainous and  hilly  with  relatively  flat and rolling  land  along  Erer River.  Owing  to  intensive deforestation,  cultivation  and  overgrazing the land degradation is serious problem in the Erer River catchment
The catchment area of Erer River at bridge on  Harar -Jijiga road  is 469  km2  where discharge data are available for shorter length  of time The discharge of Errer is mainly dependent on  rainfall which  is highly  variable in  time and  space.  The water demand  for irrigation  does not match  with  the water availability  in  the river,  therefore storage dam is proposed to store the flood discharge and utilise in the times for irrigation and other uses.
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Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES
2.2  Climatic Conditions
The Erer valley command area is situated in sub-tropical climate having mean annual temperature 22°C,altitude between 1280 to 1365 meter above mean sea level, annual mean evaporation of 1658 mm and mean annual rainfall 650mm ( effective rain fall 292 mm).
Table 1 Climatological Parameters of Command Area
Data
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Rainfall (mm)
13.4
20.6
54.1
115.4
92.2
59.4
88.5
100.7
85.8
39.7
16.4
7.1
75% Dep. rainfall (mm)
0
0
10 2
48.6
46.2
22.9
48 1
60.6
44.3
11.0
0
0
Max temperature (oC)
22.2
23.0
24.2
24.0
23.1
22.4
22.8
23.3
23.7
22.5
22.2
21.8
Min temperature (oC)
17.5
19.2
20.0
18.9
19.5
19.1
19.2
19.4
18.6
19.4
16.0
17.2
Wind speed (m/scc)
1.61
1.62
1.30
1.09
0.95
0.94
0.95
0.94
0.95
0.99
1.36
1.55
Sunshine hours (hrs)
8.8
8.3
7.9
7.5
8.5
8.1
7.5
7.8
7.6
8.4
9.3
9.2
Relative Humidity (%)
52.6
52.7
54.0
56.1
50.9
45.7
51.3
54.4
54.1
45.6
46.1
51.2
A   summery   of   important   climatic   parameters   relevant   to   planning   of   irrigated   agriculture representing   the   command   area   indicate   that   the   rainfall   in   the   command   area   has   bimodal pattern,   first   peak   in   April   -May   and   second   in   August-September.   The   rain   fall   during   the months  of  June  and  July  is  low  and  uncertain.  In  remaining  months  there  are  no  rains  This shows  that  crop  growth  season  has  to  coincide  with  the  rainy  months.  This  is  responsible  for poor productivity.
Length  of growing  periods and  sowing  times of crops depend  mainly  on  minimum and maximum temperatures which  vary  within  a narrow limit.  This permits the sowing  and harvesting of crops at convenience depending upon availability of water.
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Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES
The  remaining  parameters  such  as  wind  speed  and  relative  humidity  have  only  moderate  values and do not affect crop productivity and crop water use significantly.
The sun shine hours indicate long bright days having eight to nine and half hours of bright sun shine.  During  the rainy  season  the sunshine hours get reduced  to  six  to  seven  hours owing  to clouds.
The climatic parameters indicated above suggest that crop production cannot be increased 
and stabilised without assured irrigation in the proposed command area of Erer project
2.3 Topography of Command Area.
The topography  of proposed  command  area varies from flat to  gently  slopping.  The altitude of command area varies from 1280 to 1365 m above mean sea level. The surrounding cultivated areas of Harar and Babile Woreda are situated on higher elevation. No major effort would be required for levelling of land if irrigated agriculture is to be practised. Also, natural vegetation is sparsely located  and  shallow rooted  excepting  some patches where acacia trees exist.  Only  moderate expenditure will be involved  in  removing  the natural vegetation  and  preparation  of land  for irrigation.
2.4 Population
The total population of the rural communities of two regions is 40,317 who are clustered in about 7,934 households. Eleven Kebeles fall in command and reservoir areas. It is estimated that about
3,462  households  will  need  to  be  displaced  from  their  villages  and/or  lands  from  reservoir  area (approximately 1985 ha). These households need to be settled at other places.
The quality of housing in project affected area is good. The majority of people live in wood and mud  houses'with  corrugated  iron  sheet roofs.  The majority  of houses tend  to  give shelter to  both people and  their livestock  The coverage of potable water is limited  to  about 48  % households (feasibility study, volume, sectoral report 13.
________________________________________________________________ 6 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES
2.5  Land Use
The  designated  area  of  Erer  irrigation  project  is  surrounded  by  extensive  coverage  of  natural vegetation  comprising  of  cactus,  thorny  bushes,  shrubs  and  acacia  trees  with  very  little  grazing land which is located beneath the natural vegetation and on steep sloping lands As observed, the cultivation is mainly rain fed in majority of areas situated in the proposed command area of the project excepting in riverbed where some irrigated agriculture is being practised. There arc three small irrigation schemes already operative in the command area. These are said to have been constructed and operated by Munchen fur Munchen, a NGO. The total irrigated area from these schemes is of the order of 20 ha. The agriculture practices are traditional oxen-cultivation based and local ploughs and hand tools are used in cultivation.
Amongst the crops,  most commonly  cultivated  crops observed  are maize,  groundnut,  vegetable crops (of onion, tomato, pepper) and fruit trees of mango. To some extent sorghum, sweet potato, haricot beans, banana, papaya and citrus are grown in and around command area Chat, a stimulant is also  grown  extensively  The local crop  varieties are used  No  fertilizers and insecticide/pesticides arc being used in rain fed agriculture.
2.6   Project Components
The Erer Irrigation project is proposed to comprise of the following components-
i)       A storage reservoir on river Erer situated at about 6.0 km distance upstream of its crossing with  Harar-Jijiga  road  which  intends  to  controls  the  flow  of  river  water  to  provide supplementary irrigation water to the area situated in the downstream side of the proposed dam site.
ii)     A network of canal and drains working in complementary and supplementary manner by serving the irrigation supply and removing the excess water in appropriate time from
irrigated command. 
'
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Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES
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3.0 Soil Suitability
Soils influence crop  suitability,  choice of land  utilization  types,  drainability  etc.  Therefore extensive soil surveys and  investigations are carried  out in  fairly  large area encompassing  the whole of the proposed  command  of Erer irrigation  project.  The soil surveys and  investigations have provided  detailed  information  on  the soils and  land  of command  area for selection  of crops and irrigation designs.
3.1 Physical Characteristics
3.1.1  Texture
Mosty  the soil is of has clay  loam and  loam texture.  The soils derived  from volcanic ash  and limestone has loam or silty  clay  loam texture The soils derived  from sandstone fall under the sandy textural class.
3.1.2   Drainage Class
The concept of soil drainage refers to  the frequency  and  duration  of periods when  soil is free of saturation  or partial saturation  by  water.  The soil drainage is reflected  by  colours of soil materials. The soil drainage of the project area falls in  moderate drainage class.  The soils situated  in  flood plains are imperfectly drained because they are situated in low areas.
3.1.3   Soil Depth
The soils in  proposed  command  area are deep  to  very  deep,  except the dissected  to  undulating dissected  and  rolling  dissected  soils,  which  are shallow to  very  shallow soils.  Thus depth  of soils will not cause any problem for irrigated agriculture.
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Annex E‘: Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES
3.1.4   Soil Type
Medium texture soils are found  to  be situated  in  higher elevation  areas which  are either luvisols or cambisols.  These are easy  to  manage and  have good  permeability  and  productivity.  The soils mainly  along  riverbed  are vertisols which  arc black  to  dark  brown  in  colour.  These soils have low permeability  and  are expanding  and  cracking  type.  These soils require special management and attention for adequate drainage.
3.1.5  Infiltration Rates
The  permeability  tests  have  been  carried  out  along  the  alignment  of  primary  canal  and  secondary canals   at   only   four   places   because   on   visual  examination   the   soils   along   the   entire   alignment   of primary   canal   and   secondary   canal   were   found   almost   identical.   It   was   also   revealed   in   pre feasibility   and   feasibility   reports   that   the   soils   along   the   proposed   canal   alignment   were   of   the same   type   and   were   not   having   high   infiltration   rates   Therefore   no   lining   was   proposed   in   the feasibility  report  In  view  of  this  only  a  few  infiltration  tests  are  proposed.  The  observed  rates  of permeability and infiltration are given as below:
Table 2 Results of Infiltration and Permeability tests
Site             Location
Av Infiltration rate
Av. Permeability
( cni/hr)
(cm/s)
1
N: 1025471, E:0196270
5.48
2.08*10^
2
N: 1020752, E:0177012
15.02
1.04*10^
3
N: 1012146, E:O196380
1.96
1.62*1 O'5
4
N: 1016979, E:0193575
2.13
2.08* 10-6
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Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES
If test results at either of the sites had  indicated  higher infiltration  rates more sites would have been  selected  to  identify  selected  reaches for provide lining  The above table reveals that the infiltration  rates are in  medium range and  do  not warrant the provision  of the lining in any part of canal system.
3.2 Chemical Characteristics
On chemical analysis of the soil samples following parameters are obtained:
(i)   pH ranges from6 7 to 8.89 which shows neutral to alkaline. At this level availability 
of micronutrients will reduce.
(ii)  Nitrogen percentage ranges from 0.02 to 0.44 Which is considered low to medium.
(iii) Organic Carbon Content varies from 0.479 to 2.99 which is quite low.
(iv)  Carbon: Nitrogen Ratio ranges from 7.94 to 10.56 which shows that there will be
general response to the Nitrogen fertilizers
(v)  Cation Exchange Capacity varies from 18.81 to 31 93 which is medium to high.
(vi) Base Saturation Percentage is greater than 74.22% which shows that the soils are
fertile.
(vii)   Exchangeable Sodium Percentage varies from 1.98 to 6.3 % which is low to 
medium and are within acceptable limits.
(viii)   Electrical   Conductivity   varies   from   0.12   to   0.45   dSm'1     which   indicates   low concentration  of  soluble  salts.  The  salinity  can  not  be  a  problem  in  this  type  of soils.
(ix)  The  soils  have  low  to  medium  levels  of  phosphorus  ranging  from  4.82  to  18.23 ppm  For  crops  which  demand  more  phosphorus  need  in  excess  of  20  %.  Thus  in general response to the phosphorus fertilizers is expected to be good
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Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES
* •
4.0 Crop Water Requirement
4.1 Cropping Pattern
Climate,  soils,  availability  of water and  requirement of food,  fibre,  money  etc decides the nature, scope and  extent of crops to  be grown  in  a particular area Basically  people settled  in  any  area decide the type of crops required to be grown for their own consumption
The main  crops to  be grown  in  the command  area should  be determined  in  due consultation  with the Agriculture Department and  the agriculturists,  looking  to  the crops being  grown  presently  and cropping  pattern  to  be introduced  for irrigated  farming  Crop  Calendar,  crop  water requirement and cropping  intensities should  be finalized  in  consideration  with  socio-economic factors of the area and also on the basis of the experience gained in irrigation projects implemented in the country.
4.2 Proposed Cropping Pattern
On  interaction  with  farmers of project area and  on  the basis of preliminary  surveys,  referring  to  the studies done in  past,  the Project Agronomist has proposed  the following  Cropping  Pattern  for Erer Irrigation Project.
Table 3 Cropping Pattern Proposed for Erer Project
Season 1 Meher
Crop type
Planting date
Area%
Maize
July
30
Sorghum
July
5
Ground nut
July
20
Rice
July
10
Haricot Bean
July
5
Vegetables
July
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Annex  E  :  Irrigation  &  Drainage  Design  /Final  Detail  Design  Report  /2009 Erer Dam & Irrigation Project /CECE & CES
Alfalfa
July
5
Sugarcane
July
10
Orchard
July
5
Total
100%
Season 2 Belg
Maize
Feb
30
Tomato
Feb
5
Rice
Feb
12
Potato
Feb
5
Okra
Feb
5
Sweet potato
Feb
5
Vegetables
Feb
5
Haricot beans
April
3
Sugarcane
July
10
Alfalfa
July
5
Orchard
July
5
Total
90
Total Cropping intensity
For Season-1 and Season-2 170% ( 20 % crops are perennial crops)
4.3   Crop Water Requirement
Crop  water  requirement  is  computed  on  the  basis  of  well  known  water  balance  equation  as  given below.
ETo   i.e   is   worked   out   by   using   universally   accepted   Penman-Monthieth   equation   CROWAT   4.3 software which is developed most recently is used to work out crop water requirement.
WR= (ETo* Kc ( C.T.F )—ER (R,ET,S ) + Ti ) / E 
Where:
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*
WR -Gross water requirement
ETo -Reference crop evapotranspiration (computed by Penman-Mothieth equation ) Kc - Crop coefficient- a function of C,T,F
C         - Crop type
T         - Stage of crop development
F - Frequency of soil wetting in the first crop development stage only
ER - Effective rainfall (which has been assumed as 80 %)
R
- Rainfall
ET 
- Actual evapotranspiration
S
- Soil moisture storage factor
Ti
- Technical irrigation( Application Loss )
E 
- Irrigation efficiency
The nearest climatological stations close to  Erer irrigation  project area are Harar Dire Dawa, Bisidimo  and  Jijiga The climatic parameters viz.  mean  monthly  rainfall,  temperature,  sunshine hours,  wind  velocity  and  relative humidity  as recorded  at these stations are utilised  in  working  out project climatological parameters after making suitable adjustments for difference in altitude etc
4.4   Irrigation Scheduling
•       Irrigation  schedule  is  designed  to  start  irrigation  from  the  first  planting  date  of  the  crops  when all  of  the  readily  available  soil  moisture  has  been  used  The  irrigation  amount  will  be  equal  to soil moisture deficit. The soil moisture deficit will return to zero after the irrigation.
•       The   water   application   time   is   planned   when   all   (100%)   of   the   readily   available   moisture   has been used up In this situation the crop will not become moisture stressed
•       The  water  application  depth  is  calculated  to  refill  the  soil  moisture  storage  so  that  the  soil  may return to its field capacity. (100% of the readily available moisture is replenished).
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•     Monthly ETo and monthly rain fall are distributed using polynomial curve fitting. To generate rainfall events, each 5 days of distributed rainfall is accumulated as one storm.
•     For total and readily available soil moisture the calculation procedure is indicated below. TAM = Total Available Moisture = (FC% - WP %)♦ Root Depth [mm], RAM = Readily Available Moisture = TAM * P [mm]
Where:
FC = Field Capacity
WP = Wilting Point
P = Depletion Percentage
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5.0 Irrigation Water Quality
Water   samples   form   Erer   River   were   collected   and   analyzed   at   the   Water   Works   Design   and Supervision   Enterprise   (WWWDE)   laboratory   at   Addis   Ababa   for   their   physical   and   chemical properties.   These   tests   were   conducted   to   find   out   the   turbidity,   total   solids,   dissolved   solids, electrical     conductivity,     PH,     ammonia,     sodium,     potassium,     magnesium,     manganese,     fluoride, chloride,  bicarbonate,  sulphates,  phosphates  etc.  The  test  results  are  given  in  table  2  attached  with the  feasibility  report  of  irrigation  and  drainage  part.  The  suitability  of  water  for  irrigation  has  been analyzed  in  this  report  and  it  is  confirmed  that  the  Erer  river  water  is  suitable  for  irrigation  and  is not likely to cause any adverse effect on plants or sails if applied for a long time.
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6.0 Field Irrigation
6.1 Depth of Watering
The plant uses the soil moisture available between  field  capacity  (at 0.1  or 0.33  bar pressure) and permanent wilting  point (at 15  bar pressure) which  commonly  called  as Available Water holding Capacity  usually  denoted  by  AWC.  In  practice the soil moisture is not allowed  to  go  up  to permanent wilting  point and  next water is applied  when  available soil moisture is depleted  by about 75% or so.  This is known  as Readily  Available Water holding  Capacity( TRAWC ) However some agronomists use a rule of thumb  and  assume two  third  of the total available
moisture   between   field   capacity   and   permanent   wilting   point   as   available   soil   moisture   for   plant. In case of Erer project this figure is taken as 70 %
On   studies   of   soils   in   command   area   following   AWC   values   were   found   (refer   Pre-   Feasibility Report)
Table 4 AWC Values for different soils of Command Area
Profile No.
FAO Soil Units
AWC mm/m
TRAWC mm/m
(E)DP3
Vertic Luvisols
143
100
(E)DP5
Eutric Cambisols
142
85
(E)DP8
Eutric Vertisols
159
111
(E)DP9
Vertic Cambisols
165
99
(E)SP1
Chromic Luvisols
155
93
(E)SP3
Vertic Luvisols
179
107
(E)SP5
Eutric Vertisols
152
106
Average
100
Average Readily Available Water Holding Capacity=100 mm
The peak evapo-transpiration are given as under( Refer Sectoral Report on Agronomy).
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Crop
Peak Daily ETc (mm)
Sorghum
4.7
Maize -I
4.9
Rice
5.1
Ground nut
4.4
Vegetables
2.6
Alfalfa
4.7
Sugarcane
4.7
Maize-II
4.7
Since Rice is not a dominant crop hence it is ignored for fixing the irrigation intervals. Daily ETc for most of the crops vary  between  4.4  and  4.9  For calculation  of irrigation  intervals the maximum ETc of Maize-I is used  Maximum interval at peak  irrigation  requirement shall be 100.0/4.9 = 20.40 say 20 days. The root depth of maize is 1.0 m.
6.2 Field Irrigation Efficiency
Field irrigation efficiency of 70% can be achieved and hence the same is assumed for ascertaining the feasibility of this project.
6.3 Field Channel Discharge
lhe field  channel discharge must be limited  80  lit/sec ( average about 60  lt/s ),  which  can  be conveniently managed by the individual farmer. Under no situation it may be allowed to exceed 80 lt/s. Therefore, it is recommended that the design capacity of the field channels may be adopted
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equal  to  or  less  than  80  lit/sec.  preferably  60.0  lt/s.  Normally  a  discharge  of  201t/s  is  considered  as minimum flow rate to irrigate a field.
6.4  Field Size
The field size can be determined as below:
Unit watering depth
=90.0mm
Field efficiency
=70%
Gross unit watering depth
=128.6mm(90/ 0.7)
Irrigation interval
=20 days
Field channel discharge(max)
=60 lit/sec
Field size (ha) max
=(60*20*24*3600)/(1000*0.1286* 10 )
4
= 80.5
Say 80ha
80 ha max field size is adopted for the design of quaternary canal. This is the size of command of
quaternary canal carrying discharge of 60 lt/s. The field is divided into 3 to 5 sub fields depending 
upon topography. Each sub field of 20 to 40 ha will be served by a field channel taking water from
quaternary canal. A small masonry structure termed as tum-out is provided as per requirement for
delivery of water in to field channels at suitable places.
6.5   Furrow Spacing
Considering  loamy  soils  and  0.1-  0.2%  slope  of  land  the  furrow  length  of  250m  is  adopted  Most of the crops are sown on furrows having 0.9m spacing. The same spacing is adopted in this project.
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7.0 Irrigation System
7.1 Canal System
7.1.1  Primary Canal
Canal system comprises of primary  canal which  off takes from Irrigation  Outlet located  on  the right bank  of river downstream of dam structure The layout of the primary  canal is guided  by minimum drawdown level in the reservoir and topography of the command area.
The full supply  level (FSL) of the primary  canal is fixed  in  such  a way  that it is able to  provide flow irrigation  under gravity  to  its entire command  In  design  of the dam sufficient working  head has been  provided  between  proposed  FSL  of the primary  canal and  maximum drawdown  level in the reservoir.  The full supply  level of the primary  canal at its head  is kept at EL.  1365.0  m above msl.  The primary  canal is aligned  as a contour canal providing  sufficient slope ensuring  adequate velocity.
As per nomenclature followed  in  Ethiopia the primary  canal is termed  as “P”.  Tertiary  canals off taking  from primary  canal are designated  as Tl-P,  T2-P etc.  The quaternary  canals off taking  from primary canal are designated as Ql-P, Q2-P and so on.
7.1.2  Secondary Canals
*
Two  secondary  canals off take from primary  canal at change km 14.67  and  are designated  as SI and  S2.  Both  these canals have head  regulators which  act as cross regulators for other secondary canal
First secondary canal (SI) travels across the contour and negotiates a fall of 40.0m through small
’vertical falls of 0.5m drop. The depth of drop is taken as 0.5m according to economy 
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considerations.  After  reaching  a  level  of  ELI  320.0m  the  canal  is  planned  as  a  contour  canal  to irrigate an area situated on its left side at a level lower than FSL.
r*
Second  secondary  canal (S2) off takes from the tail of primary  canal and  passes through  the rugged mountains comprising  of ridges and  valleys.  The canal is planned  as a contour canal on  the hill slopes and has a very tortuous alignment till it crosses river Dencho.
Tfae alignment of this canal,  as proposed  in  feasibility  report is not considered  appropriate around the site it crosses Dencho  river because the required  height of aqueduct will be very  high. Therefore the alignment is amended  considerably  around  its crossing  with  Dencho  river and  the height of aqueduct has been reduced.
7.1.3   Tertiary Canals
The   selected   system   provides   for   total   number   of   six   tertiary   canals,   one   off   taking   from   each primary canal and secondary canal II and four off-taking from secondary canals I.
7.1.4   Quaternary Canals
Quaternary  canals are the smallest canals which  off take from primary  secondary  and  tertiary canals.  The quaternary  canals carry  the full supply  discharge for the area it is serving.  All the water is diverted  in  to  field  channel of one field  to  irrigate the same.  The layout of the quaternary  canal is planned in such a way that it provides proper orientation of fields in proper direction of irrigation.
There are 51 no. of quarterly cannels off takihg from primary, secondary & tertiary canals.
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7.2         GCA AND CCA
The area which  can  be economically  irrigated  from a scheme without considering  the limitation  of quantity  of water is known  as Gross Commanded  Area (GCA).  The Culturable Commanded  Area (CCA) is that part of GCA where cultivation  is possible.  Therefore,  the areas which  are occupied by  ponds,  group  of houses,  alkaline soils,  reserve forest,  gully  etc.  are deleted  from GCA to  find CCA.  For any  new area proposed  for irrigation  about 10  to  15% of GCA is allocated  for non agriculture purposes to be occupied by roads, canals, drains etc.
At feasibility  level about 4000  ha has been  identified  as CCA and  scheme has been  drawn  up  on the basis of this area However at detailed  design  stage the estimates of GCA and  CCA have been reviewed as under:
On  field  visit of the site it has been  observed  that a lot of area,  much  more is available on  both banks of river in  the downstream of proposed  dam site which  can  be economically  commanded from the storage created  in  the upstream side of the dam but the quantity  of water is limiting  factor which  will decide the size of GCA and  CCA.  In  the present case therefore an  indirect approach  is followed to work out the size of CCA and GCA as below.
Net  Irrigation  Requirement  for  100  ha  area  =571.2  *103    m3  (refer  table  9.15  of  Sect  oral  Report on Agronomy)
Gross  Irrigation  Requirement  for  100  ha  area  =571.2  *  103/  0.50  (assumed  over  all  efficiency  as 50%)
= 1142.4* 103 m3 Water allocated for irrigation (75% availability) =38 484 Mm3
CCA (Culturable Commanded Area )
GCA( Gross Commanded Area) cultivable use)
=(38.484 *106 m3)* 100/ 1142.4* 103
= 3368.7 ha say 3400 ha
=3368.7/0.85 (15% area considered for non = 3963 ha say 4000ha
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The Gross Commanded Area of 4000 ha has been delineated on the basis of following 
considerations and indicated on the map appended with the report
1.     Topography   -   favourable   for  extending   gravity   flow.   Lands   situated   on   the   periphery   having slopes more than 5% are excluded.
2.     Agronomical   potentials   -   good   soils   having   adequate   depths,   suitable   physical   and   chemical characteristics,   water   holding   capacity,   infiltration   rates,   permeability   and   free   from   erosion and salinity hazards.
3.   Location - Accessible and closest to source of irrigation water.
The command  area is divided  in  two  parts; first part lying  in  the head  reach  proposed  to  be served by  primary  canal.  The command  area in  this part is a narrow belt,  nearly  12.0  km long  having  0.5 
to  2.0  km.  width.  After  deleting  unsuitable  areas,  the  net  CCA  of  this  part  works  out  to  about  1000 
ha
The command area beyond Dencho River is served by two secondary canals. This area comprise of
bit wider belt of about 8 km length and 4 to 5 km width. The net CCA of this command works out
to about 2400 ha.
7.3  Irrigation Intensity
The percentage of CCA proposed  to  be annually  irrigated  is called  Irrigation  Intensity.  Extensive irrigation  is preferred  to  intensive irrigation  on  a smaller area on  account of two  reasons.  Firstly quantity  of water may  be limited  and  secondly  over irrigation  entails harmful effects like water logging, soil salinisation etc.
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A higher intensity  may  be allowed  if an  effective drainage system is provided  in  the irrigated  area. In  the present case 170  % intensity  is assumed  which  comprises of 100  % during  Meher season and 90 % in Belg season with 20 % annual crops.
7.4  Night Irrigation
The irrigation  water is proposed  to  be supplied  on  a continuous basis through  a system of main canals,  secondary  canals and  tertiary  canals which  will run  24  hours.  In  case,  irrigation  is provided in  day  time only  for a period  of 12  hours or so,  night storage reservoir is necessary.  However,  the day time irrigation only has not been recommended for the following reasons:
In  case of Gelana Irrigation  project,  a field  size of about 48  hectare has been  designed  with  the irrigation  parameters and  based  on  each  watering  at an  interval of 13  days.  With  consideration  of individual farm holding  of about one hectare per family,  there would  be more or less 48  farmers in each  field  Individual irrigator will have a turn  of watering  in  a 13  day  cycle for his land  of about one ha.  With  this rotation  of watering  each  farmer would  get two  turns to  receive irrigation supply in one month, it may be once in night and once in day time. Thus individual farm requires
6.5   hours  in  day  and  6.5  hours  in  night  once  in  a  month  (13*24/48).  It  would  not  be  difficult  for  the cultivator  to   work   only   6.5   hours  in   the  night  once   in   a  month   against   the  huge  saving  to  the Government   exchequer   on   account   of   not   providing   the   night   storage   irrigation   reservoirs   in   the command The layout has also been planned accordingly.
Following   disadvantages   of   night   irrigation   with   the   installation   of   night   storage   reservoirs   are described below:
i)        The   construction   of   the   night   storage   irrigation   reservoirs   at   the   head   of   individual   tertiary canal would add to the cost of the project
ii)      Night   storage   irrigation   reservoirs   occupy   substantial   potentially   irrigable   land.   For   one   cubic meter per second discharge in the canal, 12 hours storage of 1.5 meter deep night storage
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reservoir would require permanent acquisition of about 3.00 hectare of command area land for each field unit, totaling a huge area to be acquired for the purpose.
iii)    Additional head would also be required in the canal system to provide water to the night storage irrigation reservoirs and moreover, these would be required to be constructed above the ground levels to provide operating head of water to run the distribution system situated below it This will add to the project costs
iv)  In case of 12 hours’ irrigation, the distribution system in the downstream of the night storage reservoir has to carry double the discharge since it has to accommodate full day’s demand in 12 hours only which will add to extra cost.
v)   There would be additional day time evaporation loss of water in the night storage irrigation reservoirs in addition to the losses of water which are envisaged for design of canals which will affect the efficiency of irrigation.
vi)  It would be preferable for the cultivators to work during nights in hot weather conditions
viijThe night storage irrigation reservoirs may be potential breeding reservoirs to the vectors of
diseases like malaria and schistosomiasis.
In  view of above,  night irrigation  is proposed  to  be adopted  in  Gelana command  area as per general practice in  different parts of the world  without any  special arrangements of lighting  in command  areas.  The farmers normally  use torch  lights to  manage watering  during  night hours. Therefore no  special arrangements of lighting  are being  proposed  in  the command  area of this project
7.5  Irrigation Efficiencies
As per International Irrigation and Drainage Committee the efficiency in use of water can be
separated in to three components.
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7.5.1  Storage Efficiency
It  is  the  ratio  of  water  diverted  for  irrigation  or  for  any  purpose  and  volume  of  water  entering  the reservoir. Losses in reservoir are caused by seepage, spillage from spillway and evaporation
7.5.2  Conveyance Efficiency
It is the ratio  of water reaching  irrigation  field  and  water diverted  from the supply  source. Conveyance losses comprise of seepage losses,  evaporation  losses (total called  Absorption  losses) and  leakage loss from irrigation  system.  This is comprised  of two  efficiencies i.e conveyance efficiency  of canals and  conveyance efficiency  of field  channels.  For design  of canal system assumed  to  80  % and  90  % respectively  giving  total conveyance efficiency  as 72  %.  The conveyance losses of canals are worked  on  the basis of wetted  perimeter of canal and  absorption loss per million  sq.m,  of wetted  area.  The absorption  loss from field  channel is taken  as some percentage of water delivered to the field channel. Therefore both are considered separately
In  detailed  design  of this project conveyance loss from canal system is assumed  as 2.5  m3/s per million  sq.m of wetted  parameter which  are normal for the types of soils encountered  in  Erer command  area.  The wetted  perimeter for main  canal is of the order of 6.0  m.  Hence the absorption loss in  main  canal is taken  as 15  0  lt/s per Km Similarly  the wetted  perimeter of secondary  and tertiary  canals is of the order of 3.0  m and  therefore the absorption  loss has been  taken  as 7.5  lt/s per Km length of these canals.
7.5.3  Field Application Efficiency
It is the ratio  of the volume of water used  by  plant by  evapo  transpiration  and  volume of water reaching  the field.  Water used  in  transpiration  includes the effective rainfall also.  This efficiency  is assumed as 70 % considering 30 % loss.
Total Efficiency of Water Use for Irrigation is multiplication of above three efficiencies. The overall efficiency of system is assumed as 50 % (0.8*0.9*0.7=50.5 say 50 % )
Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES
8.0 Planning and Design of Canal Network
8.1 Canal Alignment
The alignment of primary,  secondary  and  tertiary  canals had  been  marked  on  1:4,000  scale map  in such  a way  that primary  canal and  secondary  canals are aligned  as a contour canals and  tertiary canals aligned  as watershed  or side slope canals for the purpose of the feasibility  study.  For detailed  designs special strip  surveys have been  carried  out along  the proposed  alignment of primary  canal and  secondary  canals and  topographical maps have been  prepared  having  scale
1   4000   and   contour   interval   1.0m.   The   alignment   marked   in   the   feasibility   report   has   been transferred  on  the  1:4000  scale  maps  by  adjusting  the  scale  of  map.  The  alignments  as  proposed  in the  feasibility  report  are  found  by  and  large  in  order  excepting  at  places  where  some  modifications have been carried out.
The quaternary  canals are generally  aligned  along  watershed  lines and  are proposed  to  provide irrigation  on  both  sides of their alignment However in  some cases it is not possible due to topographical limitations.  In  such  situation  they  are aligned  along  contour lines and  proposed  to provide irrigation only on one side.
The primary  canal is generally  carried  on  a contour alignment until it bifurcates in  to  two secondary  canals so  that these may  command  the full area to  be irrigated.  The secondary  canals are also planned on contour alignment on account of topographical reasons.
As  far  as  possible  the  Tertiary  canals  are  taken  off  from  main  canal  from  or  near  the  points  where the parent canal crosses the watershed.
The alignment of contour canals especially  in  upper reaches is decided  after careful consideration of economy.  Alternative alignments,  their benefits and  costs have been  considered,  while deciding the final alignment.
Deep cuttings or high embankments have been avoided by suitable detouring. ■
Careful judgments have been exercised in fixing the points of drainage crossing.
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In  sum,  the alignments of primary  canal and  secondary  canals as proposed  in  the feasibility  report have been  checked  and  are found  to  be generally  in  order excepting  in  some reaches where it has been  modified  The general layout of the fields and  the arrangement of tertiary,  field  canals have been  made on  the same line as that in  the feasibility.  However,  some changes have been  affected wherever necessary  for the presence of natural drainage channels in  the field  orientations as verified from the detailed survey map of command area
Where  the  straight  canal  alignment  is  not  possible  for  topographical  reasons,  simple  circular  curves with limiting radius have been provided as follows.
Capacity of canals (m  /sec)
3
< 0.3 0.3-3.0 3.0- 15 
Limiting radius (m)
100
150
300
The canals are kept in balanced earthwork as far as possible for economic consideration.
8.2  Canal Design
The Erer canal networks have been  proposed  as earthen  channel The requirement of lining  to  be provided  in  differant reaches are influenced  by  the classification  and  permeability  of soils encountered  along  the canal alignment The observed  data indicates that the soils encountered along  the proposed  alignments of primary  and  secondary  canals are relatively  impervious therefore no lining is proposed
Hydraulic sections of main  canals,  secondary  canals and  tertiary  canals are designed  as per Manning’s formula as stated  in  the design  criteria keeping  velocities in  safe limits.  Free boards, bank  widths,  cross roads,  bank  roads,  side slopes,  berms and  dowels have been  provided  in accordance with the provisions made in the design criteria.
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The quaternary  canals are designed  to  have uniform cross section  from head  to  tail.  However primary  canal,  secondary  canals and  tertiary  canals are designed  to  have telescopic section, reducing from head to tail depending upon the reduced discharge on account of off taking channels.
8.3   Design Criteria
The design of earthen channels has been based on the following desgn criteria.
Kennedy’s Theory, Lacy’s Theory and Manning’s Formula are used in design of earthen canals
For canals of small discharging capacity such as in Erer Project not much change is going to 
happen in channel dimensions if worked out by either of the formula. Therefore on account of
simplicity Manning’s Formula is used in designs of Erer Project As per Manning’s Formula
V = 1/n * R2/3S1/2
Where:
V - Velocity in m/sec
R = Wetted Mean Radius = Cross section Area/wetted Perimeter
S = Water Slope
n = Manning Roughness Coefficient. (0.025 for main, branch and 
tertiary canals and 0.030 for field channels).
The  bed  width  and  water  depth  ratio  of  the  canals  are  normally  based  on  Lacy’s  Regime  Theory However from practical considerations following criteria be adopted
Q < 0.5 m /sec
3
B = D (in clay)
B = 2D (in sand)
Q = 0 5 - 1.0 m /sec
Q - 1.0 - 5.0 m /sec
3
3
B = 2D (in clay)
B = 3D (in sand)
B = 3D (in clay)
B > 3D (in sand)
Where:
B = bed width in m
D = depth of water in mQ = discharge in m /sec
3
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8.3.1 Limiting Velocities
« an
The higher the velocity, the smaller will be the section and thus affect the economy. But to avoid 
•A
siltation and scouring of earthen canals the following velocities may be adopted.
rl'
r*r*
Maximum velocity 
=
0.75 m/sec in all canals
Minimum velocity 
=
0.25 m/sec in all canals
8.3.2    Working Head
For  preparing  command  statement  and  deciding  the  full  supply  levels  in  the  different  component of the canal system the following minimum working heads arc required:
o          Head over field 
o          Head for field channel at its off take from quaternary = 15 cm o             Head for quaternary in tertiary canal
o             Head for tertiary canal in the secondary canal
o             Head for secondary canal in the primary canal o             Head for primary canal at main outlet (dam site)
8.3.3   Longitudinal Slope
= 15 cm
= 15 cm
= 15 cm
= 30 cm
= 60 cm
Lacy’s following regime equation for given discharge and silt factor provides guidance in choosing slope for unlined earthen channel. The same is used in computations of canal dimensions, 
s = 0.00031 (f3/2 Q1/6)
Where:
S = longitudinal slope
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Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES Eg?
W
Q = discharge in m /s
f= silt factor =1.76 mr,/2 for silts, 
3
p4
Very fine to fine, it varies from 0 4 to 1 Ojy
And for fine sands from 1.25 to 1.50
Where:
mr = average particle size of the boundary material
In actual practice slightly steeper slope is provided than the one worked out by above equation.
'-*■
■V
8.3.4 Critical Velocity Ratio (CVR)
X. •
According  to  Kennedy  for  non  silting  and  non  scouring  channels  in  steady  regime  there  is  only one   velocity   called   ‘critical   velocity’   denoted   by   Vo,   which   is   function   of   depth   of   water   in channel and obtained by following equation:
Vo = 0.546 D° 64
Where
Vo = critical velocity in m/s
D = depth of water in meter
This equation was applicable to the grades of silt existing in the observation channel (in UBDC
canal in Pakistan). To take in to account of varying silt grade another factor called ‘critical velocity 
ratio’ was introduced which is denoted by ‘m’ and the above equation was amended as below:
V = 0.546m D064
Where:
m = V / Vo = CVR
The value of m depends on  type of silt.  For channels carrying  appreciable suspended  loads,  the value of m should  be taken  1.10  at head  and  0.85  towards tail end.  In  case of Erer Project,  water is released  from the reservoir and  expected  to  be silt free and  thus m will lie between  1.02  and  0.85. The same has been adopted in design i.e. in head reach 1.02 and in tail reach o 0.85
■n
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Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES
8.3.5   Free Board
The  following  minimum  free  board  has  been  adopted  in  design  of  canals  for  different  discharges
indicated below:
Discharge (m /sec)
3
Minimum Free Board (m)
<0.4
0.2
0.4- 1.2
0.3
1.2-5.0
0.4
8.3.6   Bank Width
As per Indian  Standard  Code of Practice IS: 7112-2002  titled  “Criteria for Design  of X-Section  for Unlined  Canals” the recommended  top  width  of bank  is 1.5  m for discharge 0.15  to  7.5  m3/s for non  inspection  bank  and  5.0  m for inspection  bank.  The same is adopted  in  design  of canals in  Erer project.
8.3.7   Saturation Gradient
Types of Soils
Saturation Gradient
Clayey Loam
1:4
Sandy Loam
1:5
The top  width  of canal banks indicated  above is absolutely  minimum as required  from stability considerations only.  However if functional requirement is integrated  with  the stability considerations, the width of canal banks will change.
Ensure a minimum cover of 0.5m on saturation line
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Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES
<•
8.3.8   Inspection Roads
The  alignment  of  inspection  roads  of  main  canal  and  secondary  canals  shall  be  planned  on  their left  banks  as  all  the  head  regulators  of  off-taking  channels  are  located  on  the  left  banks  only.  These roads   will   provide   free   excess   to   regulatory   structures   for   their   inspection   and   maintenance   which otherwise will not be possible from roads on right side without provision of bridges on each site
Bank Side Slopes for Main Canal
Type of Soil
Side Slopes
Cutting Filling
Loamy Soils
1 : 1
1.5 : 1
Sandy Soils
1.5 : 1
2: 1
For tertiary canals and field channels cutting and filling slopes have been kept 1.5:1. 
The bank slopes indicated in the above table are only generalized values which are found adequate in majority of cases. However in extreme cases when the banks are too high the stable slopes have been checked for stability to withstand following conditions during operation of canals:
(1)  Sudden drawdown condition for inner slopes.
(2) Water running full with banks saturated with rainfall for outer slopes.
8.3.9   Canal Embankment Material
For canal embankment materials following criteria are used:
o          Liquid limit > 25%
o          Plasticity index > 10%
o Gypsum <2% (to avoid solution holes)
o Sulphate < 0.2% (to avoid sulphate attack on ordinary Portland Cement)
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Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES
! 1
J
] 1
fl
8.3.10    BERM
Berm is the horizontal space left at ground level between the toe of the bank and excavation
Following criteria shall be used for location and size of berms in different situations.
(1) When Full Supply Level(FSL) is above Natural Surface Level( NSL) and bed level is below
NSL  i.e.  the  canal  is  partly  in  cutting  and  partly  in  filling,  berm  is  provided  having  2D  width at the NSL, where D is full supply depth of canal.
(2) When FSL and bed level are above NSL i.e canal is fully in filling the berm of 3D width is kept at FSL
(3) When FSL and bed level are below the NSL i.e. the canal is in full cutting, the berm having width 2D is provided at FSL
8.3.11 Catch Water Drain
fl
For
the
canals
excavated 
on
the
slopping 
ground 
alon
g 
contour, 
a
catch   water
drain,   having 
fl
desi
gned 
carrying 
capacity 
to 
carry 
expected 
discharge
of
fl
ood  from
its
catchment
and  leading  to 
J
fl
fl
natural  stream,  is  required  to  be  provided.  These  drains  are  designed  to  carry  overland  flow  from the area where regular drains do not exist.
In  this  project  the  catch  water  drains  of  1.0m  width  and  1.0  m  depth  having  side  slopes  of  1:1  are recommended.
These   drains   are   proposed   on   upland   side   of   primary   canal   and   both   the   secondary   canals.   The drains shall outfall in to natural drains crossing the canals.
fl
]
33
fl
 _______________________________________________________________________________ Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009
1
1
I.Erer Dam & Irrigation Project ZCECE & CES
8.4  Command Area And Design Discharges For Quaternary Canals
There are total 51  number of quaternary  canals.  Out of these 16  off take directly  from primary canal and  7  and  14  offtake directly  from secondary  canal-I and  secondary  canal-II respectively However 14  number offtake from the tertiary  canals.  The alignments of all the quaternary  canals are finalised  on  the basis of topographical parameters.  The areas proposed  to  be commanded  by these quaternary  canals are measured  from the map  The following  table gives the areas served  by each quaternary canal and tertiary canal.
Table 8.1 Culturable Command Area and Design Discharges for Quaternary
Canals taking off from Primary Canal
Chainage
(km + m)
Canal Name
Canal
Length
(km)
Area
Covered
(ha)
Discharge
(l/sec)
Design Discharge
(l/sec)
1+100
Q1P
1.40
35
19.25
22.14
2+300
Q2P
1.00
30
16.50
18.98
3+430
Q3P
1.30
60
33.00
37.95
3+700
Q4P
1.50
55
30.25
34.79
4+200
Q5P
2.30
85
46.75
53.76
5+600
Q6P
1.40
45
24.75
28.46
6+000
Q7P
1.40
55
30.25
34.79
6+400
Q8P
1.20
40
22.00
25.30
7+200
Q9P
1.20
60
33.00
37.95
7+600
Q10P
1.20
55
30.25
34.79
8+300
Q11P
0.90
45
24.75
28.46
8+850
Q12P
1.20
33
18.15
20.87
9+400
Q13P
3.00
80
44.00
50.60
10+100
Q14P
1.30
45
24.75
28.46
10+900
Q15P
2.10
60
33.00
37.95
12+950
Q16P
1.60
70
38.50
44.28
sub total
24.00
853.00
469.15
539.52
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Annex E ; Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES
Table 8.2 Culturable Command Area and Design Discharges for Tertiary & Quaternary Canals Taking off from Primary Can l
a
Chainage
(km + m)
Canal Name
Canal
Length
(km)
Area
Covered
(ha)
Discharge
(l/sec)
Design Discharge
(I/sec)
12+900
T1P
1.00
175
96.25
110.69
12+900
Q1T1P
1.70
75
41.25
47.44
12+900
Q2T1P
1.20
40
22.00
25.30
12+900
Q3T1P
1.50
60
33.00
37.95
Sub total
175
96.25
110.69
Note: the discharge of the tertiary canal is the sum of the quaternary canal (the same is true for the area)
Length of primary canal = 13600 m
Absorption loss of primary canal 15 lit/sec per km length of canal
Table 8.3 Culturable Command Area and Design Discharges for Quaternary and Tertiary
Canals
Chainage
(km + m)
Canal
Name
Canal
Length
(km)
Area
Covered
(ha)
Discharge
(l/sec)
Design Discharge
(l/sec)
1+900
T1S1
2.10
255
140.25
161.29
0+950*
Q1T1S1
1.35
55
30.25
34.79
1+275*
Q2T1S1
1.50
50
27.50
31.63
1+700*
Q3T1S1
1.30
65
35.75
41.11
2+100*
Q4T1S1
3.10
85
46.75
53.76
2+500
Q1S1
1.80
90
49.50
56.93
3+300
Q2S1
1.10
35
19.25
22.14
3+900
Q3S1
1.30
40
22.00
25.30
4+450
Q4S1
2.20
75
41.25
47.44
5+000
Q5S1
2.20
65
35.75
41.11
5+500
Q6S1
2.20
100
55.00
63.25
6+750
T2S1
3.00
190
104.50
120.18
2+300*
Q1T2S1
0.50
20
11.00
12.65
2+600*
Q2T2S1
1.00
25
13175
15.81
2+800*
Q2T2S1
1.00
:30
16.50
18i98
7+200
Q7S1
3.50
135
74.25
85.39
7+700
T3S1
0.70
130
71.50
82.23
0+700*
Q1T3S1
1.90
95
52.25
60.09
8+200
T4S1
0.70
130
71.50
82.23
0+700*
Q1T4S1
1.90
95
52.25
60:09.
sub total
1245
684.75
787.46
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Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES
* quaternary canal length started from Tertiary canal
Table 8.4 Culturable Command Area and Design Discharges for Quaternary and Tertiary
Canals Taking off from Secondary Canal Two
Chainage
(km + m)
Canal
Name
Canal
Length
(km)
Area
Covered
(ha)
Discharge
(l/sec)
Design Discharge
(l/sec)
0+350
Q1S2
0.80
30
16.50
18.98
1+500
Q2S2
1.20
40
22.00
25.30
3+200
Q3S2
1.80
80
44.00
50.60
4+000
T1S2
0.10
105
57.75
66.41
4+000
Q1T1S2
1.70
60
33.00
37.95
4+000
Q1T1S2
1.20
45
24.75
28.46
5+650
Q4S2
3.10
60
33.00
37.95
6+500
Q5S2
3.00
110
60.50
69.58
7+000
Q6S2
2.00
105
57.75
66.41
7+500
Q7S2
2.20
110
60.50
69.58
8+600
Q8S2
1.30
60
33.00
37.95
9+100
Q9S2
1.50
50
27.50
31.63
9+775
Q10S2
1.60
65
35.75
41.11
10+350
Q11S2
1.50
70
38.50
44.28
11+550
Q12S2
1.10
40
22.00
25.30
11+900
Q13S2
0.90
40
22.00
25.30
12+400
Q14S2
1.00
50
27.50
31.63
sub total
26.00
1015
558.25
641.99
total length of secondary canal two is 12+400 km
8.5   Calculations of Design Capacities
8.5.1   Quaternary Canals
(off- taking from any Tertiary canal or directly from Primary or Secondary Canal)
Discharge required at the head of Quaternary Canal = CCA of quaternary Canal *0.498/0.9 The section of Quaternary canal shall remain the same in its entire reach from head to tail and connected to the nearby natural drain to dispose off surplus discharge.
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Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES
The flexibility  of 15% is kept in  entire canal system to  account for the poor maintenance conditions.  If the canal is not maintained  in  good  condition  and  there is deposition  of silt and growth  of weeds,  the rugosity  coefficient is changed  and  discharging  capacity  is reduced.  It is desirable to make sufficient allowance for this purpose. In Erer project this allowance is kept as 15%.
8.5.2 Tertiary Canals
(off-taking from Secondary Canal or directly from Primary canal)
Discharge at the head  of any  tertiary  canal = Discharge required  at head  of all off-taking Quaternary  Canals+ absorption  loss in  Tertiary  canal.  The absorption  loss in  Tertiary  canal is taken@7.5 1/s/km length of tertiary canal
Design Discharge at Head of any Tertiary canal is multiplied by 1.15 to account for flexibility 
The Design section of Tertiary canal shall reduce from head to tail depending on the discharge of
off-taking Quaternary canals.
8.5.3 Secondary Canals
( Off-taking from Primary Canals)
Discharge required at Design section of Tertiary canal shall reduce from head to tail depending on the discharge of off-taking  Quaternary  canals.  The discharge at head  of Secondary  Canal is equal to total required discharge of the off-taking canals i.e tertiary canals and quaternary canals directly off-taking  from secondary  canal plus losses in  Secondary  canal taken  @7.5  lt/s per km length  of secondary  canal.  Design  discharge at the head of secondary canal is found out by multiplying the discharge arrived as above by 1.15 to take in to account the flexibility.
The design section of secondary canal shall reduce from head to tail depending on the discharge of off-taking canals.
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Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES
• ♦
8.5.4  Primary Canal
Similarly  the discharge of the Primary  canal at Head  is equal to  total required  discharge of all off- taking  canals i.e.  secondary  canals,  tertiary  and  quaternary  canals directly  off taking  from primary Canal plus losses in  Primary  Canal head  to  tail taken  as @ 15  lit/s per km length  of primary  canal. Design  discharge at head  of Primary  canal is equal to  the discharge worked  out above multiplied by 1.15 factor.
Like  secondary  canal  the  design  section  shall  reduce  from  head  to  tail  depending  upon  the discharge of the off-taking canals.
Capacity of Secondary canal-I (CCA=1345 ha)
Net irrigable area = 1345 ha
Peak irrigation requirement of plant = 0.349 1/s/ha
Field application efficiency = 0.7
Peak irrigation requirement at field=0.349/.7
= 0.49857 1/s/ha
Peak irrigation requirement at the head of quaternary canals
= 0 49857/0.9
= 0.55396 1/s/h
Loss in secondary canal (8.366 km) and tertiary canal (5.3 km)
= 13.666*7.5
= 102.45 1/s
Water required at the head of secondary canal-I
= 1345*0.55396+102.45
= 847.52 1/s
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•Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES
Increase this capacity by 15% for flexibility
The design capacity of secondary canal-I at head =847.52*1.15
=974.65 1/s
=0.974 m3/s
On the same basis the design capacities of primary canal and secondary canal-II at their heads have
been worked out which come to 2.709 m /s and 0.773 m /s respectively.
8.5.5   Capacity Statements for Different Reaches
Before designing  the canals,  the capacity  statements have been  prepared  giving  the reach  of canal under consideration,  discharge at head  of reach,  conveyance losses in  this reach,  name of off- taking  channel,  its CCA and  its required  discharge.  After deducing  this discharge the discharge of the next reach has been worked out. This statement is also known as cut-off statement.
Table 8.5 Statement showing Total discharge utilized in different Canal systems
3
3
S.No
Name of Canal
CCA
(ha)
Water diverted in Quaternary' and Tertiary canals (1/s)
Length of Canals
(km)
Absorplio n loss in canal
(1/s)
Length of Tertiary 
canal
(km)
Absorption loss in
tertiary canal 1/s
Total
water
utilized
(1/s)
1
Primary Canal
1022
562.1
13.392
200.88
1.30
9.75
772.73
2
Secondary Canal-I
1345
739.75
8.366
62.74
5.30
39.75
842.24
3
Secondary Canal-II
1042
573.1
13.10
98.25
0.1
0.75
672.05
Total
3409
1874.95
34.858
361 87
6.7
50.25
2287.02
Design Capacity of primary canal = 2.356 x 1.15 = 2.709 m /s
3
Design Capacity of S1
Design Capacity of S2
= 0.842 x 1.15 = 0.968 m3/s
= 0.672 x 1.15 = 0.773 m3/s
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Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES
r
Table 8.6 Capacity Statement of Primary Canal
S.N
0
Reach (m)
Discharge
at the
head of
reach
(m /s)
Lengt
hof
reach
(km)
Seepage
less in
reach
(m /s)
Name of
off-taking
channels
3
3
Discharge
diverted in
off-taking
channels
(m’/s)
Discharge at
the tail of
reach
(m’/s)
Design discharge
of the reach
(m’/s)
1
2
3
4
5
6
7
8 = Col 3-5-7
9 = 1.15 x Col 3
1
0+0 to 2+200
2.356
2.2
0033
Q^.QiP
0.071
2.252
2.709
2
2+200 to 3+600
2.252
1.4
0.021
QsP, Q<P
0.061
2.170
2.590
3
3+600 to 5+400
2.170
1.8
0.027
Q’P, Q6P
0.074
2069
2.49
4
5+400 to 6+250
2.069
0.85
0.013
Q?P. Q.P
0.052
2.004
2.38
5
6+250 to 7+500
2.004
1.25
0.019
QsP,QioP
0.063
1.922
2.30
6
7+500 to 8+700
1.922
1.2
0.018
Qii+Qu
0.055
1.849
2.21
7
8+700 to 9+900
1 849
1.2
0.018
Ql3+Q|4
0096
1.735
2.12
8
9+900 to 13+394
1.735
3.49
0.052
Q  +T,p
1}
0.131
1.552
2.00
Table 8.7 Capacity Statement of Secondary Canal - I
1 S.N
o
Reach (m)
Discliar
ge at
die
head of
reach 
(nP/s)
Lengt
hof
reach 
(km|
Seepage
loss in 
m /s@
3
7.51t/s/
km
Lengt
h of
Tertjar
y
Canal
in 
reach 
(km)
Seepag 
e loss
in 
Tertiar y Can al
(m’/s)
Name of OCT-taking 
channel
Discharge
diverted in 
o(T taking 
channels
(nP/s)
Dischar
ge of the
tail of
reach 
(m’/s)
Design
Discha
rge
(m’/s)
1
2
3
4
5
6
7
8
9
10
11
1
0+0 to 1+500
0.842
1.5
0.011
1.6
0.012
TtSi
0.154
0.665
0.968
2
1+500 to 3+000
0.665
1.5
0.011
-
-
QiSi and Q^S|
0.082
0.572
0.765
3
3+000 to 4+400
0.572
1.4
0.01
-
-
Q3S) and Q^Si
0.077
0.485
0.660
4
4+400 to 5+500
0.485
1.1
0.008
-
-
Q5S1 and QaS|
0.104
0.373
0.557
5
5+500 to 7+050
0.373
1.55
0.012
2.30
0.017
T2S1 and Q7S1
0179
0.165
0.429
6
7+050 to 7+550
0.165
0.5
0.004
0.7
0.005
TS
3l
0.0715
0.084
0.189
7
7+550 to 8+366
0.084
0.82
0.006
0.7
0.005
T<S>
0.0715
0.001
0.116
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Table 8.8 Capacity Statement of Secondary Canal - II
S.N
0
Reach (m)
Discharge
at the
head of
reach
(m’/i)
Length
of
reach
(km)
Seepage
loss in
m’/s @
7.5lt/$/km
Length
of
Tertiary
Canal
in reach
(km)
Seepag
e loss
in
Tert i ar
y Canal
(m’/s)
Name of off-taking
channel
Discharge
diverted in
off- taking
channels
(«»’/«)
Discharge
of the tail
of reach
m’/scc
Design
Discharge
m’/sec
1
2
3
4
5
6
7
8
9
10
11
1
0+0 to 1+500
0672
1.5
0.012
-
-
Q]S and Q S
2                22
0.0467
0613
0.773
2
1+500 to 3+500
0613
2.0
0.015
1.3
0.01
Q S and T|S
32                    2
0.115
0.483
0.705
3
3+500to 5+600
0.483
2.10
0.016
-
-
Q4S2 and Q5S2
0.103
0.364
0.555
4
5+600 to 6+600
0.364
1.0
0.007
-
-
QfiS2 and Q7S2
0.096
0.261
0418
5
6+600 to 8+200
0.261
1.6
0.012
-
-
Qg S  and Q? S
22
0.057
0.192
0.300
6
8+200 to 9+600
0.192
1.4
0.010
-
-
Q10 S  and Qu S
22
0.082
0.100
0.221
7
9+600 to 10+700
0.100
1.1
0.007
-
-
Q12 S2 and Q13 S2
0.046
0.047
0.115
8
10+700 to 13+100
0.047
2.4
0.018
-
Qu S2
0.024
0.005
0.054
Table 8.9 Hydraulic Parameters-Primary Canal
Reach (km)
Discharge (m /s)
n
3
Slope
(m/m)
Depth
(m)
B.W.
(m)
W.P.
(m)
V(m/s)
Vo=0.55D°w
CVR
F.B
(m)
0 0-2.2
2.709
0.025
0.0035
1.10
2.50
647
0.59
0.58
1.01
0.40
2.2-360
2.59
0.025
00035
1.07
2.50
6.37
0.59
0.57
1.01
0.40
3.60-5.40
2.49
0.025
0.0035
1.05
2.50
6.30
0.58
0.566
1.02
0.40
5.406.25
2.38
0.025
0.0035
1.04
2.40
6.17
0.57
0.563
1.01
040
6.25 -7.50
2.30
0.025
0.0035
1.03
2.40
6.10
0.57
0.56
1.01
0.40
7.50-8.70
2.21
0.025
0.0035
1.01
2.40
6.02
0.56
0.553
1.01
0.40
8.70-9.90
2.12
0.025
00035
1.0
2.30
5.91
0.56
0.55
1.01
0.40
990-13.394
(tail
2.00
0.025
0.0035
1.0
2.13
5.73
0.55
0.55
1.00
0.40
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Table 8.10 Hydraulic Parameters-Secondary Canal I
Reach (Km)
Discharge
3
Q m /scc
n
Slope
(m/m)
Depth
(m)
B.W.
(m)
W.P.(m)
V(m/se
c)
Vo = 0.55D
0.64
CVR
F.B
(m)
0-1.50
0.968
0.025
0.0004
0.82
1.20
4.14
0.49
0.488
1.0
0.30
1.5-3.0
0.765
0.025
00004
0.74
1.16
3.81
0.46
0.459
1.0
0.30
3.0-4.4
0.650
0.025
0.0004
0.69
1.15
3.63
0.44
0.44
1.0
0.30
4.4-5.5
0 557
0025
0.0004
0.64
1.10
3.39
0.42
0.4207
0.998
0.30
5.5-7.05
0429
0.025
0.0004
0.58
1.00
3.08
0.40
0.3966
1 00
0.20
7.05-7.55
0.189
0.025
0.0004
0.41
0.80
2.29
0.32
0.322
0.99
0.20
7.55-8.366
0.116
0.030
0.00045
0.33
0.75
1.94
0.28
0.2827
0.99
0.20
Table 8.11 Hydraulic Parameters-Secondary Canal II
Reach (km)
Discharge (m /s)
n
3
Slope
(m/m)
Depth
(m)
B.W.
(m)
W.P
(m)
V(m/
sec)
Vo = 0.55D
064
CVR
F B (m)
0-1.50
0.773
0.025
0.0004
0.74
1.15
3.82
0.46
0.4590
1.0
0.30
1.5-3.50
0.705
0.025
0.0004
0.72
1.08
3.68
0.45
0.4516
0.996
0.30
3.50-5.60
0.555
0.025
0.0004
0.64
1.08
3.39
0.42
0.420
1.0
0.30
4.60-6 60
0.418
0.025
0.0004
0.57
1.0
3.06
0.39
0.3925
0.99
0.20
6.60-8.20
0.300
0.025
0.0004
0.50
0.90
2.71
0.36
0.3628
0.99
0.20
8.20-9.60
0.221
0.025
0.0004
0.43
0 88
2.44
0.33
0.3314
0.99
0.20
9.60-10.70
0.110
0.025
0.0004
0.33
0.60
1.79
0.28
0.2828
0.99
0.20
10.70-13.10
0.054
0.030
0.00045
0.25
0.42
1.31
0.24
0.239
1.00
0.20
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Table 8.12 HYDRAULIC PARAMETER -T4S1
Reach
(km)
Q
(m /s)
N
3
Slope
(m/m)
Side
slope
(h/v)
Depth
(m)
B.W. (m)
W.P
(m)
V M/sec
V0 =
0.55D
CVR
FB
(m)
0.64
0-0.700
0.088
0.025
0.00045
1.5:1
0.32
0.45
1.62
0.28
0.312
1.01
0.20
Table 8.13 HYDRAULIC PARAMETER -TiS2
Reach
(m)
Q
(m3/s)
N
Slope
(m/m)
Side
slope
(h/v)
Depth 
(m)
B.W.
(m)
W.P.
(m)
V
(m/s)
Vo =
0.55D
CVR
=V/Vo
F.B.
(m)
0.64
0-0.10
0.069
0.025
0.00045
1.5:1
0.29
0.45
1.51
0.26
0.2616
0.99
0.20
Table 8.14 HYDRAULIC PARAMETER -TiP
Reach
(m)
Q
(m3/sec)
N
Slope
(m/m)
Side
slope
(h/v)
Depth 
(m)
B.W. (m)
V
(m/s)
Vo =
0.55D 0 64
CVR
F.B. (m
0-1.30
0.154
0.025
0.00045
1.5:1
0.41
0.53
0.32
0.3221
0.993
0.20
Table 8.15 HYDRAULIC PARAMETER -TiSi
Reach 
(m)
Q
(m3/sec)
N
Slope
(m/m)
Side  slope (h/v)
Depth
(m)
B.W. (m)
V (m/s)
vo =
0.55D o m
CVR
F.B,
(m)
0-1.60
0.126
0.0
25
0.00045
1.5:1
0.39
0.48
0.31
0.3126
0.992
0.20
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Table 8.16 HYDRAULIC PARAMETER -T2S1
Reach 
(m)
Q
(m3/s)
N
Slope
(m/m)
Side
slope
(h/v)
Depth 
(m)
B.W. (m)
V (m/s)
Vo =
O.55D 0 64
CVR
F.B.
(m)
0-2.30
0.072
0.025
0.00045
1.5:1
0.30
0.46
0.27
0.2671
1.01
0.20
Table 8.17 HYDRAULIC PARAMETER -T3S1
Reach 
(m)
Q
(m3/s)
N
Slope
(m/m)
Side
slope
(h/v)
Depth 
(m)
B.W.
(m)
V
(m/s)
Vo =
0.55D 0
CVR
F.B.
(m)
0-0.70
0.072
0.025
0.00045
1.5:1
0.30
0.46
0.27
0.2671
1.01
0.20
8.6 Procedure Adopted for Design
Following procedure has been adopted for design of earthen canals:
(1) Lacey’s regime slope has been found by using following formula,
S= 0.0003 l(f5/2Q,/6
) for primary canal Q=2.709 m /s and f=1.0
3
The slope is worked out to 0.00036. The slope of primary canal has been
considered as O.OOO35 in calculations.
(2)        Appropriate values of B and D assumed.
(3)       Velocity calculated by Manning’s Formula using appropriate value of rugosity coefficient (0.025 in this case )
(4)       Critical velocity Vo calculated by using Formula Vo=0.55D0 64
(5)        Calculations were continued till the selected value ofD and computed value of V satisfy
• the critical velocity ratio (CVR)
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44Erer Dam & Irrigation Project /CECE & CES
9.0 Irrigation Structures
The   detailed   design   of   irrigation   and   drainage   structures   are   carried   out   in   two   phases   In   first phase   hydraulic   designs   are   earned   out   which   are   intended   to   determine   the   optimal   location, configuration    of    components    of    hydraulic    structures,    waterway    requirement,    protection    against sour,   seepage   and   uplift   pressures,   energy   dissipation   arrangements   etc.   In   second   phase   Structural designs   are   carried   out   which   aims   at   evaluating   the   forces/   stresses   on   each   component   of structures   on   account   of   dead   loads,   dynamic   loads,   seismic   loads   and   earth   pressures   and   each component is designed to resist the forces and bending moments caused by all these loads.
The canal structures are hydraulically  designed  as per aforesaid  design  criteria set out for Erer project.  The detailed  structural designs are carried  out as per detailed  procedures in  vogue internationally
9.1  ESCAPE Structures
These are the structures meant for escaping  surplus or excess water for the purpose of safety  of canal and  its structures and  depleting  the canals for repair and  maintenance purposes.  There are two types of escapes, Weir Escapes and Sluice Escapes
9.1.1  Choice of Types of Escape
Weir Escapes are constructed in masonry or cement concrete with or without crest shutters capable
of escaping surplus water from canal. Sluice Escapes however comprise of a head regulator of
sluice escape, cross regulator on canal located just downstream of location of escape (if entire
discharge of the canal is required to be escaped) and escape channel. Sluice escape besides
removing surplus water act as scouring sluice and helps to remove silt from the canal Sluice
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escapes   are   therefore   preferred   over   weir   escapes   generally   unless   site   conditions   limit   the   use   of weir escapes.
Surface escapes may  be used  in  case of an  escape opposite an  inlet when  an  inlet does not bring considerable amount of silt Surface escapes also  become useful at the tail end  of canal where there are fluctuations in  withdrawals from canal and  excess quantity  of water can  be suitably  disposed off Sluice escapes are necessary  where the canal is required  to  be emptied  quickly.  Sluice escapes become essential when the inlet can bring considerable amount of silt.
After considering  all the above said  points in  Erer project,  it is proposed  to  go  with  for sluice type ofcscape with  out any  crest so  that the canal may  be emptied  folly  to  facilitate repair works.  The escape is proposed to be designed as a simple flat regulator.
9.1.2   Criteria for Location
Following criteria are adopted
•       The  location  of  escape  is  decided  by  availability  of  suitable  drain,  depression  or  river  with bed  level  at  or  below  canal  bed  level  for  disposing  off  surplus  water  through  escape  directly or through escape channel.
•      Provision  of  escapes  at  every  15  to  20  km  is  desirable  on  main  canals  and  10  to  15  km  on secondary canals.
•        Escapes   may   be   located   at   up-stream   of   major   structures   such   as   aqueducts,   railway crossings, major diversion structures etc.
•        Escapes   may   be   provided   in   combination   with   aqueducts   or   siphons   for   affecting   the economy.
•       Escapes   are   necessary   at   important   points   where   branches   take   off   from   main   canal   or several   distributaries   take   off   from   branch   canal.   In   case   of   lift   channels   escapes   are essential up-stream of pumping station.
•      When  canal  is  very  close  to  the  edge  of  river  bank,  its  bed  level  near  the  head  works  being considerably  lower  than  the  flood  plain  of  the  river,  there  is  a  risk  of  flood  flow  entering  in to canal by way of breaches. If there is no escape provided the canal system may be
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Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES
r
*
severely  damaged  by  excessive flow.  The escape may  be located  at a point downstream of the reach  where canal bank  is vulnerable to  the flood  damage to  restrict the damage to  the reach upstream only.
•       When   the   canal   runs   along   the   steep   side   of   the   hill   or   along   a   steep   bank   of   a comparatively   soft   material,   an   escape   may   be   located   at   the   upstream   end   of   the   canal section  where  it  first  approaches  a  steep  bank  In  case  of  a  land  slide  occurring  in  the  hill slope  the  entire  canal  may  be  blocked  resulting  in  abrupt  rise  of  water  level  in  the  upstream for   a   considerable   distance.   This   intern   can   cause   extensive   damage   to   canal   section   An escape  provided  at  a  suitable  place  on  the  upstream  of  such  reach  would  act  as  a  safety  plug to arrest the rise of water level and avoid consequential effects.
•      When  canal  is  confined  by  bank  on  one  side  and  the  unbanked  side  allows  surface  inflow, escapes  need  to  be  provided  at  appropriate  location  in  the  vicinity  to  dispose  of  the  water  so received.
•      Escapes  opposite  the  inlets  or  at  a  nearest  suitable  location  may  be  needed  whose  drainage water  is  let  into  the  canal  without  reserve  capacity  to  receive  such  water  over  and  above  the authorized full supply discharge of the canal.
•      Certain  quantity  of  heavy  bed  silt  may  find  its  way  through  the  regulator  into  head  reach  of canal  and  thereby  reduce  the  water  way.  In  such  cases  sluice  escape  within  5  km  of  canal head reach may be provided.
After having  considered  above points the location  of the proposed  escape is decided  at about 4+150  chainage point of primary  canal where it crosses a sizeable drain  designated  as CD5P ( Estimated Q2s=l 5.8 m /s ) which outfalls in River Erer.
9.1.3  Criteria for Escapes Capacity
The flow requirement to  be diverted  through  escape may  vary  from small quantities to  total discharge of canal.  No  general rules are laid  for deciding  the discharge capacity  of escape.  The criteria are location and requirement specific. Following guidelines are adopted:
_______________________________ _______________________________________________ 47 Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009
3Erer Dam & Irrigation Project /CECE & CES
• If the canal passes near important town or important installations where breach of canal can affect costly properties or human lives the capacity of escape should be equal to maximum flow which can pass in the canal. In other cases it should seldom be greater than the half of discharge of canal or not less than the difference between maximum discharge of canal at the proposed escape site and maximum flow at next escape
♦    When the escape is used mainly to empty the canal for maintenance, the capacity should be
fixed taking into account the number of days in which the canal is to be emptied.
•    In general the design capacity of escape is normally taken to be 50 to 60% of canal discharge at the point of escape.
After considering above issues the capacity of proposed escape of Erer Project is proposed to 60 %
of the capacity of canal at the site of escape.
9.1.4  Design Considerations
The structural as well as hydraulic design criteria adopted in this case are the same as that of other simple flat regulators.
•     The  safety  of  escape  structure  has  been  checked  for  exit  gradient.  The  maximum  exit gradient has been worked out on the basis of difference in maximum water level in canal and minimum water level in escape channel.
•    The escape structure has been checked for safety against uplift pressure and sliding.
•      The  required  water  way  has  been  computed  by  using  broad  crested  weir  formula  with appropriate discharge coefficient considering the conditions of flow.
•     In  this  escapes  the  sill  is  kept  at  the  bed  level  of  primary  canal  This  will  enable  quick emptying of canal and silt removal besides providing economical waterway.
•     The  safety  arrangements  have  been  made  adequately  to  cater  for  all  flow  conditions  and operation.
•    Adequate protection works have been provided on down stream side of structure same as in case of other regulatory structures.
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9.2 Canal Head and Cross Regulators
A   head   regulator   is   provided   at   the   head   of   channel,   which   controls   the   supplies   entering   into channel.  A  cross  regulator  on  the  other  hand  is  located  at  the  down  stream  side  of  an  off  taking point  on  main  channel  to  head  up  water  level  to  enable  the  off-taking  channel  to  draw  the  required supplies   Head   regulators   also   control   the   entry   of   silt  into   distributaries   besides  serving  as  meter for measuring discharges
There are two  head  regulators provided  in  the system These are head  regulators of both  the secondary  canals off-taking  from the tail of primary  canal.  One acts as cross regulator to  the other regulator and vice versa These have been designed as per design criteria.
Since  the  sizes  of  parent  channel  and  off-taking  channels  are  very  small,  only  one  bay  of  regulators are considered adequate and no piers are provided
The structure has been  checked  for exit gradient and  adequate length  of floor and  downstream cut off wall have been  provided  for safe value of exit gradient Bligh’s coefficient has been  assumed  as 7 and accordingly length of floor is worked out.
The  thickness  of  floor  provided  is  sufficient  to  resist  uplift  pressure.  The  uplift  pressure  is  to  be calculated in following two conditions:
(a)  When upstream water level is headed up to full supply and off-taking channel is dry.
(b)   When  the  upstream  water  level  is  headed  up  to  full  supply  and  varying  discharge  pass  down stream.
The  upstream  cut-offs  have  been  provided  up  to  Lacey’s  scour  depth  below  the  upstream  bed  level or ground level, which ever is low.
Channel Capacity (m /scc)
3
Minimum Depth or Cut off (m)
Up to 3.0
* 1.0
3.1 to 30
1.20
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Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project ZCECE & CES
The downstream cut-offs have been provided from safe exit gradient considerations
Channel Capacity (m /sec)
J
Minimum Depth of Cut off (m)
Up to 3.0
1.0
3.1 to 30.0
1.20
When  the  available  working  head  in  off  taking  canal  is  more  than  half  of  the  full  supply  depth  in parent channel, cross regulator may not be provided in conjunction with head regulator.
9.3  Outlet Structures:
It  is  a  device  through  which  water  is  released  from  a  distributing  channel  to  quaternary  canal. 
Out let must full fill following requirements
o It shall be structurally strong and shall have no moving parts so that
■    It does not require periodic attention
■    It is not tampered by farmers or unauthorized persons
o It shall draw its fair share of silt carried out by parent channel.
o It shall work efficiently with small working head
o It shall be economical.
Various types of canal out lets have been  evolved  from time to  time to  obtain  suitable performance. No  one has come out to  be suitable universally.  In  fact it is very  difficult to  achieve good  design with  respect to  flexibility  and  sensitivity  because of various indeterminate conditions both  in distribution  channels and  the water courses,  namely,  discharge levels,  silt charge,  capacity  factor, rotation  of channels,  regime condition  of distributing  channels etc affect their functioning.  Even  a particular outlet considered  suitable upstream of control structure in  a channel may  not remain suitable at a considerable distance on the same channel.
In  Erer  irrigation  scheme  pipe  outlets  are  proposed  to  be  used.  The  pipes  are  placed  horizontally and  at  right  angle  to  the  centre  line  of  the  distributing  canal.  Discharge  through  the  pipe  outlet  is given by formula;
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'Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES
Q=CAj^H
Where  C  =  Coefficient  of  discharge  which  depends  on  friction  factor,  length  and  size  of  pipe outlet.
f= coefficient of fluid friction for pipes, slightly encrusted pipe
L= Length of pipe in meters D= diameters of pipe in cm
its  value  would  be  0.005  for  clean  iron  pipe  and  0.01  for
H= Head of water measurement form central line of pipe to the FSL
In  Erer irrigation  project steel pipes are proposed  to  be used  for outlets assuming  slightly  encrusted (f=0.01) for design  purposes It is proposed  to  place the pipes at bed  of the distributing  channel to enable the outlet to  draw its fair amount of silt.  The inlet and  exit ends of pipe are proposed  to  be fixed in stone masonry to prevent its tempering.
Table  given  below  gives  discharges  for  different  heads  and  different  diameter  of  steel  pipes.  The sizes of outlet pipes are selected from the table given below.
Table 9.1 Discharges of pipe outlets for different Heads Coefficient of Friction f= 0.01
Length of
the pipe
m
Diameter of
pipes
cm
Discharge Q in Cumecs
0.20m
0.30m
0.40m
0.50m
0.75m
1.0m
3
10
15
20
25
0.009 5
0.023 1
0.043 0
0.069 0
0.011 6
0.028.3
0.052 5
0.0S4 4
0.013 4
0.032 7
0.060 7
0.097 7
0.015 0
0.036 5
0.067 9
0.109 2
0 01S4
0.044 S 0 0S3 0 0.134 0
0.021 2
0.051 6
0.096 0
0.154 4
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Length of
the pipe
m
•
Diameter of pipes
cm
0.20m
0.30m
Discharge (
0.40m
J in Cumecs 0.50m
0.75m
1.0m
5
10
15
20
25
0.008 3
0.020 8
0.039 4
0.064 1
0.010 2
0.025 5
0.048 0
0.078 3
0.011 8
0.029 4
0.055 6
0.090 6
0 013 2
0.032 9
0.062 0
0.101 3
0 016 0
0 040 2
0 076 0
0.123 9
0 018 6
0 046.5
0 087 9
0 143.3
7
10
15
20
25
0.007 47 0.019 1 0.036 5 0.060 1
0.009 16 0.023 4 0.044 6 0.073 4
0.010 6
0.027 0
0.051 6
0.084 9
0.0119
0.030 2
0.057 6
0 095 0
0.014 5
0.037 1
0 070 6
0.1162
0 016 8
0 042 6
0 081 6
0 134 4
9
10
15
20
25
0 006 86 0.017 7 0.034 2 0.056 7
0.008 42 0.021 7 0.041 8 0.069 3
0.009 74 0.025 0 0 048 3 0.080 2
0.010 9
0 028 0
0.054 I
0.0S9 6
0.013 4
0 034 3
0 062 3
0 109 6
0015 4
0 039 6
0 076 4
0 126 S
12
10
15
20
25
0.006 17
0.016 1
0.031 5
0.052 6
0.007 56 0.019 8 0.038 5 0 064 4
0.008 76 0.022 8 0.044 5 0.074 4
0.009 S
0.025 5
0.049 7
0.083 2
0 012 0
0 031 3
0 060 9
0 101 7
0 013 9
0 036 0
0 070 4
0 1177
15
10
15
20
25
0.005 66 0 014 9 0 029 4 0.049 2
0 006 94 0.018 2 0 035 9 0.060 1
0 008 03
0 021 0
0 04 1 5
0 069 6
0 009 0
0 023 5
0 046.4 0.077 8
0011 0
0.02S S 0 056 8 0 095 0
0 012 7
0 033 3
0 065 7
0 110 1
A typical drawing of outlet structure has been given in Drawing Volume.
Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES
9,4  Drop Structures
Canals are constructed  with  permissible bed  slopes so  that the velocity  of water in  the canal will neither produce scouring  nor silting  of the canal It is not always possible to  carry  the canal along the ground  slope unless heavy  earth  work  is done.  This will be unwise and  uneconomical.  Hence,  it becomes imperative that at suitable position, the canal bed is given a vertical or inclined drop.
Drop  structures are provided  on  the ridge section  of canals where bed  level gradient is less than  the existing  land  slope available along  the ridge line.  The difference is adjusted  by  constructing suitable drop structures at suitable interval
In  main  canals,  which  do  not irrigate adjacent lands directly,  the drop  structures are located  from the consideration  of economy  in  cost of excavation  the channel.  The drop  structures are located  in relation  to  ground  level and  channel bed  level so  as to  balance cut and  fill between  reaches as far as possible.
In secondary or tertiary canals, which irrigate surrounding lands, the drop structures are located in 
such a way that they don’t cause any loss of command The full supply level in the channel may 
be so marked that it covers all the command points and allows a minimum working head of 0 15 m
for off- taking regulators and outlets
Location and Design Criteria
The  Location  depends  upon  the  ground  conditions  of  the  area  through  which  the  canal  is  flowing and the type of canal
o   In   main   canals,   which   do   not   irrigate   adjacent   lands   directly,   the   drop   structures   are   located from the consideration of economy in cost of excavation of the channel.
o   The   drop   structures   are   located   in   relation   to   ground   level   and   channel   bed   level   so   as   to balance cut and fill between reaches as far as possible.
o   In   secondary   or   tertiary   canals,   which   irrigate   surrounding   lands,   the   drop   structures   are   located in such a way that they don’t cause any loss of command.
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o The full supply level in the channel may be so marked that it covers all the command points
and allows a minimum working head of0.15m for off- taking regulators and 0.15m for outlets, 
o The Froude Number (i.e. V/^gd) is not allowed to excess 0.5 in approach channel, 
o The drop structures are designed to have straight drops and standard impact basin, 
o Dead load of concrete and soil, lateral earth pressures and earthquake forces (not generally 
significant) are considered to decide component structures
o  There  are  various  types  of  falls  constructed  in  the  world  such  as  ogee  falls,  rapid  falls,  vertical drop  falls,  glacis  falls,  modified  glacis  type  etc.  However  on  extensive  research  carried  out  in Poona   Research   Station   of  Central  Water  Commission,  Govt,  of  India  un-flumed  vertical  falls
with  discharge  up  to  15  m /s
3
and  fall  height  up  to  1.5m  are  found  most  satisfactory.  Hence  un
flumed   vertical   falls   (crest   length   equal   to   width   of   canal)   are   recommended   in   the   present context. The cost of this type of fall is the lowest.
In  vertical  drop  fall  the  nappe  impinges  in  to  water  cushion  down  below  and  dissipation  of  energy is affected by the turbulent diffusion. No standing waves are created.
The Cistem Length = 5( Hl* D )°5
The Cistern Depth = 0.25 (H  ♦ D)
L
273
l
Where:
H  = Drop of fall (m )
D = Depth of crest below T.E.L.(m)
o In main canals the cistern may be constructed with side and floor thickness of 300mm thick in
C.C.   C-30.   In   secondary   and   tertiary   canals   drop   structures   may   be   constructed   with   stone masonry  laid  in  1:4  cement  mortars.  The  inner  side  of  cistern  may  be  plastered  with  1:3  cement mortars.
A typical drawing of drop structure has been given in Drawing Volume
9.5   Tertiary canal Head Regulator
Tertiary  canal  head  regulator  structures  shall  comprise  of  a  single  gated  intake  followed  by  a  pipe conduit under the canal embankment often opening into a measuring weir outlet structure.
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The  gates  on  the  head  regulator  will  be  simple  straight  lift  gates  that  can  be  operated  by  an individual man.
Preferably gates shall be locked, to safeguard against unauthorized operation/tampering. A typical drawing of tertiary canal head regulator has been given in drawing Volume.
9.6 Duck Bill Weir Structure
Duck  Bill  Weirs  are  very  simple  structures  used  as  cross  regulators  in  small  secondary  canals  for controlling the water level in upstream of head regulators.
Duck Bill Weir is preferred over the straight weir because the level control in the parent channel is affected  by  minimum afflux.  A Duck  Bill Weir may  or may  not be followed  by  a fall structure depending upon the site conditions
In  case  of small  discharges  a simple broad crested weir having the same width as that of parent channel followed by a fall will be adequate.
A typical drawing has been given in Drawing Volume.
9.7 Tail Escape Structures
At  the  end  of  every  canal,  whether  secondary  or  tertiary,  a  tail  escape  is  provided.  This  is  very simple structure made in masonry or concrete as broad crested weir followed by a masonry cistern whose  crest  is  kept  at  the  full  supply  level  (FSL)  of  the  last  reach  of  the  channel.  The  length  of broad crested weir is proposed to be about 2.0 times the width of the end channel at FSL so that effluxes  caused  by  weir  are  minimized.  The  tail  escape  channels  are  provided  to  join  the  existing drain  falling  in  their  alignment  and  have  been  provided  to  have  the  same  section  as  that  of  its parent  channel  but  with  reduced  bank  width.  A  free  board  of  0.2ft  (=60mm)  has  been  provided above FSL.
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r
10.0 Cross Drainage Structures
Following  types  of  structures  are  proposed,  depending  on  the  site  conditions,  size  of  drains  and 
economy.
A total of 33  cross drainage works are proposed  on  praimary,  secondary  canal I and  secondary canal II. Their location, design discharge and type of structure choosen is tabulated as shown in the table below (table 10.1)
Table 10.1 Cross Drainage works
No
Name
Chainage (m)
Discharge (m3/s)
Type of Structure Proposed
1.
CD3-P
3,100.00
0.9
Single pipe
2.
CD4-P
3,880.00
2
Single pipe
3.
CD9-P
10,660.00
0.75
Single pipe
4.
CD10-P
11,040.00
0.9
Single pipe
5.
CD12-P
12,400.00
0.75
Single pipe
6.
CD13-P
12,860.00
0.9
Single pipe
7.
CD14-P
13,000.00
0.9
Single pipe
8.
CD2-S2
2,400.00
2
Single pipe
9.
CD2-P
1,720.00
0.84
Double pipe
10.
CD15-P
13,180.00
2.4
Double pipe
11.
CD3-S2
2,840.00
2.4
Double pipe
12.
CD10-S2
9,220.00
2.4
Double pipe
13.
CD1-P
420.00
2.8
Triple pipe
14
CD8-P
9,800.00
2.6
Triple pipe
15.
CD5-S2
5,220.00
23.8
Slab culvert
16.
CD13-S2
10,660.00
38.3
Slab culvert
17.
CD6-P
5,040.00
2.49
Syphon
18.
CD7-P
8,080.00
2.38
Syphon
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19.
CD11-P
11,656.00
2.21
Syphon
20.
CD16-P
13,340.00
2
Syphon
21.
CD5-P
4,280.00
2.49
Syphon
22.
CD1-S2
1,480.00
0.77
Syphon
23.
CD4-S2
4,480.00
0.555
Syphon
24.
CD6-S2
6,360.00
0.418
Syphon
25.
CD7-S2
7,680.00
0.3
Syphon
26.
CD8-S2
8,300.00
0.221
Syphon
27.
CD9-S2
9,020.00
0.22
Syphon
28
CD2-S1
2,460.00
0.767
Syphon
29
CD3-S1
2,740.00
0.65
Syphon
30.
CD4-S1
3,640.00
0.65
Syphon
31.
CD1-S1
860.00
267.5
Aqueduct
32.
CD5-S1
6,160.00
92.2
Aqueduct
33.
CD11-S2
10,340.00
87.8
Aqueduct
1. Aqueducts
2. Culverts
Pipe culverts
a.           Single pipe culvert b Double pipe culvert
c. Triple pipe culverts
Box culverts
a. Single box culvert
b. Double box culvert
c. Triple box culvert
3. Syphones
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10.1 Aqueducts
There are three sites where aqueducts have been  proposed  because the discharge of drains crossing  canals are too  high  where culverts shall be costly  in  comparison  to  troughs carried  over the drains on piers
Two  secondary  canals one shall be crossing  Decho  River to  extend  irrigation  on  other side of Decho River. Besides, two aqueducts are also proposed for secondary canal-I and secondary canal- II crossing Kebanawa River.
Following are the design criteria proposed for design of aqueduct structures
o The choice of type of aqueduct depends up on consideration of economy which in tum will depend on size of drain to be crossed and size of canal It will also depend on foundation strata  at  crossing  site,  dewatering  requirements,  envisaged  head  loss  and  topography  of  the site.
o The design flood for drain crossing a canal depends on size of canal, size of drainage channel and location of cross drainage structure For choosing appropriate frequency of design flood following table has been referred:
Canal Discharge       Estimated drainage           Frequency of Design Flood
(cumecs) 0-0.5
0.5-15
discharge (cumecs) All discharges
0-150
1 in 25 year
1 in 50 year
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On  this  basis  the  design  flood  of  1  in  50  years  is  recommended  and  the  design  has  been  done  for this frequency of flood.
In   plain   the   channels   are   in   alluvium   and   water   way   provided   is   60   to   80   %   of   water   way calculated by Lacey’s formula as below:
p w = c Q m
Where:
Pw = Wetted perimeter in m
C = Coefficient whose value is normally 4.83
Q = Design discharge in m /sec
This  is  the  distance  between  two  abutments  However  in  this  design  the  water  way  has  been  taken almost equal to Lacey’s width and no contractions are assumed.
o   In   the   present   option   the   earth   banks   are   discontinued   over   the   drain   and   canal   water   is carried   in   a   rectangular   RCC   trough.   The   sides   of   canal   are   connected   in   either   side   of aqueduct   to   the   earthen   banks   preferably   by   means   of   transition   walls.   Canal   is   generally flumed  to  effect  economy.  But  in  this  design  no  fluming  is  assumed  because  the  sizes  of canals are very small.
o  The  layout  of  the  aqueduct  is  so  fixed  that  it  is  in  straight  reach  of  drainage  channel.  The canal crosses the drain at right angle
o   The   transition   in   canal   has   been   provided   with   1:2   splay   in   upstream   and   1:3   in   down stream sides respectively. It will ensure that the flow to follow transition boundaries.
o   In   case   of   canal   trough   supported   on   piers,   expansion   joint   of   sufficient   width   have   been provided at the centre of pier.
In  Erer project the Primary  canal and  secondary  canal-II are designed  as contour canals,  therefore, no  drop  structures are required  on  these canals.  However in  case of secondary  canal-I it descends about 48  feet in  about 1.0  km length  before it crosses Dencho  river a series of drop  structures shall be required  to  negotiate this descent Considering  the above points a number of drop  structures of
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1.50  m  fall  are  recommended.  These  drop  structures  will  have  5.54  m  length  of  cistern  and  0.30  m depth of water cushion. Rest of the details are indicated on the drawing.
Depending  upon  the canal passing  over the drainage channel,  an  aqueduct may  be classified  in three categories.  Type I is one where canal continues over the drainage channel in  its normal earthen  section  including  the banks and  earthen  slopes In  this case the length  of culvert through which  drainage water is passed  should  have sufficient size to  accommodate the canal and  its banks. Type II is one in  which  canal continues in  its earthen  slopes and  outer slopes of banks are replaced by  the retaining  walls which  shorten  the length  of culvert.  Type HI is one where earthen  banks are discontinued  over the drainage channel and  canal water is carried  through  the masonry  or concrete trough,  box  barrel or pipe.  The sides of the trough  are connected  on  either to  earthen  banks of canal by means of transition walls. Generally the canals are flumed to affect economy.
In  large rivers aqueducts of type III are adopted  because it ensures overall economy.  This type of structure is recommended  in  providing  drainage crossing  for secondary  canal-I and  secondary canal-II over Dencho  River whose discharge is of the order of 270.0m3/sec.  The discharges of secondary  canals are low (varying  between  0.7  to  0.9m3/s) in  comparison  to  flood  discharge of Dencho  river.  Troughs of an  adequate size are adopted  and  a free board  of 0.3m is considered adequate.  The trough  is proposed  to  be of reinforced  cement concrete proposed  to  be designed  as beam.  This is carried  over a no  of piers and  side abutments made of stone masonry  laid  in  1:4 cement mortar.  The joint have been  provided  in  centre of pier across the trough  to  accommodate the movement in  either direction.  At every  joint a gap  of 15mm is provided  and  water stops (PVC seal) are also embedded to protect water loss through the joint.
The  recommended  width  of  pier  for  the  span  of  5  to  6m  is  of  the  order  of  0.85m.  Hence  1.0m width  is  adopted  for  the  span  of  10m.  On  the  top  of  pier  a  bed  block  of  0.2m  thickness  is  provided The  pier  is  proposed  to  have  semi-circular  nose  and  cut  water  radius  of  0.5m.The  thickness  of  the pier  is  proposed  to  be  increased  from  1.0  m  to  1.6  m  in  two  steps  below  the  scour  level  The  piers are  based  on  the  foundation  concrete  of  appropriate  size  located  at  level  which  is  equal  to  the  depth of anticipated scour around the pier plus 1.0m as a grip length.
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The minimum width of abutment at scour level is kept 0.6 times of the scour depth below FSL. The abutments are designed to stand earth pressure coming from its back side created by dry and submerged soil.
The width of abutments is increased from 570 mm at the top to 1100 mm at the bottom i.e. above
the level of foundation concrete. Foundation concrete of 1800 mm wide and 600 thick is proposed 
to be provided below the abutments.
10.2       Culverts
There are eighteen  small drains crossing  primary  canal.  Their 25-year return  period  discharges vary from 0.75 to5.9 m /s. For the drains carrying discharge up to 1.57 m /s, a single pipe culvert is provided.  For discharge lying  in  between  1.57  to  3.04  m3/s twin  pipe culverts are provided. Similarly triple pipe culverts are provided for discharge varying from 3 04 to 6.4 m /s (with 0.5m submergence)
There are five cross drainage structures proposed on secondary canal-I. Out of these there are two aqueducts as mentioned under “aqueducts” above. Of the remaining three are siphon.
Similarly  thirteen  natural drains cross secondary  canal-II.  One is designed  as aqueduct being  a major drain crossing. One is designed as single pipe culvert, two as twin pipe culverts, two as slab culverts and remaining are siphon.
In every system, canals cross some natural drains along its alignment. Provisions are required to be made to cross the drain across the canal safely without damaging the canal structure and interfering with its functions.
The cross drainage works may be three types depending upon the level at which a drain crosses the canal. If the level of canal bed is higher than the full supply level of drain the drain is designed to cross through an aqueduct or siphon aqueduct or culvert. If the situation is other way round, the
3
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drain  will  cross  through  super  passage  or  siphon.  In  a  special  situation  when  water  level  in  drain and canal is approximately the same the structure in this category will be level crossing.
The   cross   drainage   culverts   have   been   designed   to   have   sufficient   size   to   pass   25-year   return period flood.
The catchments area of these drains have been  demarcated  on  topographical sheets in  1:50,000 scale US SCS method  has been  used  for determining  25-year and  100-year return  period  flood discharges.
The  rDF-  curves  which  have  been  developed  from  data  of  self  recording  rain  gauges  situated  in  the region and surrounding area have been used for finding out the peak discharges.
The natural drains which  cross the canals shall have adequate cross section  to  pass flood  discharge of 10-year return  period.  If the existing  section  is smaller than  the one required  for passing  10-year return period flood the drain section has been recommended for resection to the desired size
Following  design  criteria  have  been  used  for  various  components  associated  with  cross  drainage structures:
(a)   Joints-Joints  have  been  provided  along  and  across  the  drainage  barrel  length  at  a  spacing  not exceeding  20m  in  either  direction.  A  gap  of  15mm  has  been  provided  at  each  of  joint  and  water seals (made of rubber or synthetic material) are provided across all these joints.
(b)   Collar  -In  case  of  barrels  resting  on  compressible  soils  collars  encircling  the  joints  have  been provided.   This   will   protect   water   stops   from   shearing   due   to   differential   settlement.   Cross section of collar has been assumed not be less than 300mmx300mm.
(c)   Free  board:  A  free  board  of  300  mm  has  been  provided  in  trough  of  the  canal  as  the  discharge of canal is less then 3.0 cumecs. However the free board provided in the drainjs as below:
1
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Discharge of drain (cumecs)
Up to 30
30-100
100-300
4
Free board (mm)
400
500
600
(d) Allowable velocity: Maximum velocity in case of concrete and stone surface is not allowed to 
increase beyond 4 m/s.
(e) Inlet submergence : In case of siphon and siphon aqueducts the submergence has been decided 
on the basis of topographical considerations.
(fIMinimum pipe cover: A minimum cover of 600mm has been provided.
10.3  Inverted Siphons
Siphons are proposed  when  the high  flood  level of the natural drain  is higher than  the bed  level of the crossing  channel.  The structure mainly  consists of inlet transition,  circular barrel and  outlet transition.
Out of the total cross drainage works 5, 3 and 6 siphons are proposed on primary, secondary canal
1  and  secondary  canal  2  respectively  Detail  hydraulic  design  is  shown  in  ANNEXE  (calculation  of irrigation structures).
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11.0 Field Drainage System
In  general  the  drainage  system  comprises  of  field  drains,  tertiary  drains,  secondary  drains  and  main drains
The excess water from the land  is gathered  by  a network  of field  drains.  The excess water which ponds on  the surface,  flows laterally  in  the form of overland  flow and  enters the field  drains The field  drains discharge into  tertiary  drains which  finally  cany  water to  secondary  or main  drain.  The field  drains are aligned  along  the field  boundaries.  The surface drainage system is most effective in case of soils which  are impermeable (vertisols or black  cotton  soils) or in  special situation  when vertical flow of infiltrated water is impeded by presence of impermeable layer
There is total 40  number of field  drains planned  in  entire command  area.  These comprise of 13 field  drains.  The list is given  in  three tables as given  below.  These drains are aligned  along  the depression  lines so  that the fields may  directly  discharge in  them under gravity.  The lengths of majority  of these drains are within  the range of 1000  to  1500  m.  However there are few drains which  are above 2000m long.  These drains directly  drain  into  existing  drainage system in  the area. This has happened  because the canals are proposed  to  irrigate their commands comprising  of strips of lands situated  on  their left sides in  widths varying  from 500  m to  2000  m.  On  account of this special layout the need  for tertiary  drains has minimised  There are only  two  tertiary  drains proposed in the whole of command area.
The field  drains are designed  to  evacuate superfluous rain  and  irrigation  water from the command area in  24  hours as the dominant crops are maize and  cotton  which  can  stand  flooding  of 24  hours In  a situation  when  any  field  is being  irrigated  and  heavy  rain  occurs,  the field  drainage system should  be capable of removing  excess rain  and  irrigation  water effectively  during  stipulated  time otherwise it will result in impairment of crop growth and farm operations.
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Erer project Field drainage of the main canal
Name
Area
Length
Location
Drain
(ha)
(m)
( chainage)
to
FD1P
15
300
1+350
Erer River
FD2P
30
700
1+950
Erer River
FD3P
35
1400
3+150
Erer River
FD4P
60
1000
3+700
Erer River
FD5P
35
500
4+250
Erer River
FD6P
50
1500
4+800
Erer River
FD7P
35
900
5+800
Erer River
FD8P
50
1400
6+600
Erer River
FD9P
55
1100
7+450
Erer River
FD10P
45
1200
9+000
Erer River
FD11P
40
1400
9+400
Erer River
FD12P
40
900
10+400
Erer River
FD13P
35
800
11+300
Erer River
FD14P
50
1400
12+600
Erer River
FD15P
30
1400
13+300
Decho River
FD16P
70
1700
*0+050
Erer River
FD17P
50
1700
*0+500
Erer River
FD18P
40
1600
•1+000
Erer River
‘chainage started from secondary 
canal
Table 11.2 Drains of Secondary canal-1
Name
Area
Length
Location
Drain
(ha)
(m)
( chainage)
to
FD1S1
50
1700
2+000
Dencho River
FD2S1
30
1400
2+700
Natural Drain
FD3S1
35
1400
3+200
T1DS1
FD4S1
30
1300
4+200
T1DS1
FD5S1
60
1900
4+800
T1DS1
FD6S1
55
1400
3+000
Erer River
FD7S1
50
1300
3+400
Erer River
FD8S1
40
1200
3+900
Erer River
FD9S1
20
1000
3+700
Erer River
FD10S1
25
1000
3+900
Erer River
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FD11S1
50
1000
5+200
Kebenaw River
FD12S1
30
900
5+700
KebenawRiver
FD13S1
65
1600
6+000
Kebenaw River
FD14S1
70
2700
6+800
Erer River
FD15S1
80
1600
7+300
Erer River
FD16S1
50
2600
8+300
Erer River
Table 11.3 Drains of Secondary Canal- II
Name
Area
Length
Location
Drain
(ha)
(m)
( chainage)
to
FD1S2
40
800
0+000
Dencho River
FD2S2
30
800
0+600
Dencho River
FD3S2
20
600
1+200
Dencho River
FD4S2
60
1700
3+200
Natural Drain
FD5S2
45
2500
3+600
Natural Drain
FD6S2
90
1800
6+800
Natural Drain
FD7S2
90
1300
6+800
Decho River
FD8S2
90
1800
8+100
Ija Oda River
FD9S2
50
1300
10+200
Natural Drain
FD10S2
60
1000
11+000
Kebenaw River
FD11S2
30
900
11+400
Kebenaw River
2
11.1   Excess Rain Water
Surplus  rain  water  is  found  out  by  US  SCS  method.  The  surplus  rain  water  depends  mainly  upon type of soil, vegetative cover, land use and rainfall.
Q = (P- 0.2 S ) /( P + 0.8 S )
Where Q= Surplus Rain in mm
P= Rainfall in mm
S=Retention Parameter in mm derived from SCS Curve Number.
Assuming  the condition  of moderate runoff potential CN = 76,  S = 80.2,  precipitation  depth  in  24 hr of return  period  5  years is equal to  60.0  mm.  (refer Hydrology  report,  IDF curves are reproduced  below) This is found  by  converting  the available IDF curves on  semi-log  paper
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because   interpolation   of   24-hr   rainfall   of   5-year   return   period   is   not   possible   from   the   available plot being on mathematical scale.
Intensity-Duration -Frequen cy
Regions A1 & A4
Figure 5-9
Duration, min.
Q=( P-0.2 S) / (P + 0.8S)
2
Q = ( 60 - 0.2* 80.2 ) / ( 60 + 0.8*80.2 )
2
= 15.41 mm in 24 hr = l5.41*l000*l04
1000*24*3600 = 1.78 1/s/ha
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11.2  Excess Irrigation Water
*
At the time when  a field  is receiving  irrigation,  heavy  rainfall may  be experienced  at the same time In  this situation  field  drainage system should  be in  position  to  evacuate the total surplus water caused by rainfall and irrigation, both.
It is assumed  as 70% of field  water supplied  for irrigation  per ha during  the months of maximum demand  be evacuated  along  with  surplus rain  water The field  water supply  in  October is of the order 0 60 1/sec/ha. The 70% of this works out to 0.42 1/sec/ha.
11.3  Field Drain Capacity
Total surplus rain and irrigation water works out to 1.78 + 0.6 * 0.7 = 2.2 L/s/ha
Drainage requirement of 60ha field will work out to 60 * 2.2 1/s = 132 1/sec
The field drains shall be designed to evacuate 1321t/sec (0.132m /sec) excess water. As mentioned in design criteria, the field drains are proposed to be aligned along drainage lines at the existing slopes. These are proposed of triangular section with side slopes of 6:1. There is no need of providing of any free board. The field drains shall be designed with Q = 132 1/s (0.132m /s), N = 0 030, Side slope 6:1, Triangular section and Manning’s N = 0.030 if maintained well and free from vegetation and 0.035 otherwise.
Table 11.4 Permissible Bed slopes for different sizes of field drains ( N=0.03 )
3
3
Area of field
(ha)
Drain discharge
(m3/s)
Side slope
H:V
Depth of
flow (m)
Bed slope
(%)
Velocity
(m/s)
30
0.066
6:1
0.13
1.8
0.70
40
0.088
6:1
0.15
1.36
0.69
50
0.110
6:1
0.16
1.28
0.72
60
0.132
6:1
0.18
1.2
0.68
80
0.176
6:1
0.20
1.0
0.73
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In  the table above designs of field  drains draining  areas from 30  ha to  80  ha are given.  The maximum allowable velocity  which  does not cause erosion  is assumed  as 0.75  m/s The limiting bed  slopes are worked  out by  using  Manning’s formula.  The depths vary  from 0.13m to  0.20m for discharges varying  from 66  1/s to  176  1/s.  As may  be revealed  from the above table,  when  the bed slope increases beyond  1.0% for field  channel draining  80  ha area the velocity  increases beyond 0.75m/sec (allowable).  Drop  structures shall be provided  at suitable points when  available slope increases beyond  1.0  % to  control flow velocities and  consequent erosion  Similarly  for field  drain draining  40  ha area the limiting  bed  slope will be 1.36  % beyond  which  the velocity  will increase beyond  permissible limit.  Hence for this size of drain  the drop  structures shall be provided  at suitable locations when available bed slope increases beyond 1.36 % to ensure non-erosive flow.
11.4 Tertiary Drains
The field  drains discharge into  tertiary  drains.  All the tertiary  drains shall follow drainage lines or depression  ditches from the consideration  of economy  and  shall have drop  structures at regular interval to  control erosion.  Small drop  structures at frequent intervals shall be preferred  over few large structures because in doing so, the earthwork will be economized.
Tertiary  drains normally  discharge into  existing  drains or gullies.  The sites where the tertiary’ drains join  existing  gullies shall be protected  to  avoid  erosion.  The cross sections of tertiary  drain shall be trapezoidal with side slope 3:1 and minimum bed width 1.30m and shall be designed
Manning’s formula with  N = 0.030.  If the existing  gradient along  the drain  alignment is higher than required  for maintaining  the safe velocity,  drop  structures having  straight foil of 1-2  m height are recommended to be provided at suitable locations.
There are only  two  tertiary  drains in  the command  of Secondary  canal -1.  In  rest of the command, there are no  tertiary  drains and  there are only  field  drains.  The tertiary  drains of secondary  canal-I are designated  as T1DS1  and  T2DSl.The length  ofTIDSl is 1500m and  three field  drains namely F3DS1.F4DS1 and F5DS1 join it. The available slope of this drain is about 1.6%. The total area
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drained  by  these field  drains is 155  ha.  The required  size of the tertiary  drain  will be equal to  0.341 m3/s (155*2.2  =341  1/s ).  However T2DS1  is 2600  m long  drain  which  drains 130  ha area.  In  the head  reach  of about 1600  m length  till the area of its drainage is about 80  ha it will be a field  drain and  have triangular section.  In  the last reach  of 1000m it will be designed  as tertiary  drain  having discharging  capacity  of 0.286  m3/s (130*2.2=286  1/s).  The available slope of this drain  is 2.33  %. The design parameters of these drains are indicated below in the table:
Table 11.5 Hydraulic Parameters of Tertiary drains
Name
of
drain
Discharge (m3/s)
Manning’s
‘N’
Slope
(m/m)
Depth (m)
B.W.
(m)
H:V
V
(m/s)
Vo 
=0.55* 
d °64
CVR
F.B.
(m)
T1DSI
0.341
0.03
0.0004
0.42
1.50
3:1
0.31
0.32
0.97
0.3
T2DS1
0.286
0.03
0.0004
0.46
1.40
3:1
0.29
0.31
0.94
0.3
The available slope in  T1DS1  is 1.6% and  as that of T2DS1  is 2.33  %.  These are more than  the required  slope of 0.04%.  Therefore drop  structures of 1.0  m fall shall be required  to  be constructed after every 83 m distance in case ofTIDSl and 52 m in case ofT2DSl respectively.
11.5  Drain Layout
The command  area which  is proposed  to  be irrigated  by  Primary  canal is to  drain  directly  in  to  Erer river as the Erer river flows at about 1.0  km from the other end  of irrigated  area and  all the field drains are designed to out fall in this river .
The command  area of Secondary  canal-I is proposed  to  drain  in  to  Dencho  river,Kebenew River, Erer River and  partly  to  a natural drain.  The layout of field  drains and  tertiary  drains (only  two  in number) is indicated on the layout plan of this command included in Drawing Volume.
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Similarly the entire command area of Secondary canal —II is drained by Dencho River, Kebenew River and few small natural drains. The proposed drains of this area are designed to drain in these existing rivers/drains.
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♦
12.0 Flood Protection Embankments
The proposed irrigated area is situated in the right side of Erer River. Primary canal and secondary canal-I extend irrigation to the area located just adjacent to the river course. In some reaches the area is prone to inundation and consequent damage to agriculture. To safe guard this area from flooding suitable flood protection works have been designed as per practices in vogue in different parts of the world.
To start with the contour plan of the area has been deeply studied and area prone to inundation has been demarcated. No flood protection works already exist in the area. To decide on the important aspects like degree of protection  to  be provided  and  alignment and  spacing  of embankments following studies have been conducted:
1.      River characteristics, whether aggrading/ degrading, braided/ meandering, alluvial/incised. Silt carrying capacity, Nature of bank and bed materials, Active food plains of the river etc.
2.      Hydrological data, recorded discharge data, length and reliability of data, recorded flood levels and highest historical floods, rain fall data.
3.      L-section and X-section of the river, safe carrying capacity
On having studied the above the following design criteria has been short listed and adopted in 
design of embankments.
12.1 Design Criteria
•    The flood protection embankment shall safely contain routed 100-year return period flood 
(routed through Erer dam reservoir) without spilling to the adjacent agriculture lands.
•     The  spacing  between  flood  protection  embankments  planned  on  both  banks  shall  not  be  less than  three  times  the  Lacey’s  wetted  perimeter.  If  the  embankment  is  planned  on  one  side  of river, which is the present case, the distance between embankment and centre line of river shall not be less than 1.5 times the Lacey’s perimeter. The size of Erer River is small therefore the spacing between protection bank is reduced to two times of Lacey’s perimeter.
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« *
•     The embankment alignment shall be located on the ridge of natural bank where land is high and both the ends of embankment shall be natural high ground or existing road embankments.
•     Homogeneous embankment shall be adopted for the reasons of simplicity.
•     For surface protection of embankment from rains or wind 0.3 m thick turfing shall be provided.
•     Since the velocities in the close vicinity of embankment will be low, therefore no protection is provided.
•     The minimum top width of embankment shall not be less than 5.0 m. However in case of Erer river which is small in size, top width of 3.0m is considered adequate.
•     The side slopes of upstream and downstream side of embankment shall be steeper than 2:1 slope.
•     The HG line shall have slope of 1:4 to 1:6 for different types of soils of varying texture Considering the embankment material of medium texture a slope of 1:5 is adopted in designs. A minimum cover of 0.6 m shall be kept over HG line by adjusting the downstream slope.
•     Borrow areas shall be located on the river side only. For low embankments (height<6.0m ) the borrow areas shall not be selected within 25 m of the toe/heel of embankments.
Besides above design criteria following aspects are recommended for adoption at the time of construction:
1.   Soil investigations be carried out to identify and locate the borrow areas
2.   Maximum depth of borrow pits shall be limited to 1.0 m to preclude the chances of disturbing regime of river.
3.   In order to obviate chances of developing flow parallel to banks cross bars of the width 8-times of depth of borrow pit shall be spaced minimum 60 to 80m centre to centre
4.   Settlement allowance of 1 to 2 % shall be made in the height of embankments
5.   All borrow areas shall be stripped of top soil a minimum of 30 cm and all objectionable materials shall be removed.
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12.2  Design of Embankments
The flood  protection  embankments are designed  for containing  routed  flood  of lOOyr return  period. The routed  flood  hydrograph  is coursed  through  the existing  river sections and  levels corresponding  to  routed  flood  are worked  out.  If the bank  full capacity  at the existing  sections is found  adequate no  embankments are provided.  In  the reaches where bank  full capacity  is found inadequate flood protection embankments are provided with proper free board.
Flood  peak  of 100  return  periods in  upstream of dam site is estimated  as 366.6m3/s.  The hydrograph  of this peak  is routed  through  reservoir and  attenuated  flood  peak  comes as 250.5  m3/s Lacey’s perimeter (P= 4.83*  Q03) corresponding  to  Q= 250.5  m3/s,  worked  out to  76  m.  If the flood  protection  embankments are required  to  be provided  they  should  have minimum 150  m spacing to ensure a stable regime in the river.
The entire course of river has been checked for discharge carrying capacity of this order and 
reaches having inadequate capacity are identified These reaches are given as below:
(a)  Pocket-I  This  is  about  55  ha  area  situated  in  the  proposed  command  of  primary  canal.  It  is located  in  1500  m  long  reach  of  river  extending  from  1025500  Northing  to  1023000  Northing. This  area  is  practically  at  the  bed  level  of  river.  The  river  course  is  proposed  to  be  jacketed between   two   flood   protection   embankments   spaced   at   150   m   apart.   If   routed   flood   of   250.5 m3/s  is  coursed  through  the  depth  of  flood  water  will  rise  to  about  1.2  m(  slope  of  the  river  in this  reach  is  1/300  and  Manning’s  n  is  assumed  as  0.04,  average  velocity  will  work  out  as  1.6 m/s  )  Hence  river  protection  embankment  of  1.7  m  height  (  1.2m+  0.5m  for  free  board  )  is proposed  along  the  river  in  the  aforesaid  reach  running  parallel  to  river  course  at  75  m  distance away from the centre line of the river.
(b) Pocket-II- This is an area of about 12 ha This is also part of the command of primary canal This is situated in the downstream side of Harar -Jijga road crossing of Erer river between 
1022200 Northing to 1021000 Northing. This area is also having the same level as that of river
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bed. Second flood protection embankment is proposed to protect this area. This embankment
of 600 m length is proposed to be constructed parallel to existing river course and have the
same dimensions and location with respect to river as proposed for pocket-I.
Considering  above  criteria  the  section  of  embankment  has  been  designed  and  the  drawing  has  been given in Drawing Volume.
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13.0 Construction Materials
13.1 Earth Works
The excavated  earth  materials available from the canal and  drain  construction  shall be suitably used in construction of adjacent roads and embankments. If possible, surplus earth available during construction of canals and drains shall also be used as backfill of structures.
13.2  Masonry and Concrete Works
There is very small requirement of stones and aggregates for masonry and concrete to be used in irrigation  structures.  These materials are locally  available as investigated  in  connection  with  the requirement of aggregates in dam and appurtenant works. The same investigated quarries may be used to avail these materials.
Suitable local stones may be utilized for concrete construction works.
Portland cement as available locally may be utilized.
The river sand which is in plenty shall be used in masonry and concrete works.
The construction materials pertaining to the concrete works shall conform to the relevant BS codes.
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14,0 Operation and Maintenance of Irrigation System
The success and  failure of any  irrigation  system depends upon  its proper operation  and maintenance.  If the operation  and  maintenance of any  system is poor,  it will not be able to  serve its objective function.  The canal system should  supply  the entire requirement of water of the crops in the command  area; at the appropriate time so  that crops may  grow to  their full maturity  and  yield good  production  without wasting  any  water.  Similarly  the drainage system should  he operated  and maintained  in  such  away  that excess water (rain  water and  irrigation  water) may  he drained  with promptitude without causing  any  damage to  the crops on  account water logging.  These duties are to be handled by the agencies responsible for the operation and maintenance of the system.
As per system existing  in  Ethiopia there will be two  agencies who  will be involved  in  these duties. These are government agency  and  beneficiary  agency.  The government of Ethiopia through Ministry  of Water Resource can  form a special Erer Project Authority  (EPA) or Erer Project Control Centre (EPCC) to  operate and  maintain  this system on  behalf of the government.  However, the beneficiary  committee can  handle its responsibilities on  behalf of all the farmers benefiting from irrigation  system.  The responsibilities among  these agencies are proposed  to  the apportioned in the following manner
14.1  Dam Structure
All  dam  structures  including  main  dam,  spill  way  and  outlet  structures  shall  the  operated  and maintained by the government agency and no other agency is recommended to be involved.
14.2  Regulatory Structures
This responsibility is proposed to be divided between two parties as below;
i) As the proposed government agency EPA / EPCC shall own all the dam, canal and drainage structures, therefore this agency shall be responsible for maintenance and upkeep 
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of  all  the  structures  built  at  the  expense  of  the  govt  Also,  the  operation  of  all  regulator)' structures up to tertiary canal and tertiary drain level shall vest in this govt agency only.
ii) The operation of canal and drainage system below the quaternary canal and field drains
shall vest in the beneficiary agency.
14.3  Operation Of Reservoir And Conyeyance System :
The operation  of reservoir and  conveyance system requires special responsibilities during  dry season  because in  the event of scarcities it is challenging  task  to  optimise the benefits from available water.  In  rainy  season,  however,  the availability  position  is good  and  demand  is low and therefore it is easier to run the system without facing the scarcities.
For  skilful  management  of  scarce  water  resource  during  the  dry  season  it  is  proposed  that  at  the beginning  of  dry  season  the  EPA/EPCC  should  find  out  the  total  amount  of  water  stored  in  the reservoir   and   estimate   the   likely   available   water   during   dry   season   on   the   basis   of   dependable flows.  The  total  availability  of  water  during  dry  season  i.e.  the  sum  of  stored  water  in  reservoir  and quantity   of   dependable   flows   shall   be   communicated   to   the   beneficiary   agencies   who   will   decide their  weekly  demands  in  view  of  availability  of  these  supplies  in  dry’  season.  This  will  help  them  to appreciate the handicaps of the system and avoid unnecessary misunderstanding
Regular interaction between EPA/EPCC and beneficiary agencies shall help them to decide
schedule of releases with their mutual consent so that the available supplies may be fruitfully used 
Thus the operation of reservoir and conveyance system is recommended to be done exclusively by 
EPA/EPCC as per demand of beneficiaries and availability of supplies.
14.4  Field Irrigation
The   operation   of   field   irrigation   system   shall   be   solely   handled   by   farmers   who   will   divert   the supplies from quaternary canals in to their field channels and furrow by creating check bunds or
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♦ •
using  flexible  pipes.  Schedules  shall  be  drawn  up  for  amounts  of  water  required  for  each  unit  and furrow and time of flow during each watering.
14.5  Maintenance
14.5.1 Canal Network
There are two  type of maintenance required  in  canal system i.e.  repair of rain  cuts and  breaches caused  by  overtopping  of banks and  removal of silt and  weeds.  Both  of these type of maintenance are seasonal and  periodical These are recommended  to  be undertaken  by  regular gangs of labourers to be controlled and supervised by govt, agency.
14.5.2 Field System
All field  channels need  to  be repaired  every  now and  then.  It is recommended  that this type of maintenance may  be undertaken  by  irrigators themselves either individually  or jointly  by  all farmers availing water from that field channel.
14.5.3   Drains
Drains need  only  seasonal maintenance when  their cross sections are blocked  by  accumulation  of debris or weed  growth  This is recommended  to  be undertaken  by  govt agency  by  employing labourers seasonally.
i
14.5.4  Roads
The proposed roads are gravel roads which require maintenance in form of grading regularly and continuously. This is proposed to be undertaken by a gang of labourers specially employed for the
job.
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15. Land Grading
Land   grading   is   the   reshaping   of   the   surface   to   ensure   even   application   of   irrigation   water   and quick disposal of the excess surface water for proper growth of the crops
Plane method  type of land  levelling  has been  used  for this project for its simplicity.  The area of the sample block  for which  land  levelling  has conducted  is 88  ha that has been  divided  in  to  four blocks The first block  is divided  into  200m wide & 150m wide sub-blocks.  The 2nd block  is divided  into  two  200m wide sub-blocks.  Each  sub-block  is divided  into  units having  50m length and  either 200m or 150m width.  Grid  points of the blocks and  their units are based  on  letters and numbers on Y axis & X axis respectively.
The levelling  operation  will be undertaken  for each  fifty  meter length  along  the canal.  The slopes of the best fit as calculated  for the sample block  are 0.9% and  1.6% for cross and  along  the canal. Since the topography  of the land  is steepy,  the maximum allowable slope for loamy  soil 0.4%,  has been  used  for both  directions The maximum cut and  fill depth  that may  reach  lm at extreme ends for the block units having 200m width will be reduced by reduction of block unit width to 150 m.
Grading   has   been   done   in   such   away   that   cut   volumes   exceed   fill   volume   by   at   least   30%   to account for compaction.
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Table 1.0 Cut and fill values for each unit (
1
2
m)
3
4
5
6
7
8
Q
0.9940
0.9365
0.8400
0.8920
0.8605
0.8700
0.6775
0.6120
Q
P
0.5740
0.5365
0.4400
0.4120
0.4205
0.4000
0.2875
0.2620
p
O
-0.0160
0.0765
0.0100
-0.0080
-0.0495
-0.0900
-0.0825
-0.0780
o
N
-0.6060
-0.4335
-0.3700
-0.4180
-0.4295
-0.4000
0.5375
-0.4680
N
M
-0.2386
-0.0939
-0.0641
-0.0943
-0.1101
-0.1428
-0.2081
-0.1990
M
L
-0.0213
0.2481
0.2419
0.1694
0.1994
0.1644
0.1163
0.1200
L
K
-0.2513
-0.2594
-0.2081
-0.1406
-0.1406
-0.1256
-0.1237
-0.1300
K
J
0.1294
0.0913
0.0809
0.0759
-0.0001
0.0527
0.0426
-0.0010
J
I
0.3400
0.4220
0.3800
0.3325
0.2305
0.1910
0.1690
0.1580
I
H
-0.0300
0.0020
-0.0100
-0.0275
0.0005
-0.0590
-0.0910
-0.0320
H
G
-0.4600
-0.3880
-0.3200
-0.2975
-0.2595
-0.2290
-0.1910
-0.1220
G
F
-0.7400
-0.8180
-0.7400
-0.6375
-0.4995
-0.3590
-0.2410
-0.1720
F
E
0.7660
0.8450
0.9410
1.0470
0.9835
0.8360
0.9120
0.8230
E
D
0.3360
0.2350
0.5210
0.5770
0.6135
0.6060
0.4920
0.4530
D
C
0.1160
-0.1750
-0.0690
0.0170
0.1035
0.1760
0.0520
-0.0070
C
B
-0.0340
-0.6050
-0.7090
-0.5430
-0.5065
-0.4040
-0.3880
-0.3870
B
A
-0.1640
-0.7250
-1.0690
-1.1530
-1.0965
-0.9740
-0.8280
-0.8270
A
1
2
3
4
5
6
7
8
Cut
3.2554
Fill"-" -2.5611
3.3929
-3.4978
3.4548
-3.5592
3.5228
-3.3194
3.4119
-3.0918
3.296063
-2.7834
3.2864
-2.1534
2.4280
-2.4230
Table 2.0 Cut and fill values for each unit (m)
9
10
11
12
13
14
15
16
Q
0.7130
0.7675
0.8055
0 8130
0.7355
1.6100
0.6945
0.6860
Q
P
0.3430
0.3675
0.4055
0.3730
0.3455
1.2300
0.3245
0.3360
P
O
-0.0170
0.0075
0.0455
-0.0570
-0.0445
0.8500
-0.0355
-0.0240
O
N
-0.3670
-0.3525
-0.3445
-0 3870
-0.3645
0.5400
-0.3255
-0.3240
N
M
-0.1610
-0.2238
0.0865
-0.1679
-0.1151
0.3444
-0.0693
-0.0795
M
L
0.1150
0.1825
0.1138
0.0813
0.1144
0.1988
0.1569
0.1450
L
K
-0.1250
-0.1075
-0.1063
-0.1687
-0.1456
-0.4613
-0.1531
-0.1650
K
J
-0.0347
0.0373
0.0749
0.0176
0.0487
-0.0194
-0.0353
-0.0578
J
I
0.1005
0.1320
0.2360
0.1840
0.1330
0.1425
0.1825
0.1595
I
H
-0.0295
-0.0480
0.0860
0.0640
0.0330
0.0125
0.0225
0.0195
H
G
-0.0895
-0.0480
-0.1040
-0.1160
-0.1670
-0.1975
-0.1475
-0.1505
G
F
-0.1795
-0.1980
-0.3140
-0.3660
-0.3670
-0.3675
-0.3575
-0.3505
F
E
0 8240
0.6975
0.6315
0.5955
0.5805
0.5615
0.5355
0.4545
E
D
0.4440
0.4175
0.3315
0.2955
0.2805
0.2615
0.2355
0.2345
D
c
0.0340
0.1875
0.0315
0.0355
0.0505
0.0315
0.0055
0.1045
c
B
-0.3760
-0.2125
-0.2685
-0.3045
-0.3195
-0.2785
-0.2545
-0.1955
B
A
-0.7760
-0.6325
-0.6385
-0.6045
-0.6095
-0.5785
-0.5345
-0.4455
A
9
10
11
12
13        L ™
15
16
SI
Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES
"+’
2 5735
2 7967
2.8481
2.4594
2.3216
5.782625
2.1574
2.1395
Fill”-"
-2.1553
-1.8228
-1.7758
-2.1716
-2.1327
-1.9026
-1.9128
-1.7923
Table 3,0 Cut and fill values for each     it 17              18
un  (m) 19
20
21
22
23
Q
0.7410       0.7595
0.4550
0.0225
-0.0760
0.2120
0.1250
Q
P
0.3410
0.4395
0.2250
0.2475
-0.1060
0.0220
-0.4050
P
O
0.0410
0.1195
0.1250
0.2575
-0.0960
-0.1080
-0.5450
O
N
0.2890
-0.2005
-0.0950
0.2775
-0.0860
-0.0880
-0.5550
N
M
0.0517
0.0151
0.0428
0.2525
-0.0427
-0.0565
-0.5013
M
L
0.1656
0.2106
0.1306
0.1575
-0.0394
-0.0350
-0.4175
L
K
0.1444
-0.0394
-0.0494
0.1275
0.0306
0.0650
-0.3575
K
J
0.0459
0.0783
0.0048
0.0725
0.1796
0.1312
-0.2928
J
I
0.1525
0.1860
0.2390
0.2425
0.1885
0.1375
-0.2480
I
H
0.0075
-0.0040
0.0390
0.1475
0.0485
0.0175
-0.3880
H
G
0.1675
-0.2440
-0.1710
0.0875
-0.1715
-0.1525
-0.5080
G
F
0.3775
-0.4040
-0.3310
0.2475
-0.3115
-0.3325
-0.6080
F
E
0.0320
0.8280
0.4125
0.3790
0.2060
0.0290
-0.3330
E
D
0.2220
0.6080
0.2025
0.1890
0.0460
-0.0710
-0.3130
D
C
0.4520
0.4080
-0.0275
0.0410
-0.1040
-0.0810
-0.2630
C
B
0.6320
0.1680
-0.2375
0.2310
-0.1740
-0.0210
-0.1830
B
A
3.8820
0.0080
-0.3975
0.2610
-0.1940
-0.0210
-0.1330
A
17
18 I            19
20
21
22
23
Cut"+"       1.4411       3.8285           1.8763        0.9055 0.699187 0.61425
0.125
Fill"-" 3.3035
-0.89188        -1.30888       2.3355 -1.40106            -0.9665        -6.051
Summary:
Depth wise:
Total cut needed (sum of the “+”) = 58.62 m Total fill needed (sum of the = 51.21 m
Volume wise:
S2
Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009Erer Dam & Irrigation Project /CECE & CES
Area of each unit = !4 ha = 2500 m2
Total cut needed = 58.62 x 2500 = 146,550 m3
Total fill needed = 51.21 x 2500 = 128,025 m3
Total unit = 23 x 17 = 391 (each unit is '/« of a ha)
Using the four point method, the volume of cost and fill is approximated as follows;
<z^)’
4
4 £C + X F
Vc,Vf = volume of cut, fill
L = grid spacing , m
C = sum of cut on four comers of a grid unit
E/ = sum of fill on four comers of a grid unit
Thus, the volume of fill = 996,395m3
The volume of cut = 1,41 l,556m3
Covering on area of 3370 of on average depth of cut and fill to be 7cm respectively.
Annex E : Irrigation & Drainage Design /Final Detail Design Report /2009. I
Erer Dam & Irrigation Project ZCECE & CES
♦ *
16. Bill of Quantities, Cost Estimates and Tentative Construction Schedule
16.1 Dam Appurtenance Works
The quantities of the various items of works related  to  the Erer irrigation  infrastructure have been defined  with  reasonable accuracy  compatible with  the present knowledge of the technical aspects of the project.  The prices adopted  for this report are current prices (December 2008) that are based on  experience gained  from similar projects being  undertaken  in  the country.  The bill of quantities and  cost estimate shall be used  for the purpose of project worth  analysis and  to  have an  estimate of the project investment.
The tentative construction period is estimated to be 24 calendar months as shown in the annexure The bill of quantitities and specification is included in volume IV section 2 of the detailed design report.
Annex E : Irhgation & Drainage Design /Draft Detail Design Report /2009
85L AQUEDUCT FOR SECONDARY CANAL -I ON DENCHO RIVER
DESIGN DATA
(1) Canal
Trapezoidal Earthen section Discharge = 0.968 m /sec
Depth of water= 0.82 m
Bed width = 1.20m
Velocity = 0.49m/s Free Board = 0.30m
3
3
Manning’s coefficient (n) - 0.025 
Slope = 0.00040
Side slope = 1.5:1
(2) River
Flood discharge (Tr= lOOyr) = 274.0 m /sec
High flood level (HFL) = ?
River bed level = 1315.8m
(3)   Type of Structure Proposed
The  earthen  banks  are  discontinued  and  the  canal  is  taken  in  rectangular  trough  supported on piers. This is adapted to effect over all economy.
(4)   Drainage Waterway
Lacy’s Regime perimeter              =4.83 Ve
= 4.83
“ 79.95 say 80m
1Let clear span between the piers is 6.0m and there are 11 spans and ten piers. 
Total water way between abutments = 66+10x1.0
= 76m
(5)   Canal Waterway
For  reasons  of  economy,  the  trapezoidal  section  of  earthen  canal  is  reduced  to  rectangular section. The clear width of trough = 1.15m, the same as width at Earthen canal.
Flour area of trapezoidal section               = 1.15x0.82 + 0.82 x 1.23 = 0.943 + 1.0
= 1.94 m2
Provide 1:2 splay in contradiction and 1:3 in expansion
Note: dimensions are in meters
Fig 1. Canal Waterway
2(6)   Head Loss and Bed Levels at Different Sections Velocity at section 1-1 = 0.49 m/s
Velocity at section 2-2 = 0.968/0.943 = 1.03 m/s
Head loss in contraction = 0.2        I J
02  <105-0^1 
t 2x9.81           ) = 0.0082m
Head loss in expansion = 0.3
= 0.012m
Head   loss   in   rectangular   channel   using   manning   formula   (assume   n=   0.015   for   concrete surface)
V=
n
V= 03 m/sec
R= A -            0 943
P 1.15x2x0.82 = 0943
2.79 = 0.33
1.03 =
1
0.015
2 1 (0.33)’S*
31
1
] ] ] ] 1
] ] ] ] 1
1
1
1
1
] 1
1
1
]
|      1.03x0.015 0.475
= 0.00095
Head loss in the rectangular trough           = 00045 x 76 = 0.072m
Secondary  canal  crosses  river  Decho  at  chainage  0  +  850  after  passing  through  a  series  of falls.
The  FSL  in  secondary,  canal  at  its  crossing  point  is  1320.00.  This  is  the  level  which  can command the proposed command area of secondary canal
Elevation of total energy line = 1320.00 + velocity head
0.492 = 1320.0+--------------
2x9.81
= 1320.0 + 0.013
= 1320.013
Bed level of cannel at section 1-1 = 1319.18
Head loss in contraction  = 0.008 Head loss in expansion  =0.012
Head loss    in trough Total
= 0.072
= 0.092
Elevation of total energy line at 4-4 = 1320.013 -0.092 
= 1319.92m
Bed level at section 4-4 = 1319.92 - 0.82 
= 1319.12
As may  be revealed  from the above the loss of head  in  contraction,  expansion,  and  trough  portion is negligible.  Therefore the bed  level of canal in  the beginning  of trough  is the same as in  the end.
4The size of trough will be = 1.15 xl.12 (assuming free board — 0.3m)
These  are  inner  dimensions.  However  the  outer  dimensions  shall  be  1.75  xl.12  assuming  0.3m  as thickness of trough wall.
(7)  Piers and Abutments
Piers and  abutments are proposed  to  be constructed  in  stone masonnary  laid  in  1:4  cement mortar.  The recommended  thickness of pier for span  5  to  6  m is 0.85m.  Hence 1.0m in  thickness is adopted.
The pier width  shall be increased  to  1.6m in  two  steps.  Foundation  concrete 1.0m thickness shall be provided  below the pier.  Thus the foundation  concrete shall comprise of 2  2m wide and  1.0m thick  base.  On  the top  of pier a cement concrete bed  block  of 0.2m thickness shall be provided which will be projecting to 0.15m outside on all directions.
"P I:
The pier shall have semi circular nose and  cut water radius of 0.5m.  The width  of abutment at scour level should  be approximately  0.6  times the scour depth  below FSL.  The abutments shall stand  the earth  pressure of dry  soil above the pressure gradient line and  submerged  soil below the line.
The width  of abutment shall increase in  steps standing  from 570mm at the top  to  1100mm at the bottom i.e.  above the level of foundation  concrete of 600mm thickness.  The foundation  concrete 1800 x600mm shall be provided below the abutment.
(8)   Depth of Foundation
Normal depth of scour according to Lacy’s equation is
R= 0.47
f= 1.5 assumed for river bed material—
R= 2.62 m
Anticipated depth of scour around pier = 2R
= 2x2.62
= 5.24m
The  minimum  depth  of  foundation  below  anticipated  scour  level  should  be  less  than  1  Om  or  1/3 of scour depth.
Hence,  depth  of  foundation  below  FSL  =  5.24  +1  0 
= 6.24m
The level of foundation concrete will be HFL in rever = 6.25m
= 1317-6.25 = 1311.75m
B
Fig 2 Aqueducts on Secondary Canal I
61
11
J
1
] 1
] ] ] ]
J
ScfcnCC15
Radius ■ 500
Section C - C
Note: All dimensions are in mm
8n. DESIGN OF AQUEDUCTS ON SECONDARY CANAL I AND II
There  are  two  aqueducts  on  secondary  canal  -  I  and  one  remaining  aqueduct  on  secondary  canal
-  II.  In  design  of  these  aqueducts  the  same  procedure  is  followed  as  in  the  case  of  aqueduct designed on Decho River.
1. Name of Aqueduct
Kebanawa on S2
Abiyo on
Si
Kebanawa on Si
Remarks
2 Chainage of x-ing points (km)
10.200
3.30
6.10
3 Data of canals at crossing points
a) Q(m /sec)
3
0.11
0.66
0.429
b) Depth (m)
0.43
0.69
0.58
c) B .L
0.88
1.15
1.0
d) Velocity
0.33
0.44
0.40
e) Side slopes
1.5:1
1.5:1
1.5:1
f) Slope
0.00045
0 0004
0.0004
4 Flood discharge of drains (m3/s) Return period of 25 years.
87.8
46.1
92.2
5. Lacy’s per meter (m)
i
P=4.83Qi
45.2
32.79
46.37
6. Width off one span (assumed ) (m)
6.0
5.0
6.0
7. No of spans
7
6
7
8. No of piers
6
5
6
9 Thickness of pier (m) assumed
0.85
0 70
0.85
10 Total water way (m)
47.1
33.5
47.10
11. Size of tough (mxm)
a) internal dimensions BxD
0.88x0.75
1.15x1.0
1.0x0.88
Assumed: Free board = 0
b) outer dimensions BxD
1.28x0.75
1.15x1.0
1.40x0.88
Thickness of wall = 0.22
12. Bed level of trough
Same as the bed level of canals at the beginning of crossing
point *
_____________________________________________13. Scour depth (m) ‘R’
1.80
1.66
1.82
R-O.47'(£)|
F=    1.50   assumed for river bed
14.   Anticipated   depth   around   (m)   Pier =2R
3.60
3.32
3.64
15     Minimum     depth     of     foundation below FSL (m)
= 2R+1.02
4.60
4.30
4.64
16.  Maximum  depth  of  flow  at  the  time of flood (assumed) *
1.0
0.7
1.0
17.     Minimum     depth     of     foundation below bed level (m)
3.60
3.60
3.64
18.   Length   of   pier   with   indicated   cut water radius(m)
Figure3-a
Figure3-b
Figure3-c
19. Size of form
Depth
0.7
0.6
0.8
Width
2.05
1.90
2.05
* Level may be indicated after finalization of L-section of SI & S2
*May be get collected if possible
** See the figure below.
Provide cc bed block of 0.2m thick at the top, projecting 0.15m on all the side
Width of abutment at scour level shall be 0.6time the scour depth below FSL
The width of abutment shall increase in steps from 570mm at top to 1100mm at the bottom i.e above the level of foundation concrete of thickness 600mm The foundation concrete of 1800m x 600m shall be provided below the abutment. The size of abutment will work out the same with case of all the aqueducts.
10Note: All dimensions are in meter
Fig 3-a Length of pier
Fig 3-b Length of pier
Fig 3-c Length of pierHI. SAMPLE DESIGN OF DUCK BELL WEIR
Chainage = 13.300km of primary canal
Primary canal parameter
Bed width          = 0.13m               Bed level 1359.24
Depth
= 1.0m
FSL= 1360.24
Velocity
= 0.55m/s
Top bank level = 1360.64
Discharge
= 2.0 m3/sec
ground level = 1360.08
Side slope
= 1.5:1
Slope — 0.00035
Tertiary canal (T.P) parameters
Q= 0.154 m3/sec
Depth = 0.41 m
Bed width = 0.53m
F.B = 0.20 m
Velocity = 0.32 m/s
Using broad crested weir formulas j
Q= CLH5 C= 1.705
Q= discharge of primary canal - discharge of off taking canal Q= 2.0-0.154
Q= 1.846 m3/sec
Fig 4. Water flow over a weirLength of weir =         e  g_ CH | CH"
r
 1.846
L 
1.705xH" Let H= 0.352
j
L =—1846— = 5.41m say 5.4m
1.705x0.20
2A+ 1.5 = 6.72
2A = 6.72-1.5
2A = 5 22
A= 2.61
Cosa = — =0.5747 
2.61
a =55°
This is acceptable figure which lies between 45° and 70°
Cut off wall and floor thickness required:
Discharge intensity over the crest = 1 846 = 0.21 m /sec
3
6.72
Normal scour depth =1.35
Up stream depth provided = — + 0.6
= — + 0 6 = 0.93 3
say lm, Provide 1.0m deep cutoff
Down stream cutoff depth = — + 0.6= 1.1m, Provide 1.20m cutoff 2 
Maximum static head H= water level up to crest of duck bill weirand no water on down stream side = 0.69m
Assuming Bilght coefficient = 7
Total length of floor required = 7x0.69
= 4.83 (provide 5.0m floor length)
Provide 2m in the up stream and 3.0m in the d/s of Duck bill weir
Total unbalance head just downstream of weir = ^^x3
= 0.414m
The   discharge   coefficient   depends   upon   shape   and   angle   of   crest.   The   volume   of coefficient of discharge up stream rounded crest
=0.360 V2g
=0.360x4.43 
=1.59
Using coefficient of discharge as 1.59, the length of weir will increase to 1.846
L=
1.59x0.20
5.80
14
‘X..The use of Duck bill weir is preferable to the angle ‘ a ’ varying between 45 to 70° The end of duckbill weir crest is fixed independent of the bed width of canal
Let it is 1.5m
2A+1.5 = 5.8
A= 5.8-1.5 = 43
A= 2.15m
Cost a = -^- = 0.6976 
2.15
a = cos_1 0.6976
a = 45.76°
It is the margin case
Let the head over crest the reduced to 0.3 lm
1.59x(0.31)5             L59x0 1726
The thickness required = —414 = 0 33 m 1.24
Provide 400mm thickness in half length of downstream toe of crest wall and 300mm in rest of the floor as shown below.
i
15
l]
]
]
]
]
]
]
]
]
]
C»n«rtarf Slana
PLAN
Fig 5. Typical Drawing of Duck Bill Weir
Flow
2000
- — 
1500
1500
_150
Section A—AIV. DESIGN OF OUTLET STRUCTURE
Given: Discharge Length
= 40 let/sec = 7.0m
Slightly encrusted cast iron pipe f = 0.01 height from centre of outlet to FSL 0.75m
Let us choose 15cm diameter pipe q = CA figH
C =       1       I d
2x10  l
s
W")
J  MQf
c =   1       1 15
2x10  J
s
0.01(7    +    15X15       ) 400x0.01
1
1 15
2x10s      ’ 0 01(7 + 5.625) 1  11   15
2x10  V (0.01x12.625)
s
c=
—1—xl0.95 = 5.45X10 5 2x10s
s
q= 40 lit/sec = 0.04 m3/sec
0.04 = 5.45 x 10'5 x A-79.81x2x0.75 0.04
A=
5.4 5x10~  x>/9.81x2x0.75
A=
A=
0 04x10s
4000
A=------ = 191.63 4
4x191.63 
5.45x3.83 ~ 5.45x3.83 " 191 & 0.04x10s                    4000
5.45x3.83 “ 5.45x3.83 = 191 63
7id2
-------------4x   191.63   =244.11 7T
,
17use 15.0cm diameter pipe, for 401it /sec discharge
? 5
PLANTBL
OGL
Section B-B
Fig 6. Typical Outlet Structure
IV. DESIGN OF CROSS REGULATOR CUM HEAD REGULATOR
(a)   Primary canal parameters
Length of primary canal = 13.394k
FSL at of taking point of Dam outlet = 1365.0 Longitudinal slope 35cm per km
FSL at tail of primary canal = 1365.0 - 0.35 x 13.394
= 1365.0-4.68 = 1360.31 m Depth              =1.0m
Bed level        = 1360.31 - 1.0 = 1359.31
Bed width =2.13m (b)   Secondary canal one parameters
Head discharge Bed width
= 0.968 m3/sec
= 1.20m
Water depth
= 0.82m
Assume operating head for secondary canal I as 0.10m FSL of secondary canal = 1360.31 -0.10
= 1360.21m Bed level = 1360.21-0.82
= 1359.39
19
-Gate size and operating platform
Crest of the secondary canal is kept at the bed level of the primary canal.
Gate  of  1.40m  wide  and  0.95m  high  shall  be  provided  to  control  the  flow  in  the  secondary canal
Level  of  operating  platform  will  be  2x0.95  +  0.95/2 
= 2.375m above the bed of secondary canal
The  level  of  operating  plat  form  will  be  =  1359.39  +  2.375 
= 1361.76m from bed level.
Operating platform of 2.0m x 150m shall be provided.
Floor length
When secondary canal I is closed. The water level is primary canal will be at FSL =
1360.31
Bed level of secondary canal I = 1359.39
Difrence of head = 1360.31 - 1359.39
= 0 92
Taking blight’s coefficient = 7 
Total length of floor = 0.92 x 7 
= 6.44m
Provide 7.0m floor, 3.5m up stream of gate and 3.5m d/s of this gate
Vertical cutoff
Minimum depth of up stream and downstream cutoff for discharge < 3.0m3/sec = 1.0m
Provide 1.1m deep vertical cutoff on upstream side R.L. of cutoff in upstream side = 1359.31-1.1
20= 1358.21m
Provide 1.1m deep vertical cutoff on the downstream side RL. of cutoff in downstream side
= 1359.39-1.1
= 1358.29m
Floor thickness
Draw  hydraulic   gradient   line   at   1:7   for  maximum  static  head   of  0.92m  that  is  when  water  is headed up to FSL on upstream side and no water on dawn stream side
The  ordinate  between  H.G  line  and  floor  level  would  give  unbalanced  head Provide 0.30m thick floor on the upstream side of gate.
Maximum  unbalanced  head  =  ——  =  0.46/n 
2
Floor thickness required = —— = 0 368
1.25
Provide 0.4m thick concrete floor on the downstream of gate. Downstream protection
Q  0.968 
b ~ 1.15
= 0.84 m3/sec/m
f= 1
For straight reach depth of scour = 1 25R
= 1.25 x 1.19
= 1.49
Depth below bed = 1.49 - 0.77
= 0.72m
This is less than the mandatory requirement of 1. Im
21Concrete blocks
Downstream of the impervious concrete floor, suitable protection works is the length 2D
- = 2x1.1 = 2.20 say 2.40m. Provide four rows of 600x600x250 cement concrete blocks or stone masonry blocks over 150mm thick well graded stone ballast.
Launching Apron:
Beyond protection work, launching apron shall be provided. The cubical content of the material in launching apron will be 2.25D m3/m length
Cubic content                  = 2.25 x 1.1 = 2.464
Keeping the thickness as 600mm 2.46
The length of apron =
0.6
= 4.125
Provide 4.5m long launching apron
Provide 250mm thick 500mm deep wall between block protection and launching aprom. (c)Parameters of secondary canal II
Discharge at the head = 0.773 m3/sec
Bed width 1 15m
Water depth = 0.74m
Assuming 0.15m as driving head
The FSL in secondary canal -II is = 1360.31 - 0.15
= 1360.16m Bed level in secondary canal II = 1360.17 - 0.79
= 1359.43m
Adopt gate size of 1 35m x 0.85
Level of operating platform = 1359.43x2x0.85 + 0.425 = 1359.58 + 1.6 + 0.4 = 1361 96m
22Thickness of operating platform is 150mm Operating platform of 2m x 1.5m shall be adopted
When secondary canal -II is closed
Floor length
Water level in primary canal = 1360.31m Bed level in secondary canal = 1359.43m Head = 1360.31 -1359.43
= 0.88m
Taking Blights coefficient = 7
Total length of floor required = 0.88 x 7
= 6.16
Say 6.0m
Provide 3m floor length in the upstream and 3.0m in the down stream of gate
Vertical cutoff
The  minimum  depth  of  upstream  and  downstream  cutoff  for  this  range  of  discharge  will be 1.0m.
Provide 1.1m deep cutoff in the upstream side & downstream side
The level of upstream cutoff will be = 1359.31 - 1.1 
= 1358.21m
The level of the downstream cutoff will be 1359.48 - 1.1 = 1358.33
23Floor thickness
-•.j.
. ..Draw hydraulic gradient line at 1:7 for the maxim static head.of 0_88m i.e. When water is
*    .j. i ? . headed to FSL in primary canal and no water in the secondary II canal . The ordinate
.r- :         between the HG line and floor level will give the unbalanced head
The   maximum   up   lift   pressure   in   the   upstream   side   will   be   balanced   by   the   wight   of water. Therefore a minimum of 0.3m of thickness is to be provided to the upstream side.
Maximum unbalanced head in downstream side = —— = 0.44m 2
0 44
Floor  thickness  required  =  ——  =  0.352/w
1.25
Provided 0.40m thickness in the down stream side. „ Q 0.773
Q= — =--------- = 0.67 1.15
R=1.35
R=1.35
(q v
2
3
I— I (/ = lassumed') ( f = 1 assumed)
1/3
R= 1 04m
Depth of scour in the straight reach = 1.25 x R
= 1.30m Depth below bed = 1.30 -0.74
D= 0.56m 50 provide 1.1m deep cutoff
Protection works
Suitable protection shall be provides Blocks length 2D = 2x1 1 = 2.20 say 2.40m
24Provide   4   rows   of   concrete   /masonry   blocks   of   600m600mx250mm   size   over   150mm graded basalt.
Launching apron
Beyond protection work, launching apron shall be provided. The cubic content of
launching apron material = 2.25D
= 2.25x1.1
= 2475 m3/m
Keeping apron thickness as 0.6m (600m)
Length of apron = 2.475 /0.6 = 4.125 say 4.50m
Provide   250mm   thick   and   0.4m   depth   stone   masonry   wall   between   block   protection   and launching apron.
Upstream protection
Block Protection: the upstream protection shall be provided to cater for scour depth D= 1.1m below floor level.
Length of block protection = 1.0D = 1.1m say 1.20m
Provide two rows of 600x600x250 cement concrete or stone masonry blocks. Launching apron
Cubic content of launching apron = 2.25D m3
= 2.25 x 1.1 = 2.475 m3/m
Provide 600mm thick ness
Length of launching apron = 2.475 /0.6
= 4.125 m
Provide 4.5m length of apron
Provide 250mm thick 500mm deep wall between block protection and launching apron
25Fig 7. Cross (head) regulator
V. ESCAPE STRUCTURE
Hydraulic Design of escape structure
(a) Important Parameters
Full supply discharge at escape site = Bed width of canal
Full supply depth
Side slopes
Location of escape
Velocity in canal
Slope of canal
Silt factor
FSL of the primary canal at its head
:  2.49 m3/sec
= 2.50m
= 1.05m
= 1.5:1
= 4.15km chainage of primary canal = 0.58 m/sect
= 0.00035 = 1.0
= 1365.0m
26FSL  of  canal  on  escape  site  =  1365  —  0.00035x4150m
= 1365-1.45m
= 1363.55m
= 1365.55 - 1.05m
= 1362.5m
Bed level canal
= 1363.55 - 1.05m = 1362.5m
Taking 60% of discharge of primary canal for escape
Discharge of escape channel = 2.49 x 0.60
= 1.494 m3/sec
Say 1.50m3/sec
(b) Crest Length
Crest  of  escape  is  kept  at  the  bed  level  of  canal  to  facilitate  the  quick  depletion  of  parent channel.
Crest of escape will function as broad crested weir
Q= c(L-0.1nH ) H3/2
Where L = Total clear waterway
n= no of end contraction
H= Head over the crest
C= coefficient of discharge for broad crested weir = 1.70 1.50= 1.705 (L-0.1 x 2x1.05) 1.053/2
1.50 = 1.705 (L-0.21) 1.076 1.50
L=
1.705x1.076
L= 0.817 + 0.21
L= 0.917m
Provide crest length of 0.92m
Provide vertical left gate having 1120mm wide and 1150mm high gate with side rollers. Provide hoisting arrangement at the operating platform
+ 0.21
27The elevation of operating platform is kept at such a level where clearance of the half of height of gate is available.
Elevation of lifting platform= 1362.5 +2 xl.15 + ——
= 1365.375 m
The crest length is 0.92m, the operating platform is provided 200mm support on both sides.
The total width of operating plat form shall be
= 0.920 + 2x 0.2
= 1.320m
The size of operating platform may be kept as 2.5m x 1.5m and thickness as 150mm The canal section at the escape starching will be rectangular, suitable transition shall be provided on upstream and downstream to change the canal section from normal trapezoidal section to rectangular section;
Area of trapezoidal canal section = 2.50 x 1.05 + 1.05 xl.575 = 2.625 + 1.653
= 4.278
2.49
Velocity =---------- = 0.58/n/sec 4.278
Velocity head = ~ = (
2g 1^2x9.81)
1 = 0.017lm
Level of total energy line in upstream side = 1362.5 + 1.05 + 0.0171
= 1363.567 m
Area of rectangular section = 2.50 x 1.05 = 2.625 m2
2 49
Velocity =---------- = 0948 5m/sec 2.625
.1'
28Area pf rectangular section - 2.50 x 1.05 = 2.625m2
2 49
Velocity = —-— = 0.9485/m/ sec 2.625
Loss of head in contraction
i
<0 9485*-0.58^
2x9.81 J
= 02 (0-899-0-336A
2x9.81       )
= 0.0057
Level of total energy line at the end of contraction 
= 1363.567-0.0057 
= 1363.56
Since the length  of canal from end  of contraction  to  start of expansion  is kept only 25.30m.  Hence three will be negligible loss is rectangular portion  of canal.  Therefore level of total energy line at the beginning will be 1363.56m
(y _y
Loss head in expansion = 0.3 —------------ —
I2S
= 0 3 ( 0 948S" ~ 0 582
I 2?
= 0.0085
The level of total energy line at the downstream end of expansion will be
= 1363.56 - 0 0085 = 1363.555
FSL = 1363.555 - Velocity head 
= 1363.555 - 0 0185
29
22= 1363.536m
Bed level = 1363.536 - 1.05
= 1362.486
Clear opening for gate = 2.5m
Gate of size 2.7m width and 1.15m height may be provided.
Provide 200mm support to the slab of gate operating platform the total width of scale
= 2x0.2+2.50
= 2.90m
Provide gate operating platform of 2.9m x 2.5m
Level of operating plate form = 1362.5 + 2x 1.15 +--------= 1365.375
2
Case I: Primary Canal is Closed
Floor length
Water level in primary canal = 1363.55
Bed level of canal in downstream side = 1362.486 
Head = 1363.55- 1363.486 
= 1 065m
Taking Blight’s coefficient = 7
Total floor length = 7x1.065 
= 7.455m
Provide 10.0m long floor, 5.0m upstream of gate and 5.0m downstream of gate
Vertical cut off
The minimum depth of upstream and downstream cutoff for this range of discharge =
1.0m, hence provide 1.1m deep vertical cutoff on upstream i.e. upto R.L 1362.50 -1 1 = 1361.4m
30Provide 1.1 m deep vertical cutoff an downstream side, The level of cutoff 1362.486
1.1 = 1361.386m
Floor Thickness
Draw hydraulic gradient line at 1:7 for the maximum static head (1363.55 — 1362.486)
1.064m i.e. when the water is headed up to FSL on up stream side and these is no water on the downstream side.
The (ordinate between  H.G line and  floor level would  give the unbalanced  head.  The upstream hydrostatic pressure will be balanced by the weight of water. Provide minimum thickness of 0.3m on up stream side of the gate.
1362.486
Maximum unbalanced head = 1363.551362,486
2
1.064
= -- = 0.532m
2
0 5321 25
Floor thickness required = —------ — = o 44
1.25
Provide  0.5m  thick  floor  upto  2.5m  length  and  0.3m  in downstream end.
remaining 2.5m upto the
Downstream Protection
Q= discharge per unit width
2 49
Q=  —-  =  1.0m3/sec  1.0  m3/sec x,. J
31R=1.34
l/ WJ ’
= 1.34 (f= 1.0 assumed)
Depth of scour for straight reach = 1.25R
» 1.25 x 1.34 
= 1.675 m
Depth below bed = 1.675 - 1.05 
= 0.625m
Provide 1.1m deep cutoff
Downstream of the impervious floor, suitable protection is to be provided in a length 
2xD = 2x 1.1 =2.2m
Provide four rows of cement concrete blocks of 600x 600x250 mm size over 250mm thick well graded blanket.
Beyond  protection  work  launching  apron  shall  be  provided.  The  cubical  content  of launching apron will be 2.25 x D m3/per meter length.
Cubical content = 2.25 xl.l = 2.475 m3/m
Keeping 0.6m as thickness of launching apron, the length will work out to 2.475/0.5= 4.95m
Provide 5.00m length of apron
Provide 250mm thick and 600mm deep sline masonry wall between block protection and launching apron.
Upstream Protection
The upstream protection work shall be provided to cater for the scour depth of D= 1 I m below the floorJDepth of block protection on upstream side= 1.0 x D i.e 1.1m so provide
K' 2 raws of 600x600x250 stone masonry blocks over 25Qmm well graded ballest.Launching apron
Cuibic content of launching apron = 2.25D
Volume /m = 2.25 xl. 1 = 2.475 m3/m
If the thickness is 600m
,        ■_   2.475 A
Length =---------= 4.95m
0.5
Provide 5.0m length of 600mm thick launching apron provide 250mm thick 600mm deep wall between launching apron and block protection,
Case II - When Escape is closed
FSL of Primary Canal
Bed Level of Escape Channel
Water Head = 1363 - 1362.50 
Taking Blights’ coefficient Total length of floor
Provide 5.0 m floor upstream si
= 1363.55m
= 1362.50
= 1.05m
= 7.0
7 x 1.05 = 7.35m
: of gate and 5.0m on downstream side
Vertical cut off
The minimum depth of up stream and downstream cut off for this range of discharge = 10m
Provide 1.1m deep vertical cut off on the upstream side and 1.1m deep vertical cutoff on the downstream end of cutoff.
R.L of upstream cut off        = 1362.50- 1.1 = 1361.40m
R.L of down stream cut off = 1362 5 - 1.1 =1361.40m
33Floor Thickness
Provide 0.3 m floor thickness on the upstream side of gate
Maximum unbalance head in the just downstream point of gate —
= 1.05/2 
= 0.525
Floor thickness required = 0.525     = 0.42m
1.25
Provide 0.45m thickness up to 2.5m downstream of the gate and 0.30m thickness up to the end of the floor
Downstream Protection
q = Q/6= 1.50/0.92 = 1.63
R = 1.34 ( q2 ) 1/3 assume f = 1.0 f
R= 1.34(1.38)
R= 1.855
For straight reach depth of scour = 1.25 x R
= 1.25 x 1.855 = 2.32m
Depth below bed = 2.32 - 1.05 D = 1.27m
Provide 1.30m deep cut off.
34Protection is to the provided in 2 2 D length (i.e. 2 x 1.30 12.60 say 3.00) by cement concert blocks in five rows of 600 x 600 x 250 mm size laid over 250mm graded ballast. 
Beyond protection work launching apron shall be provided. The cubic content of materials in launching apron will be 2.25D cubice meter / meter length
Cubic Content =2.25D = 2.25 xl.30
=        2.925m3 / m
Keeping the thickness of launching apron as 0.5m
Length of apron = 2.925 = 5.85 say 6.0m
0.5
Provide 250mm 600mm deep stone masonry wall between block protection and launching apron.
Upstream Protection:           upstream protection is required as Cement concert flour of primary canal exists in the upstream said No damage is expected in the upstream side.
35--------------- *u • «oo c/c----------
rCOSO» 50
y-«i2 • *00 C/C f
r . _______
.................
6000
plan
361
1
1
] ] 1
] ] ] ] I ] J J ]
J
3
VI. BRIDGE
Hydro lice Design of Harer / Babile Road Bridge Over Primary Canal
(a)  Canal parameters
Location = change 5 + 900 primary canal
Discharge = 2.49m /m
Bed width = 2 40m
Depth = 1.04m
Side slope = 1.5: 1
Longitudinal slops = 0.0035F
FSL at off take point = 1365.0
FSL at Read crossing = 1365.0 - 5.9 x O.OOO35
= 1362.935m
Bed level of canal =           1361.89.5m
The canal section is given transition from trapezoidal and rectangle on up stream side of bridge and from rectangle to trapezoidal in the downstream side.
Clear span of bridge = 1.04m
Provide overall depth of SLas = 300m
Free board provide in canal = 400mm
Provided extra free board of 400mm
Total Free board = 800mm
i
37Level of bottom slab = 1362.935 +0.80
= 1363.735
Level of the top of bridge = 1363.735 + 0.30 
= 1364.035m
(b)  Design of Abutment
Scour depth below cannel bed = Depth / 3 
= 1.04/3 = 0.35m say 0.4 m
Level of scoured bed = 1361.89 - 0.4
= 1361.49
Depth of scoured bed below Road Level
= 1364.35- 1361.49
= 2.545 - say 3.0m
Width of abutment at scour level = 0.7 depth of scour bed level or road level
= 07x3.0
= 2.10m
(c)Upstream Protection
Upstream cut off
Minimum depth of cut off below upstream bed level of canal for 2.45m3
/sec discharge = 10
Provide 1. Im deep cut off.
Level of bottom of cutoff = 1361.895 - 1.1
= 1360.795
Upstream Block Protection
Two rows of 600 x 600 x 250mm C.C blocks over 250mm graded ballast may be provided.
383
Upstream Launching Apron
Quantity of apron / m = 2.25Dm  / m
= 2.25 x 1.1 = 2.475m3 / m
Provided 600mm thick apron
Length of apron = 2.475 / 0.6
= 4.125m say 4 50m Provide 600mm thick apron for 4.50m length
Provide 300mm thick and 0.5m deep wall in between block protection and launching apron.
(d)  Downstream Protection
Cutoff
3
Minimum depth of cut off below d/s canal bed for 2.49m  / sec
Discharge = IO"1
Provide 1.1 m deep cut off
Level of batton cut off = 1361.895 -1.1
= 1360.795
Block Protection
Provide 4 rows of 600 x 600 x250 cc blocks laid over 250 thick graded blankets.
Lunching Apron
Quantity of apron per meter = 2.25D m3
= 2.25x1.1m3
= 2.475 m3
Provide 600mm thick apron
Apron length = 2.475 / 0.6
= 4.125m say 4 5m
39
r
-
ri
‘
Provide 600 mm thick launching Apron of 4.5m length Provide 300mm thick and 0.5m
nc‘ rvu’’» r deep wall between block Protection and launching apron. .. i i
This bridge is structurally design for heaviest type of loading as it is main road.
It is to be designed with RCC decking and masonry substructure
As per span consideration it is very small bridge therefore the foundation shall consist of cement concrete floor with curtain walls.
tk 7
25. On
(ram haei/toe of embwrferi
Fig 9 Flood Protection Embankment
40Fig 10. RCC Pipe Culvert
]
]
1
J
J
J
] ] ]
Fig 11. Slab Culvert
Section B-BJ
I 1
I
1
1
]
IntM A-*
Fig 12. Slab Culvert Across Primary canal
]
]
]
]
■ Fig 13. Pipe turn out
]
1Details of Tertiary canal Head Regulators
Name of Tertiary canal
Off taking Point
Name of parent
channel
Hydro lice Parameters at off taking points
3
Q m /s
b(in)
d(m)
q . 3
(m /s)
bl
()
m
dl
(m)
P
(cm)
T,P
13.300km of primary c.
Primary C
2.0
2.13
1.0
0.154
0.53
0.41
30
T, Sa
3.500km ofS-II
Secondary C -II
0.705
1.08
0.72
0.069
0.45
029
20
T.s,
1.500km ofS-I
Secondary C-I
0.968
1.20
0.82
0.126
0.48
0.39
25
T S,
a
5.500km ofS-I
Secondary C-I
0.552
1.10
0.64
0.072
0.46
0.30
20
t
3>1
7.550km ofS-I
Secondary C-I
0.189
0.80
0.41
0.072
0.46
0.30
25
Section A-A
Fig 14. Distribution box in quaternary canal
43VLI. DROP STRUCTURES
To Erer project vertical drop/ falls which have no glacis or sloping floor downstream of the crest
are recommended.
The dissipation of energy is achieved by impact of falling water on the cushion of water specially created for the purpose.
The energy is dissipated by means of impact and deflection of velocity , suddenly from
horizontal to vertical direction.
The cushion  is formed  by  depressing  the floor below the downstream head  of channel.  The following  dimensions are formed  suitable and  therefore recommended  in  computation  of drop strictures
Cistern Length (L) = 5 (HlxD) 0 5
Cistern depth (x) = 1_ (Hl xD) 2/3
4
Where   HL = drop in meter
D = depth of west below upstream T.E.L. in m
L = the length of cistern in m
x = is the depression below down stream bed of channel.
On the basis of this formula cistern dimension i.e. length and depression depth are worked out for drop depth of 1.0m. These have been worked out for earthen canals having bed slope 0.00045, Manning’s n = 0.025 and side slope 1: 1. The same may be provided at appropriate, places in Quaternary canals, drains where ever the discharge matches with the one indicated in the table given on the drawing of drop structure.
44However incase of Secondary canal -I which is required to descend about 48m in about 1.0km length a server of drop structure ( about 32 in no) of 1.5m drop are recommend The cistem dimensions are calculated below
Secondary Canal -I parameters Discharge = 0.968 m3 / sec Velocity = 0.49 m/s
Depth of flow = 0 82m Bed width = 1,20m
Side slope = 1.5:1
Slope = 0.0004
Manning’s - n = 0.025
Free board = 0.3m
Cistern Length   = 5 (H XD )
w
L
0'5
2
D = depth + Velocity head (V )/2g 
2
= 0.82+ (0.49)  / (2x9.81)
= 0.82+01
= 0.83m
HL= 1.5m
L = 5 (0.83 X 1.5)05
L = 5.58 m provide L = 5.60m
Depression depth below downstream, bed level of canal X = 14 (H XD)^
l
X = 14 (1.5X0.83) 2/3
X= '/« (1.158)
X = 0.289m
Provide 0.30m deep cistern.
Provide 2.5m length of pitching on the bed and side of canal in the upstream side of drop stricture and 2.0m in the down stream side.
45I
I
• is r a l
• IB CBL
*00.
S e ctio n A -A
Fig 15. Typical Drop Structure
46No
Q m3/se
Bed with (m)
Depth (m)
♦
Cistern size
Length
(m)
Depth
(m)
Pitching Length Li Upstream
Pitching length d L2 down sueam
1
0.03
0.35
0.23
2.39
0.09
2.0
1.5
2
0.05
0.45
0.27
2.59
0.10
2.0
1.5
3
0.075
0.50
0.33
2.87
0.11
2.0
1.5
4
0.10
0.58
0.36
3.0
0.12
2.0
1.5
5
0.25
0.82
0.41
3.1
0.14
2.5
2.0
6
0.50
0.86
0.43
3.28
0.15
2.5
2.0
7
1.0
1.22
0.61
3.63
0.16
2.5
2.0
8
2.0
1.56
0.78
3.90
0.17
3.0
2.5
• bed width and depth of channel are for trapezoidal earthen channel
.side slope 1:1, bed slope 0.0045, manning n=0.025
VIII. AQUEDUCT FOR SECONDARY CANAL - II ON DENCITO RIVER
Design data
(a) Canal:
Trapezoidal earthen canal
Discharge = 0.773 m  /sec
Bed with = 1.15m
Velocity = 0 46m/sec
Side slope =1.5:1
Slope = 0.0004
Manning’s Coefficient (n) = 0.025
Depth = 0.74
(b) River
Flood Discharge (Tr= lOOyr) = 267.5m 3/sec
High flood level = 1.2M above Bed Level (as informed) River bed level = 1354.5
3
47(c)  Type of Structure Proposed
The earthen banks are discontinued and the cannel is taken in a rectangular trough supported on piers. This is adopted to affect overall economy.
(d)  Drainage Waterway
Lacy’s Regime Perimeter P=4.83 -J Q
P = 4.83 V267.5
P = 79.0m
Let clear span between piers is 6.0m and there are 11 spans and ten piers. 
Clear water way =11x6 =66m
Provide lOpiers of 1 0m with.
Total water way between abutments = 66+ 10 x 1.0 =76m
(e)  Canal Waterway
For reason of economy the trapezoidal section of earthen canal is rectangular section The clear width of trough =1.15m, same as width of canal
Flow Area of trapezoidal Section = 1.15 x 0.74 + 1.11 x 0.74
= 0.85 + 0.82
= 1.67m2
Dimensions of rectangular section = 1.15 x 0.74
= 0.8436m2
Provide 1:2 splay in contraction and 1:3 in expansion, because the canal is very small in size(f)  Head loss and bed levels at different sections Velocity at section 1-1 = 0.46m/sec Velocity at section 2 - 2 = 0.773 2/0.8436
= 0.91m/sec
22
(k2 —ki )
1l
Head Loss in Contraction =
2g
22
=  (0.91  -0,42 )c0.2
2x9.81
=0.006m
22
Head Loss in expansion =0.3 
= 0.009m Head Loss in rectangle section:
(K3  -K4 )
'
2g
Use managing equation
V = l/nRMSw
R=A/P= 1,15x0.7
1.15 + 2x0.74
= 0 85 = 0.32m
2.63
n<= for concrete surface = 0.015
49Head loss in strength of Length of 76m
= 0.0008 X 76 
= 0.06
Secondary Canal crosses river Decho at Chainage 3+000 FSL in Secondary Canal at its head = 1360.16
FSL in Secondary Canal at 3 km d/s = 136016 - 1.12 
(Slope = 0.004)
=1359.04m
2
Elevation Total Energy line = FSL + Velocity head
=1359.04 + (0.46)  / (2x9.81) = 1359.04+0.01
= 1359.05m Bed level of canal at 1-1      1358.30
Head loss in contraction between 1-1 and 2-2
= .006
Head Loss in trough = 0.06
Head Loss in Expansion = 0.009
Elevation on of total energy line at section 4-4 = 1359.05 - (.006 + .06+.009) = 1359.05 -0.075
=1358.975
Bed Level at section 4-4
= 1358.975 —depth of flow1
J
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The loss of head in expansion, contraction and trough is negligible. Therefore the bed level of
channel before and after trough remains partially same.
Through:
The size of trough will be 1.15 x 1.05m assuming 30cm free board
The walls of trough are propose as 0.30m thick to be constructed in Reinforced comment
concrete (RCC), For small Channels of this size 0.30m free board is quite sufficient.
1
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Joints should he provide across and along the trough length. The maximum spacing of joints in 
this direction should be limited to 20m. A gap of 15mm with water stops at all the joints across
1
]
1
1
1
and along the length should be to accommodate movements.
PIERS and ABUTMENTS
Piers and abutments are proposed of stone masonry using 1:4 cement mortar The recommended thickness of piers for span 5 to 6m is 0.85m Hence 1.0 thickness is recommended. Provide 1.0m
thick pier from top to 1.0m below river bed level.
The pier width shall be increased to 1.6m in two steps. Foundation concert of 1.0m is provided 
below the piers. A concrete base of 2.2m wide and 1.0m thick shall be provided at the foundation 
]
]. ] ] ]
level. On the top, a cement concrete bed block of 0.2m thickness shall be provided, which will be projecting to 0.15m outside on all directions
The piers shall have semi circular nose and cut water radius of 0.5m
51Note: All dimensions are in meter
The width of abutment at scour level should be approximately 0.6 times the scour depth below FSL.  The abutment shall stand  the earth  pressure of dry  soil above the pressure gradient line and submerged soil below the line
The width  of abutment shall increase in  step  starting  from 570  mm from the top  and increasing  to  1100mm at the top  level of foundation  concert of 600mm thickness. Foundation  concrete of 1800m wide and  600m deep  shall be provided  below abutment level
Depth of Foundation
Norma depth of scour according to Lacy’s equation is
R= 0.47
er
( f = 1.5 for river bed material)
R= 0.47
R = 2.59
(?*>■
Anticipated depth of soccer around pier = 2R
= 2X2.59
= 5.18m
The minimum depth of foundation below anticipated scour level should not be less than 1,0m or 1/3 of scour depth, which ever maximum
521
I
Hence Depth of foundation below HFL = 5.18 + 1.0
= 6.18m
Level of foundation concrete will be HFL River -6.18m
HFL of river is 1.2m above the bed level as observed at the site.
Depth of foundation = 6.18 - 1.2 = 4.98
Say 5.0m below bed level
]
]
J
Wing wall
The width of wing wall at scour level is taken as 0.4 times the scour depth below HFL. The top 
shall be provided with 0.20m thick coping width c c (1:2:4) Provide 50mm diameter holes at of interval of 3.0m approximately.
J
J
] ] 1
] 1
] ] 1 ] ]
53Fig 16. Aqueducts on Secondary canal
54IX Inverted Siphon
Out of the total cross drainage works, when the high flood level of the natural dann is higher than the bed level of the crossing channel 14 siphons are proposed The structures mainly consist of inlet transition, circular barrel and outlet transition.
a.  Design Consideration
i.   The velocity of water in the siphon is kept greater than 1 m/s to prevent silting in the barrel.
ii.   Water surface at the enterance is kept about 15-^ - (where V2 is the velocity in the
2
barrel) or a minimum of 0.30m about the top of siphon barrel to prevent air entering in to the barrel.
iii.   A minimum earth cover of 0.60m below drain bed level is provided.
iv.   A trash screen is proposed to be instoled at the inlet to prevent the barrel from
clogging
b.  Hydraulic Design
1.  Cross Sectional area sizing
The discharge formula controlled by orifice inlet is given by:-
Q= ChJteh
Where Q= Discharge (m3/S)
A= Sectional area of the pipe (m2)
h= Driving head (m)
C= Coefficient = 0.81
2.  Head Loss
i. Friction loss
Friction  loss in  the inlet transition,  barril and  outlet transition  can  be determined  by  the average friction  slope,  using  Manning’s equation and  the total loss may  be attained  by  multiplying  the respective horizontal length.
i
Hf=sfLWhere: - n = manning’s roughness coefficient V= Flow velocity (m/s) R= Hydraulic radius (m2/m) L= Horizontal length (m) Sf= Friction slope (m/m) Hf= Friction loss (m)
ii) Minor loss
• Convergence at inlet transition Divergence at outlet transition
= 0.6
>22 -K32>l I 2g J
Barrel bend loss
Where : VI = Velocity at inlet
V2 = Velocity at barrel
V3 = Velocity at outlet
g= acceleration due to gravity
The Hydraulic parameter of all Siphons is calculated and the result is summarized as shown the table below.Table K-l Hydraulic Parameter
No
Name of
Siphon
Discharge
(m3/S)
Pipe
Diameter
(m)
Flow
velocity in
the pipe
(m/S)
Head loss
(m)
Number of
pipe
1.
CD5-P
2.49
1.05
1.4
0.25
Double
2.
CD6-P
2.49
1.05
1.44
0.24
Double
3.
CD7-P
2.38
1.05
1.30
0.22
Double
4.
CD11-P
2.21
1.05
1.29
0.18
Double
5.
CD16-P
2.00
1.05
1.15
0.15
Double
6.
CD2-S1
0.765
0.90
1.21
0.18
Single
7.
CD3-S1
0.65
0.90
1.10
0.12
Single
8.
CD4-S1
0.65
0.75
1.47
0.29
Single
9.
CD1-S2
0.773
0.90
1.22
0.18
Single
10.
CD4-S2
0.555
0.75
1.26
0.22
Single
11.
CD6-S2
0.418
0.60
1.48
0.33
Single
12.
CD7-S2
0.30
0.60
1.10
0.17
Single
13.
CD8-S2
0.221
0.45
1.40
0.36
Single
14.
CD9-S2
0.221
0.45
1.40
0.36
SinglePlan
Section
FEDERAL DEMOCRATIC REPUBLIC OF ETHIOPIA ministry of water RESOURCES
CONCERT KNCI KI BRI NG AND CONSULTING ENTERPRISE
IN association with
CONSULTING EMNNEERJNC SERVICE ( INDIA ) PVT. LTD pRDJECT-erer irrigation project detail design
TITLE:- INVERTED SIPHON STRUCTURE (TYPE 2)
SURVEYED
DRAWN
D*TE
SCALE
LEVEL
ORA WING Mt1
] J
.1
]
.3
] J
] ] ]
JDetermination of the plane of the best fit
Where,            D=distance from reference line
H=grid level
n=total number of grids
48353914
T,CD H ) =
xy
64451916
|(X -p,)’/"-
48145360 94084375 70624375
j 0.00889
£dJ£h,)   In =
65137840
|(s                -
5
W)-(ZAX2X)/"
1.72E+08
1.29E+08
-0.01595
-
-
i
i
I
1
/
. — ■• . < * • ••
■ •-
• -Detrmination of cut &'fill
Detrmination of cut & fill
Q
0.911
0.781
P
0.511
0.301
0
0.081
-0.119
N
-0.299
-0.529
M
-0.739
-0.899
3
4
6th unit
8th unit
M
298
297.64
M
297.64
297.22
L
297.36
297.01
L
297.01
296.68
K
296.71
296.5
K
296.5
296.14
J
296.14
295.91
J
295.91
295.48
3
4
4
5
Determina
Determinati
Centroid level=
Centroid point is K&L, 3&4
595.64 594.37 593 21
592.05
2375.27
296 90875
Centroid level=
Centroid point is K&L. 4&5
594.86 593.69 592.64
591.39
2372.58
296.5725
M
297.30875
297.10875
M
296.9725
296.7725
L
297 10875
296 90875
L
296.7725
296.5725
K
296.90875
296.70875
K
296.5725
296.3725
J
296.70875
296.50875
J
296.3725
296.1725
3
4
4
5
Detrmination of cut & fill
Detrmination of cut & fill
M
0.69125
0.53125
L
025125
0.10125
K
-0.19875
-0 20875
J
-0.56875
-0.59875
3
4
9th unit
11th unit
Q
299.64
299.16
Q
299.16
P
299
298.49
298 54
P
298.49
O
298.33
297.8
297.95
O
297.8
N
297.75
297 29
297 38
N
M
297.22
296 74
297.29
296.8
M
296.74
5
6
598 8 597 49 596.13 595 04 593.96
2981.42
296.23
6
7
597 7 596.44 595  18 594 09 592 97
2976 38Determination of Formation level Centroid level=
Centroid point is O. 586
298.142
Determination of Formation level Centroid level=
Centroid point is O, 687
297.638
Q
298.642
298.442
Q
298.138
297.938
P
298.442
298.242
P
297.938
297.738
O
298.242
298.042
O
297.738
297.538
N
298.042
297.842
N
297.538
297.338
M
297.842
297.642
M
297.338
297.138
5
6
6
7
Detrminal
Detrmlnati
Q
1.022
0.602
P
0.552
0.212
O
0.062
-0.158
N
-0.248
-0.538
M
-0.598
-0.908
6
7
10th unit
12th unit
Determination of Formation level Centroid level=
Centroid point is K&L. 5&6
593.96 592.92 591.69 590.74
2369.51 296.18875
Determination of Formaton level Centroid level=
Centroid point is K&L. 687
592 97 591.97 591 04 590 12 2366 1
295.7625
M
296.58875
296 36675
M
296.1625
295.9625
L
296.38875
296.18875
L
295.9625
295.7625
K
296.18875
295 98875
K
295.7625
295.5525
J
295.98875
295.78875
J
295.5625
295.3625
5
6
6
7
Dctrmination of cut & fill
Dctrmination of cut & fill
M
0.63125
0.35125
L
0.29125
0.05125
K
-0.04B75
-0.23875
J
-0.50875
-0.52875
5
61st unit
Table: Ori
For the first two blocks
level
3rd unit
Q
301.1
300.83
P
300.48
300.23
O
299.69
299.57
N
298.9
298.86
M
298.24
298.16
1
2
Determination of Formation level
Centroid level=
Centroid point is O, 182
601 93 600.71 599.26 597.76
596.4
2996.06
299.606
Determination of.Formation level Centroid level=
Centroid point is O, 2&3
601.28 600 08 598.79
597.5
596.16
2993.81
299 381
Q
300.106
299.906
P
299.906
299.706
Q
299.881
299 681
O
299.706
299.506
P
299.681
299.481
N
299.506
299.306
O
299.481
299 281
M
299.306
299.106
N
299.281
299.081
1
2
M
299.081
298.881
2
3
Detrminatlon of cut & fill
Detrminati
Q
0.994
0.924
P
0.574
0.524
O
-0.016
0.064
N
-0.606
-0.446
M
-1.066
-0.946
1
2
2nd unit
4th unit
M
298 24
298.16
L
297.43
297.5
M
K
297
296.83
298.16
298
L
J
296.53
296.32
297.5
297.36
K
1
2
596.4
594 93
593.83
592.85
2378.01
296.83
296 71
J
296.32
296.14
2
3
596.16 594 86 593 54 592.46
2377 02
JDetermination of Formation level Centroid level =
297.25125
Centroid point is between K&L, 1&2
Determination of Formation level Centroid level =
Centroid point is K&L. 2&3
297.1275
M
297.5275
297.3275
L
297.3275
297.1275
K
297.1275
296.9275
J
296.9275
296.7275
2
3
Detrmination of cut & Fill
Detrmination of cut & fill
Sth unit
7th unit
Q
300.45
300.12
Q
300.12
299.64
P
299.85
299.44
P
299.44
299
O
299.22
298 82
O
298.82
298.33
N
298.64
298.21
N
298.21
297.75
M
298
297.64
M
297.64
297.22
3
4
600.57 599.29 598.04 596.85 595.64
2990.39
4
5
599.76 598.44 597.15 595.96 594 86
2986.17
Determination of Formation level
Determination of Formation level
Centroid level=
299.039
Centroid level=
298.617
Centroid point is O. 3&4
Centroid point is F2. 4&5
Q
299.539
299.339
Q
299.117
P
299.339
299.139
298.917
P
298.917
O
299.139
299.939
298.717
O
N
298.939
298.717
298.739
298.517
N
M
298.739
298.539
298 517
298.317
M
3
4
298.317
298.117
4
513th
1 Sth unit
Q
297.9
297.3
Q
298.54
297.9
P
297.35
296.73
P
297.95
297.35
59644 595.3
594.19 595.02 591.92
2972.67 297.287
O
296.81
296.17
O
297.38
296.81
N
296.22
295.62
N
298.6
296.22
M
295.69
295.1
M
296.23
295.69
8
9
ZJ
8
Determination of Formation level Centroid level=
Centroid point is O, 788
Determination of Formation level Centroid level=
Centroid point is O, 8&9
595.2
594.08
592.98
591.64
590.79
2964 89
296.489
Q
296.989
296.789
Q
297.787
297.587
P
296.789
296.589
P
297.587
297.387
O
296.589
296.389
O
297.387
297.187
N
296.389
296.189
N
297.187
296.987
M
296.189
295.989
M
296.987
296.787
8
9
7
8
Dctrmination of cut & Fill
Dctrmination of cut & fill
Q
0.911
0.511
P
0.561
0.141
O
0.221
-0.219
N
-0.169
-0.569
M
-0.499
-0.889
8
9
16th unit
591 92 590.94 590.05 589.21
2362 12 295 265
M
295.69
295.1
L
295.21
294.65
K
294.76
294.21
J
294.35
293.75
8
9
Determinati
Centroid level=
Centroid point is K&L. 8&9
590.79
589.86
586 97
568 1
2357.72
294 715
M
295 115
294.915
L
294.915
294.715
K
294.715
F 294.515
J
294 515
294.315
8
9Detrmlnation of cut & fill
Detrmlnation of cut & fill
M
0.565
0.225
M
0.575
0.185
L
0.265
-0.055
L
0.295
-0.065
K
0.025
-0.305
K
0.045
-0.305
J
-0.205
-0.515
J
-0.165
-0.565
6
7
8
9
17th unit
19th unit
Q
296.72
295
Q
297.3
296.72
P
296.12
295.4
P
296.73
296.12
O
295.56
294.84
O
296.17
295.56
N
295
294.25
N
295.62
295
M
294.53
293.78
M
295.1
294.53
10
11
9
10
Determination of Formation level Centroid level=
Centroid point is O, 9&10
594.02 592.85 591.73
590.62
589.63
2958.85
295 885
Determination of Formation level
Centroid level=
Centroid point is O, 10&11
592.72 591.52
590.4
589.25
588.31
29522
295 22
Detrmlnation of cut & fill
Q
0.915
0.535
P
0.545
0.135
O
0.185
-0.225
N
-0.165
-0.585
M
-0.485
-0.855
9
1020th unit
18th unit
M
294.53
293.78
M
295.1
294.53
L
294.65
294.1
K
294.21
293.61
J
293.8
293.24
9
10
Determination of Formation level Centroid level=
Centroid point is K&L. 9&10
589.63
588.75
587.82
587.04
2353.24
294.155
L
294.1
293.25
K
293.61
292.83
J
293.24
292.5
10
11
Determination of Formation level Centroid level=
Centroid point is K&L. 10&11
588.31
587.35
586.44
585.74
2347.84
293.48
M
294.555
]
294.355
L
294.355
294 155
J
K
294.155
293.955
J
293.955
293.755
J
J
9
10
Detrmination of cut & fill
Dctrmlnation of cut & fill
M
0.545
0.175
L
0.42
-0 23
]
] ] ]
L
0.295
-0.055
K
0.13
-0.45
K
0.055
-0.345
J
-0.04
-0.58
J
-0.155
-0.515
10
11
9
10
23th unit
21th unit
Q
295.09
294.02
Q
296
295.09
P
294.45
293.43
P
295.4
294.45
O
293.82
292.84
O
294.84
293.82
N
29329
292.32
N
294.25
293.29
M
292.77
291.82
M
293.78
292.77
12
13
11
12
Determination of Formation level Centroid level=
Centroid point is O, 11 & 12
591.09 589.85 588.66
587.54
586.55
2943.69
294.369
Determination of Formation level Centroid level=
Centroid point is O. 12&13
589.11 587.88 586.66 585.61
584.59
2933 85
293 385
Q
294.869
294.669
Q
293.885
293.685
P
294.669
294.469
P
293.685
294.469
294.269
293.465
O
O
293.485
293.285
N
294 269
294.069
N
293.285
M
294 069
293.869
293.085
M
293.085
11
12
292.885
12
13
h
L)
h
L
.'4 ■Dctrmination of cut & fill
Dctrmination of cut & fill
Q
1.131
0.421
P
0.731
-0.019
O
0.371
-0.449
N
-0.019
-0.779
M
-0.289
-1.099
10
11
22nd unit
24th unit
M
293.78
292.77
M
292.77
291.82
L
293.25
292.28
L
292.28
291.3
K
292.83
291.83
J
292.5
291.5
11
12
586.55 585.53 584.66
584 2340 74
K
291.83
290.84
J
291.5
290.5
12
13
Determination of Formation level Centroid level=
Centroid point is K&L. 11&12
584 59 583 56 582.67
582 2332.64
291 605
292.5925
Determination of Formation level Centroid levels 
Centroid point is K&L. 12&1327th unit
25th unit
Q
293
292
Q
294.02
293
P
292.42
291.43
P
293.43
292.42
O
291.84
290.87
0
292.84
291.84
N
291.33
290.38
N
292.32
291.33
587.02 585.85 584.68 583.65
582.64
2923.84
292.384
M
290.82
289.87
M
291.82
290.82
14
15
13         |         14
Determination of Formation level Centroid level=
Centroid point is O, 13&14
Determination of Formation level Centroid level-
Centroid point is O, 14&15
585 583.85 582.71 581 71
580.69
2913.96
291.396
Q
291.896
291.696
Q
292.884
290.884
P
291.696
291 496
P
292.684
290.684
O
291.496
291.296
O
292.484
290.484
N
291.296
291.096
N
292.284
290.284
M
291.096
290.896
M
292.084
290.084
14
15
13
14
Detrmlnatlon of cut & fill
Dctrmination of cut & fill
Q
1.104
0.304
Q
1.136
2.116
P
0.724
-0.066
P
0.746
1.736
O
0.344
-0.426
O
0.356
1.356
N
0.034
-0.716
N
0.036
1.046
M
-0.276
-1.026
M
-0.264
0.736
13
14
28th unit
M
, 290.82
289.87
26th unit
L
290.36
289.33
K
289.5
M
291 82
290.82
288 82
L
291.3
290.36
K
290.84
289.5
J
290.5
289.39
13
14
582.64 581.66 580.34 579 89
2324 53
J
289.39
288 36
14
15
Determination of Formation level Centroid level=
Centroid point is K&L 14&15
580.69 579 69 578 32 577.75
2316.45 289.55625Determination of Formation level Centroid levcl=
Centroid point is K&L, 13&14
290.56625
Detrmlnation of cut & fill
M
0.86375
0.11375
Detrmlnation of cut & fill
L
0.60375
-0.22625
K
-0.05625
-0.53625
J
0.03375
-0.79625
12
13
31 st unit
27th unit
Q
291
290
P
29045
289.4
Q
292
291
P
291.43
290.45
583 581.88 580 76 579 77 578.74
2904 15 290 415
O
289.89
288.9
N
289.39
288.37
0
290.87
289.89
M
288.87
287.86
N
290.38
289.39
16
17
M
289.87
288.87
15
16
Determination of Formation level Centroid level=
Centroid point is O, 15&16
Determination of Formation level Centroid level=
Centroid point is O, 16&17
581 579.85 578.79 577  76 576 73 2894.13
289 413
Q
290.915
290.715
P
290.715
290.515
O
290.515
290.315
N
290.315
290.115
M
290.115
289.915
15
16
Dctrmination of cut & fillDctrmination of cut & fill
Q
1.087
0.287
P
0.737
-0.113
Q
1.085
0.285
O
0.377
-0.413
P
0.715
-0.055
N
0.077
-0.743
0
0.355
-0.425
M
-0.243
-1.053
N
0.065
-0725
16
17
M
-0.245
-1.045
15
16
32nd unit
30th unit
M
288.87
287.86
M
578.74 577.66 576.64 57568
2308.72
Determination of Formation level
Centroid level=                                  288 59 Centroid point is K&L. 15&16
289.87
288.87
L
288.33
287.33
L
289.33
288.33
K
287.82
286.82
K
288.82
287.82
J
287.32
286.29
J
288.36             287.32
16
17
15                    16
Determination of Formation level Centroid level=
Centroid point is K&L, 16&17
576.73 575 66 574 64 573.61
2300.64
267 5833rd unit
35th unit
a
290
288.73
Q
288.73
286.73
■p
• 289.4
288.21
P
288.21
286.3
0
288 9
287.69
578.73 577.61 576.59 575.54 574.58
2883.05 288.305
O
287.69
286
N
288.37
287.17
N
287.17
285.58
M
287.86
286.72
M
286.72
285.23
17
18
18
19
Determination of Formation level Centroid level=
Centroid point is O. 17& 18
Determination of Formation level Centroid leve(=
Centroid point is O. 18&19
575.46
574.51
573.69
572.75
571.95
2868.36 286.836
Q
288.805
288.605
P
288.605
288.405
O
288.405
288.205
N
288.205
288.005
M
288.005
287.805
17
18
Detrmlnation of cut & fill
Detrmlnation of cut & fill
Q
1.195
0.125
Q
1.394
-0.406
P•
0.795
-0.195
P
1.074
-0.636
O
. 0.495
-0.515
O
0.754
-0.736
N
0.165
-0.835
N
0 434
-0.956
M
1 -0.145 •
-1.085
M
0.184
-1.106
16
17
18
19
34 th unit
36th unit
M
287 86
286.72
M
286.72
L
287.33
286.25
285.23
L
286.25
K
286.82
285.8
284.83
K
285.8
J
286.29
285.32
284.45
J
17
18
574 58
573 58
572.62
571 61 2292 39
285.32
284.04
18
19
571 95
571 08
570.25
569.36
2282 64Determination of Formation level Centroid level=
Centroid point is K&L, 17&18
286.54875
Determination of Formation level Centroid level=
Centroid point is K&L, 18&19
285.33
M
286.94875
286.74875
L
286.74875
286.54875
K
286.54875
286.34875
J
286.34875
286.14875
17
18
Oetrmlnation of cut & fill
Detrminatlon of cut & fill
M
0.91125
-0.02875
M
0.99
-0.3
L
0.58125
-0.29875
L
0.72
-0.5
K
0.27125
-0.54875
K
0.47
-0.68
J
-0.05875
-0.82875
J
0.19
-0.89
16
17
18
19
37th unit
39lh unit
Q
284 5
283.02
Q
286.73
284.5
P
284.03
282.79
P
286.3
284.03
O
283.82
282.6
O
286
283.82
N
283.6
262 41
N
285.58
283.6
M
283.35
282.29
M
285.23
283 35
20
21
19
20
Determination of Formation level Centroid levels
Centroid point is O, 19&20
571.23
570.33
569.82
569.18 568.58
2849.14 284.914
Determination of Formation level Centroid level=
Centroid point is O. 20&21
567 52 566  82 566.42 566 01 565.64
2832.41 283.241
Q
283.741
283.541
Q
285.414
285.214
P
P
285.214
283.541
285.014
283.341
O
283.341
O
285.014
284.814
283.141
N
N
284.814
284.614
283.141
262.941
M
282.941
282.741
M
284.614
284.414
20
20
19
21Detrmlnation of cut & fill
Detrmlnation of cut & fill
Q
0.759
-0.521
Q
1.316
•0.714
P
0.489
-0.551
P
1.086
-0.984
O
0.479
-0.541
0
0.986
-0.994
N
0.459
-0.531
N
0.766
-1.014
M
0.409
-0.451
M
0.616
-1.064
20
21
19
20
40th unit
38th unit
M
283.35
282.29
M
285.23
283.35
L
284.83
283 17
568 58 568
567.45
566.92
2270.95
283.86875
L
283.17
282.13
K
283
282
K
284.45
283
J
282.88
281.87
J
284.04
282.88
20
21
19
20
Determination of Formation level Centroid level*
Centroid point is K&L. 19820
Determination of Formation level Centroid level*
Centroid point is K&L, 20&21
565.64 565.3
565 564.75
2260.69 282.58625
M
284.26875
284.06875
L
284.06875
283.86875
K
283.86875
283.66875
J
283.66875
283.46875
19
20
Detrmination of cut & fill
Detrmlnation of cut & fill
M
0.96125
-0.71875
L
0.76125
-0.69875
K
0.58125
-0.66875
J
0.37125
-0.58875
19
2041st unit
4 3rd unit
Q
283 02
282.29 I
281.63
P
282.79
281.9
P
281.9
280.9
O
282.6
281.57
O
281.57
280.56
N
282.41
281.39
565.31 564 69 564.17
563.8 563 54
2821.51 282 151
Q
282.29
N
281.39
280.35
M
282.29
281.25
M
281.25
280.21
21
22 I
22 |         23
Determina
Determinate
Centroid level=
Centroid point is O, 21 £22
Centroid level=
Centroid point s O. 22A23
563.92
56Z8
56Z13
561.74
561 46 2S12.05
281 205
IQ
282.651
282.451
p
282.451
282.251
0
282.251
282.051
N
282.051
281.851
M
281.851
281.651
21
22
Dctrmination of cut A fill
Detrmination of cut A fill
Q
0.369
-0.161
O
0 585
0 125
P
0.339
-0.351
P
0.395
-0.405
O
0.349
-0.481
O
0.265
-0.545
N
0.359
-0461
N
0.285
M
-0 555
0.439
-0.401
M
0.345
-0.495
21
' 22
22
23
42nd unit
44th unit
M
282.29
261.25
L
282.13
281.1
K
282
281
J
281.87
280.78
21
22
563 54 563 23
563 5G2.65
2252 42
M
251.25
260 21
L
281.1
280.1
K
281
279 96
J
280.78
279.74
22
23
561 46 561 2
560.96 560 52
2244 14Determination of Formation level Centroid level=
Centroid point is K8L, 21822
281.5525
Determination of Formation level Centroid level=
Centroid point is K8L, 22823
280.5175
Dctrmination of cut & fill
For the 2nd two blocks
1st unit
3rd unit
J
296.32
296.16
1
295.79
295.6
H
295.17
295 01
G
294.58
294.5
F
293.95
293.88
2
3
Determination of Formation level Centroid level=
Centroid point is H, 182
592 84
591 67
590.48
589.26
588.15
2952 4
295.24
Determination of Formation level Centroid level=
Centroid point is H, 182
592.48 591 39 590.18
589.08
587 83
2950.96
295.096
J
295 74
295.54
1
295.54
295 34
H
295.34
295.14
G
295.14
294.94
F
294 94
294.74
1
2Octrmlnation of cut & fill
Octrmlnation of cut & fill
J
0.78
0.78
1
0.34
0.45
J
0.724
0.764
I
I
I
I
I
I
I
I
I
I
I
I
I
I
]
H
-0.03
0.03
I
0.394
0.404
G
•0.46
-0.36
H
-0.026
0.014
F
-0.74
-0.79
G
-0.416
-0.296
12
F
-0.846
-0.716
1
2
2nd unit
4th unit
E
293.63
293.39
0
293
292.58
C
292.58
291.97
B
292.23
291.34
A
291.9
291.02
1
2
Determination of Formation level
Centroid level= Centroid point is C, 1&2
587.02 585.58
584 55
583.57
582 92
2923 64 292.364
Determination of Formation level Centroid levels
Centroid point is C. 182
586.6
585.17
583.77
582.3 581 42
2919 26 291.926
E
292.426
292.226
D
292.226
292.026
C
292.026
291.826
B
291.826
291 626
A
291.626
291.426
2
Detrmination of cut & fill
3
Detrmination of cut & fill
E
0766
0.726
D
0336
0.116
E
C
0.116
-0 294
0 964
0.984
D
-0.034
-0.724
0 354
B
0.564
A
-0.164
-0.844
C
-0.056
-0.026
B
1
2
-0.486
-0.666
A
-0.606
-1.026
2
35th unit
7th unit
J
296.16
295.93
I
295.6
295.38
H
295.01
294 82
G
294.5
294.35
F
293.88
293.81
3
4
Determination of Formation level Centroid level=
Centroid point is H, 182
592.09 590.98 589.83 588.65 587.69
2949.44 294.944
Determination of Formation level Centroid level*
Centroid point is H, 485
591.56
590.44
589.45
588.52
587.54
2947.51 294.751
Dctrmination of cut & fill
Detrmination of cut & fill
J
0.679
0.579
I
0.329
0.209
H
-0.031
-0.021
G
-0.301
-0.281
F
-0.641
-0 521
4
5
6th unit
8th unit
E
293.21
293.29
D
292 59
292.62
E
291.8
293 29
C
291.86
293.28
D
292.62
292.71
B
290.96
291.1
C
A
290.4
291.86
290.29
292
B
3
4
586.5
585 21
583 66
582.06 580.69
2918 12
291.1
291 19
A
290.29
290 4
Determination of Formation level
4
5
585 57 585 33 583 86
582.29
580.69
2918 74Centroid level= Centroid point is C, 1&2
291.812
Determination of Formation level Centroid levels
Centroid point is C. 4&5
291.874
Detrmination of cut & fill
Detrmination of cut & fill
E
0.898
1.178
D
0.478
0.708
E
0.916
1.106
C
-0.112
0.148
D
0.446
0.736
B
-0.752
-0.412
C
-0.114
0.226
A
-1.112
-1.022
B
-0.674
-0.384
2
3
A
-1.284
-0.974
4
5
9th unit
11th unit
590 91 589.81 588.93
588 1 587.33
2945.08
590 15
589 15
588.24
587.57
586 99
2942 1
294 508
Determination of Formation level Centroid level=
Centroid point ts H. 6&7
294 21
IDetrmination of cut & fill
Detrmination of cut & fill
J
0.622
0.472
I
0.252
0.142
J                  0.57
0.36
H
0.022
-0.108
I
0.24
0.09
G
-0.238
•0.278
H
-0.01
-0.17
F
-0.478
-0.408
G
-0.18
-0.27
5
6
F
-0.31
-0.32
6
7
10th unit
12th unit
E
293.28
293.11
D
292.71
292.68
E
293.11
293
C
292
292.05
D
292.68
292.38
B
291.19
291.27
C
292.05
291.74
A
290.4
290.5
B
291.27
291.1
5
6
586.39 585.39 584.05 582 46
580.9
2919 19
291.919
A
290.5
290.46
6
7
Determination of Formation level Centroid level= Centroid point is C, 5&6
Determination of Formation level Centroid level=
Centroid point is C. 6&7
586.11 585.06 583.79 582 37 580.96
2918.29 291 829
E
292 329
292.129
D
292.129
291.929
C
291.929
291.729
B
291.729
291.529
A
291.529
291.329
6
Detrmination of cut & fill
7
Detrmination of cut & fill
E
0.861
0.891
D
0.491
0.661
C
-0.019
0.231
8
-0.629
-0.349
A
-1.219
-0.919
5
615th unit
)
3
J
,1
Determination of Formation level Centroid level= Centroid point is H. 7&6
589.23
588.38
587.53
586.94
586 44
2938.52
293.852
Determination of Formation level Centroid level-
Centroid point is H, 889
588.16
587.39
586.67
586.12
585.56
2933 92
293.392
Detrmination of cut & fill
Detrmination of cut & fill
J
0.518
0.208
1
0.248
0.028
J
0.468
0.108
H
-0.012
-0 162
1
0.288
G
-0.112
-0.082
-0.252
H
F
0 098
-0.162
-0.302
-0.212
G
0 008
7
-0.272
•8
F
-0 042
-0.362
8
9
292.57
16th unit
E
293
D
292.38
292
C
291.74
291.34
E
292 57
292.13
e
291.1
290 76
A
290.46
290.12
7
8
585.57 584 38 583.08 581 86 580.58
2915 47
D
292
291 55
C
291.34
290 94
B
290 76
A
290.33
290 12
289 73
8
9
584 7 583  55 582.28
581.09 579 85
291 1 47
1
1
]
1
I J
I
]Determination of Formation level Centroid level=
Centroid point is C. 7&8
291.547
Determination of Formation level Centroid levcl=
Centroid point is C. 8&9
291.147
E
292.047
291.847
D
291.847
291.647
C
291.647
291 447
B
291.447
291 247
A
291.247
291.047
7
8
Detrmination of cut & fill
Detrmination of cut & fill
E
0.953
0.723
D
0.533
0.353
E
0.923
0.683
C
0.093
-0.107
D
0.553
0.303
B
-0.347
-0.487
C
0.093
-0.107
A
-0.787
-0.927
B
-0.287
0.517
7
8
A
-0.727
-0.917
8
9
17th unit
19th unit
J
293.8
293.24
1
293.41
292.82
J
293 24
292.5
H
293.08
292 44
I
292.82
292.15
G
292 82
292 24
H
292.44
291.8
F
292.53
291.89
G
292.24
291.41
9
10
F
291 89
291
10
11
Determination of Formation level Centroid level=
Centroid point is H. 9810
293.327
293 127
Determination of Formation level Centroid level=
Centroid point is H, 10&11
J
I
293.127
292.927
J
H
292.927
292.727
292.649
292.449
I
292 449
G
292 727
292 527
F
292 527
292 327
9
10
587.04
586.23
585.52
585.06 584.42
2928.27 292.827
586.454 586.054 585 654 585 254 584.854 2928 27
292.249
H
292 249
292.049
G
292.049
291.849
F
291.849
291.649
10
11
585.74 584.97
584 24
583.65
582 89
2921 49 292 149
585.098 584.698 584.298 583 698 583.498 2921 49■-X*
Dctrmination of cut & fill
Detrmination of cut & fill
IJ
0.473
0.113
I
0.283
-0.107
J
0.591
0.051
H
0.153
-0.287
1
0.371
-0.099
G
0.093
-0.287
H
0.191
-0.249
F
0.003
-0.437
G
0.191
-0.439
9
10
r
F
0.041
-0.649
10
11
18th unit
20th unit
E
292 13
291.4
D
291.55
290.92
C
290.94
290.49
B
290.33
289.89
A
289.73
289.27
9
10
Determination of Formation level Centroid levels
Centroid point is C. 9&10
583 53 582.47 581.43 58022
579 2906.65
290.665
Determination of Formation level Centroid level=
Centroid point is C, 9&10
581.9
580.92
579.99
578 89 577 7
2899.4 289 94
E
291 165
290.965
D
290.965
290.765
C
290.765
290.565
B
290.565
290.365
A
290.365
.290.165
9
10
Dctrmination of cut & fill
E       I 0.965
0 435
Detrmination of cut & fill
D
0.585
0.155
C
0.175
-0.075
E
0 96
0.26
0
-0.235
-0.475
D
0.68
-0.04
A
-0.635
-0.895
C
0.45
-0.34
B
9
10
0.05
0 64
A
-0.37
-1.01
—
9
1021 th unit
23rd unit
Determination of Formation level Centroid level=
Centroid point is H, 11A12
J
291.779
291.579
1
291.579
291.379
H
291.379
291.179
G
291.179
290.979
F
290.979
290779
11
12
584
583.3
562.63
581.86
581
2912.79
291.279
583.358
582.958
582.558 582.156 581.758 2912.79
Determination of Formation level Centroid level=
Centroid point is H, 12A13
582 561.2
560.56 579.6
578 95
2902 53
290 253
531 306
580 906
560 506 580 106 579 706 2902 53
Dctrmination of cut A fill
Dctrmination of cut & fill
J
0.721
>0 079
I
0.571
-0 229
J
0.747
-0.053
H
0.421
-0.349
1
0.597
-0.303
G
0.231
-0.529
H
0 477
-0.403
F
0.021
-0.779
G
0 297
-0.603
11
12
F
0 047
-0.803
12
13
22nd unit
24 th urut
E
290.5
289.5
0
290
269
C
289.5
288.54
B
289
288
A
288 43
287 5
L-------------
11
12
580 579
578 04 577
575 93 2889 97
Determination of Formation level
Centroid level=
Centroid point is C. 11A12
288 997
Determination of Formation level
C cntroid level = Centroid point is C. 12AI3
578 577
576 11 575
574 01
2880 12
28S 012Detrminatlon of cut & fill
Detrmination of cut & fill
E
1.003
0.203
D
0.703
-0.097
C
0.403
-0.357
B
0.103
-0.697
A
-0.267
-0.997
11
12
25th unit
579.89
27 th unit
579.05
578.42
577.61
576.84
577.75 577
2891 81
576.31
575.53
574.75
2881.34
Determination of Formation level Centroid levels
Centroid point is H. 12&13
Determination of Formation level Centroid level=
Centroid point is H. 12&13
J
289.681
289.481
I
289.481
289.281
J
288.634
288.434
H
289.281
289.081
I
288.434
288.234
G
289.081
288.881
H
288.234
268.034
F
288.881
288 681
12
13
289.181
579.162 578.762 576.362 577.962 577.562 2891 81
G
288.034
287 834
F
287.834
r 287.634
12
13
288.134
577.068 576.668 576.268 575.868 575.468 2881.34Detrmination of cut & fill
Detrmination of cut & fill
J
0.756
-0.074
I
0.566
-0234
H
0.436
-0.394
G
0 226
-0.564
F
0.056
-0.774
12
13
26th unit
26th unit
E
288.5
287 5
D
288
207
E
287.5
286.5
C
287.57
286.57
D
287
286
B
287
286.06
C
286 57
285.57
A
286.51
285.56
B
286.06
285.11
13
14
A
285.56
284.63
14
15
Determination of Formation level
Centroid level=
Centroid point is C. 13814
576 575
574.14
573.06
572.07
2870 27
287.027
Determination of Formation level Centroid level=
Centroid point is C. 13814
574 573
572.14
571.17
570.19
2860.5
286 05
E
286.55
286 35
D
286.35
286.15
C
286.15
285 95
B
285.95
28575
A
285.75
285.55
12
13
Detrmination of cut & fill
Detrmination of cut & fill
E
0.973
0.173
D
0.673
-0.127
E
0.95
C
0.443
-0.357
0 15
D
B
0.073
0 65
-0 667
-0.15
C
A
-0.217
-0 967
0 42
-0.38
B
12
13
0 11
-0 64
A
0 19
-0.92
12
1329th unit
31 st unit
J
268.36
287.32
1
288
286.93
H
287.64
286.59
G
287.27
286.22
F
286.86
285.62
15
16
Determination of Formation level Centroid level=
Centroid point is H. 12&13
575.68 574 93
574.23
573.49
572.68
2871.01 287.101
575.002 574.602 574.202 573 802 573.402 2871.01
Determination of Formation level Centroid level=
Centroid point is H, 12&13
J
286 54
286.34
I
286.34
286.14
H
286.14
285.94
G
285.94
285.74
F
285.74
285.54
12
13
573 61 572.79
572.09
571 36
570.55
2650 4
266 04
572 86
572  48 572.08 571.68 571.26 2650.4
Dctrmination of cut & fill
Dctrmination of cut & fill
J
0.759
-0.081
I
0.599
-0.271
J
0.78
-0.05
H
0.439
-0.411
I
0.59
-0.28
G
0 269
-0.581
H
0.45
-0.44
F
0.059
-0.781
G
0.28
-0.6
- 12
13
F
0.08
-0.81
12
13
30th unit
32nd unit
E
286.5
285.42
D
286
285
C
285.57
284.67
B
285.11
284.17
A
284.63
283.72
15
16
571.92 571
570 24
569.28
568.35
2850.79
E
285.42
284.32
D
285
283.93
C
284.67
283.5
9
284.17
283.12
A
283 72
282.67
16
17
569 74 566  93
568 17
567 29
566.39
2840.52Determination of Formation level Centroid level=
Centroid point is C, 13& 14
285 079
Determination of Formation level Centroid level=
Centroid point is C, 13&14
284.052
Dctrmination of cut & fill
Dctrmination of cut & fill
E
0.921
0.041
D
0.621
-0.179
E
0.868
-0.032
C
0.391
-0.309
D
0.648
-0 222
B
0.131
-0.609
C
0.518
-0.452
A
-0.149
-0.859
B
0.218
-0.632
12
13
A
-0.032
-0.882
12
13
33rd unit
571.61 57069 569 94
569 14
568 37
2849 75
284 975
570.75 570.35 569.95 569 55 569 15
2849 75
Determination of Formation level Centroid level=
Centroid point is H, 12& 13
J
264.413
284.213
I
284.213
284.013
H
284.013
283 813
G
283.813
283 613
F
283.613
263 413
12
13
569.36
568.64
567 85
567 566.26
2839 13 283 913
568 626 568 226 567 826 567 426 567.026 2839 13Detrminatlon of cut & fill
Detrminatlon of cut & fill
J
0.815
0.045
1
0.585
-0.245
H
0.425
-0.435
G
0.265
-0.675
F
0.055
-0.835
12
13
34th unit
3oth unit
E
284.32
283.26
D
283.93
282.84
C
2283.5
282.44
0
283.12
282
A
282.67
281.64
17
18
567 56
566 77
2565 94
565.12
564.31
4829 72
565.51
564.68
563.85
563 562.28
2819.32
Determination of Formation level
Determination of Formation level
Centroid level=
482 972
Centroid level=
281 932
Centroid point is C, 13814
Centroid point is C. 13814
Dctrmination of cut & Hit
Detrmination of cut & fill
I37th unit
39th unit
J
284.04
282.88
I
283.81
282.73
H
283.41
282.14
G
283
282
F
282.64
281.64
19
20
Determination of Formation level Centroid level=
Centroid point is H, 12&13
566.92 566.54 565.55
565
564.26
2828.29
262.829
566.458 566 058 565.658 565.258 564.858 2828.29
Determination of Formation level Centroid level=
Centroid point is H. 12& 13
J
282 246
282.046
I
282.046
281.846
H
281.846
261.646
G
281.646
281.446
F
281.446
281.246
12
13
564.75 564.33
563.4 562.84
562.14
2817 46
261 746
564.292 563 892 563.492 563.092 562.692 2817.46
Dctrmination of cut & fill
Detrmination of cut & fill
J
0.711
-0.249
I
0.681
-0.199
H
0.481
-0.589
G
0.271
-0.529
F
0.111
-0.689
12
13
38th unit
40th unit
E
282.25
281.23
E
281.23
280.11
D
281.84
280.84
D
260 84
281.41
280.41
279.75
C
C
280.41
279.4
B
281
280.02
A
280.64
279.79
19
20
563.48
56268
561.82
561.02
560.43
2809.4 3
B
280.02
279.13
A
279.79
278.91
20
21
561.34
560 59
559.81
559.15 558 7
2799 59Determination of Formation level Centroid level=
Centroid point is C, 13&14
280.943
Determination of Formation level Centroid level=
Centroid point is C, 13&14
279 959
E
280.459
280.259
D
280.259
280.059
C
280.059
279.859
B
279.859
279.659
A
279.659
279.459
12
13
Detrmination of cut & fill
Detrmination of cut & fill
E
0.807
-0.013
D
0.597
-0.203
C
0.367
-0.433
B
0.157
-0623
A
-0.003
-0 653
12
13
41 st unit
4 3rd unit
J
281 87
280.78
1
281.6
280.5
H
281.26
280.18
G
280 84
279.81
F
280.5
279 43
• 21
22
Determination of Formation level Centroid level=
Centroid point is H, 12& 13
562.65
562 1
561 44
560.65
559.93
2806 77 280.677
562 154 561.754 561.354 560 954 560 554 2606 77
Determination of Formation level Centroid level=
Centroid point is H, 12&13
560 52 560
559.34
558 65
557 97
2796 48 279.646
560.095 559 696 559 295 558.895 556 495 2796 48Dctrmination of cut & fill
Dctrmination of cut & fill
J
0.693
-0.197
I
0.623
-0.277
H
0.483
-0.397
G
0.263
-0.567
F
0.123
-0.747
12
13
42nd unit
44th unit
E
280 11
279.1
D
279.75
278.8
C
279.4
278.59
B
279.13
278.45
A
278.91
278.25
21
22
559.21
558.55
557.99
557 58 557.16
2790.49
557 36 556.68 556.52
556 26
555 91
2782.93
Determination of Formation level
Determination of Formation level
Centroid level=
279.049
Centroid level=
278.293
Centroid point is C. 13814
Centroid point is C. 13814
E
279.549
279.349
D
279.349
279 149
C
279.149
278 949
B
278.949
278 749
A
278 749
278 549
12
13
Dctrmination of cut & fill
Detrmination of cut & fill
F.
0.561
-0.249
E
0.307
-0.333
D
0 401
-0.349
D
0 207
C
0.251
-0.313
-0.359
C
0.197
B
0.181
-0.299
-0.263
B
0.257
A
0.161
-0.299
-0 183
A
0.257
12
13
-0 133
12
13Q
P
0
N
M
I
K
J
I
H
G
F
E
D
C
B
A
296,72
296.12
295.56
295
294.53
294.1
293.61
293.24
296
295.4
294.84
294.25
293.78
293.25
292.63
292.5
295.09~] 294.02
293.43
292.84
292.32
291.82
291.3
293
292.42
291.84
291.33
290.82
292
291.43
290.87
290.38
289 87
291
290.45
269.69
289.39
288.87
290
289.4
268.9
286.73
266,3
286
292.62 292.44 292.24 291.89
291.4 290.92 290,49 289.69 289.27
10 4980.24
475 2365614
292,15 291.6
291.41 291
290.5 290
289.5 289
268.43 11
4966.64
525 2607486
294.45 293.62 293.29 292.77 292.28 291.83
291.5
291.15
290.63
290.45 290
289.5 289
288,54 288
287.5
12 4950
575
290.84
290.5
290.05
289.75
290.36
289.5
269.39
269
288.67
289.33
288.82
288.36
288
288 33
287.82
287.32
286.93
268.37
287.86
287.33
286.62
286.29
285.86
287.64
286.59        285.5
269.35 286.95
288.5 288
287,57 287
286.51
13 4932.75
625
288.26
287.89
267,5
287
287.27
266.86
286.5
286
286.57
286.06
285.56
285.57
286.22
285.82
285.42
285
284.67
285.11
284.63
285.14
284,73
284.32
283.93
283.5
283.12
282.67
17
268.73
268.21
287.69
287.17
286.72
286.25
285.8
265.32
284.83
264.44
284
283.64
283.26
282.64
262.44
282
281.64
18
285.56 285.23 284.63 284.45 284.04 283.61 283.41
283
282.64
282.25
281,84
281.41
281
280.64
19
Hy
Dx 
Hy.Dx
2846250 3082968.8
4915.17    4898.64"     4881.61      4863.74      4844 98      4823.16
675            725            775            825             875             925
3317740    3551514    3783248     4012586     4239358     4461423
14’              15
264.17
283.72
16

Summery

Erer Dam & Irrigation Project Summary

Erer Dam & Irrigation Development Project Summary

1. Project Overview

The Erer Dam & Irrigation Development Project is a major infrastructure initiative in Ethiopia designed to address food scarcity through irrigated agriculture. The project includes:

A zoned earth-fill dam on the Erer River (tributary of Wabe Shebelle River)
An extensive irrigation network serving 3,370 hectares of cultivable land
Associated drainage systems and infrastructure

Key Project Features:

Feature	Specification
Location	530 km from Addis Ababa, 19 km from Harar town (between 9°07'17"N to 9°17'40"N and 42°12'24"E to 42°16'03"E)
Dam Type	Zoned earth fill (36.6m max height)
Reservoir Capacity	Gross storage: 5,067.50 Ha-m, Live storage: 2,303.40 Ha-m
Command Area	Gross Commanded Area: 4,000 ha, Culturable Commanded Area: 3,370 ha
Financial Viability	FIRR: 11.16%, EIRR: 14.56%, B/C ratio: 1.50

2. Irrigation System Design

2.1 Canal Network

The irrigation system consists of a hierarchical canal network:

Primary Canal: 13.6 km long, design capacity 2.709 m³/s
Secondary Canals: 2 canals (S1: 8.366 km, 0.968 m³/s; S2: 13.1 km, 0.773 m³/s)
Tertiary Canals: 6 canals
Quaternary Canals: 51 canals

2.2 Design Criteria

Parameter	Value
Maximum Velocity	0.75 m/sec
Minimum Velocity	0.25 m/sec
Field Irrigation Efficiency	70%
Overall System Efficiency	50%
Irrigation Intensity	170% (100% Meher season + 90% Belg season)

2.3 Cropping Pattern

The proposed cropping pattern includes:

Meher Season (July planting)

Maize (30%)
Groundnut (20%)
Rice (10%)
Vegetables (10%)
Sugarcane (10%)
Others (20%)

Belg Season (Feb planting)

Maize (30%)
Rice (12%)
Vegetables (10%)
Sugarcane (10%)
Others (28%)

3. Key Infrastructure Components

3.1 Major Structures

Structure Type	Quantity	Key Features
Aqueducts	3	Including one over Dencho River (274 m³/s design flood)
Culverts	18	Single, double and triple pipe culverts
Siphons	14	For canal crossings where drain HFL > canal bed level
Drop Structures	Multiple	1.5m fall structures on Secondary Canal-I
Escape Structures	1	Sluice type at 4+150 chainage of primary canal

3.2 Drainage System

The comprehensive drainage system includes:

40 field drains (triangular section, side slopes 6:1)
2 tertiary drains (trapezoidal section, side slopes 3:1)
Designed to evacuate excess water within 24 hours
Drainage capacity: 2.2 L/s/ha (1.78 L/s/ha from rain + 0.42 L/s/ha from irrigation)

4. Soil and Water Characteristics

4.1 Soil Properties

Parameter	Range/Value
Texture	Mostly clay loam and loam
Drainage Class	Moderate to imperfect
Infiltration Rates	1.96-15.02 cm/hr (no lining required)
pH	6.7-8.89 (neutral to alkaline)
Available Water Capacity	100 mm/m (average)

4.2 Water Quality

Erer River water is suitable for irrigation with:

Electrical Conductivity: 0.12-0.45 dSm^-1 (low salinity)
Exchangeable Sodium Percentage: 1.98-6.3% (low to medium)
No adverse effects expected from long-term use

5. Implementation Aspects

5.1 Construction Materials

Earthworks: Utilized from canal and drain excavation
Masonry/Concrete: Locally available stones and aggregates
No lining required for canals due to low infiltration rates

5.2 Operation & Maintenance

Proposed institutional arrangement:

Component	Responsible Agency
Dam structures	Government (EPA/EPCC)
Canal regulators (up to tertiary)	Government
Field irrigation (quaternary canals and below)	Beneficiary farmers
Drain maintenance	Government (seasonal labor)

5.3 Construction Schedule

Estimated construction period: 24 months

6. Project Benefits

Addresses food scarcity through reliable irrigation
Stabilizes agricultural production in semi-arid region
Creates employment opportunities
Reduces food imports and saves foreign exchange
Provides raw materials for agro-industries

7. Key Challenges

Resettlement of 3,462 households from reservoir area
Management of vertisols (black cotton soils) in parts of command area
Operation of night irrigation without storage reservoirs
Maintenance of extensive earthen canal network