GOVERNMENT OF ETHIOPIA
WATER RESOURCES DEVELOPMENT AUTHORITY
AMIBARA IRRIGATION PROJECT II
DRAINAGE & SALINITY STUDY AND RECOMMENDATIONS FOR
FIELD DRAINAGE
VOLUME 1-STUDY & RECOMMENDATIONS
APRIL 1982
Sir William Halcrow & PartnersGOVERNMENT OF ETHIOPIA WATER RESOURCES DEVELOPMENT AUTHORITY
AMIBARA IRRIGATION PROJECT II
DRAINAGE & SALINIlT STUDY AND RECOMMENDATIONS FOR
FIELD DRAINAGE
VOLUME 1-STUDY & RECOMMENDATIONS
APRIL 1982
Sir William Halcrow & Partners Consulting Engineers
Burderop Park Swindon
Wiltshire SN4 OQD United KingdomAMIBARA IRRIGATION PROJECT II
DRAINAGE AND SALINITY STUDY
AND RECOMMENDATIONS
FOR FIELD DRAINAGE
CONTENTS
PART A
PART B
PART C
MELKA   SADI   AREA,   MELKA   SADI   FARM.   SOIL   AND   SALINITY   STUDY   AND DRAINAGE DESIGN
AMIBARA AREA. SOIL AND SALINITY STUDY
MELKA SADI AREA, STATE FARMS I & II.
SOIL AND SALINITY STUDY
IPART A
MELKA SADI AREA
MELKA SADI FARM
SOIL AND SALINITY STUDY AND DRAINAGE DESIGNPART A
MELKA SADI AREA MELKA SADI FARM
SOIL AND SALINITY STUDY AND DRAINAGE DESIGN
CONTENTS
PAGE NO
SECTION I : SOIL AND SALINITY STUDY
1.         Summary 
2
2.         Background and Previous Studies
2
3.         Geology and Hydrogeology 
3
4.         Climate
5
5.         Field Studies and Methods
H
6.         Soils of the Study Area
12
7.         Hydraulic Conductivity 
17
8.         Water Quality 
17
9.         Alkalinity Hazard 
20
10.       Salinity Hazard 
20
11.       Reclamation of Saline Soils
23SECTION II : DRAINAGE DESIGN
PAGE NO
I
1.
Introduction
25
25
25
26
27
27
32
33
33
37
40
53
I
2.
Drainage Requirements
3.
Drainable Excess
4.
Drain Spacing Equations
5.
Data from Field Observations
6.
Field Drain Design
7.
Interceptor Drains
8.
Block Drains
I
I
R
ft
9.
Collector Drain Design
10.
Phasing of Construction
11.
Quantities and Cost Estimates
12.
Estimates of Benefits
II
11
11
Schedule of Figures
II
Figure 5 In-field Drainage Requirements
Figure 6 Drain Construction Phasing
28
29
30
34
35
h
Figure 7 Phase No and Drain Type Locations by Field
Figure 8 Typical Field Drainage Layout
M
Figure 9 Drains SD1, SD2 - Long sections
Drain SD2 - cross sections
Figure 10 Longitudinal Sections of Drains TD1, TD2, TD3, TD4, TD5 Figure 11 Programme for Drainage Works within MAESCO Farm Area
Figure 12 Marketed Production of Bananas by Melka Sadi Agricultural Enterprise
B
36
38
56I
I
Schedule of Tables
| 
Table 6        Field Drain Details - Comparison of open and tile
drain requirements
Table 7             Schedule of Equipment Required for Trials on Pilot
Drainage Area and Further Salinity Studies
Table 8                  Melka Sadi Drainage,            Phase     I   -        Bill of         Quantities
Table 9                   Melka Sadi Drainage,            Phase    2   -        Bill of         Quantities
Table 10                 Melka Sadi Drainage,            Phase    3   -        Bill of         Quantities
Table 11                 Melka Sadi Drainage,            Phase    4   -        Bill of         Quantities
Table 12                  Melka Sadi Drainage,            Phase    5   -        Bill of         Quantities
Table         13         Melka         Sadi         Agricultural         Enterprise         -         Rationalisation of Areas
Table 14 Melka Sadi Agricultural Enterprise - Development of Banana Area
Table 15 Melka Sadi Agricultural Enterprise - Bananas - Estimated Returns and Production Costs
Table 16 Melka Sadi Banana Unit : Cash Analysis
PAGE NO 31
39
47
49
50
51
52
54
55
58
59Schedule of Figures
Fig 1 
Location of Study Area
Fig 2                 Detail of observation well
Fig 3  Detail of AIP observation well
Fig 4 
Soil Map - Melka Sadi Farm
PAGE NO
1
9
11
13
Schedule of Tables
Table 1 Water table depths and water analysis results for 6 wells
at Melka Sadi farm.
Table 2 Depth and EC of groundwater at AIP observation wells and deep bores.
Table 3 Water table levels and salinities from selected sites at different dates.
Table 4             Results of hydraulic conductivity and infiltration tests. Table 5             Analysis of Awash river water.
Schedule of Maps (contained in separate folder)
Map No 1 Contour map of the groundwater levels
Map No 2 Contour map of the groundwater salinity Map No 3 Contour map of the impervious layer(s)
Map No 4 Location of field test sites and observation wells Map No 5 Farm layout and saline areas
Schedule of Annexes (Bound separately) Annex 1           Observation Well Records Annex 2           Soil Profile Descriptions Annex 3 Results of Soil Chemical Analysis Annex 4 Variation in Rainfall Amounts
4
5
7
18
21FIGURE I
LOCATION OF
STUDY AREA
N
II
HEADWORKS
0
L
5
±
IO JPART A
MELKA SADI AREA, MEL KA SADI FARM SOIL AND SALINITY STUDY
AND PILOT DRAINAGE DESIGN SECTION I : SOIL AND SALINITY STUDY
1.          SUMMARY
The field studies for this report were carried out between March and September 1981. Forty-one sites were examined and tested for infiltration into the
topsoil and permeability both above and below the water table. Depth to impermeable layers was determined by auger bore to 5 metres depth at 48 sites. The 5 m bores were described and water levels and salinities recorded throughout the period. 2 m deep pits were excavated at a further 19 sites, and these were described and subsequently sampled for full chemical analysis.
These field studies were subsequently used to design a suitable drainage system for the Melka Sadi farm based on the findings described in the report. The section of this report which covers the drainage designs is contained in Part A, Section II, and discusses the need for drainage, field drainage design criteria, hydraulic conductivity values, choice of field drainage system and recommendations for leaching and drainage trials.
2.          BACKGROUND AND PREVIOUS STUDIES
The Melka Sadi study area occupies some 4,200 ha of the Middle Awash valley 
floor as shown in Figure 1.
1,328 ha are occupied by the Melka Sadi farm,
previously MAESCO Farm, now under State Farm management. The remainder of the study area of 2,870 ha is presently under development for cotton production by 
the Amibara Irrigation Project II. Irrigation water is supplied by gravity 
canal from a weir on the Awash River,
The principal crop at the Melka Sadi farm is banana, grown on the flat in small irrigation basins. Since cultivation was started in 1971 approximately one
third of the area has been abandoned due to salinity and rising water tables.
On the remainder of the farm almost every plot is showing signs of poor growth with resultant loss of yield. Some 46 ha of the abandoned areas have been planted with grass and lucerne for fodder production with varying results.
The existing drainage system, which mirrors the irrigation layout, was designed to deal with rainfall, excess irrigation water, spillage, seepage and ground water control. The system originally discharged into the Awash river.
The depth of the field drain system is about 1.2m and the main drain is about 1.5 m deep. The main drain is now connected to the Amibara Project primary 
drain which is 1.86 m deep at the point of junction. (See Map 5)
Previous studies of the area in 1969 and 1971 by Italconsult included soil and land classification mapping at 1:20 000 scale and limited infiltration and permeability measurements. The irrigation suitability classification showed the Melka Sadi Farm to be of Class I suitability and the area North of the present farm to be Class II.
2In 1969 a number of observation wells were installed, but unfortunately some
were blocked or destroyed and the records lost. In mid 1980, the Amibara
Project authority provided a 2 km grid of observation wells throughout the Melka
Sadi area. These have been checked monthly since August 1980 both for water
level and salinity (EC).
A     geological     study     by     FAO     in     1973     included     a     section     on     the     ground     water     levels at Melka Sadi.
In 1980 the Water Management Adviser of AIP carried out an investigation into 
the water/salinity problems at Melka Sadi Farm. It was found that a minimum of
60 cm of water per year was applied in excess of banana crop needs, leaching 
requirements and irrigation losses, and this 60 cm excess was a major
contributing factor to the rise in the water tables.
3.         GEOLOGY AND HYDROGEOLOGY
3.1     Geology
The Middle Awash Valley lies in the Ethiopian rift of the Tertiary age,
extending north east towards the Red Sea. The Floor of the valley is built up 
from recent alluvial/colluvial deposts from the Awash river and outwash from the
escarpment. Underlying sediments consist of nearly horizontal beds of basalts,
pumice, tuffs, gravel, sands, silts and clays, and the latter are often saline.
These beds are exposed in the Arba river gorge and on the escarpment south of
Melka Sadi village.
Within the study area there are several features of volcanic origin. An axamp Ip
is the small Aseda hill where the bedding is turned through 90° exposing the
silt and clay beds, which still contain small amounts of soluble salts.
Volcanic activity in the valley at present is limited to fumeroles and hot
springs.
The present fault controlled Awash river course was established in Plio -
pleistocene times; previously the river flowed in the Alledeghi graben to the
south of its present course.
The new course of the Awash was periodically blocked by lava flows or outwash 
from the escarpment creating temporary lacustrine conditions. The Valley floor
was then some 50 m below its present level.
3.2      Hydrogeology
There are two separate aquifer systems in the study area. One is the deep,
confined aquifers of the basalt - tuff - lava - gravel sequence which occurs at
depths between 50 and 70 m. These confined aquifers have alkaline water,
pH 8 - 9, with a high bicarbonate content and temperature in the range
35° - 40°. The electrical conductivity (EC) is usually between 1 and 2 
millimhos/cm (mmhos/cm).
The well drilled at the Project headquarters tapped a confined aquifer at 80 m
and the static water level rose to within 11 m of the groundlevel.
The other system comprises the shallow aquifers of the recent alluvium/colluvium deposits which  have a variable salinity, according  to  location  and  depth. Where comparatively non-saline water is entering the aquifer the salinity of thataquifer is low and the water level is usually close to the surface at around 
1 - 3 m below groundlevel. An example is borehole AIP 3 where the water level fluctuates between 3.0 and 1.8 m in response to the irrigation water applications and the salinity is less than 1 mmhos/cm. These aquifers are perched over soil horizons of low permeability.
The very high salinities which occur at shallow depths in the abandoned areas in tne vicinity of observation wells AIP 10, Pll, DRH 6 and DRH 24 are the result of the applied irrigation water joining up with an existing shallow saline water table causing an upward movement of soluble salts leading to the formation of a salt crust on the soil surface. Chemical analysis of six samples from observation wells are given in Table 1 below.
TABLE 1
Water table depth and water analysis results from 6 observation wells in the Melka Sadi farm
r
1 AIP 1 Well 1 No 1
7“
1    Depth 
to
|     Water
(m) 1 table
1
1
1
1
1 EC | (mmhos/cm 1
“1
1
I Acidit ) 1 (pH)
1
n
I 8.7
n----- 1
r
1 
y I Na+
1
1
T
1 132.6
1
I Ca++ 1
1
r
1 16.0
1----------- 1
1 Mg++ 1
1
r
I1
1 2.80                  11' 6.3
1 17.3
1
1
1 B 1
1
F
1 4.0
1
1
1 C03 1
1
r
1 79.3
1              1 1             1 1 SAR     | 1             1
1             1
1 1
1 68.63 I
1 2              I 1.23                   1     1.0
1 3              I 1.37                   1     1.0
1 6              1 3.40                   1     2.7
1 8.5                I 73.2               1 56.1 11 21.4        1 0.9        1 341.6             1 2.10 I
I 8.3
1 207.4 1    1   38.5 1         5.8            1 3.8 I     1 475.8 |            8.2 |
1 8.3                1 425.0 1           1 11.2 |      2.4      1   1.7 I            73.2 I  29.8        |
1 8
I 1.45
1     0.63
1 8.4
1 117.3 I
15.2 I
3.4
1 0.6 1
268.4 |
2.08 I
1 10
1
I 2.55
1     5.6
I 6.7
1
1
1
1 595.0 1
1 1
136.3 I
1
1.99 i
1
1 43.6 |
1
36.6 |
1
7.61 |
1
At borehole Pll (Table 2) the water table has risen 5 metres in 9 years to within 1.8 metres of the surface. The salinity of the groundwater at Pll is
37.2    mmhos/cm while the salinity of the water in the observation well is 10.0 mmhos/cm. Table 2 shows the depths and EC of the groundwaters at all AIP observation wells and at open bores.
Where the water levels are deeper, around 5-15 metres below ground level, the salinities are high or very high. The recharge of these deep aquifers is partly derived from irrigation water but it probably also includes seepage from the very deep confined saline aquifers passing up through the salt rich clay/silt
beds of low permeability. Another source of recharge water in the past was the seasonal flood from the River Awash which left behind shallow pools of evaporating and therefore saline water some of which entered the aquifer in the course of time. Such flooding is now prevented since completion of construction of the Eastern and Western Dykes.
Some water is entering the aquifer from the river, particularly at times of high flows. Observation wells AIP 5, PPI, AIP 11 showed a rise in the water table following the prolonged high flows during August and September 1981.
Deep auger bores at the Melka Sadi farm headquarters area revealed very saline waters, which are slightly confined and associated with weathering calcareous tuffs and clays which may be charged from the high ground around (Jnda Evu hill
- 4 -Depth and EC of groundwater at open
Site
EC of Open Bore Water
(nnnhos/cm)
TABLE 2
5 m bores and adjoining observation wella
EC of Observation Well Water
(mmhos/cm)
AIP 1 U                    21.6
AIP 2 B
s
AIP 3 B
AIP 4 U
AIP 6 U
2.2
2.2
12.4
7.0
AIP 7 U                    - AIP 8 B
0.67
AIP 10 A
AIP 12 C
11.2
12.7
AIP 13 C                   - AIP 14 C
7.8
AIP 22 C                   - PH           A              37.2
DRH 20 P
22.5
DRH 21 B3                       60.1
DRH 22 A                40.1
DRH 23 A                 20.2
DRH 24 A                 14.4
DRH 25 A                 15.8
2.89
1.50
2.66
2.75
3.72 1.62
2.30
4.75
3.50
2.7
3.17
2.99 
3.71 
1.22 
2.14
2.18
4.3 0.98 0.97
8.6 2.8
10.0 0.69
4.0 4.8 
11.2
2.2
4.6
9.6
Depth (m) 3.00
1.50
1.97
3.00 3.51 6.00 1.88 2.60 5.14 7.97 7.00 9.31 2.09
Key to crop at site
DRH 26 A
2.6
DRH 27 A
7.2
U
Uncultivated
DRH 28 B
s
2.2
C
Cotton
DRH 29 A
-
B
Banana
DRH 30 A
1.21
B
s
Banana - saline
DRH 31 A
36.0
P
Pasture
DRH 32 A
28.4
A
Abandoned plot
DRH 33 A
8.8
DRH 34 B
6.2
DRH 35 B
4.0
DRH 36 B
s
11.2
DRH 37 B
s
2.6
DRH 38 A
14.6
DRH 39 B
6.0
DRH 40 B
1.0
DRH 41 B
7.4
DRH 42 B
6.75
DRH 43 B
0.92
DRH 44 U
2.60
DRH 44 U
0.66
DRH 45 A
4.20
DRH 46 A
0.72
DRH 47 B
0.32
DRH 48 B
g
0.79
DRH 49 U
1.97
DRH 51 B
2.5
DRH 52 B
8.25
DRH 53 B
g
1.2
DRH 54 B
s
2.2
2.52 
2.89
2.54 
5.00 
2.86
5.10
3.58
3.61
3.45
2.14 
1.30
1.54
2.26
0.65
0.89
1.07
1.07
0.70
1.80
3.25
1.43
3.16
2.53
1.72
2.70
0.64
1.60
2.40
1.5
-5-or from springs associated with the local vents and lava cones. (A similar
situation has been detected around the Amibara and Ambash volcanics). The sites with these very high salinities are DRH 20, DRH 21, DRH 23, DRH 25, DRH 32 and DRH 36. The EC of DRH 21 was 60.0 mmhos/cm at 4 metres, and the water level rose 1.0 metre after 6 hours.
The present groundwater levels are shown on Map No 1 and the salinity values on Map No 2. The depth to impermeable or very slightly permeable horizons is shown on Map No 3.
The groundwater contour map produced by Curry in 1971 from a small number of observation wells showed the Melka Sadi and Amibara areas as two separate drainage basins with the Dofan volcanic constricting the valley between the two basins. The Melka Sadi basin is shown as draining towards the river from a
water table mound to the south east of the study which originated from river
seepage at the start of the upper plain. However it was suspected that two 
water systems, both of which were under pressure, were being read as
representing one system. Since this study was made the groundwater levels have risen considerably, especially within the Melka Sadi farm area as can be seen 
from Map No 1. Curry also noted a relationship between high river flows and 
rises at some of the observation wells.
3.2.1                   Observation wells
There are 20 AIP observation wells in the Melka Sadi area on a 2 km x 2 km grid and four of the earlier wells are still in operation. Seven of these 24 wells
are in the Melka Sadi farm. Records for the earlier wells are available for the
years 1970 - 1979 but only cover water levels.
The AIP observation wells have records of monthly readings from mid 1980 to 
date, both for water levels and salinity. The earlier wells are now also 
recorded monthly.
Water table levels and salinities from the Melka Sadi farm area for selected 
dates are shown in Table 3 and all records are shown in Annex 1. Figures 2 and 
3 show the construction details of both types of observation well. A further 3 observation wells are planned for the farm area and are to be installed as soon 
as possible.
4. CLIMATE
The climate of the study area is semi-desert with a bi-annual rainfall pattern.
Rainfall amounts at Melka Warer Research Station range between 300 mm and 660 mm per year with an annual mean of 550 mm, approximately half of which falls in 
July and AuguBt with another lesser peak during February, March and April. 16 
years of records are available.
There are two rainfall stations at Melka Sadi but records are incomplete with 
many years' data missing. However from the data available it is clear that
there are considerable variations in the amounts of rainfall recorded over the
area from site to site and from year to year as can be seen in Annex 4, titled 
"Variation in rainfall amounts".
Temperatures range between a mean maximum of 37°C in June and a mean minimum of 12.8°C in December. The annual variation in mean monthly temperature is only about 8°C.
- 6 -TABLE 3
Water     levels     and     salinities     (EC     in     mmhos/cm)     of     groundwater  observation  wells_at Mello Sadi farm on selected dates
—I
Well
I Date
Location                             1 1
1
----------1
I Water | Level (m) 1
1
I 6.92
I 6.45
- ---------1------------------------------------- 1 1 EC
| (nnnhos/cm) 1 1
Well Pll
1 30/7/70
1 3/1/71
1 
1-
1 - 1
1
1
1
1 31/5/72
I 6.33
1 - 1
1
1 7/1/72
I 6.17
1 - 1
1
1 1/2/73
1 5.70
1 - 1
1
I 24/11/73
1 5.29
1 - 1
1
I 10/6/74
1 4.41
1 - 1
1
1 19/6/75
I 2.21
1 - 1
1
1 7/6/76
1 2.10
1 - 1
1
1 7/1/79
1 1.95
1 - 1
1
1 4/12/80
1 2.17
1 9.6 
I
1
1 25/5/81
1 1.47
1 9.0 CD
|
1 5/11/81 1
1 1.85 1
1 9.9 1 
| 1
r
1------------------------- ----------- 1--------------------------- ----------- 1--------------------
1 Well
1 Date
1
1
1 Water
I Location
1 Level (m)
1 EC
1 (mmhos/cm)
1
r
1
"T"
1 26/6/80
1
1 3.40
1
T
I Well AIP 1
1 -
1
1 4/12/80
1 3.50
1 6.3
I
1
I 25/5/81
1 3.00
1 7.2 (2)
1
1
1 4/11/81
1
1 2.56
1
1 6.0
1
1
I Well
r
| Location
1
1
1 Date
1
1
r
1 Water
1--------------------
1 EC
1 Level (m)
1
| (nunhos/cm)
1
I Well AIP 2
"T~
1 7/6/80
1
1 2.60
“T
1 -
1
1 4/12/80
1 1.55
1 0.90
1
1 25/5/80
1 0.59
1 0.95
1
1 4/11/81
1 0.92
1 1.00
1
1
1
1
-7-TABLE 3 (Continued)
r
---------1--------------------------- ----------- 1----------------------------
I Well
I Date
I Location                                   1
1
1
I Water
I Level (m)
1
------------ ,
I EC
| (mmhos/cm)
1
1
-------- 1
1 12/7/80
T
1 Well AIP 3
1 2.15
1
1 -
1
1 4/12/80
1 3.12
1 1.0
1
1 25/5/81
1 2.23
[ 0.9
1
1
1 5/11/81
1
1 1.76
1
1 0.94
1
1
I Well
1
I Date
| Location                                   1
1
| Well AIP 6 1
1 1 1
1
T
I 12/7/80
I 4/12/80
I 28/5/81
1 5/11/81
1
1
I Water 1 Level (m) 1
1
1 3.25 1 3.93 1 3.45 1 3.22 1
---------- 1
I EC | (mmhos/cm) 1
~r
i-
1 2.2
1 2.4
1 2.6
1
------------ !
1
-----------1
-----------1-------------------------------------
I Well
I Date
I Water
1 EC
I Location
1
1
I Level (m)
1 (mmhos/cm)
1
1
1
1
---------- 1
T
I AIP 8
I 12/7/80
1 2.40
1
1 -
1
I 4/12/80
1 2.14
1 0.60
1
I 26/5/81
1 2.18
1 0.66
1
1
1 5/11/81
1
1 2.15
1
1 0.62
1 1
r
I Well
-------- 1
I Date
1------------------------------------- )
| Location                                   1
1----------------------------- 1 Water
1 Level (m) 1
1
1 2.60
1 EC 1 (mmhos/cm)
|
|
1
r
I Well AIP 10
1
I 12/7/80
T  1   ~----------------------------------- I|
I-
1
1
I 7/12/80
1 3.05
1 5.0 
1
1
1 25/5/81
1 2.64
1 3.6 (3)
|
1
I
1 5/11/81
1
1 2.58
1
1 3.6 
|
!1
Notes
(1)
Groundwater
level
in 
open 
bore
was
2.70  m
and  EC   37.2
(2)
Groundwater
level
in 
open 
bore
was
2.89  m
and  EC   21 6
(3)
Groundwater
level
in 
open 
bore
was
2.66  tn 
and  EC    112FIGURE 2
1660m
ITALCONSULT
OBSERVATION WELL
No. P.llFIGURE 3
All dimensions in mm
AIP OBSERVATION WELL
10Evaporation figures, "E-Pen", range from a monthly mean of 170 mm in August to 
252 mm in June. The average mean evaporation is 196 mm.
5.       FIELD STUDIES
5.1 Methods and Equipment
Fifty-five sites were examined  in  the Melka Sadi area, and  forty  one of these were within  the Melka Sadi farm Area of 1  328  ha. This gave a density  of one site per 32 ha.
At each of the sites the following tests and observations were made:-
i)          Infiltration rate at the soil surface using 3 sets of double rings and a
10 cm head of water. Each test was run for at least 8 hours and values expressed in mm/hr.
ii)        Hydraulic conductivity (permeability) measurement within the dry soil profiles at 3 depths below the surface using the "pour in method”. These tests were run for at least 6 hours and results expressed in metres/day.
iii)       Hydraulic conductivity measurements within the soil profile below the water table using the "pump out method" and values were expressed in metres/day.
iv)       At each site a 5 metre deep auger bore was excavated and the soil profile described, with water levels and salinities being recorded.
v)         At 19 of the sites 2 m deep soil pits were excavated, described and sampled for laboratory analysis.
Equipment used in the study incuded:-
1        No        4 wheel drive vehicle
1        No        2 wheel water trailer (see note below)
3          No Sets double infiltration rings
4          No Graduated plastic 45 litre Jerrycans with taps
4 No Modified petrol engine carburettors and plastic pipes
1          No      10 cm Edelman auger heads
2          No      13 cm "Jarret" auger heads
2         No        10 cm Jarret type auger heads (local manufacture)
2         No        Edelman 6 cm augers
20 No 1 metre lengths of 3/4" galvanised pipe
2         No        Portable EC meters
The 4 wheel drive vehicle and water trailer was replaced in June by a 1 ton Mercedes truck fitted with a 1000 litre tank. Apart from a few times during heavy rain this proved ideal for the work.
The field studies were carried out by the soil salinity specialist, with part time assistance of the drainage engineer and a team of 3 labourers. Soil pits were excavated by sub-contract labour.
11 -5.2 Field Work Programme
The soil salinity specialist arrived on site on 11 February 1981.
Excavation of soil pits started on March 8, sampling of the pits was completed by 27 March and the samples sent to Addis Ababa for analysis at the Holetta Soils Laboratory of the Institute of Agricultural Research. Levelling of the observation wells was carried out by Project survey staff in February and March 1981.
Field testing of infiltration rates and soil permeability commenced on May 18 and was concluded at the end of September when field work was started at the
Amibara Extension area. The delay in starting the field studies was due to transport problems and to lack of equipment.
6.       SOILS OF THE STUDY AREA
Three principal soil groups were found in the Melka Sadi area. The first of these are the saline alluvia 1/colluvial soils found in the south east of the
area at the foot of the escarpment. These have variable textures, usually medium to coarse, with weathering tuffs and clays in the deep sub-soils.
The second soil group is the normally non-saline, medium and fine textured alluvium with stratified and laminated profiles on which the greater part of the Melka Sadi farm is established.
The third group, and the most wide spread in the Melka Sadi area as a whole are the fine textured vertisols of variable depth overlying stratified and often coarse textured alluviums. The vertisols vary in depth from a few centimetres to more than 3 metres in the north of the area. This soil group is limited to 
the north and western portion of the Melka Sadi farm.
All three soil groups are readily identified in the field by colour, texture, surface appearance and sometimes by the natural vegetation. Each of the groups is shown in Figure 4.
In addition there is alongside the Awash river a narrow strip of recent coarse textured alluvium, but very little of this is present within the proposed irrigation area.
Soil profile descriptions are shown in Annex 2 and results of soil analysis in Annex 3.
6.I Soil salinity
7
The levels of soil salinity  in  the presently  cultivated  land  at the Melka Sadi farm are generally  lower than  shown  by  Italconsult, this being  due to  leaching by  the applied  irrigation  water over time. However the salinity  levels in  the abandoned areas are now higher than shown in the Italconsult reports.
It would appear that leaching of soluble salts in the early stages of development were successful, but later the existing saline water tables rose,
met with the infiltrating irrigation water and saturated the soil profiles above Che water table. This resulted in an upward movement of soluble salts which was accelerated once the area was abandoned. Rainfall is insufficient to leach out
the salts.
12 -I
I
Figure 4
GENERALISED SOIL MAP OF MELKA-SADI FARM
After Italconsult 1969
01
fl
1
I
I
I
I 1
I
I
uvial
ne soil
Fine textured vertisols Recent Alluviums
13These abandoned areas have a damp surface crumb or crust (hygroscopic) overlying 
a deflocculated layer which is of very low permeability and up to 25 cm thick.
This layer prevents the entry of rainfall which together with spillage and 
runoff forms evaporation pans which have become progressively more saline.
A similar situation can be seen alongside many canals where typically seepage
through the bank causes the adjacent road to become damp with salts.
Consequently after rain its surface layers deflocculate, causing the road to 
become impassable to vehicles.
Abandoned       areas       together       with       other       areas       affected       by       salinity/high       water       tables are shown on Map 5.
6.2     Previous Mapping
The soil map produced by Italconsult in 1969 was found to be accurate as far as soil units mapped and general arrangement of the different horizons are described. However the present saline areas are now far more widespread than as mapped in the Italconsult report. (See Soil Unit 10, Saline and Alkaline soils) The report does not cover the water levels and salinities of the groundwater apart from a comment that soil unit 10 often had a fluctuating water table.
The frequent alteration of soil texture in unit 6, soils on recent alluvium, was also noted in the Italconsult report. This was found to be correct as large variations in soil texture were found in bores only 1 - 2 m apart. Unit 6 is the most widespread soil unit at the Melka Sadi farm.
6.3     Results of Soil Analysis
6.3.1               Electrical Conductivity Values (EC)
Measurement of the EC of a soil/water mixture gives a good indication of the total amount of ionized salts present in the soil. The amount of salt that comes into solution is dependent on the soil water ratio. EC measurement is best carried out with moisture contents in the field and as the testing routine is difficult to carry out the preferred method is to use a saturated extract.
The accepted interpretation of EC values of the saturated extract of a soil are as follows:-
EC of Saturated Extract
0  - 2               mmhos/cm
2  - 4               mmhos/cm
4   - 8               mmhos/cm
8  - 16             mmhos/cm
Crop Reaction
Effect
Yields
almost negligible
of sensitive crops may
be reduced
Yields      of many crops may be reduced
Only   a yields
Only a f
tolerant crop will give
> 16
mmhos/cm
few very tolerant crops
a reasonable yield The banana plant is of low salt tolerance and  reduction the EC of saturated extract is greater than 1.0 ^hos/cm ?
f , ■ ta
n
reasonable will give occur ifField electrical conductivity values were determined on a 1:1 soil/water mixture which due to the dilution of the soluble salts will give a different
conductivity to that of a saturated extract. A general guide for comparing 1:1 soil water EC with saturated extract is to multiply the 1:1 results by a factor of 2.0.
By checking the EC of infiltration sites before and after the test an indication of the leaching effect can be obtained. Results below show that the EC of the 1:1 soil/water mixture in the top 25 cm of the soil profile was reduced after
8 hrs as follows:-
SITE
EC 1:1
EC AFTER
(Top 25 cm)
(mmhos/cm)
INFILTRATION
(Top 25 cm)
(mmhos/cm)
DRH 6
10.2
6.8
DRH 23
6.5
3.1
DRH 21
3.7
1.6
AIP 10
2.1
0.46
DRH 24
6.6
5.6
DRH 5
8.7
3.2
DRH 7
8.4
5.3
Average EC values of saturated extract for the Melka Sadi area are shown below:-
SOIL
LEVEL
AVERAGE EC
RANGE OF EC VALUES
(mmhos/cm)
(mmhos/cm)
Topsoils
2.24
6.0 - 0.98
Upper subsoils
2.94
Subsoils
8.5 - 0.72
3.12
8.1 - 0.16
Deep sub-soils
3.22
(> 150 cm deep)
High  EC values were found  during field tests on the top-soils of the abandoned
9.5 - 0.68
areas, for example at DRH 3  - 10  cm depth. High  EC clays, as measured  within as 60 mmhos/cm, as can be
2 where the EC of the top soil was 22.0 mmhos/cm at values were also found in the weathered tuffs and the 5 m deep bores. At one site its value was as high seen from an inspection of Table 2.
The results of chemical anlayses are shown in Annex 3.
6.3.2             Exchangeable Sodium Percentage (ESP)
A high concentration of exchangeable sodium causes break down of the soil structure, which results in reduced permeability, aeration and workability. The amount of exchangeable sodium present is expressed as ESP which is determined from the extracted cations less soluble cations to give the sodium absorbtion ratio, SAR, which may be determined as follows:-i
SAR = Na Exchangeable
Ca ♦ Mg
2
ESP may then be found from the relationship:
ESP =         100 (-0.0125               0,01475 SAR)
1+     (-0.0126 ♦ 0.01475 SAR)
An ESP figure of 15 or less is considered acceptable for a non-alkaline soil, although higher ESP values can be tolerated if the soil is a fine textured 
vertisol such as those found in the north of the Melka Sadi area. A high value
for exchangeable sodium can have an effect on plant growth and some authorities quote a figure of 3 mi 1li-equivalents of exchangeable sodium per 100 g soil as the upper limit of a non-alkaline soil. ESP values for the Melka Sadi area are given below:-
ESP VALUES OF NON SALINE NON ALKALINE SOILS (EC less than 4.0 mmhos/cm and ESP less than 15)
SOIL LEVEL
ESP
Topsoils
2.76
Upper sub-soils
4.36
Subsoils
4.36
Deep sub-soils
4.68
(greater than 150 cm deep)
ESP VALUES FOR SALINE  ALKALINE SOILS (EC greater than 4.0 mmhos and ESP greater than 15)
SOIL LEVEL
Topsoils Upper Sub-soils
sub-soils
ESP
7.13 12.70 24.20 
Deep sub-soils 38.65
(greater than 150 cm deep)
The high ESP values in the deep sub-soils are generally associated with weathering tuffs and clays, as are the high EC values mentioned above.
6.3.3              pH Values (Saturated Extract)
The average pH values for all samples was 7.55 with the range between 7.15 and 9.6.
A pH value greater than 8.5 is generally regarded as indicating an ESP greater than 15. High pH values coincided with high ESP values.
16 -6.3.4              Soluble Anions
Traces of SO4 were present in half the samples, and of the remainder high, and 
often very high values of SO4 were obtained indicating the presence of gypsum
(CaS04), an important factor associated with high sodium levels. In many cases
high levels of SO4 were present in the samples with large amounts of
exchangeable sodium.
7.       HYDRAULIC CONDUCTIVITY
7.1 Pour in Tests
Pour     in     tests     following     the     USBT     method,     were     carried     out     in     soil     profiles     above the water table, usually at 3 depths below ground surface. Viz: 0-60 cm,
60 - 120 cm and 120 - 180 cm.
Each  test section  was 60  cm deep  and  5  cm radius giving  a wetted  area of 1963  sq cm. When  swelling  clays (vertisols) or loose sands were encountered  a filler of gravel or volcanic ash was placed in the hole prior to the test.
Tests were run for a minimum of 6 hours to ensure that the surrounding soil
envelope was saturated. Water used in the test was taken from an adjacent canal
or from the main canal within the farm area. Results were expressed in 
metres/day and are reproduced in Table 4.
7.2      Pump out Tests
Pump out tests, following the ’’Auger hole method" of Hooghoudt et al, were made
on the soil profiles below the water table. Owing to the laminated variable
textures of many profiles wide variations in results were obtained from site to 
site. Where sightly confined water was found in coarse textured aquifers,
particularly high values were recorded. Results are again reproduced in 
Table 4.
7.3      Infiltration tests
Infiltration tests using 3 sets of double rings per site and a water depth of
10 cm were run for a minimum of 8 hours. At many sites the rings were set in by 
hand but at others it was necessary to use a hydraulic jack springing from the
back of a vehicle to drive the rings into the soil. On the finer textured soils
with a strong deep cracking pattern initial wetting of the soil was prolonged to 
allow the clay to swell sufficiently to hold water in the rings. The mean of
the results from each of the three rings was calculated and is reproduced for
each site in Table 4.
8.       WATER QUALITY
The quality of irrigation water is dependent on the total salt content
(particularly sodium), its nature, the ratio of sodium to the other cations, and 
the ratio of calcium and magnesium to bicarbonates.
Total      salt      content      is      related      to      electrical      conductivity.      A      typical      value      of      EC recorded at Melka Sadi Farm was 0.28 ramhos/cm corresponding to 160 ppm salts.TABLE 4 Results of Hydraulic Conductivity and
Infiltration Tests 1. POUR IN TESTS
|      Hydraulic      Conductivity      "K"      (m/day) I
| Depth below ground level
i 60 - 120 cm I 120 - 180 cm I
I
I
| Infiltration (m/day)
1I
’I
1 0.34
1 -
I
DRH
DRH
DRH
DRH
DRH
1
2
3
4
6
0.048
0.059
0.09
0.041 
0.063 
0.134 
0.120
0.098 
0.15 
0.09 
0.197 
0.156 
0.103 
0.096 
0.21
0.078 
0.11
0.031 
0.09 
0.154 
0.081
0.17 
0.0072 
0.067 
0.137 
0.065 
0.014 
0.114
0.116
I
| _
I
0.016
1 0.63
I
0.50
1 0.13
1 0.14
I
0.096
0.033
0.03
0.190
0.180
0.40
0.10
0.194 
0.10
0.11
0.085
0.054
0.231 
0.09
0.11
0.0024
0.018
0.09
0.041
0.0156
0.06
0.019
0.103
0.054
0.067
0.109
0.194
I
DRH 7
0.25
1 0.73
I
DRH
DRH
DRH
20
21
22
0.102
I 0.31
I
0.144
1 0.72
I
I 0.42
I
DRH 23
0.028
1 0.61
I
DRH 24
0.43
1 0.50
I
DRH 25
1 0.78
I
DRH
DRH
DRH
DRH
DRH
DRH
DRH
DRH
DRH
DRH
DRH
DRH
DRH
DRH
DRH
DRH
DRH
DRH
DRH
DRH
DRH
DRH
DRH
DRH
DRH
DRH
DRH
Pll
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
44
45
46
47
48
49
50
51
52
53
0.07
0.122
1 0.64
I
0.0337
I 0.60
I
I
0.108
1 0.54
0.083
1 0.75
I
0.12
1 0.30
I
0.036
1 0.43
I
0.0024
I 0.10
I
0.04
1 0.35
I
0.3217
1 0.57
I
0.039
1 0.71
I
0.072
I 0.08
I
0.072
1 0.53
I
-
1 0.53
I
-
I 0.53
I
0.08
-
1 0.69
I
-
1 0.96
I
0.06
0.103 
0.0296 
0.118
0.02
0.061
0.0346
0.083
0.130
0.06
0.09
1 1.71
I
-
I 1.86
I
0.06
1 -
I
0.102
0.062
-
1 1-18
I
0.052
1 0.69
I
0.063
1 0.61
I
0.045
0.216,0.212
0.120
0.033
0.06
-
1 0.33
I
I
-
1 0.50
-
1 0.58
I
0.072
1 1.75
I
0.08
1 0.04
I
I
- 18 -TABLE 4 (Continued)
2. PUMP OUT TESTS
I Depth SITE |            (m)
DRH 1 1 2.52 DRH 2 1 2.23 DRH 4 1 3.41 DRH 20 1 4.05 DRH 20 1 4.89 DRH 21 1 3.79 DRH 23 1 1.78 DRH 23 1 1.83
DRH 24    1 2.32
DRH 24    1 2.36
DRH 25    1 2.58
DRH 28    1 3.00
DRH 30    1 3.03
DRH 32    1 3.70
DRH 32 1 4.10 DRH 33 1 3.75 DRH 34 1 7.31 DRH 34 1 7.52
DRH 35    1 2.35
DRH 37    1 1.73
DRH 39    1 0.85
DRH 40    1 1.0
DRH 40    1 1.07
DRH 41    1 1.35
DRH 41    1 1.64
DRH 42 1 1.35 DRH 45 1 1.64
DRH 46    1 3.46
DRH 47    1 2.75
DRH 48    1 1.86
DRH 48 1 2.75 DRH 51 1 1.08 DRH 54 1 1.90
1
I Hydraulic Conductivity "K" I (m/day)
I 2.37
I 0.884
I 0.969
I     0.0379 I      0.0326 I     0.9915 I 0.198
I 0.154
I 4.30
I 1.46
I 4.43
I 0.4
I     1.62 
I 2.23
I 1.35
I 0.874
I 0.171
I     0.924 I 5.0
I 0.837 I 0.683 I 1.44
I     1.87 I 0.28
I 2.90
I 10.5
I 4.85
I 0.358
I     2.41 
I 1.62
I 0.065
I 0.406
I 0.89
I Infiltration
I (m/day)
I
I
I
I
I   0.63 I 0.43
I-
I   0.31 I   0.42 I-
I 0.61
I-
I   0.50 
I   0.60 
I   0.76 
I   0.43 I-
I   0.10 I   0.35 I-
I   0.57 I   0.08 I   0.53 
I   1.10 
I 0.69
I   0.96 
I 1.86
I-
I   1.18 I 0.69
I-
I 0.50
I
I
19 -Sodium percentage is the percentage of sodium cations in the total cations
expressed in milli-equivalents per litre. Residual sodium bicarbonate is
carbonate CO3 plus bicarbonate HCO3 less the calcium plus magnesium all
expressed in Meq/litre.
The water from the Awash river varies in quality throughout the year. During 
periods of low flows there is usually an increase in disolved salts and thus a
lowering in quality. The USDA guide for water quality shows the Awash water to 
be of CjS} quality meaning low sodium, low salinity hazard, but during low flows
the quality may drop to CjS2, which indicates low sodium hazard but medium
salinity hazard.
Both sodium percentages and amounts of residual sodium bicarbonate are below
those required for first quality water, the upper limits for which are 6.5Z and 
1.25 Mg/litre respectively.
Nevertheless it must be stated that water of first quality contains soluble
salts in appreciable quantities. Water containing 200 ppm of disolved salts, a
concentration related to an EC of 0.35 mmhos/cm, will add 200 kg of salt to each 
hectare each year when the water is applied at the rate of 1 m per year.
Results of the analysis carried out on Awash river water are shown in Table 5.
9.    ALKALINITY HAZARD
Irrigation water with a high concentration of both carbonates and bi-carbonates
usually precipitates insoluble calcium and magnesium carbonates in the soil and 
thus the relative proportion of sodium in the soil water is increased. Some of
the sodium will be absorbed into the soil colloids which will affect the
physical structure of the soil, reducing its permeability and creating a high 
level of sodium in the soil which in turn is toxic to plants.
In Sir William Halcrow & Partners* Hydropedological Report, dated 1975, two 
waters were selected on the basis of highest SAR values, one of which was that
for Melka Sadi having a SAR of 2.0. The expected SAR of the drainage water was
then calculated using various values for the leaching requirement.
The      results      obtained      indicated      that      there      is      not      likely      to      be      an      alkalinity hazard      unless      the      amount      of      water      percolating      below      the      rootzone      is      reduced      to less     than     5Z     of     the     applied     water,     taking     the     critical     level     of     the     SAR     of     the drainage      water      as      15.      At      Melka      Sadi      farm      deep      percolation      losses      are      expected to     be     in     the     range     of     15     -     20Z     and     thus     the     problem     of     excessive     quantities     of exchangeable sodium in the soil colloid complex is not expected.
10.    SALINITY HAZARD
Irrigation waters contain dissolved salts and these must be removed or reduced in the rooting zone before they can built up to a level harmful to the crop,
each of which has its own level of tolerance. Such removal can prove difficult if there is a shallow saline water table present.
During the irrigation season each water application moves under the influence of gravity down into the soil carrying dissolved salts and further salts from the
soil itself. When irrigation stops there is an upward capillary rise of water and dissolved salts towards the soil surface. If there is a shallow water table the upward capillary movement is maintained from that water table also
- 20containing dissolved salts, leading to increasing amounts of salts deposited at or near the surface of the soil. This is generally referred to as secondary salinisation.
If there is a large volume of water passing through the soil and the water table can be kept at a suitable level by drainage then there is little risk of build 
up of salt in the soil profile. However irrigation water is usually limited and the adopted drainage system will be dictated partly by cost, partly by the amount of land lost to drains, (particularly where a surface drainage system is used), and partly by the physical condition of the soils. Hence several factors may dictate the depth or effectiveness of the drains and a compromise often has to be arrived at which will allow the water table to be controlled at an acceptable depth and the dissolved salt content of the soil water kept below the tolerance limit of the crop.
In order to ensure the removal of the dissolved salts from the soil profile into the drainage system a proportion of the irrigation water must move through the soil to the drains. This proportion is referred to as the leaching requirement and is usually expressed as a percentage of the total applied irrigation water together with any effective rainfall amounts.
The leaching requirement (LR q) is determined by the following equation:-
E
lr EC                  ECjw        x     1 ECdw f
Where EC£W ECdw
is the EC
is the EC
of
of
the irrigation water,
the water below the root zone,
and f is the leaching efficiency
Leaching efficiency is dependent on a uniform movement of water through the soil profile. The medium to light textured soils of the Melka Sadi farm are expected 
to have a leaching efficiency around 0.6, while the fine textured cracking clays
will have a lower value around 0.4 as a result of the concentration of water in 
the cracks causing uneven water distribution in the soil profile.
With a value for EC£W of 0.28 mmhos/cm, a value for ECdw of 4.0 mmhos/cm and an efficiency factor of 0.6, the leaching requirement will be:-
LRec =
0-28 x               1 
s 11.72 of the applied water
4.0 
0.6
The calculated water requirement for banana at Melka Sadi farm is 10 cm applied every fifteen days and allows for a leaching requirement of 10Z.
The fine textured soils have a lower leaching efficiency factor of 0.4 and their leaching requirement will be:-
LRgc “               0*28 4
x
0.4
=     17.5Z
This higher requirement on the fine textured soils is the same as the calculated field percolation losses, assuming an irrigation efficiency of 652
22By growing a more salt tolerant crop such as cotton, the ECjw can be raised to 12.0 mmhos/cm, giving a LRgQ of:-
0.28              x            1                  = 5.82
12 
0.4
This is considerably less than the calculated field percolation losses of 17.5Z.
11.     RECLAMATION OF SALINE SOILS
It is recommended that the water table within the Melka Sadi farm be lowered by means of a sub-surface drainage system as described in Part A, Section II of
this report, and that full scale development of the drainage network be preceded by trials on pilot areas in order to confirm or revise the proposed designs.
Permanent reclamation of saline - alkaline soils requires four essential steps
and the attainment of four basic conditions. These are:-
1.       Lowering of the water table
2.       Satisfactory infiltration and permeability
3.       Removal of excess salts by leaching
4.       Careful soil and water management
The minimum water table depth required for leaching is dependent on the crop and the irrigation system being used. For Melka Sadi farm, where banana is
irrigated by the application of 10 cm of water once every 15 days throughout the year, the minimum water table depth below ground level required is 1.8 m.
The infiltration and permeability rates recorded are satisfactory and at present
a reduction of permeability during and after leaching is not expected. Nevertheless soil permeability should be monitored during the drainage and leaching trials.
Removal of excess salts requires large amounts of water to be applied during the initial stages. The present water distribution system at Melka Sadi farm is considered capable of supplying this water in addition to that for normal irrigation needs.
Careful management of the leached land is required to maintain a satisfactory salt balance, to ensure that there is no over watering to overload the drainage system and consequently raise the water table, and to avoid leaching out plant nutrients, while at the same time sufficient water for crop growth must be provided.
The characteristics of the banana plant related to the problems of salinity and drainage are as follows:-
(a)     Root System
The vertical rooting of the banana plant is between 65 and 75 cm in depth. The roots of a vegetatively propogated plant are adventitious roots and upwards of 40 cm are produced by each plant, spreading laterally to some 4.5 metres. The majority of these roots are found in the top 75-65 cm of the soil profileforming a dense mat.
(b)       pH and Salinity (soluble salts)
Banana will tolerate a wide range of soil reaction, between about pH 4.5 and 
8.0, but outside the range of pH 6.0-7.2 some problems of nutrient absorption can be expected. The average pH at the Melka Sadi farm is 7.0.
Soluble salts in excess of 500 ppm are toxic to the banana plant. This level approximately corresponds to an EC value of 0.78 mmhos/cm. The EC of the irrigation supply is normally in the range 0.2-0.3 mmhos/cm which corresponds to soluble salts of around 190 ppm. The difference between the EC of the
irrigation supply and the toxic level is therefore small and it is vital to keep 
the soluble salt content below the 500 ppm level, particularly in the top 
60-75 cm of the soil profile.
(c)       Water Requirements
The ideal water requirement would be 2.5 cm of rainfall per week throughout the year, which is equivalent to 1.3 m per annum. This would ensure uniform growth which is important if high yields are to be obtained. The proposed water application is 10 cm every 15 days, which is equivalent to 2.43 metres per annum and allows for a 10Z leaching requirement, assuming a 65Z irrigation 
efficiency.
It is recommended that the drainage trials be carried out initially on some 15Z of the saline area within the Melka Sadi farm and the loction of this first area is described in section II following. Section II also includes recommendations for improvement of drainage in the remainder of the farm area.PART A (CONTINUED)
The existing drainage system of the Melka Sadi farm area has proved inadequate, and the implementation of a drainage programme is now required to lower the water table and reverse the soil salinity build-up by leaching. A high water
table will not necessarily prevent the area from being productive since shallow- rooted crops can generally be grown, but indications from Section I of this report are that salinity levels are likely to rise further and a continued 
increase in salinity will inevitably lead to severe restrictions on the land 
use.
A system of drainage based on the results of the field studies described in Section I has been determined and is outlined below. A suggested programme for implementation of the work has also been prepared together with an estimate of costs and likely benefits arising from increased crop yields.
2.    DRAINAGE REQUIREMENTS
The present main crop in the Melka Sadi area is banana, which is a moderately deep rooted plant with roots extending down to about 1.2m. Of the other crops likely to be grown, the deep-rooted ones such as alfalfa, cotton, maize and sorghum, have roots extending to about 1.8 m.
So as not to preclude the growing of these crops, drainage design has been considered on the basis of lowering the water table to a depth of 1.8 m where possible. However where the permeable soil layer is shallow and drain spacing to obtain a water table at this depth would be very close, design has been based on drawing the water table down to 1.5 m depth. The area so affected comprises some 25Z of the irrigated area.
After each application of irrigation water, the water table rises within the
soil to a level dependant on the amount of deep percolation and the porosity of the soil. The acceptable limit for this rise has been set at 0.3 m and thus the minimum depth to the water table is 1.5 m. (1.2 m in areas of shallow permeable soil).
In order to remove the salts in the soil within the rooting zone, sufficient
water has to be applied at the surface such that deep percolation is adequate
for this leaching requirement.
The minimum amounts for leaching on clay and medium textured soils have been determined to be 10Z and 17.5Z of field application respectively. Since losses to deep percolation for furrow and basin irrigation (as practised at Amibara)
are estimated to be 20Z and 25Z of field application respectively, the leaching requirements are more than satisfied.
3.       DRAINABLE EXCESS
The drainable excess within the area (other than rainfall runoff) comprises seepage losses from the canals, percolation losses from the fields and surface runoff.The peak gross field application is 100 mm every 15 days for bananas. This represents 70Z of the diverted water into the area, some 20Z having been lost by seepage from distribution channels, 10Z by spillage onto banks and evaporation. The seepage losses are (100 x 20)/70 = 28.5 mm per irrigation.
In-field losses to deep percolation amount to 25Z of the irrigation application for basin irrigation, and for an application of 100 ram some 25 ram per irrigation is to be drained.
Surface runoff losses are 10Z of field application, or 10 mm per
4.        DRAIN SPACING EQUATIONS
The various methods of calculating drain spacing from details of the soils characteristics fall into two main categories - steady-state and non steady state. Since the time interval between each irrigation application is large,
the method chosen for the calculations is the non steady-state type by Glover Dumm^ where the water table is assumed to reach the highest permitted level immediately preceding the subsequent irrigation. The formula is:-
irrigation.
=         /Kd t\ *
<7-) *   ( )
/in 1.16 ho\
where L       35           drain spacing (m)
K
35
hydraulic conductivity of the soil (m/day)
d
modified value of the depth from the drain water level to the
impervious layer from Hooghoudt^ (m)
soil porosity (expressed as a decimal)
ho
S
maximum height of water table above drain water level
(tn)
t
and d
=          desired     height     of     water     table     above     drain     water     level t days (m)
15 days
after time
SD
1  ♦  8D  In  D
Lu
where D actual depth  from drain  water level to  the impervious layer (m)
u
S
wetted perimeter of the drain (open drains) (m)
or
u
1fr0 where r
0 is effective radius (pipe drains) (m)
ILRI Publication No 16 "Drainage Principles and Applications"5 DATA FROM FIELD OBSERVATIONS
The measured values of hydraulic conductivity (K, expressed in m/day) of the soils essentially split the area into five parts as shown on Figure 5. tor the purpose of the drain spacing calculations, K values of 0.4, 0.8, 1.85 and 2.5 m/day have been used (the 1.8 and 1.9 areas being taken together with average K of 1.85).
The depth (D) from designed drain water level to the impervious layer is calculated from the difference between observed permeable soil depth and required drain depth. Contours of depth to the relatively impermeable layer are plotted on Figure 5.
Although not directly measured, the porosity can be deduced from the hydraulic conductivity of the soil from the general relationship according to the USBR2.
Since sand layers form part of the soil mass where greater values of hydraulic conductivity have been observed, porosity of these soils has been taken to be less than that indicated by the USBR and the rate of increase of porosity with hydraulic conductivity has conservatively been estimated at half that given. The values used are listed below:
K
(m/day)
(uIbr)
(used in calculations)
0.4
0.08
0.08
0.8
0.12
0.10
1.85
0.16
0.12
2.5
0.18
0.14
6. FIELD DRAIN DESIGN
The in-field drainage requirement has been shown to be 25 mm for each irrigation application. For this depth of recharge to the water table, field drain 
spacings for each value of K were found to be most significantly affected by the depth of permeable soil for a given water table, and hence drain depth. From
the large range of spacings and depths possible, a compromise was decided upon for each area of hydraulic conductivity with a total of 8 different types of
drains being required. These are listed in Table 6 as options for open or tile drains and the areas to which the type numbers refer are shown on Figures 5 and 7. The northern area (9) shown on Figure 5 as ’Not drainable at present1 lies below the 739.75 contour as shown on Figure 6 and was found to be too low relative to the expected level of water (from irrigation losses) in the primary drain as it exists. Deepening and widening of this drain from the Melka Sadi area for some considerable distance would be necessary before it would be possible to drain this area (9) adequately, unless of course pumping is later considered to be a practicable option.
2 USBR - Drainage Manual. Figure 2.5 ’’Curve showing general relationship between specific yield and hydraulic conductivity”.Sir William Halcrow B Partneri.
.. X.
•***
V.,1
. :7S0C
-:.p> 740 20
741 10 741 SO
awash R|V
LEGENO
, 0 Contours of depth to ✓  'Jmperwlout layer
u
• ■■Soil permeability (K)boundary Boundary between oreas with
dram of different types.
> E                DRAIN            DRAIN
DEPTH
SPACING
1
2.3m
90m
2
3
4
2 3m
50m
2 3m
75m
MELKA SADI FARM
2.3m
35m
5
6
7
6
2.0m                20m
2 0m                30m
2.0m                35m
2.3m              4 5m
9       Not drainable      at present
GOVERNMENT OF ETHIOPIA AWASH VALLEY D EVE LOPME NT AGENCY AMIBARA IRRIGATION PROJECT H
IN-FIELD DRAINAGE REQUIREMENTS
/
0                 0 5                 10 I__________ I__________I
Km
Scale
C
«» -sesEBEjeseeCR H H
□ WA q| -IFIGURE 6
Sir William Holcrow B Portners
'T'.'f.r
•- • *•               —ttF IGUKt
oicrow a PartnersTABLE 6
FIELD DRAIN DETAILS COMPARISON OF OPEN AND TILE DRAIN REQUIREMENTS
1 1
1 Hydraulic
1 Conductivity 1
1
1-------------------- 1
1 Depth to            | I Impervious 1
1 Layer
1 Depth to 1 water table 1
1
1
1 Drain I Spacini 1
1
“1----------------------------------- 1 Open Drain Option 
?1
1
1 Depth to              Bed 
1 Pipe Drain Option
I Design             Min 1
Side
T~ 1
1------------------- 1
1 Pipe        Gravel              Depth to
1 
| (m/day)
1
r
1
1 l.t*
1
1 (m)
1
1
1 (m)
1
1 
1 
1
T
(m)
1
1 (m)
1
“T"
I invert
1 (m)
1
width
(m)
Slope
(m)
I Diam 1 (m)
1
Surround
(m)
1---------- 1 1
1  Drain I
1  Type I
1 + 1
invert
Pipe
of
(m)
1
1 0.4
1
1
1
1
2.5    1 1.5 
11
1 
1
1.2 
r
1 20
1
1 2.0
1
1 2.3
1
Nil
1.5:1
1
1 0.1
1 1
1 1
1 1
1-------
-1
0.175
1.9
1 5 
1 1 
11 |
1 0.4 
i
1
1  g.e.* 
I
1
2.5 1 1.8
1
1 1
11
.5
1 35
1
Nil
1.5:1
1 0.1
1
0.175
2.2
1 4 
1 1 
|
11
I 0.8
1  l.t
i
3.0 1 1.5
1
1
1 1
.2
1 35
1
1 12.0
Nil
1.5:1
1 0.1
1
0.175
1.9
1 8 
1
11
1 1 
|
11
1 0.8 1
I 1.85 1
I 1.85
1 g.e.
i
1
1     l.t. i
1
3.0 1 1 1.8 l
1 
1 1
1   1.5 I 1 45              1 2.3                       Nil
i1
0.175
2.2                 1 7 1 
|
1
1 1
3.0 I 1.8
I
1   1.5 1 1 50              1 2.3 1           1
0.25                  2.25
1 2 i1
i
I   3.0   to  4.0 I  1 1.8
i
1
1 g.e. i
1 1 l.t.
i
1
4.0 1 1 1.8 I
1
1   1.5 1 1 75
1
I 1.85 1
1 2.5 1
1 2.5 1
I
I
1
I 2.3 j
1   1.5 1    90              1 2.3
1.5:1  1 0.1
1
1.5:1  1 0.15 |
1.5:1  1  0.15 |
1.5:1  I 0.15 |
1.5:1  1 0.15 |
1.5:1  1 0.15 1
0.25 2.25
0.25 2.25
I
1           1
i
2.5 1 1 1.5 ii
1
2.5 1 1.8
1 1.2 I       30 1           1
1           1
1
1
1 2.0 1
0.3
0.3
0.3
0.3
0.3
0.25
1.95
1 3         | 1          1
1 1 1
1 1
1 6 | 1 1
1 g.e. 1
1   1.5 1    50              1 2.3
1
1           1
1
0.25                  2.25               1 2         I 1            1
*1. t. g.e.
less than
greater than or equal to
Refer also to Figure 5Table 6  lists design  data for the alternatives of adopting  either tile drains or open  drains. The advantages and  disadvantages of each  type may  be summarised  as follows:-
(a) Advantages of Tile Drains
-               Considerably     less     irrigable     area     would     be     taken     up     by     the     presence     of permanent drainage works,
-               Maintenance     would     be     less     costly     as     there     would     be     no     requirement     for continual excavation of accumulated silt and weed from open drains,
Tile drains would not be in danger of becoming clogged with wind-bourne debris as would open drains
Difficulties of access throughout the area would not be compounded
Tile drains would be cheaper to install
The programmed time for completion of the works would be considerably shorter.
(b) Advantages of Open Drains
There would be no need to import sophisticated pipe laying equipment
There may be difficulties in effecting timely fabrication of tiles and procurement of filter material.
Consideration has been given to each alternative and cost estimates and a programme prepared for both tile and open drains. The results of these studies
have concluded quite clearly in favour of the use of tile drains for the
in-field drains and also perimeter block drains where none are already existing. Where however open collectors are already in existance it would be preferable to form the block drains by enlarging them into deep open drains to carry the required discharge.
A decision on whether to proceed with tile drains or revert to a system of open drains, perhaps only for the perimeter block drains, could always be made after
the success of the initial phases has been proved, but it is thought that the
need to make such a change will not be necesary and with present knowledge would not be recommended.
7 INTERCEPTOR DRAINS
Conveyance losses have been shown to be some 28.5 mm per irrigation at a field application rate of 100 mm each 15 days. It has been calculated that this would amount to a total of 100 1/sec for a typical 10 ha field, which would normally be drained by percolation to the in-field drains, particularly where these are closely spaced. However, for the wider spaced drains, interceptor drains constructed parallel to the canals at about 30 m from the canal centre line
might be necessary, especially in areas of steeper ground slope where the depth to the impervious layer is not great. The eastern area of Phase I adjacent to drain SD2 as shown on Figure 6 is, by inspection, an area where problems may occur. It is recommended that the water table be monitored in a number of areas after the construction of drains in Phase I and action taken as necessary shouldinterceptor drains be found to be required.
8         BLOCK DRAINS
Block drains are required to convey percolation and run off losses away from the fields. It has been assumed that the irrigation losses by surface runoff of 10 mm per irrigation are drained in 24 hours at an average rate of 0.4 mm/hr, and for a typical 10 ha block this would amount to some 12 1/s. Total block drain capacity for 10 ha would be about 16 1/s, and an adequate design for open drains would be depth 2.15 m or 2.45 m to suit in-field drains, bed width 0.5 m and minimum bed slope 0.00015. The depth of flow for this design would be of the order of 0.2 m as for the in-field drains.
Where the block drains are constructed from tiles the pipe diameter and bed slope would have to be capable of discharging the sums of the flows from each field drain entering upstream. Requirements for slope and diameter should be calculated again assuming a total capacity of 16 1/sec at the downstream end of a 10 ha field. The locations of each type of block drain are shown on 
Figure 6.
9        COLLECTOR DRAIN DESIGN
The overall losses each 15 days are field application losses of 25 mm and conveyance losses of 28.5 mm, and for the irrigated area of approximately 1000 ha (excluding the northern area), amount to some 0.5 m /s. Drain SD1 has been 
3
designed for a flow of 0.4 m /s and drain SD2 for 0.1 m /s at their lower ends.
3
3
Outflow from the area is limited  by  the capacity  of the Primary  Drain, and  it has been  calculated  that the depth  of flow in  this drain  is 0.58  m for a flow rate of 0.5  m3/s. It has been  assumed  that no  significant backing  up  effects occur as a result of drainage of areas downstreeam of the Melka Sadi farm.
This depth of flow effectively limits the drainable area to land lying above the
739.75 m contour. Since the ground slope through which the Primary Drain flows
is small, considerable enlarging of the drain for a distance of several
kilometres would be necessary before affecting the drain water level, and it is
not considered that this would be cost effective at this time. It is
recommended that alterations to the Primary Drain be carried out as part of the
normal maintenance programme.
Figures     9     and     10     show     the     longitudinal     sections     of     the     collector     drains     for     the area and typical cross sections of drain SD2.L
9
9
9
9
9
9
I fe n
H
II h
n
n
iFIGURE 8
SECTION A-A
Scale 1: 50
SECTION B-B
Scale 1:50
Field canal
(SHOWING TYPE 8 DRAINS WITHIN 10 ha FIELD )
Scale 1:2000
34
— —- -Idrain sdi-longitudinal section
drain SD2-longitudinal section
f 745
ED
WAGE Km’
GROUND
LEVEL
r---------------- —
WIDTH 0 7m
CHAIN AGE Km°
h-
-------   -------
9                             o                             o ®
SIDE SLOPES 1 5h Iv, B
F|
SLIDE SLOPES 5h: lv,
BED WIDTH I Om
SLIOE   SLOPES   2h;lv, BED WIDTH 4m
K
[ground         9
LEVEL              5
8
m 4
•0
-9l------------- v
*
lOLSlGNwYRm LEVEL    FOR    * IRRIGATION     $
| LOSS ONLY b-
: F»
b.
*1
♦
fM
g
n
8
utijiUN WTRo LEVEL  FOR <* IRRIGATION £ LOSS 0M.Y *
o
------------- £
in
s
d»
K
-----------------------t 3
«
§
r
REVISED *
BED LEVEL j
h.
1------------------------
b-
—5
(revised £ bed LEVEL <m!
__________________
u>
01
3
<
<n
N
A
-
b-
o
®
*>
h-
existing ffl
OG.L 742 50
r
EXISTING DRAIN SECTION
EXISTING FFL
REVISED FFL
VISED
OG L 739 79
-existing
DRAIN SECTION
-------  SECTION
GOVERNMENT OF ETHIOPIA
AWASH VALLEY
DEVELOPMENT AGENCY
AMI0ARA IRRIGATION
PROJECT H DRAWS S0I.SD2-L0NG SECTIONS
DRAINS S02-CROSS SECTIONS
REVISED DRAIN SECTION
Km 1+400
DRAIN SD2 - CROSS SECTIONS
/3764
t900
T——
Z06EZSir Williom Holcrow 6 Porlners.
DRAIN TD2
NOTE:
For   local   ion   of   these drains see Figure 2
GOVERNMENT OF ETHIOPIA AWASH VALLEY DEVELOPMENT AGENCY AMIBARA IRRIGATION PROJECT II
LONGITUDINAL SECTIONS OF DRAINS T.D.I, TD2, T.D3.T.D.4, 8 TD.5.10 PHASING OF CONSTRUCTION
The area has been  split into  five phases for construction  of the drainage system as shown  on  Figure 6. Each  phase represents approximately  one fifth  of the work involved  in  construction, and  is ordered  such  that the relative cost per hectare of construction increases from phase 1 to phase 5 as shown below.-
~1
Phase
Area to be
Drained
1 
I Estimated Cost I Notes
I per hectare
1 (Birr)
1
1
1
1
1
2
3
4
5
210 ha
1 2,200
1
219 ha 1 2,350
I
252 ha I 2,420
i
l
192 ha 1 2,890
1
1
145 ha
1 3,400
1
“T
1 -
i
1
1       Not       including       non-saline       area
I
I Not including non-saline area
l|
1 Not including lucerne area
I
1
1 Not including pasture area
1
The programme recommended for construction of the works is shown in Figure 11, from which it can be seen that the activity limiting rapid progress is the enlargement of the existing open collector and secondary drains. It is intended that excavation will take place using one back-acting hydraulic excavator working either double shift, or single shift supplemented by a team engaged on excavation by hand, throughout the full three year period of implementation.
It is further recommended that a pilot drainage area be established first in the area shown on Figure 7. The purpose of this pilot area will be twofold.
Firstly it will be necessary to verify the assumptions used as a basis for the designs described in this report. The soil parameters on which these designs
are based were of necessity determined from relatively small volumes of soil in the auger hole method, and consequently it would be sensible to make use of the pilot plots to verify the assumptions made. Modifications to the design of
future phases could then be made if necessary.
The second point concerns the programme shown on Figure 11. Rather than awaiting delivery of suitable tile laying equipment before commencing the works it would be preferable to commence right away using alternative equipment, and it would be advantageous to install the field drains in a clearly defined area where development costs are least. The tile drains could be laid using a
back-acting hydraulic excavator perhaps trailing a travelling shutter to support the walls of the excavation. In this way the need for a sophisticated tile laying machine, which although thought at present to be essential and is included in the programme and cost estimates, could be confirmed.
A schedule of equipment required for the trials on the pilot drainage area, together with that required for further studies within the Amibara and Melka Sadi areas, is shown as Table 7.FIGURE II
AMIBARA IRRIGATION PROJECT H PROGRAMME FOR DRAINAGE WORKS WITHIN MAESO FARM AREA
ITEM
NO
ACTIVITY
OUANTITY
METHOD
OF EXECUTION
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
Mobilise, prepare working drawings and set out
Procure / Fabricate clay tiles
Enlarge secondary drain for pilot area
Lay tile drains for pilot area
Construct structures for pilot area
Leach salts and monitor results
Review and revise designs if necessary
Procure trenching machine
Delivery of trenching machine
Test and commission trenching machine
Enlarge open drains for remainder of Phase 1
Lay tile drains for remainder of Phase 1
Construct structures for remainder of Phase 1
Enlarge open drains for Phase 2
Lay tile drains for remainder of Phase 2
Construct structures for Phase 2
Monitor/Review results for Phases 1&2
Enlarge open drains for Phase 3
Lay tile drains for Phase 3
Construct structures for Phase 3
Enlarge open drains for Phase 4
Lay tile drains for Phase 4
Construct structures for Phase 4
Enlarge open drains for Phase 5
Lay tile drains for Phase 5
Construct structures for Phase 5
266 km 1, 800m3 13,600m
2 No
Local or offshore
1 Excavator 1 Excavator
-
1 NO
-
-
54,800m3 28,200m
7 No
83,450n? 46,700m
5 No
-
96,650m3 55,700m
6 No
35,350 m3 62,400m
6 No
19,300 m3 59,700m
8 No
1 Excavator ♦ hand Trencher
-
1 Excavator ♦ hand Trencher
-
1 Excavator ♦ hand Trencher
-
1 Excavator ♦ hand Trencher
-
1 Excavator ♦ hand Trencher
Completion
CompletionJ
pilot area
Completion
^Completion
Completion
Phase 1
Phase 2
Phase 3
Phase 5
.Completion
Phase 4
38TABLE 7
SCHEDULE OF EQUIPMENT REQUIRED FOR
TRAILS ON PILOT DRAINAGE AREA AND FURTHER SALINITY STUDIES Description
Discharge recorders for attachment to drain outlets
Calibrated buckets and stopwatches for measurement of drain discharge
Low lift high volume pump to be moved by and powered from tractor, strainer and foot valve
Diesel pump set with water meter. 100 1/m capacity, strainer and foot valve
Water sampler to recover samples from within observation well tubes and below water level
Water sounding tape with electric indicator Auger hole kit (Eijkelkamp - Holland)
Evaporation pan, complete with gauge and cover, Class A Soil moisture probes - walking stick type
Top pan balance 500 gm capacity
Soil sample rings with plastic caps and carrying case Rung holder for above, sampling above the water table Ditto for sampling below water table (Eijkelkamp Holland) Munsell Soil colour charts
50 mm Galvanised (or plastic) pipe Sockets for above pipe
End plugs for above pipe
Plastic pipe, rigid 25 mm internal diameter Screw type auger head 25 mm diameter
4-wheel drive pick-up
CIF cost for budget purposes approximately Birr 50,000)Within each phase of development, including the pilot area, an area of high or moderately high salinity which has been abandoned is included. Further leaching trials should be performed on small sections of such areas within each phase,
the results from which may affect the design or implementation of the remainder of the drains for the area. For this reason the main inclusion of the saline
areas is towards the end of the implementation period for the drainage system as a whole, as is shown below:-
3
the block drain coincides with an existing open drain, the locations of which are shown in Figures 6 and 7.
The cost of development within Phases 1, 2 and 3 is approximately Birr 2300 per ha and the overall cost of providing the drainage works described for Phases 1 to 5 is estimated as Birr 2600 per ha.
The locations of abandoned areas of both moderate and more severe salinity are shown on Map No 5, bound separately.
11. QUANTITIES AND COST ESTIMATES
The quantities, tabled for each phase of construction, include all major items
of work required to implement the system, and are included in the form of priced bills as Tables 8-12. These tables follow the detailed analysis of excavation rates and costs given overleaf.
Since the longitudinal and cross sectional details of all existing drains other than drain SD2 and the primary drain are not available, a reduction has been made for the existing excavation within the proposed revised design cross section for drains SD1 and TD1 to TD5 based on the known drain details. In the case of open block drains a reduction of 4.5 m  per m run has been made whereCOST ESTIMATES
11.1    DETERMINATION OF RATE FOR TILE DRAINS
11.1.0 GENERAL
Tile drains may be layed using a back acting hydraulic excavator with a
travelling shutter following close behind within the excavation to support its
near vertical walls. Such a method is envisaged for laying tile drains in the
pilot area a9 it is recommended that the work is commenced without delay, but it
would be costly to adopt for all tile drains at Melka Sadi and Amibara. The
rate for laying tile drains has therefore been built-up on the assumption that a
trenchless or trenching machine will be imported for the purpose. There are two 
principal types of tile or pipe laying machines available, namely those that
plough open the ground and those that excavate with a ladder or chain excavator
sometimes trailing a shield to supoprt the walls of the excavation. The capital
costs of each type are similar but it is thought that a machine of the
trenchless plough type would be preferable for use at Amibara, providing one can 
be found which is capable of laying tiles as deep as 2.3 m. However, this depth 
is approaching the limit of most trenchless machines and a trencher/ladder
excavator type may be necessary as a result.
11.1.2      MACHINE DESCRIPTION
Fully      tracked      trenchless      or      trenching      machine      with      250      hp      diesel      drive,      twin      500 
mm wide tracks.
11.1.3             OPERATIONAL LIFE
A reasonable assumption for rate of use is 1750 hrs per year with an economic
life of 10 years. During this period the machine will be assumed to be
available for 60% of the time, 40% being taken up in mechanical maintenance,
awaiting setting out and other instructions and moving to location.
Depreciation is taken as linear over the operational life of the machine and 
interest charges are omitted.
11.1.4             RATES OF OUTPUT AND PROGRESS
The total area to be drained within the MAESCO farm is 1018 ha, and the total
length of tile drains required for this area is 266,300 m.
Total output is estimated as 200 m per operational hour, or
200     x     1750     xO.6/1000     =     210     km     per     year.     Total     time     required     for     completion     of the MAESCO area is therefore 266.3/210 - 1.3 years or 16 months.
The average density of drains is 266,300/1018 «= 262 m per ha, and a reasonable rate of progress to be expected from the machine in terms of area would be 210,000/262 * approximately 800 ha per year.
11.1.5           SPARE PARTS
The cost of spare parts is assumed to be 70% of the total machine cost, (including deivery), spread equally over its operational life.11.1.6             FUEL AND LUBRICANTS
Rate    of    useage    of    fuel    is    assumed    to    be    5    gall    per    hour.    Rate    of    consumption    of lubricants is assumed to be 7iZ of that for fuel.
1.1.7 Assume
LABOUR
1 operator full time,
1  relief operator/banksman full time, 2  mechanics for 2.5 months per year, 4 labourers full time,
1  surveyor full time,
2  chainmen full time,
1 supervising engineer full time.
11.1.8             ASSISTANCE WITH COMMISSIONING OF TRENCHING MACHINE FROM EXPATRIATE TECHNICIAN
It is expected that one technician from the supplier of the trenching machine
will visit the site for two months directly after it is delivered for the
purpose of transferring knowledge in its operation and maintenance to local
staff and operatives.
11.1.9             DRAINAGE PIPES
These will either be clay tiles manufactured locally or alternatively perforated 
PVC plastic tubing procurred offshore and despatched at the same time as the
trenching machine. It is thought that the costs will be similar whichever
option is chosen.
11.1.10           FILTER MATERIAL
Filters should  consist of crushed  stone or ash  and  it is assumed  that such material and  facilities for grading  and  removal of fines will be available locally.11.2 COST ESTIMATE FOR TILE DRAINS
Capital
(Birr)*
I Annual
I Recurrent
I (Birr)*
11.2.1           MACHINE COSTS
Basic Cost of Trenching Machine:
Delivery:
Costs Associated with Provision of Technician for Commissioning and Training:
Av Depreciation over each year of Operational Life:
Av useage of Spare Parts:
Fuel (5 x 1750 x 0.6 gall @ Birr 5.2/gall):
Lubricants (0.075 x 5 x 1750 x 0.6 gall
@ Birr 8.2/gall):
11.2.2          LABOUR COSTS
Machine Operator (1 No for 12 months @ Birr 720/month): Relief Operator/Banksman (1 No for 12 months
@ Birr 720/month):
Mechanics (2 No for 2.5 months @ Birr 600/month):
Surveyor (1 No for 12 months @ Birr 800/month): Supervising engineer (1 No for 6 months
@ Birr 1,200/month):
Chainmen (2 No for 12 months @ Birr 300/month):
Labourers (5 No for 12 months @ Birr 150/month):
40Z on-cost on each of above for administration, transportation etc:
TOTALS OF MACHINE COSTS AND LABOUR:
BASIC ANNUAL MACHINE AND LABOUR COSTS:
3
* An exchange rate of Estg 1.0   Birr 3.70 has been taken in the
370,000 48,100
50,000
468,000
46,800
I      29,300 I      27,300 I
I 3,200
I 8,600
I 8,600
I 3,000 I 9,600
I 7,200 I 7,200 I 9,000
I 21,300
46,800
I 134,300
Birr 181,100
determination of machine capital costs and costs of spare parts. Output has been estimated at 210 km/year.SUMMARY OF 11.2.1 AND 11.2.2
Rate    for    machine    and    labour    costs    may    be    taken    as 181,100/210,000 =
11.2.3 MATERIALS COSTS
(a)      Cost      of      clay      tiles      (manufacutred      locally)      or PVC Plastic pipe (imported)
(b) Crushed stone or ash filter
Birr 0.86/m
Add contingencies at 10Z
TOTAL
Birr 2.1/m
Birr 3.40m
Birr 6.36/m
Birr 0.64/m
Birr 7.00/m
- 4411.3 DETERMINATION OF RATE FOR EXCAVATION USING BACK-ACTING HYDRAULIC EXCAVATOR
11.3.1             TYPICAL EXCAVATOR CHARACTERISTICS
Gross Weight : 11 Cons
Engine Horespower : 90 bhp at 2,200 rpm
Size of Bucket : 5/8 cu yd
Range of Boom Lengths : 4-6 m (two piece or monobloc)
Range of Dipper Arm lengths : 2-4.5 m
Typipcal Reach : 9.5 m
11.3.2             OPERATIONAL LIFE
A reasonable assumption for rate of use on this type of work would be 1 ,750 hrs
per year and an economic life of 8 years. During this period the excavator will
be assumed to be available for excavation 80Z of the time, 20Z being taken up in 
mechanical maintenance, moving to location and awaiting setting out.
11.3.3             EXCAVATOR OUTPUT
Assumptions:             5/8 cu yd bucket
50 minute working hour
25 sec cycle time for 180° swing
90Z bucket factor
80Z operator efficiency (This is low since drains are small)
15Z allowance for bulking of fill
Output     is     therefore     (5/8     x     (50/60)     x     (3600/25)     x     0.9     x     0.3)/l.     15 
= 47 
ional hour
or 36m >
hour
and annual output is 36 x 1750 x 0.8 - 50,400 m^
11.3.4             SPARE PARTS
The     cost     of     spare     parts     is     assumed     to     equal     70Z     of     the     total     machine     cost (including delivery) spread equally over its operational life.
11.3.5             FUEL AND LUBRICANTS
Rate     of     usage     of     fuel     is     assumed     as     being     2     gall/hour.     Rate     of     consumption     of lubricants is assumed to be 7|Z of that for fuel.
11.3.6             LABOUR
Assume :         1 Operator full time
1  Relief operator/banksman full time
2      Mechanics    each    for    2    months    per    year 1 Labourer full time
- 4511.4 COST ESTIMATE FOR EXCAVATION WORKS
Capital
(Birr)
I Annual
I Recurrent
1 (Birr)
1
11.4.1            MACHINE COSTS
Basic Cost of Machine:
Delivery:
255,000
33,100
1-----------------
1
1
1
1
1
288,100
1
1
1
Av Depreciation over each year of Operational Life:
36,000
Av Useage of Spare Parts:
1
1
1
1 25,200
Fuel (2 x 1750 x 0.8 gall @ Birr 5.2/gall):
I 14,600
Lubricants (0.075 x 2 x 1750 x 0.8 gall @ Birr 8.2/gall):
11.4.2           LABOUR COSTS
Machine operator (1 No for 12 months @ Birr 680/month):
Relief Operator/Banksman (1 No for 12 months
@ Birr 680/month):
Mechanics (2 No for 2 months @ Birr 600/month):
Labourer (1 No for 12 months @ Birr 120/month):
40Z on-cost on each of the above for administration,
transport etc:
1 1,700
1
11
1
1 8,200
11
1 8,200
1 2,400
1 1,400
1
1
1 8,100
1
36,000
1
1 69,800
1
BASIC COST PER (based on output of 50,400 m^/year):                                                           0.71      +     1.39 TOTAL :                                           Birr 2.1/m3TABLE 8
MELKA SADI DRAINAGE - PHASE I BILL OF QUANTITIES
r
I Item
1
I Unit
1
1
I Description
1
"T“              ~
| Construct Type 1 drains (90m c/c, 2.3m
1
T"
| Quantity
1 
I Rate 1
1 11.1
1
1
1
1
1
T
1
r
| Amount I
1 1
1 1
1 1
1              I nominal depth) in fields of area of                                            1               1                       1             1 1
1
1
1 38.90 ha 1 1
I
1
1
I lin m  1 4,400 1
1
1 7.0 I
1
1 1.2         I Construct Type 2 drains (50m c/c, 2.3m
1
1
1   30,800 | 1 1
1 1
1 1
1              I nominal depth) in fields of area of                                            1               1
1
1
1 1.3
1 59.21 ha                                                                                    1     lin m  1 11,900
1 1
1 1
1
1
1
1 1          1 1 1 7.0 I
1 | 1 1
I Construct Type 3 drains (75m c/c, 2.3m I
1              I nominal depth) in fields of area of                                                              1
1 1
1 1
83,300 | 1
1 1
1
1
1
1 1.4
I 41.25 ha
I
I Construct Type 7 drains (35m c/c, 2.0m
j I
1 1 |
lin m 1  5,500
1
1
1 7.0   1 1|          38,500 |1
1
1              I nominal depth) in fields of area of                                                             1
1 1
1 1
1 1
1
1
1 1.5
1 9.97 ha
1
I Construct Type 8 drains (45m c/c, 2.3m
| 1
[
lin m  1 
1 2,900          1 7.0  1 1 11|
1
1
1              I nominal depth) in fields of area of                                                             1
1
1
1 60.96 ha
1 1
1 1
I
lin m      1 113,600           1 7. 0      | i
i
1 1.6        I Construct tile block drains of 2.3 m                                                           1
1
1           1
I
| 1 8.0 |
1 1
1
20,300 I 1 1
1
1
95,200 | 1
1
1
1
1 1.7
I nominal depth
I Enlarge existing open blockdrains to
.1
lin m     1 
3,500 1
1 1
1 1          28,000 |
1              I 2.45 m nominal depth side slopes
|               11
1 1
1 1                    1
1
1
1
1
I 1.8
1 1
1 1.5h:lv, bed width 0.5 m (cut to spoil) |  m3
1 17,300 I
2.1 |
36,330 |
1
I Excavate dram SDI (cut to spoil) from |
1              I km 0+000 (at Primary Drain) to km                                                        1                       1             1                      1
1
1
11
1 1 1
1
1
1
1
1
1
1 1.9
1 2+500
m3 | |                                                                                               1
1 Excavate drain SD2 (cut to spoil) from |
1              I km 5+215 (at Primary Drain) to km                                                        1                      1             1
1
1
1
22500           j
1
1
2.1 1 1 1 1
47,250 I 1
1 1 1
1
|
I 1.10
I 3+900
|1
m3
1| 1
m3              I 1
1
1800 |          1      2.1 1 
i            3,780 |
1
1
I Excavate drain TD2 (cut to spoil) from | 1 km 0+000 to km 2+000
I
I
1 1
15000  |
1 1.11      I Construct man holes at junctions
I between tile block drains
1
1
1
1
1 2.1 1
1
1
1
1 1
31,500 | 11
1
1
| 1
No 
|
4
7000 I
28,000 |
I 1.12
I Construct Culvert Cl
1 
|
| 
I1
No 
1I
|
1
1 1
1
4000 |
1
4,000 I
I 1.13
i
I Construct Culvert C2
1
No 
|
1
1 1
1
4000 I
1
4,000 |
- 47TABLE 8 (Continued)
MELKA SADI DRAINAGE - PHASE 1
BILL OF QUANTITIES (Continued)
"1------------------------------------------------------------------
Item
I Description
1
“1------------ I  Unit
1
1---------------- 1-------- 1
I Quantity 
1
1 Rate   1 Amount
nr
1
1
1 
1
11
r
1.14
| Construct Culvert C3
11
I No 
11
11
11
1 4000
1
1  4,000
1
1.15
I1
I     Construct     Culvert     C4 
I No 
11
1
1 4000 
1     4,000
i1
i1
11
1.16
I Construct Temporary Drop structure
I on Drain SD2
1
1
1
1 No
1
1
1
11
1
1
1
1 2500
1
1
1
1  2,500
1
1
1
| 
TOTAL
1
1
1
1
1
1 1
1
1 461,460TABLE 9
MELKA SADI DRAINAGE - PHASE 2 BILL OF QUANTITIES
I Item
I        Description 
I
I     Construct     Type     1     drains     (90mc/c,     2.3m I nominal depth) in fields of area
I 11.3 ha
I
I Construct Type 2 drains (50mc/c, 2.3m
I nominal depth) in fields of area
I 42.95 ha
I
| Construct Type 3 drains (75mc/c, 2.3m
I nominal depth) in fields of area
I 67.55 ha
I     Construct     Type     4     drains     (35mc/c,     2.3m I nominal depth) in fields of area
I 8.8 ha
I     Construct     Type     7     drains     (35mc/c,     2.0 I nominal depth) in fields of area
I 47.9 ha
I
I Construct Type 8 drains (45mc/c, 2.3
I nominal depth) in fields of area
I 52.1 ha
I
I      Enlarge      existing      open      block      drains      to 
I 2.45 m nominal depth, side slopes
| Unit | Quantity I Rate I Amount |
I 2.2 I
I
I
I 2.3 I
I
I
I 2.4 I
I
I
I 2.5 I
I
I
I 2.6 I
I
I
I 2.7
I
I Iin ml 1300
I lin m | 8600
I lin m I 9000
I lin m | 2500
I lin  m I 13700 
I 7.0       |       9,100 | II
II II
I
I
I
I    7.0    I    60,200    I
II
II
II
I 7.0       |    63,000 | II
II
II
I 7.0       |     17,500 II
II
II
I 7.0 |           95,900 I 7.0       | 81,200 II
II
I
I
I
I
II I II
I
I lin m I 11600
I
I
I 1.5h:lv, bed width 0.5 m (Cut to spoil)
I
I
I
I
I
I
I m3
| 
46850
I 2.8
I     Excavate     drain     SD1     (cut     to     spoil)
I
I
98,385
I
I
I 2.9 
I
I
2.1 I
1
| from km 2 + 500 to km 3 + 400
I m3
| 
5100
I
| Excavate drain TD1 (cut to spoil)
I
I
1
2.1 I
1
10,710
I
I
I from km 0 + 000 to km 2 + 800
I,
I m3
| 
20250
42,525
I 2.10
I Excavate drain TD3 (cut to spoil)
I
I
1
2.1 1
1
I
I
I from km 0 + 000 to km 1 + 500 
I,
I m3
| 
11250
I
I 2.11
I Construct culvert C5
I
I
1
2.1 1
|
23,625
I No |1
I
I
4000 I
4,000
I 2.12
I     Construct     culverts     on     open     block 
I drains for access requirements
I (Provisional)
I 2000 I 8,000
TOTAL
I 514.145TABLE 10
MELKA SADI DRAINAGE - PHASE 3 BILL OF QUANTITIES
I--------- 1------------------- I Item | Description
1----------1
I Unit I Quantity | Rate   I Amount I
II
I
i i i i i i i i i i i i i i i i i i i i i i
i i
r
I
II
II
I
----------------------------- ----------1---------- 1
3.1
2.3m
lin
m
3.2
I
1-----------------------
I    Construct     Type   1     drains     (90m     c/c, I    nominal      depth)   in fields of area
I 78.64m ha
I
I    Construct     Type   2     drains     (50m     c/c,
2.3m
I    nominal      depth) I 72.5 ha
in fields of area
I
I
7.0 I I 61,600 I I
I I
I
I
I
I
I
lin
m     14500
7.0
3.3
2.3m
lin
m    13800              7.0
3.4
Construct Type nominal depth) 102.6 ha
I Construct Type I nominal depth) I 22.4 ha
I
I Construct Type I nominal depth) I 36.43 ha
3     drains     (75m     c/c, in fields of area
4     drains     (35m     c/c, in fields of area
2.3m
lin
m    6400                7.0
3.5
6     drains     (30m     c/c, in fields of area
2 • Om
lin             12200
I
I Enlarge existing open block drains I 2.45 ra nominal depth, side slopes
7.0
101,500
96,600
44,800
85,400
3.6
to
i
i
i
i
3.7
I     1.5h:lv,     bed     width     0.5     m     (Cut     to     spoil)                       28200              2.1 I
I      Enlarge      existing      open      block      drains      to I 2.15 m nominal depth, side slopes
I 1.5h:lv,
bed width 0.5 m (Cut to spoil)                                                 10500
2.1
i 3.8 i
i
i 3.9
Excavate km 3+900
Excavate km 0+000
Excavate
km 0+000
drain
to km
drain 
to km
SD1 (cut
to   spoil)        from
8+000                                                                        28300              2.1
TD4      (cut
to    spoil)        from
i i i i i i i i i i i
1+900                                                                       14250              2.1
3.10
drain
to km
TD5 (cut 2+050
to    spoil)        from
3.11          Construct
Culvert
C6
3.12 Construct Culvert C7
3.13 Construet Culvert C8
59,220
22,050
59,430
29,925
32,340
4,000
4,000
4,000
i 3.14 i
i i i
Construct
Culverts on           Block     Drains       for
access requirements (Provisional)
m3            15400              2.1
No             1                      4000
No             1                      4000
No             1                      4000
No 3 2000
TOTAL
'I
I I I I I I I I I I I I I I I I I I I I I I I I I I
I I I I I I I I I I I I I I”
I 610,865 i
- 50 -TABLE 11
MELKA SADI DRAINAGE - PHASE 4 BILL OF QUANTITIES
"1-------------------------------------------------------------------- 1r
1 
1          T
Item
4.1
I Description
1
1 1
1 Construct Type 4 drains (35m c/c, 2.3m 1 nominal depth) in fields of area
I 119.6 ha
1
1
I Construct Type 6 drains (30m c/c, 2.0m 1 nominal depth) in fields of area
I 72.38 ha II
1 Unit 1
1  Quantity  1  Rate  | 1 1 1
1
1
I lin m 1
1 1
1
1
1
I 34200 1
1
1
Amount I 1
n i i
239,400 | 1 1
4.2
1
1
1 lin m    1 24200
4.3        1    Construct    tile    block    drains    of    2.3    m
1
1
1
1
1
1
n            r ii ii 1   7.0   i 1        1
1        1
1        1
1        1
1 7.0 |
1        1
1        1
1        1
1 8.0 |
1        1 1           1
1 1
169,400 | 1 1
1
1 lin m    1 3000
4.4
4.5
I nominal depth
I1
I Construct tile block drains of 2.0 m
1 nominal depth
I1
1 Enlarge existing open block drains to
1     2.15     nominal     depth,     side     slopes     1.5:lv, I bed width 0.5 m (Cut to spoil)
i1
I    Excavate    drain    SD2    (cut    to    spoil)    from I km 3+900 to km 1+400
1
1
1
1
1
1
1
1           1
1 lin m    1 1000
1
1
1
1
1 m3 1
1
1
1
1
1
1 8700 1
1
| 
24,000 I 1 1
1
8,000 I
4.6
1               1
1               1
1               1
1 18,270 I 1               1 1               1
1
1 m3 1
1
1
1 15000 1
1
1   8.0 1
1 
1
1
1 2.1 1
1
1
1 2.1 I
1
1 2.1 1
1 1
1               1
1 
1 31,500 |
1
4.7        I    Excavate    drain    TD1    (cut    to    spoil)    from I km 2+800 to km 4+050
1
1
I m3 1
1
1
1 9400 1
4.8        I    Excavate    drain    TD4    (cut    to    spoil)    from I km 1+900 to km 2+200
1
1
I m3 1
1
1
1 2250 1
1 1 11 1 1
1 1 1
1 19,740 I 1
1 1
1 2.1     1     4,725 1
4.9        I Construct manholes at junctions | between block drains
i1
1 1
1
1 No 1
1
1
1
1 7000 1
1
1
1 
1
7,000 1
5.0
5.1
| Construct culverts on Block Drains for I access requirements (Provisional)
I|
I    Allow    for    lowering    of    invert    level
1
1 No 1
1
1
1 4 1 1
1
1
1 2000  1 8,000
1
1
| of drain under Bridge
1
1
1
1
1
1
1
1
1
1
1
1 Lump
1
1
1
1
1
1
1
1 Sum
1
1
1
1
1
1
1
1 -
1
1
1 
1 
1
1
1
1 25,000
1
1
1
1
1
1
1
1
| 
TOTAL
1
1
1
1
1
1
1
1 555,035TABLE 12
MEL KA SADI DRAINAGE - PHASE 5 BILL OF QUANTITIES
Item      1 Description 1
T
1 Unit 1
1---------------- 1 1
I  Quantity  1  Rate  I  Amount 1 1 1
5.1
1
1 Construct Type 4 drains (35m c/c,
I     nominal     depth)     in     fields     of     area I 83.2 ha
1
1
I Construct Type 5 drains (20m c/c,
1     nominal     depth)     in     fields     of     area I 63.45 ha
l
2.3m
1
1
1
I lin m 1
1
1        1
1        1
1        1
1 7.0  1
1        1 1
5.2
2 • 0m
1
1
I lin m 1
1
1
1
1
I 23800 1
1
1
1
1 31800 1
1
1 1
1
1
1  7.0 1
1
1
1 8.0 1
1
166,600 1
1
1
1 222,600 1
5.3        I     Construct     tile     block     drains     of     2.3  m I nominal depth
1
5.4 I Construct tile block  drains of 2.0  m
1
I lin m 1
1
1
1
1 2100 1
1 1
1 lin m    1 2000
1
1 8.0 |
1
1
1 16,800 1
1
1
1 16,000 1
1
5.5
| nominal depth
1
1 
I Enlarge existing open block drains I 2.3 m nominal depth, side slopes
of
1
I
1
1
1
1
1
1
1 19300 i1
1
1
1
1
1
l
5.6        I     Construct     man     holes     at     junctions I between block drains
i 1
I    1.5h:lv,    bed    width    0.5    m    (Cut    to    spoil)  1 m^
1
1
I No 1
1 2.1 1
i
1
1 7000 1
1
5.7
I     Construct     culverts     on     Block     Drains | access requirements (Provisional)
for      1
1 No
1 3 11
1 1 5
1
1 2000
1 40,530 1
1
1
1 21,000 1
1
1 10,000
TOTAL II
|| 493,530 I
- 52 -12.          ESTIMATES OF BENEFITS
12.1         Benefiting Areas
A rationalisation of present cropped and damaged areas with those which would result under the scheme is given in Table 13. By coincidence the area which is regarded as too costly to salvage
is almost identical to the area at present under other crops, and 
by disregarding these, the estimation of benefits can be simplified 
to a situation of "bananas only". It is assumed that, without the project (w) , the water table would continue to rise at a rate
similar to that in recent years, and that at least as far as bananas
are concerned, the area would be progressively abandoned during the next eight years. The programme taken for reclamation of the area
for banana cultivation (w) is that described above, particularly in Section 10. The impact of both w and w is illustrated in Table 14.
12.2         Banana Yields
When production commenced in 1971 (GC) , yields were reportedly over 30 t/ha. These have steadily declined mainly with increasing 
salinity, but also under an increasing nematode problem. Since 1975, the following yields are reported by MSFD:
Year (GC)
Yield
t/ha
1975 
23.8
1976 
21.7
1977 
15.4
1978 
14.8
1979 
14.5
1980 
12.1
1981    (provisional)
12.1
On the basis that the 47 ha remaining non-saline is still yielding
30 t/ha, the average yields in usable salinized area have now fallen to 10.9 t/ha (Figure 12).
Although neither soil, soil-water, nor climate is ideal for bananas,
and consequently high commercial estate yields would not be achieved in the area, the consultant feels the estimate of the MSFD's Horticultural Department of 35 tonnes could be achieved, provided nematode control were to be introduced. For budget purposes the historic farm costs
have been taken, but increased for additional fertilizer, pest control
and nematodicides. Budget yields on non-saline land have been projected at 30 t/ha, but starting with 25 t/ha in the first year.
12.3     Product Prices and Production Costs
Production at Melka Sadi under full development would peak at 600-700 t/week. This is rather small for a regular export market and probably much of the produce would be sold locally, where the current price is Birr 520/t. A recent export consignment fetched US$ 350/t fob Asab, but after allowing transport, handling and port charges, the price ex-farm is virtually the same.
-53-TABLE 13
ETHIOPIA
MELKA SADI AGRICULTURAL ENTERPRISE Rationalisation of Areas
Present
1981 -
Programme
Reclaim
Potential
Non-saline
bananas
47
(47)
845
(653)
(160)
(32)
1,065
Low/moderate salinity
680
165
bananas
other crops
fallow
Abandoned area
empty
390
46
338
lucerne/pasture trials
52
46
Totals
1,382
1,018
1,328
(Cropped)
(906)
(1,276)
1/ Cropping (1981)
bananas
700
capsicum                                    130
onions
30
luceme/pas ture 46
906
-54-TABLE 14
55-
ETHIOPIA
FELKA SADI AGRICULTURAL ENTERPRISE Development of Banana Area (hectares)
Tresent
1981
1982
cl'
1983
R/P—1 C
1984
R/P C
1985
R/P C
1986
R/P C
1987
R/P C
1988
R/P C
1989
R/P C
A. Without Project (simulated)
Non-salinc                                                             47                  47
47
47
47
47
47
47
47
Ixiw/mod saline
Fa 11ow
653
32
Abandoned
(390)
571
32
(472)
489
32
(554)
407
32
(636)
325
32
(718)
243
32
(800)
161
32
79
32
(882)
(964)
32
(1,043)
Total bananas                                              700                618
II. Wi th Drainap.e Project (Progrnuwnc)
Non-saline 47 47 Ixiw/nodcrato salinity 653 653
536
454
372
290
208
126
47
257
728
1,065
1,065
1,065
1,065
1,065
503
91
-
-
Fallow                                                                 (32)
(32)
(32)
(32)
(5)
(5)
(5)
(5)
Abandoned                                                       (390)             (390)
(130)
(271)
(52)
(5)
(52)
(52)
(52)
(52)
Reclaimed area
of which low/mod salinity zone abandoned zone
New planted areas
Harvested area:
-
-
210
47!
337
-
-
-
-
150
412
118
-
-
-
-
60
59
219
-
-
-
-
-
-
210
471
337
-
-
-
-
nt fill 1 yield 47 47
at declining phase 653 603
47
47
257
728
1,065
1,065
1,065
503
91
-
-
-
-
-
nt improving phase
-
-
-
210
471
337
-
-
-
Total banana area harvested                     700                65O?7
550
348
728
1,065
1,065
1,065
1,065
2/ C - Cropping area
2/ R/P * Area reclaimed or re-planted
3/ 50 ha allowed ;ib disturbed during corwucnrcmcnt of activities.Figure 12
ETHIOPIA
Marketed Production of Bananas by Melka Sadi Agricultural Enterprise
(tonnes per ha)
Harvest Year (GC)
Source: Horticultural Department, Ministry of State Fanns Development.
“56-Estimates of production costs are based on MSFD’s own costs, modified as explained above. These have been calculated for each of the
average situations and are presented in Table 15.
Investment costs —in the drainage activity have been taken from
Section 11 above, though for the purpose of drawing up a cash 
flow some modifications have been made. The capital cost of the
drainage equipment has been isolated in Year 1 and a residual value
has been credited in Year 4. Depreciation has been taken out of the grossed up values of the drainage costs.
An allowance has been made for the capital costs of re-planting the bananas. Although this would not be essential throughout the area,
the drainage activities would do a good deal of damage to the
existing plantations and re-planting with vigorous stock is preferred.
With the increased area and greater inputs allowed for, the estimated requirement for working capital would rise substantially. This has
been allowed for.
12.4     Cash Flow
Once the impact of the temorarily reduced production and the
substantial increase in working capital have been absorbed, the cash flow indicates a strong position. In relation to this cash flow, the establishment loan required would be relatively small, and would 
mostly comprise working capital.
No attempt has been made to speculate on the source of funds which would be borrowed, and a simple cash flow has been calculated 
(Table 16) . This indicates that the financial return over 10 years
to government would be in the order of 362 before finance charges
or any other charges made for supplying irrigation water or recovering original land development costs. This financial rate of return would be sensitive to the achievement of the projected output (yields or price) at a drop in average yields (on non-saline land) from 30 to 24 t/ha,
which would reduce the calculated rate of return to 102.
As a State Farm operation using borrowed capital paid for at 102, the project would yield a higher rate of return than indicated above.
It is emphasised that the projected costs of the drainage programme itself have relatively little impact on the projected costs which are dominated by the increasing production costs and the associated increased need for working capital.
12.5 Economic Benefits
The cash flow has been converted into accounting values by adjusting the product value, investment and operating costs. Foreign exchange costs have been converted at the official rate (Birr 2.07 = US$ 1.00), and non tradeable items have been converted at the standard conversion factor given by the DPSA at 0.75. The only exception to this is the value of
V Costs in Section II are given at 1981 levels, and no contingency for price escalation has been built in.
-57-ETHIOPIA
MELKA SADI AGRICULTURAL ENTERPRISE Bananas - Estimated Returns and Production Coats
MARKETABLE PRODUCTION
Present
Inproving
Full Development
(solinised areas)
(first year nftcr drainage)
(non-saline areas
Yield                tonnes/ha
12
25
30
Birr/ha
Total Sales (at Birr 520/tonne)
6,240
13,000
15,600
PRODUCTION COSTS
Variable Costs
Fertilizers
303
500
540
PeGt control
-
120
145
Nematode control
-
340
340
Crate rental
343
Packaging
798
1,141
2,377
2,853
Small tools, sundries
42
42
42
Casual labour
1,581
1,713
1,739
Machinery costs
264
264
264
Total variable costs
3,331
5,356
5,923
Other Direct Costs
Permanent labour
814
814
814
Management, administration, medical
591
591
591
Miscellaneous
40
40
40
Vehicles and transport
286
464
500
Land tax
2
2
2
Total other direct cosLs
1,733
1,911
1,947
Sub total direct production costs
5,064
7,267
7,870
Finance on working capital
229
327
354
Depreciation
610
610
610
TOTAL PRODUCTION COSTS
5,903
8,204
8,834
PROFIT BEFORE LAND, WATER CHARGES ♦ TAX
337
4,796
6,766
Source:         Based     on     data     published     by     Mclka     Sadi     Agricultural     Enterprise     for     "present     (declining)"     areas and project estimates for "Improving" and "Full Development".ETHIOPIA
Mclka Sadi Banana UnLt : Cash Analysis (1981 Birr)
1981
0                1                2                3                4                5                6                7                8                9                10                 NPV                 Financial
---- Birr
Value of banana Sales
- from non-saline areas 733 733 733 733 4,009 11,357 16,614 16,614 16,614 16,614 16,614
(at 10Z
discount)
ROR
Z
from declining areas
- from improving areas
TOTAL VALUE SALES
EXPEN DI TURK
Investment in drainage works
4,075        3,763         3,139             568
-
-
-
-
2,730          6,123        4,381
-
-
-
-
-
-
-
-
-
-
4,808        4,496         3,872         4,031        10,132      15,738        16,614       16,614       16,614       16,614         16,614
66,114
- capital (residual)
-
756
-
-
(378)
-
-
-
-
-
-
- operating expenses —
-
121
644
724
897
-
-
-
-
-
Sub total drainage
-
877
644
724
519
-
-
-
-
-
-
Replanting bananas
-
-
44
99
71
-
-
-
-
Incremental working capital (B 4,705,000)
-
(253)
1,019
1,463
2,273
203
-
-
-
-
-
Total investments
-
624
1,707
2,286
2,863
203
-
-
-
-
-
5,777
Production Costs
in non-saline area6
370
370
370
2,022
5,730
8,382
8,382
8,382
8,382
8,382
8,382
in declining areas
3,307
3,054
2,547
461
-
-
-
-
-
-
-
in improving areas
-
-
1,526
3,423
2,449
-
-
-
-
-
-
Total Production Costs
3,677
3,424
4,443
5,906
8,179
8,382
8,382
8,382
8,382
8,382
8,382
rVpreciatfon (farm machinery, equipment)—
427
427
427
427
472
427
42 7
427
427
427
427
TOTAL CASH OITT
4,104
4,475
6,577
8,619
11,469
9,012
8,809
8,809
8,809
8,809
8,809
BALANCE BEFORE FINANCE CHARGES
704
21
(2,705)
(4,588)
(1,337)
6,726
7,805
7,805
7,805
7,805
7,805
Deduct u balance
704
704
607
511
415
531
434
446
349
-
-
SIMPLE NET BENEFIT
-
(683)
(3,312)
(5,099)
(1,752)
6,195
7,371
7,359
7,456
7,805
7,805
13,196
36
1/ Trencher and excavator given 50Z residual value alter 3 years of use.
2/ After cutting out depreciation included in Section 11.
2/ En lieu of replacements.
TABLEI
labour which has been shadowed at 0.50. Conversion to tradeables and allowing for an anticipated decline in the ’’real” value of the product indicates an accounting value of Birr 500/tonne marketable bananas. Conversion of the other costs to accounting values and the omission of incremental working capital (on the basis that it is an internal transfer) leaves the adjusted cash flow stronger than in the financial analysis, and indicates an internal economic rate of
return — exceeding 50Z. and should show a 10Z
The project’s sensitivity would be reduced, ERR to the new investment at yields of 17 t/ha.
1/ It should be noted that the calculations compare (a) the production of bananas, and do not consider alternative crops, (b) the incremental value of the drainage project with nematode control and (c) assume all previous investment as sunk costs.
-60-PART B
AMIBARA AREA
SOIL AND SALINITY STUDY
- 61HI
IM
IET
*PART B
AM I BARA AREA
SOIL AND SALINITY STUDY
CONTENTS
1.        Summary 
2.        Background 
3.        Geology and Hydrogeology 
4.        Soils of the           Amibara Area
5.        Infiltration            and Permeability Test Results
6.        Drainage Schedule of Tables
PAGE NO
63
63
63
64
64
65
Table 17 
Amibara Area, Observation Well
Records
66
Table 18 
Depth to Impermeable or Slowly 
Permeable Layers
67
Table 19           Groundwater Levels and Electrical Conductivity 
of Groundwater 68
Table 20          Rates of Soil Infiltration and Schedule of Annexes, (Bound Separately)
Permeability 
69
Annex 5 AIP Observation Well Records, August 1980 - November 1981 Annex 6 Soil Profile Descriptions, Pits and 5m Bores
Schedule of Maps, (Bound Separately)
Map 7 Location of Test Sites, Depth to Groundwater, EC of
Groundwater, Depth to Impermeable Layer and Soil EC ValuesPART B
AMIBARA AREA
SOIL AND SALINITY STUDY
1.        SUMMARY
During the soil salinity study at Melka Sadi farm it was agreed that the study should be extended to include the remainder of the Melka Sadi area and the whole of the Amibara area, the field work to be started directly after the Melka Sadi farm study. This field work was co include investigation of the results from a
minimum of 30 soil permeability and infiltration tests, together with 5 m deep borehole sites approximately 2 km apart over the whole area. The methods and equipment used were the same as for the Melka Sadi farm study. Field work commenced on 29 September 1981 and was completed by 9 December 1981.
pits were described and sampled for chemical analysis.
2.         BACKGROUND
The Amibara area was studied by Italconsult during their surveys of 1969 and 1971, and later in 1975 Hunting Technical Services commissioned a hydro-
pedological study of the Melka Sadi and Amibara areas. In 1980 the Amibara Irrigation Project authority installed a network of 27 observation wells, which have been in operation since late 1980. The area covers some 7250 ha of which 3056 have been under irrigation for some years. The early development was along the south bank of the Awash with irrigation water supplied by diesel pumps to a number of separate farms. In 1981 1800 ha of new area was supplied by gravity from the Melka Sadi headworks.
The principal crop is cotton but there are also some areas planted to banana, citrus and tomato. In addition there is approximately 60 ha of irrigated 
pasture in the settlement area. The Institute of Agricultural Research 
maintains a research farm of 300 ha which is also supplied by gravity from the Melka Sadi headworks.
3.         GEOLOGY AND HYDROGEOLOGY
3.1       Geology
The description of the Melka Sadi area in Section I also applies to the Amibara area. A feature of the Amibara area is the low volcanic hills and cones at Amibara and Ambash, which together with other minor extrusions indicate the line of a fault running north-north east from Dofan.
North of the developed area is a series of warm springs in the valley floor which form the Billen swamp. The water is alkali with an EC of + 1.0 mmhos/cm and probably enters the aquifer on the Alledeghi plain.
3.2      Hydrogeology
As at Melka Sadi there are two major aquifers in the area. The.deeper aquifer
is saline and has shown a slow but general rise in level since observations were started in August 1980. The recharge of this aquifer is supplied in part by infiltration upwards from the underlying confined aquifers originating in the Alledeghi plain. The Awash river, especially at times of high flow, also contributes to this aquifer. A third possible contribution is the very saline groundwater associated with the volanic cones and features, as at Amibara and Ambash, which are found within 2.5 m of the surface at borehole site DRH 71, 1 Km north-west of Amibara hill.
- 63 -
28 soilThe deep aquifer is now also receiving some water from the relatively shallow,
normally non-saline, aquifer which has developed since the introduction of
irrigation and this will continue to cause the aquifer to rise since the natural
drainage towards the Billen swamp is extremely slow.
The second, and shallow, aquifer is generally of low salinity and is confined to 
or near the presently irrigated areas, and this shallow aquifer is gradually 
rising in level. At some sites it is extremely saline, particularly where the
naturally saline groundwater was already close to the surface as at Amibara and 
Ambash.
The depth of the groundwater table as measured in November and December 1981 
together with the salinity of the water (EC) are shown in Table1^?-
The shallow aquifer and the deep aquifer are separated by a variable thickness
of very slowly permeable or possibly impermeable clays and silty clays. The
depth at which such a layer or series of layers was found while making 5 m deep 
bores is shown in Tabletogether with the depth of the groundwater. Table
14 shows the salinity of the groundwater, together with comments on the rise or
fall of its level.
4.       SOILS OF THE AMIBARA AREA
The 1:20,000 scale map produced by Italconsult in 1969 shows the soils of the
area in detail. The earlier irrigation development is on soil units 3 and 6,
"vertisols on recent alluvium" and "recent alluvium with frequent alterations in 
grain size". The present development area is mainly on soil unit 5,
"hydromorphic vertisols", and soil unit 6.
A feature of all the vertisols is the presence of stratified silts, silt loams
and fine sandy loams in the deep subsoil, the thickness of the vertisol varying 
from 50 cm to 3 metres. Soil unit 4 "non-calcereous vertisols on recent
alluvium" became calcareous following irrigation, as shown at DRH 73 for
example, due to the calcium carbonate content of the Awash river water.
Another feature of the vertisols is the very compact B horizon with a strong 
prismatic structure, with pads up to 50 cm high and 25 cm across almost devoid 
of fine cracks, and also with pores or root channels. These soils were confined 
to soil unit 5 "hydromorphic vertisols" and generally occurred in a strip about
1-1.5 km wide adjacent to the primary canal. Uneven and stunted growth with 
premature ripening of the cotton was a good indicator of these soil conditions
as at DRH 81,82, 84, 89, 91 and 92.
Some of the soil unit 6  sites were very  saline, for example as at DRH 74, with damp  saline patches on  the soil surface. Otherwise the soils were found  to  be generally non-saline or slightly saline with EC within the range
1.0 - 3.0 mmhos/cm or 2.0 - 6.0 mmhos/cm on a saturated extract.
5.        INFILTRATION AND PERMEABILITY TEST RESULTS
Results        of        the       infiltration        and        permeability       tests,       both       "pour-in"       and 
"pump-out" are shown in Table 15.
The     methods     used     are     the     same     as     for     the     Melka     Sadi     farm     study.     Water     used     in the tests was taken from the primary canal.When      testing      the      vertisols      it      was      necessary      to      pack      the      bores      with      a      filter      of volcanic      ash      or      clean      gravel      to      prevent      the      walls      of      the      bore      from      collapsing. Also      when      starting      the      infiltration      tests      it      was      necessary      to      wet      the      top      soil and      allow      some      swelling      to      occur      prior      to      starting      the      test,      otherwise      a      large amount      of      water      was      lost      down      cracks.      Permeability      tests      were      run      for      at      least 6 hours and infiltration tests were run for 8 hours.
The results obtained were much as expected. The recent alluvial soils (soil
unit 6) had satisfactory infiltration rates and permeability rates. The
vertisols had rather low permeability rates, especially in the lower part of the profile at 60-180 cm depth, 0.012 m/day being the lowest recorded value at DRH 58 which also showed the lowest infiltration rate at 3-4 mm/hr.
6.       DRAINAGE
The present need for sub surface drainage in the Amibara area is limited to those parts of the earlier development area which have shallow, often saline groundwaters. These areas are generally located around the volcanic features of Amibara and Ambash, as shown on Map 6.
To determine the extent and continuity of these shallow groundwaters it will be necessary to carry out a semi-detailed study to determine the depth of the present water table, the salinity and general character of the subsoil. Auger bores located at 70 m intervals, 1 site per 50 ha, in the first instance should 
be a sufficient density of observation. As a guide all those areas with a water table less than 2.5 meters below ground level now require to be mapped in order that a drainage layout can be designed.
The salinity of the groundwater at some sites is already very high and there has been a slow but gradual rise in the groundwater level which can only be accelerated by further irrigation development. To ensure that there is an early warning of rising groundwaters throughout the area and to provide a means of estimating probable drainage needs in the future, the number of observation wells should be increased so as to have one observation well located halfway between each of the existing observation wells, at present 26 in number. These new wells should be installed to the depth of the first water table which may be far less deep than indicated by the observation wells, where the salinities are often higher as was shown at the Melka Sadi farm.
In conclusion it is considered that tile drainage will eventually be required within the Amibara area. There is a continuing need to monitor groundwater levels and salinities as described above in order to establish the timing and extent of the drainage facilities required, but on the information presently available it is not expected that a programme for installation of a tile drainage network should be commenced before perhaps 5 years, and it is quite probable that the drainage programme could be delayed even further.
- 65TABLE 17
AMIBARA AREA, OBSERVATION WELL RECORDS
Depth to Water Table in Metres and Salinity Expressed in EC - November 1981
I SITE NO I
32
33
34
35
36
37
38
39 41 42 44 45 46 47 48 49 50 51
52
| DEPTH TO WATER TABLE                 I ELECTRICAL CONDUCTIVITY (EC) I
I (m)
I (mmhoa/cm)
I 6.03 1  7.7
I 8.53 1  1.7
1 8.71
1 0.0
1 9.27 1  9.2
1 7.46 1  3.5
1 8.21
1 2.1
1 4.36                                                          1       1.4
1 1.96
1 2.0
1 7.00                                                          1       3.0
1 12.46 1 8.44
1 > 10.0
1 > 10.0
1 2.81                                                          1       1.3
1 14.71 1 13.78 1 6.15 1 6.79
1 > 10.0
1 > 10.0
1 1.6
1 > 10.0
1 11.78                                                        1       6.3
1 13.65
1 12.89
53
1 28.0
1 > 10.0
1 13.00
54
1 6.6
1 15.48
3.9
55
1 5.92
57
1 1.8
1 14.68
P9
1 8.93
3.5 (June 1981)
P2
1 
8.7
1 8.24
PP5
I 8.36
3.5
1
1 2.2
1
- 66 -TABLE 18
DEPTH TO IMPERMEABLE OR SLOWLY PERMEABLE LAYERS
I
I
I
I Site No I             Depth      to 
I
I Depth to slowly 
| Depth   to
1------------------------- 1 I   Z   of   Amibara   Area   I
I impermeable layer I               permeable layer             I water    table
I
I (m)
I (m)
I (m)
I
I
I
I
I
I
DRH 59 77
DRH 57
“1---------
1 0 -     2 1 0 -     2 1
1
1 2 -     3
60          1 2 -     3
66          1 2 -     3
71          1 2 -     3
72          1 2 -     3
73          1 2 -     3
75          1 2 -     3
76          1 2 -     3
78          1 2 -     3
79          1 2 -     3
I
1
DRH 55
1 3 -     4
T
1 1.8 I 1.6 1
1 2.5 1 2.1
1 2.0
1 2.1
1 2.2
1 2.8
1 2.8
1 2.6 1 2.7 1 2.5 I
1 3.5
----------r~
i >    5.0 i >    5.1 1
1
1      3.6 1 > 13.0 1    12.9 1      2.5 1 >   5.0 1      2.1
1 >   5.0
1 >   5.0
1    13.0
6.25
31.25
1> 1
11.0
58          1 3 -     4
61          1 3 -     4
63          1 3 -     4
68          1 3 -     4
69          1 3 -     4
70          1 3 -     4
74          1 3 -     4
81          1 3 -     4
82          1 3 -     4
84          1 3 -     4
85          1 3 -     4
1
37.5
DRH 56
1 4 -     5
64          1 4 -     5
67          1 4 -     5
80          1 4 -     5
1
12.5
DRH 62
65          1 > 5
83          1 > 5
86          1 > 5
11
1 14.71
1 >   5.0
1    11.8
1      5.9
1>
5.0
1 > 5
1 3.3
1 3.2 1 3.3 I 3.0 I 3.9 1 3.5 1 3.1 1 3.0
1 3.2 1 3.1 I 3.9 I
1 4.3 1 4.0 I 4.8 1 4.2
|1
1- 1-
1 5.1 1-
1 7.8
1 >   5.0
1 >   5.0
1 >   5.5
1 >   3.5
1      8.9
1 6.8
1      1.5
1      2.7
1 >   3.8
1 > 3.1 1 5.9 1
1 8.5 1 > 5.0 1 15.48
I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I
I
I
12.5
I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 1
I
I
I
I
I
TOTAL
100  Z
I
I
I
I
I
I
I
- 67 -TABLE 19
CROUNDWATER LEVELS AND ELECTRICAL CONDUCTIVITY OF GROUNDWATER
1”
1 SITE
1
1
1 DRH1 AIP
“T“
1
1 Depth to
I impermeable
I layer (tn)
1
1
1
1
1
1 Depth to
1 groundwater
1 (m)
1
1
1
I
I Remarks
1 No
1
I
1
1 59
1 No
1
1
I-
1
1
1 EC of
1 groundwater
| (ambon/co)
1
1
1
1
1 -
1 -
1
1
I        2.2
i
1
1 -            1      1.8
11
1 > 5.0
1 77
1
1
1 57
1 38 nr
1
1
1 45
1
1
T
1.6 1 > 5.0
1
1       2.50
1-------------------
I        1.98
1
1 Close to main drain aod primary canal
1  AIP 38  GUL 4.36,  EC 1.4,  rose 1.2  m May-November 1981
1|
1
1 GWL rose from 3.61 to 1.88 following irrigation end
1
1
1
1
1
I September 1981 
1
1 60
1 47
1       2.10
1 > 13.0
1     13.0
1 GWL rose 30 cm in past year
1 66
1 52
1       2.00
1     12.89
1     14.8
1 GWL roae 20 cm in 15 months
1 71
1
1 -
1
1       2.15
1       2.50
1     36.0
1   Near   Amibara   volanica   -   Saline   area   EC   Cop   soil
1:1
1
1
1
I 30.0 mmhoa/cm
1 72
1 P2 nr
1       2.20
1 >    5.0
1 -
1 P2 GWL 8.24 m, EC 3.5 mmhos/cm
1 73
1 -
1       2.80
I 2.10
1 1.2
1 GWL in bore 2.4 n, roae to 2.1 after 6 hrs
1
1 75
1 32
1       2.80
1       6.03
1       7.7
I GWL was 3.25 March 1981. Irrigated Pasture Trial
1 76
1
1 51
1
1       2.60
1     15.65
1 28.0
1 GWL roae 1.16 m in May and fell again and roae 50 cm
I
1
1
1
I September-November 1981
I 78
1 53
1       2.70
1     13.0
1 6.6
1 GWL rose 1 m in 15 months
1
1 79
1
1 56
1
1      2.50
1 > 11.0
1
1-
1 No records available
T"
1
1 ""
1
I
1 1
1
1 55
1
1 3.50
1
1  3.5
"I
1
1 36
1       7.84
1 GWL rose 1.5 m in 15 months
|
1 58
1 -
1       3.30
I >    5.0
1
I Close to secondary drain
|
1 61
1 43
1       3.25
1 >    5.0
1
I AIP 43 Dry bore in rock
|
1 63 1 - I 3.30
1 63 1 - 1 3.00
1 >    5.5
1 -
I Termite nest at 4.0 m
1       3.52             1     16.4               I Near Amibara volanica 
1 69
1
1 P9
1
1 49
1
1
1
i
1
3.90 I 8.93
1
1 70
1
1 GLW roae 3.2 m June-November 1981, high river floods? 
1 EC fell from > 10-8.7 
1 GWL roae 1.87 n May-November 1981 following irrigation.
1 Near Amibara volcanics
|
|
1
|
|
1 74
1
1 39
1
1
I
3.50 1  6.79
1
3.15 1  1.85
1
1  8.7
1
1  40.0
1
1  13.2
1
1    EC    AIP    392.0    GWL   rose   2m    following    irrigation   June-September   |
I 1981. Saline area nearby (EC topsoil > 40.0 mmhos/cm)
1 81    1 34         1       3.00
I 82    1 -        1    3.20               1 >    3.8               1 -
1       2.75             1 0.86                    1 GWL AIP 34 8.71 and EC 0.88. Level rose 65 cm in 14 months 1
I 84    1 -              1     3.10
|>      3.10            1 -
1 85
1
1
1 55
1
1
1  3.90
1
1
I Too hard to auger below 3.8 m
1 Too hard to auger below 3.1 m
1 GWL rose 1.8 m May-November 1981 (High river levels ♦
1 irrigation)
1
I 44
r“
“T“                1
1  5.92
1
1
1 2.0
1
1
)
j
|
1 1
f”
1 56
1     4.30
I        8.48
1     36.4           1 
1 GWL fluctuates slightly with irrigation
1 
1
| 64     1 -
1     4.00               1 >    5.0               1 -
1 67    1 54           I 4.80
1     15.48             1       3.9               1 GWL rose 30 cm in 15 months
I 80    1-
1
1
1 62
1
“T"
1 >    5.1
1
T“
1 46
1 65    1 -
I 4.20
1
F"
I > 5.0
1 > 5.0
1  14.71
1       5.0
1     11.78             1    6.3               1 GWL rises sad falls through 60 cm following irrigation
n
1 18.0
1 -
1- 1
1 Near volcanic out crop
1 
n
1 83    1 50           1     5.10
1 GWL rose 40 cm in past year
1 
|
I
I
>
|
I 86    1 35
1
1
1  > 5.0
1
1       9.27             1       9.2
1
“T”
1
“7”
1  GWL  rose  30  cm  in  past  vear
_!_____________________________________________________ ____________________i
1
1 -
“T“        1
I AIP  33  1 N/A
1  8.53
1 8.20
1    1.70             I GWL roae 1 m in 15 months
1 - 1 AIP 37 1 -
1 - 1 AIP 38 1 -
I - I AIP 41 1 -
1 - 1 AIP 42 1 -
1 - 1 AIP 46 1 -
1 2.1
1 "Stone" ac 12.5 m when drilled. GWL rose 1.5 m in 15 months 1
I       4.36             1       1.4               1 GWL fluctuates in response to irrigation
1       7.00             1    3.0               1 GWL rose 1 m following irrigation March-November 1981 1     12.46             1 > 10.0                1 GWL rose 54 cm in 15 months
I
1       6.15             1 1.6
1 GWL roae 23 cm in past year
1 -
1 p :
1 -
1 
8.24
1 
3.5
1 GWL rose 62 cm June-November. High river flows? 
|
1 -
1 PP !
1 -
1 
8.36
1 2.2
1 Reading for September and November 1981 only
1 -
1 AIP
57
1 -
|
14.68
1 
3.5
1
1
I 3.8 km east of project boundary GWL rose 17 cm October 80 - I
1
1
1
1
1
1
1
1
I November 81 due to discharge of drainwater?
- 66 -TABLE 20
RATES OF SOIL INFILTRATION AND PERMEABILITY
1 Site     1 Infiltration I Rate of Permeability (m/day)
1 Rate of
| Depth (m)
1 No
I Rate
1 ’’Pour
in" Method
I Permeability I
1
1
1 (mm/hour)
1
1
1---------
1 "Pump out"
|
I Method
1
1
I Depth
Depth 
Depth
Depth
I (m/day)
I
1
1
1 0-60
60- 120-
180-
1 1
1
1
1
1
1 cm
1
120cm
180cm
240cm
1 1
1 1
55
1 17.3
1 0.079
0.152
0.123
0.160
56
1 13.0
1 0.168
1-
0.225
0.88
1
0.156
1 -
1
57
1 20.7
1 0.108
0.124
0.018
0.041
I 0.26
1 2.75 m
58
1   3.4
1 0.047
0.052
0.012
0.043
1 -
59
1
1 -
1 0.032
0.014
-
-
1 -
1
60
1 24.6
1 0.130
0.021
-
-
1 -
1
61
1 22.3
1 0.072
0.050
0.022
-
1 -
62
1 17.6
1 0.168
1
0.191
0.186
0.1
1 -
63
1
I 23.6
1 0.3422
0.217
0.206
-
1 -
1
66
1 11.0
1 0.041
0.105
0.127
0.033
1 -
1
67
1 20.7
1 0.040
0.01
0.004
0.067
1 -
68
1
1 22.7
1 0.139
0.222
0.190
0.098
1 -
1
69
1 17.0
1 0.167
0.098
0.098
0.296
1 -
1
70
1 26.0
1 0.097
0.039
0.039
0.081
1 -
1
71
1 22.7
1 0.163
0.028
0.036
0.108
I 0.22
1 3.63
72
1 21.7
I 0.117
0.058
0.136
0.021
1 -
1
73
1 23.7
1 0.118
0.098
0.135
0.102
1 0.60
1 2.51
74
1 11.7
1 0.204
0.194
0.218
0.166
1 4.26
1 2.26
75
1 14.7
I 0.216
0.120
0.190
0.570
1 -
1
76
1 15.0
1 0.061
0.041
0.207
0.012
1 -
1
77
1 17.4
1 0.20
0.141
0.197
0.118
1 -
1
78
1 24.0
1 0.181
0.144
0.190
0.195
1 -
1
79
1 14.0
1 0.028
0.206
0.128
0.058
1 -
1
80
1 19.4
1 0.232
0.244
0.196
0.181
1 -
1
81
1 16.0
1 0.100
0.060
0.201
-
1 2.78
1 2.52
1
1
1 0.614
1 2.69
82
1 12.4
1 0.037
0.220
0.004
0.008
1 -
1
83
1 13.0
1 0.205
0.217
0.294
0.168
1 -
1
84
1 -
1 0.128
0.025
0.151
0.180
1 -
1
85
1 -
1
1 0.291
1
0.301
0.116
0.217
1 -
1
1
1
- 69 -PART C
MELKA SADI AREA STATE FARMS I AND II
SOIL AND SALINITY STUDY
70 -' rI
f
p
I
I;
I
I 4
J
I H
i
i
I
r!niPART C
MELKA SADI AREA
STATE FARMS I AND II
CONTENTS
PAGE NO
1. Summary
2. Soils
3. Drainage
72
72
72
Schedule of Annexes, (Bound Separately) Annex 8 Results of Soil Chemical Analysis
71PART C
MELKA SADI AREA
STATE FARMS I AND II
SOIL AND SALINITY STUDY
1.       SUMMARY
The Melka Sadi area covers some 4,240  ha of which  1,330  ha are occupied  by  the Melka Sadi farm and  600  ha by  newly  developed  irrigated  cotton. The remaining 2,310  ha are to  be developed  for irrigated  cotton  under the current programme. The total area of 2,910 ha forms Melka Sadi State Farms I and II.
2.        SOILS
The majority of the Melka Sadi State Farm I is located on soil unit 3,
"vertisols on recent alluvium". These vertisols are often up to 3 metres deep 
and have low permeability and infiltration values. There is a small area on 
units 1 and 2, "soils on very recent alluvium".
About half the area of State Farm II is on soil unit 3, located in the north and 
west of the farm. The southern portion is mainly on unit 6. There are small
areas of saline soils, unit 10, in the south east corner between the primary 
canal and secondary canal SD2. These saline areas will require careful leaching 
before being brought into production.
The majority of the soil profiles in unit 3, vertisols, are non-saline with EC
of the saturated extract < 4.0 mmhos/cm, and one horizon only at 180-200 cm. At
AIP 7 the soil was saline with an EC of saturated extract of 9.5 mmhos/cm.
The soils in  unit 6  have slightly  saline soils, usually  in  small scattered patches, and  are easily  recognised  by  the damp  surface salt in  most cases. There is a general reduction in salinity northwards and westwards.
3.      DRAINAGE
In soil units 6 and 10 the infiltration and permeability rates are satisfactory, and as the groundwater table is relatively deep over most of the area, with the exception of the area close to Melka Sadi farm, no immediate problems are expected following irrigation. The area close to the farm, alongside SD2, should be provided with a drainage system for the 1983 cropping season, as the water table is saline, (7-2 mmhos/cm) and will rise once the surrounding area is fully developed. The drainage should then be extended northwards in step with the expected rise in water levels. On soil unit 3, vertisols, the present groundwater levels are deep and the water is saline or very saline.
Infiltration results are satisfactory for cotton while permeability rates are rather low. Deep ripping, cultivation and the cotton roots will help improve the situation. Drainage to control the water table will be required eventually, the time at which it is required being dependent on the rate of its rise, which has varied from 0.5 m to 1.2 m since August 1980. As the area is to be developed for planting by March 1983 a closer pattern of observation wells is required, and these should be sited between the existing AIP wells and extend down to the present water table. Once the whole area has been irrigated for 2 or 3 seaons the expected rate of rise can then be estimated with some accuracy to obtain the probable date by which drainage will be needed.
72In the small area between AIP4 and the western dyke the water table is high and also saline, and eventually this area will also need to be provided with a drainage system, installed together with the irrigation network.
Groundwater levels, salinity of groundwater, depth to impervious or slowly pervious layers and observation well sites are shown in Map Nos 1-4.
As with the Amibara area the timing of the requirement for drainage within State Farms I and II has not been identified clearly, and continued monitoring of groundwater levels and Salinities is necessary to establish this.
- 73 -BIBLIOGRAPHY Brady N C Currey D T
FAO
FAO
Foraky S A
International Institute for
Land Reclamation and Improvement
International Institute for
Land Reclamation and Improvement Italconsult
Italconsu 11
Morton B A
Sir William Halcrow &               Partners Sir William Halcrow &               Partnes
United     States     Dept     of     the Interior
Wilson E M
The     nature     and     properties     of     soils,     8th     Ed New York, 1974
Informal       technical       report       No       14,
UNDP/FAO/ETH/72/006, May 1973
Irrigation     and     Drainage     papers     Nos     1,     9     and 16
Guidelines for soil descriptions
AIP          site          investigations          report.          Bruxelles, 1975
Drainage          Principles          and         Applications,
Vols I - IV. Wageningen, 1974
The Auger hole method. Wageningen, 1971
Melka Sadi - Amibara proposed Irrigation 
Project. Feasibility study, parts I and II,
Vol I - IV. Rome, 1969
Melka       Sadi       -       Amibara       Irrigation       Project, Additional soil studies. Rome, 1971
A      field      guide      to      Ethioipian      Minerals,      rocks and       fossils.       Addis       Ababa       University       press, 1978
Angelele       and       Bolhamo       Feasibility       Study report. London, October 1975
Amibara Irrigation Project, Hydropedological studies. London, October 1975
Bureau of Reclamation
Manual, Vol V, part 2.
1953
Engineering Hydrology, 2nd Ed. London, 1974I

< <

Summery

Amibara Irrigation Project II - Summary

Amibara Irrigation Project II - Drainage & Salinity Study

Prepared by: Sir William Halcrow & Partners

Date: April 1982

1. Project Overview

The document presents a comprehensive study of drainage and salinity issues in the Amibara Irrigation Project II area in Ethiopia, focusing on three main areas:

Melka Sadi Area (Melka Sadi Farm)
Amibara Area
Melka Sadi Area (State Farms I & II)

The study was conducted between March and September 1981, examining 41 sites with various tests including infiltration rates, hydraulic conductivity, and soil salinity.

2. Key Findings

2.1 Soil and Salinity Conditions

Three principal soil groups identified: saline alluvial/colluvial soils, non-saline alluvium, and fine-textured vertisols
Salinity levels have increased since previous studies due to rising water tables and irrigation practices
Banana crops (main crop at Melka Sadi) are particularly sensitive to salinity (EC > 1.0 mmhos/cm reduces yields)
Approximately one-third of Melka Sadi farm area has been abandoned due to salinity

2.2 Water Table Issues

Two aquifer systems: deep confined aquifers (50-70m) and shallow aquifers (1-3m)
Water tables have risen significantly (up to 5m in 9 years at some locations)
Excess irrigation (60cm/year more than needed) contributes to rising water tables

2.3 Drainage Requirements

Recommended water table depth: 1.8m for deep-rooted crops, 1.5m where soil conditions require
Leaching requirements: 10-17.5% of applied water depending on soil type
Tile drains recommended over open drains for efficiency and lower maintenance

3. Proposed Solutions

3.1 Drainage System Design

Drain Type	Depth (m)	Spacing (m)	Areas Applied
Type 1	2.3	90	Areas with K=0.4 m/day
Type 2	2.3	50	Areas with K=0.8 m/day
Type 3	2.3	75	Areas with K=1.85 m/day
Type 4	2.3	35	Areas with K=2.5 m/day

3.2 Implementation Phases

The project is divided into 5 phases over 3 years, starting with a pilot area:

Phase	Area (ha)	Cost (Birr/ha)	Notes
1	210	2,200	Includes pilot area
2	219	2,350
3	252	2,420
4	192	2,890
5	145	3,400

4. Economic Analysis

Key Financial Indicators:

Total estimated cost: ~Birr 2,600/ha
Projected financial return: 36% over 10 years
Economic rate of return exceeds 50%
Banana production expected to increase from current 10.9 t/ha to 30 t/ha after reclamation

5. Recommendations

Implement the phased drainage system starting with the pilot area
Use tile drains for in-field drainage where possible
Continue monitoring groundwater levels and salinity throughout the area
Implement nematode control measures to improve banana yields
For Amibara area, delay major drainage works for approximately 5 years but continue monitoring