032-233 - 1S 
GOVERNMENT  OF  ETHIOPIA 
WATER  RESOURCES  DEVELOPMENT AUTHORITY 
AMIBARA IRRIGATION  PROJECT  II 
3. R. ". 
DRAINAGE & SALINITY  STUDY AND  RECOMMENDATIONS  FOR 
FIELD  DRAINAGE 
VOLUME  1-STUDY & RECOMMENDATIONS APRIL  1982 
Sir William  Halcrow & Partners Sh-4i2 
GOVERNMENT  OF  ETHIOPIA 
WATER   RESOURCES   DEVELOPMENT  AUTHORITY 
AMIBARA  IRRIGATION  PROJECT  I 
RY OF 
BRARY     WATER     AND         RESO, 
Do 
SLR\   IC 
DRAINAGE & SALINITY STUDY 
AND  RECOMMENDATIONS  FOR 
FIELD  DRAINAGE 
VOLUME 1-STUDY & RECOMMENDATIONS 
APRIL  1982 
TATION 
Sir William  Halcrow & Partners Consulting Engineers 
Burderop Park Swindon 
Wiltshire  SN4 OQD United  Kingdom AMIBARA  IRRIGATION  PROJECT  II 
DRAINAGE   AND   SALINITY   STUDY AND    RECOMME  NDATIONS 
FOR   FIELD  DRAINAGE 
CONTENTS 
PART   A 
PART  B 
PART  C 
ME LKA   SADI   AREA,   ME LKA  SADI   FARM.      SOIL  AND   SALINITY  STUDY   AND DRAINAGE   DESIGN 
AMIBARA  AREA.      SOIL  AND   SALINITY  STUDY 
ME   LKA  SADI   AREA,   STATE   FARMS    I   & II.    SOIL  AND   SALINITY   STUDY 
W. ,    , 
: PART  A 
ME LKA  SADI  AREA 
ME LKA  SADI  FARM 
SOIL  AND  SALINITY  STUDY 
AND   DRAINAGE   DESIGN PART   A 
MELKA  SADI  ARE A MELKA  SADI  FARM 
SOIL  AND   SALINITY  STUDY AND   DRAINAGE   DESIGN 
CONTENTS 
PAGE   NO 
SECTION   I   :   SOIL  AND    SALINITY   STUDY 
1.      Sumary 
2.  Background  and  Previous  Studies 
3.      Geology   and  Hydrogeology 
4.       Climate 
5 6. 7. 8 9. 
Field  Studies  and   Methods Soils  of  the  Study  Area Hydrau lic Conductivity 
Water  Quality Alkalinity  Hazard 
10.     Salinity Hazard 
11.  Reclamation  of  Saline Soils 
2 
2 
3 
6 11 
12 
17 
17 20 
20 
23 SECTION   II  :   DRAINAGE   DESIGN 
1. 
Introduction 
2.       Drainage  Requirements 
3. 
4. 
Drainable Excess 
Drain  Spacing  Equations 
5.  Data  from  Field  Observations 
6.      Field  Drain  Design 
7.      Interceptor  Drains 
8. 
Block  Drains 
9.      Collector  Drain  Design 10.    Phasing  of  Construction 
11. 
12. 
Quantities  and   Cost  Estimates Estimates  of  Benefits 
PAGE  NO 
25 
25 
25 
26 
27 27 
32 
33 33 37 40 53 
Schedu le  of  Figures 
Figure  5     In-field Drainage  Requirements Figure  6    Drain   Const ruction Phas ing 
Figure  7 
Phase  No   and  Drain  Type   Locations  by   Field 
Figure  8    Typical  Field  Drainage  Layout 
Figure  9 
Drains  SDl,  SD2   -   Long  sections Drain  SD2   -    Cross  sections 
Figure  1o  Longitudinal  Sections  of  Drains  TDl,  TD2,   TD3,   TD4,   TDS Figure  11  Programne  for  Drainage  Works  within  MAESCO   Farm  Area Figure  12  Marketed  Production of  Bananas  by  Melka  Sadi 
Agr icultural Enterprise 
28 
29 
30 
34 
35 
36 
38 
56 I
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 
PAGE   NO 
Fig  I 
Rig  2 
Fig  3 
Fig 4 
Location  of  Study  Area 
Detail  of  observation  well 
Det ai1 of  AIP   observation wel1 Soil  Map   -   Me lka  Sadi  Fara 
13 
Schedule  of  Tables 
Table  1 
Table  2 
Table  3 
Tab le  4 
Table  5 
Water  table  depths  and  water  analysis  results  for  6  wells at  Me lka  Sadi   farm. 
Depth  and  EC    of  groundwater  at  AIP   observation wells  and deep   bores. 
Water  table  levels  and  salinities  from  selected  sites at different  dates. 
Resu lts of  hydrau lic  conductivity  and   infiltration tests. Analysis  of  Awash  river water. 
4 
5 
18 
21 
Schedule  of  Maps    (contained  in   separ ate folder ) 
Map   No   1 
Map   No   2 
Map   No   3 
Map   No   4 
Map   No   5 
Contour  map  of  the  gr oun dwater  leve ls 
Contour  map   of  the  groundwater  salinity 
Cont  our  map   of  the  impervious  layer (s) 
Location  of  field  test  sites  and  observation  wells Farn  layout  and  saline  are as 
Schedule  of  Annexes   (Bound   separ ately ) 
Annex   1 
Annex   2 
Annex   3 
Annex  4 
Observat ion  Well  Records 
Soil Profile  Descriptions 
Results  of  Soil  Chemical  Analysis Variation  in  Rainfall  Amounts FIGURE 
I 
AMIBARA IRRIGATION PROJECT  Il 
LEGEND 
Rnods 
Aoilwey 
DEDAE 
DERMAN 
MDOLE 
VALLEY 
LOCATION    OF 
ANKDIEA 
STUDY   AREA 
AOIs  ABABA 
MOO                      eer 
stotien 
100km 
KORA 
DAM 
NAZKRETH 
N 
PREVIOUS    DEVEL OPMENT 
AMIBARA    AREA 
RESEARCH  FARM   (IAR) AWASHR. 
PROJECT   CONTROL CENTRE 
LINK   ROAD 
MELKASADI FARM 
MELKASADI   AREA 
HEADWORKS 
5 Km 
Scale 
1 PART  A 
MELKA   SADI   AREA,   MELKA   SADI   FARM SOIL  AND    SALINITY   STUDY 
AND    PILOT   DRAINAGE    DESIGN 
SECTION I:  SOIL   AND SALINITY  STUDY 
1.      SUMMARY 
The   field  studies  for  this eport  were  carried  out  between  March   and  September 1981.    Forty-One  sites  were  exam ined  and   tested  for  infiltration  into  the topsoil  and   permeability  both  above  and  below  the  water  table.    Depth   to 
imperme able  layers  was   determined  by   auger  bore  to  5  metres  depth  at  48   sites. The   5  m bores  were  described  and  water    leve  ls   and   salinities  recorded   throu ghout the  period.     2  m  deep  pits  were  excavated  at  a   further  19  sites,  and   these  were described  and   subsequent ly  sampled  for  full  chemical   analys is. 
These  field  studies  were  subsequent ly  used  to  des ign  a  suitable  drainage  syst em 
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  conduc tivity  values,  choice  of fie ld  drainage   syst em   and recommendations  for  leaching  and  drainage  trials . 
for  the  Melka  Sadi  farm  based  on   the  findings  described  in  the  report. 
The 
2. 
BACKGROUND   AND   PRE VIOUS   STUDIES 
The   Me lka  Sadi  study  area  occupies 
s ome   4,200  ha   of  the  Middle  Awash 
valley 
floor  as   shown   in  Figure  l.    1,328  ha  are  occupied  by 
the  Melka  Sadi  farn, 
The   remainder  of  the 
study  area  of  2,870  ha   is  present ly  under  development  for  cotton 
previous ly  MAESCO   Farm,  noW   under  State  Farm  madagement. 
product ion 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. 
third  of  the  area  has  been   ab andoned  due   to  salinity and   rising water  tables. 
Since  cultivation was   started in  1971  approximately  one 
On    the  remainder  of  the  farn  a lmost  every  plot  is  showing  signs  of  poor  growth 
with  resultant  loss  of  yield. 
planted  with  grass  and   lucerne  for  fodder  production  with  varying  resul ts. 
The   existin8 drainage   syst em,  which  mirrors  the  irrigation   layout, was   designed to  deal  with  rain fall, excess  irrigation water,  spillage,  seep age  and  ground 
Some   46  ha  of  the  abandoned  areas  have  been 
Water 
control.     The   syst em   or iginally  discharged  into  the  Awash   river. 
The  depth  of  the  field drain  syst em is about  1.2  m and  the  main  drain  is about 1.5 m deep.    The  main  drain  is  now  connected to the Amibara Project  primary drain whích  is  1.86 n  deep  at  the point  of junction.    (See  Map   5) 
Previous  studies of  the  area  in  1969  and  1971   by    Italconsu lt included  soil and land  classification mapping  at  l:20  000  scale and   limited  infiltrat ion  and permeability measurements.    The  irrigation  suit ability classification showed  the Me lka  Sadi  Farm  to  be  of Class  I  suitability  and   the  area North  of  the  pres ent fara  to  be  Class  II. 
-    2   -In  1969  a number  of  observat  ion wel ls were  installed, but  unfortunately some were  blocked or destroyed and  the records  lost.   In mid  1980,  the  Amibar a Project  authority provided  a 2 km   grid of  observation wells  thr oughout  the  Me lka 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  ca  excess  was   a major contributing factor  to  the rise in the water  tables. 
3.      GEOLOGY   AND   HYDROGE OLOGY 
3.1    Geology 
The  Middle  Awash   Val ley  lies  in  the 
extending  north  east  towards   the  Red   Sea. 
Ethiopian rift of  the 
The  Floor  of  the  valley  is built  up 
Tertiary  age, 
from   recent  alluvial/colluvial  deposts  from   the  Awash   river  and  outwash  from  the escarpment .      Underlying   sediment  s 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   volc anic origin.    An    ex   amp le is  the  small  Aseda   hill where   the  bedding  is  turned  through  90°   expos ing  the 
Volcanic  activity  in  the  valley  at  present  is  limited  to  fumeroles   and  hot 
silt  and   clay  beds,  which  still 
contain  small  amounts  of  soluble  salts. 
springs. 
The    pres ent    fault  controlled  Awash   river  course  was   estab lished  in  Plio  -
south  of  its  pres ent   course. The   new   course  of   the  Awash   was 
pleistocene  times;   previous ly the  river  flowed 
in  the  Alledeghi   gr aben   to  the 
from   the   escarpmen t  creating 
temporary  lacustrine  conditions.    The   Valley  floor 
periodically  blocked  by   lava  flows   or  outwash 
was   then  some   50   m below  its  pres ent   level, 3.2   Hydrogeology 
There  are  twO    separ ate aquifer  systems 
depths  between  50   and   70   m.        These  confined  aquifers  have   alkaline  water, 
confined  aquifers  of  the  basalt      tuff  -   lava- gravel   sequence  which occurs  at 
in  the  study  area. 
One   is  the  deep, 
35°- 40°.    The   electrical 
pH    8- 9, with  a  high  bicarbonate 
conductivity 
content  and   temperature  in  the  range 
millimhos/ cm  (nhos/cm). 
(EC)   is   usual ly  between  1 and   2 
The  well  drilled  at  the 
and   the  static water  level   Project      rose  to  he adquarters              within  11   m  tapped      of  the a confined  aquifer  at  80  m groundleve l. 
The   other  system  comprises  the 
depcsits  which  have  a variable 
shallow  aquifers  of  the  recent  alluvium/col luvium 
compar ative ly  non-saline  water  is 
salinity, according  to  location  and  depth.    Where 
entering  the  aquifer  the  salinity  of  that. 
-3 -aquifer  is  low   and   the  water  level  is  usually  close  to  the  surface  at  around 1  -   3 m below  ground leve l.    An    examp le  is  boreho le  AIP   3  where   the  wateI  level 
fluctuates  betveen  3.0  and  l.8 m in  response  to  the  irrigation water 
applications  and   the  salinity  is 
less  than  l   mmhos/ cm.      These aquifers are 
perched  over  soil horizons  of  low  perneab ility. 
The 
in  the  vicinity  of  observation wells  AIP   10,  Pll,  DRH    6  and  DRH    24   are  the 
very  high  salinities  which  occur  at  shallow  depths  in  the  abandoned   are  as 
result  of  the  appl lied  irrigation water   join ing  up   with  an   existing  shallow saline water  table  causing  an  upWard   mov ement  of  soluble salts  leading  to  the fornation  of  a  salt  crust  on   the  soil  surface.    Chemical  analysis  of  six  samples from  observation wells  are  given  in  Table  l   below. 
TABLE    1 
Water  table  depth  and  water   an a lysis results  from 6   observation wells  in  the  Melka  Sadi  farm 
|AIP 
Depth  to 
I Well       Water 
|EC 
| Acidity  | Nat 
Cat+ 
Mgt+   |B 
No 
tab le   (m)      (mmhos/ cm)  | (pH) 
Co3         SAR 
2 
3 
6 
2.80 
1.23 
1.37 
3.40 
1.45 
2.55 
|6.3 
|  1.0 
|  1.0 
|   2.7 
|0.63 
|  5.6 
|8.7 
|8.5 
|8.3 
|8.3 
|8.4 
|6.7 
132.6 |73.2 
| 
56.1   | 21.4 
16.0  | 17.3   |  4.0  |  79.3    68.63 
|   0.9     341.6| 2.10  | 
207.4 |    38.5| 5.8    |  3.8  | 475.8     8.2   | 
425.0 
|8 
| 10 
| 595.0 
117.3 
| 
| 
11.2  |   2.4   |    1.7| 73.2  | 29.8    | 15.2 |   3.4   |   0.6    268.4      2.08 
136.3|     1.99  | 43.6      36.6 |   7.61 
At   borehole  Pll  (Table  2)   the  water  table  ha8   Iisen  5  metres  in  9  years  to 
37.2   nmhos/ cm   while  the  salinity of  the  water  in   the  observation well  is  10.0 nmhos   / cm.      Tab le  2  shows   the  depths  and  EC   of  the   gr oundwat ers  at  all  AIP observation  wells  and  at  open  bores. 
Where   the  water   leve ls  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  probab ly  also  includes  seepage  fron  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 Seasona1  flood  from  the  River  Awash  which  left behind  shal low  pools  of 
within  l.8 metres  of  the  surface. 
The  salinity of  the  groundwater  at Pl1  is 
evaporating  and 
of  the  Eastern  and  Westera  Dykes. 
Some  water  is   enter ing  the  aquifer  from  the  river,  particular ly  at  times  of  high flows.     Observation wells  AIP  S,  PPl,  AIP   1l showed  a  rise  in  the  water  table following  the   prolonge d high  flows   dur ing August  and   Sept ember 1981. 
Deep  auger  bores  at  the  Melka  Sadi  fara   he adquarters area  revea led  very  saline waters. which  are slightly confined  and    associ at ed  with weathering calcareous 
tuffs  and  clays which  may   be  charged  tron the  high  ground  around  Unda  Evu  hill 
course  of   time. 
therefore  saline  water  some   of  which  entered  the  aguifer  in  the Such  flooding  is  now  prevented  since  comp letion of  cons truction 
-    4   -TABLE2 
Depth  and  EC   of groundwater  at  open  5 m bores  and   adjoining observation well6 
Site 
AIP  1  U AIP  2  Be AIP  3  B AIP  4 
AIP  6  U AIP  7  U AIP  8  B 
AIP   10   A 
AIP   12  C 
AIP   13  C 
AIP   14  C 
AIP   22   C 
Pll       A 
DRH   20  P DRH    21     B 
DRH   22  A 
DRH    23   A 
DRH   24  A 
DRH    25   A 
DRH   26  A 
DRH    27   A DRH   28   Bs 
DRH    29  A 
DRH   30  A 
DRH    31   A 
DRH   32  A 
DRH    33  A 
DRH    34  B 
DRH   35   B 
DRH  36  B DRH  37  Ba 
DRH    38   A 
DRH    39   B 
DRH    40  B 
DRH    4l  B 
DRH    42   B 
DRH   43  B 
DRH    44   U 
DRH    44  U DRH    45  A DRH    46  A DRH     47 DRH   48   B4 DRH    49   U DRH    51   B DRH    52   B 
DRH  53  B_ DRH  54  Bs 
EC  of  Open  Bore 
Water 
(nhos/ cm) 
21.6 
2.2 
2.2 
12.4 
7.0 
0.67 
11.2 
12.7 
7.8 
37.2 
22.5 
60.1 
40.1 
20.2 
14.4 
15.8 
2.6 
7.2 
2.2 
1.21 
36.0 
28.4 
8.8 
6.2 
4.0 
11.2 
2.6 
14.6 
6.0 
1.0 
7.4 
6.75 
0.92 
2.60 
0.66 
4.20 
0.72 
0.32 
0.79 
1.97 
2.5 
8.25 
1.2 
Depth 
(m) 
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 
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 
EC   of  Observation Well  Water 
(amhos/ ca) 
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 
Uncultivated 
Cotton 
3           Banana 
P            Pasture 
B       Ban ana -   saline 
A          Abandoned  plot 
2.2 
-   5  -or  from  springs associated with  the  local vents  and  1ava  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  l  and  the  salinity values  on 
Map   No   2. 
The   depth  to   imperme  ab le  or  very  slightly  perme  able  horizons  is  shown 
On    Map   No     3. 
The  groundwat er  cont our  map  produced 
observation wells  showed   the  Melka  Sadi  and   Amibara  areas  as   two   separate drainage  basins  with  the  Dofan  volcanic  constricting  the  valley  between  the  two 
by  Curry  in  1971   from  a   small  number  of 
basins .       The   Me lka  S adi  basin  is  shown  as  draining 
towards  the  river  from  a 
water  table mound 
seepage  at  the  start  of  the  upper  plain. 
to  the  south  east  of  the  study  which  originated  from   river 
However   it  was   suspected  that  two 
water  systems    both  of  which  were  under  pressure,  were 
being  read  as 
representing  one  syst em. 
risen   considerab ly, especially within  the  Melka  Sadi  farn  area  as  can  be   seen 
Since  this  study  was  made   the  groundwater  levels  have 
rises at   s Ome    of  the  observation wells. 
from  Map   No    l.   Curry  also  noted  a  relationship  between  high  river  flows  and 
3.2.1 
Observation wells 
There  are  20   AIP   obsevation wells  in  the 
and   four  of  the  earlier wells  are  stil1  in   operation, 
Melka  Sadi  area  on   a   2  km   x  2  km   grid 
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 
date,  both  for  water  leve ls  and  salinity. recorded  monthly. 
records  of monthly  readings  from  mid   1980   to 
The    e ar lier wells  are  now   also 
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 
A further  3 
observation wells  are  planned  for  the  farm  area  and  are  to  be   installed  as   soon 
of  observation  well. 
as   possible. 
4.        CLIMATE 
The  climate  of  the  study  area  is  s emi-desert With  a  bi-annual  rainfall  Dattern. 
Rainfall  amounts  at  Me lka Warer 
Research  Station  range  between  300  mn    and   660  mm 
per   ye ar with  an 
annual  mean   of  550  mm 
approximate ly  half  of  which   falls  in 
July  and   August  with 
ye  ars of  records  are  available. 
ano ther lesser  peak  dur ing   February,  March   and   Apri1. 
l6 
There  are   t wo   rainfall  stations  at  Melka  Sadi  but  record8  are   inc omplete  with 
many   years '   data missing. 
rhere are   considerab le variations  in  the  amounts  of  rainfall recorded  over  the 
However  from  the data available it is clear that 
area  from  site  to  site  and   trom  year  to  year  as   can  be   seen  in Annex  4,  titled "Variation  in  rainfall  amounts". 
Temper atures  range  between  a me an  maximum  of  37°C  in  June  and  a me an  minimum  of 12.8°C  in    Dec ember.     The  annual  variation in me an   month ly  temperature  is  only about  8°c. 
-6 
L TABLE   3 
Water   levels  and   salinities  (EC   in  mmhos/ cm)   of  groundwater  observation wells  at Me lka Sadi  farm  on  selected dates 
Well Location 
Well Pll 
Date 
30/7/70 
3/1/71 
| 31/5/72 
| 7/1/72 
| 1/2/73 
| 24/11/ 73 
10/6/74 
| 19/6/75 
| 7/6/76 
|7/1/79 
| 4/12/80 
| 25/5/81 
5/11/81 
Water Level  (m) 
6.92 6.45 6.33 
|6.17 |5.70 |5.29 |4.41 
2.21 2.10 
|1.95 
2.17 
|1.47 
|1.85 
EC 
(mahos/ cm) 
|9.6 |9.0  (1) |9.9 
Well 
Loc ation 
We 11  AIP  1 
Date 
| 26/6/80 
4/12/80 
25/5/81 
|4/11/81 
Water Level  (m) 
| 3.40 |3.50 |3.00 
| 2.56 
EC 
| (mmhos/ em) |6.3 
|7.2 (2) |6.0 
|Well Location 
| Well  AIP  2 
Date 
|7/6/80 
|4/12/80 
| 25/5/80 
4/11/81 
Water Level  (a) 
| 2.60 
1.55 
0.59 
|0.92 
EC 
(mmhos  /cm) 
0.90 0.95 1.00 
-7 TABLE   3  (Continued) 
Well 
| Location Well  AIP  3 
Date 
12/7/80 
| 4/12/80 
| 25/5/81 
| 5/11/81 
|Water  | Level  (n) 
| 2.15 
| 3.12 
| 2.23 
|1.76 
EC 
(mnhos/ cm) 
1.0 
0.9 
0.94 
Wel1 Location 
Well  AIP  6 
Date 
| 12/7/80 
|4/12/80 
28/5/81 
|5/11/81 
| Water Level   (m) 
| 3.25 | 3.93 
|3.45 | 3.22 
EC 
(mmhos/ cm) 
| 
| 2.2 
2.4 
2.6 
Well Location 
AIP  8 
|Date 
| 12/7/80 
|4/12/80 
| 26/5/81 
| 5/11/81 
Water 
|Leve l  (m) 
|2.40 | 2.14 | 2.18 | 2.15 
EC 
(nmhos / cm) 
|0.60 
|0.66 
|0.62 
|Location 
Well 
Well  AIP   10 
Date 
| 12/7/80 
| 7/12/ 80 
| 25/5/81 
| 5/11/81 
Water Level   (m) 
2.60 3.05 2.64 2.58 
|5.0 
EC 
(mmhos/ cm) 3.6  (3) 
3.6 
Notes 
(1) 
(2) 
(3) 
Groundwater  level  in  open  bore  was 
Groundwater  level  in  open  bore  was 
2.70  m and  EC  37.2 
2.89  n  and  EC  21.6 
Groundwat  er   level  in  open  bore  was    2.66 
and  EC    11.2 
8   -EIGURE   2 
G.L.741-89 
620 
I6-6Om 
ITALCONSULT 
OBSERVATION   WELL 
No. P.Il FIGURE   3 
300s0 
500 
IO00 
Concrete  class 21/37 
50 
Piezometer  stand pipe 
Back  fill 
I50 mm  thick gout seal 
Piezometer  head 
Sand   filter 
Base  of  piezometer 
Base of hole 
Minimum  150 
2mm   holes 
Maximum         at  50 mm   spacing 300 5000 
SCALE  l·20 
All  dimensions  in  mm 
AJP  OBSERVATION   WELL 
10 Evaporation  figures,  "8-Pen",  range  from  a monthly  mean  of  170  mm   in  August  to 252  mm    in  June.    The    aver age   me an evaporation is  196  mm. 
5.      FIELD  STUDIES 
5.1    Methods  and  Equipnent 
Fifty-five  sites  were  examined  in  the  Melka  Sadi  area,  and  forty  one  of  these were  within the Melka  Sadi  farm  Area  of  I  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 
10  cm  head  of  water. 
expressed  in m/hr. 
the  soil  surface  using  3  sets  of  double  rings  and  a 
Each  test  was   run  for  at  least  8  hours  and  values 
ii)    Hydr au lic conductivity  (permeability)  me  asur ement within the dry  soil 
profiles  at  3 depths  below  the  surface using  the  "pour  in   method'". 
tests  were  run  for  at  least  6  hours  and  results  expressed  in 
metres/ day. 
These 
iii) Hydraulic  conductivity  measurements  within  the  soil 
table  using  the  "pump   out  method"  and   values  were  expressed  in 
profile  below  the  water 
metres /day. 
iv)    At   each  site  a  5 metre  deep  auger  bore  was   excavated  and   the  soil 
described,  with  water  levels  and  salinities  being  recorded. 
profile 
v)      At   19   of  the  sites  2 m 
for   labor at ory  analys is. deep  soil  pits were   excavated,  described  and   sampled Equipment  used  in  the  study  incuded: -
1 3 
4 2 2 2 20 2 
No 
No 
No 
No 
No No No 
N 
NC No 
Ede lman   6  cm 
4  wheel  drive  vehicle 
2  wheel  water  trailer  (see  note  below) 
Sets  double  infiltrat ion  rings 
Gr   aduated  plastic  45   litre  Jerryc ans  with  taps Modified  petrol  engine   carbur et tors and   plastic  pipes 10   cm   Edelman  auger  heads 
13   cm   "Jarret"  auger   he ads 
10   cm   Jarret  type  auger  he ads  (local manufacture) 
1 metre   lengths  of  3/4"  galvanised  pipe 
augers 
No        Portable  EC 
meters 
The   4  wheel  drive  vehicle  and  water  trailer was 
Mercedes   truck  fitted  with  a   l000 
he avy   rain  this  proved  ideal  for  the  work. 
litre  tank. 
replaced  in  June  by  a1 ton 
Apart  from  a  few  times  during 
The    fie ld   studies  were   carried  out 
time   assist an ce    of 
the  drainage  engineer  and  a   team  of   3  labourers.    Soil  pits 
by   the  soil  salinity  specialist,  with  part 
were   exc avated  by   sub-contract  labour. 
-    11    -5.2   Field Work   Progr anme 
The  soil salinity specialist  arrived  on  site  on  11  Febru ary  1981. 
Excavation  of  soil  pits  started 
on   March  8,  sampling  of  the  pits  was   completed 
by   27   March  and   the  samp les  sent  to 
Soils  Laboratory  of  the  Institute  of  Agricultural  Research. 
Addis  Ababa  for  analysis  at  the  Holetta 
Levelling  of the 
observation wells  was   carried  out 1981. 
by  Project  survey  st aff  in   Febru ary and  March 
Field  testing  of 
and  was   concluded  at  the  end  of  September 
infiltration rates  and  soil  permeab ility commenced  on  May   18 
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 
gr  oups 
were  found 
in  the  Me lka  Sadi  area. 
The   first  of 
these  are  the  saline 
alluvial/colluvial soils 
found   in  the  south  east  of  the 
medium   to  coarse,  with 
ar ea  at  the  foot  of  the   escar paent. 
weathering  tuffs  and  clays  in  the  deep  sub-soils. 
These  have  variable  textur es, usually 
The   second  soil  group  is  the 
alluvium  with  stratified  and   laminated  profiles  on  which  the  greater  part 
noraally non-saline,  medium  and  fine  textured 
of  the 
Melka  Sadi  farn  is   estab lished. 
The  third  group,  and  the  most  wide  spre ad  in  the 
Me lka Sadi  area 
the  fine  textured  vertisols 
of  vari able  depth  over lying 
coarse  textured  alluviums. 
The   vertisols  vary  in  depth 
This  soil  gr   Oup   is  limited  to 
stratified  and  often 
fr on  a  few  centimetres 
a   whole  are 
the  north  and  western  portion  of  the  Melka 
to  more   than  3   metres  in  the  north  of  the  area. 
Sadi  farm. 
Al1   three  soil  groups  are 
readily  identified  in  the 
field  by   colour,   texture. 
surface   appear ance  and   somet imes   by   the  natural  veget 
at ion. 
Each  of  the groups 
textured  alluvium,  but  very  little of   this  is  present  within  the  proposed irrigation  area. 
Soil  pDrofi le  description6  are  shown   in  Annex   2 and   results  of  soil  analysis  in Annex  3. 
6.1    Soil  salinity 
The    leve ls of  soil  salinity  in  the  presently  cultivated  land  at  the  Me lka  Sadi farm  are   gener al ly  lower  than  shown   by   Ita lconsult,  this  being  due   to  le ach in 
by   the  applied  irrigation water  over   tine.    However  the salinity leve ls  in  the ab andoned  areas  are now  higher  than  shown  in  the  Italconsult reports. 
Tt  would  appear  that  leaching of  soluble salts in  the  early stages  of development  were  successful,  but  1later  the   exist ing  saline water  tables  rose, mot  with  the   infiltrat ing  irrigation water  and   satur ated  the soil profiles  above the  water  table.    This re sulted  in  an  upward  movement  of  soluble salts which  was 
is  shown   in  Figure  4. 
In  addition  there  is  alongside  the  Awash 
river  a  narrOw  strip  of  recent,  coarse 
àccelerated  once  the  area  was  abandoned. 
the  salts. 
Rainfall  is  insufficient  to  leach  out 
12  -Figure  4 
GENERALISED  SOIL  MAP  OF  MELKA-SADI  FARM 
After    Italconsult  1969 
0.5 
Km 
Scale 
LEGEND 
A1luvial  and  Colluvial saline  soils 
Alluvial  non  saline  soil 
Fine  textured  vertisols Recent  Alluviums 
13 These  abandoned  are as  have  a  damp  surface  crumb  or  crust  (hygros copic)  overlying 
a deflocculated  layer  which  is  of  very  low   perne ability and  up  to 25   cm   thick. 
This  layer  prevents  the  entry  of  rainfall which  together  with  spi1lage  and 
runo ff  forns  evaporation  p ans which  have  become  progress ively  more  saline. 
A 8imilar  situation can  be  seen  alongs ide  many  canals  where  typically  seepage through  the  bank  causes  the  adjacent  road  to  become  damp  with  salts. 
Consequent ly  after rain  it8  surface  layers  defloccu late,  causing  the  road  to become   impassable  to  vehicles. 
Abandoned  areas  together  with  other  areas  affected  by  salinity/high  wat er  tab les 
are  shown   on   Map   5. 
6.2   Previous  Mapping 
The   soil  map   produced  by   Italc onsult  in  l969  was   found  to  be   accur ate  as   far  as soil  units  mapped   and   general  arrangement  of  the  different  horizons  are described.    However   the  present  saline  areas  are  now   far  more   widespre ad      than  as mapped   in  the  Italconsu lt  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  commeat   that  soil  unit  10   often had   a  fluctuat ing water  table. 
The   frequent   alterat i on  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  n   apart.   Unit  6   is the  most  widespread  soi1  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     me   asurement  is best  carried out with moisture  contents  in  the  fie ld 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  extr act  of a soil are as  follows: -
EC   of Saturated Extract 
0- 2 
2   -    4 
4   -8 
8- 16 
)   16 
Tmhos/ cn 
mhos / cm 
mmhos/ cm 
mmhos/ cm 
mmhos/ cn 
Crop  Reaction 
Effect  almost  negligible 
Yields  of  sensitive  crops  may   be   reduced Yields  of  many   crops  may   be   reduced 
On ly  a 
yields  tolerant  crop  will  give  re  as onab le 
Only   a  few   very  toler ant 
a    reas onab le  yield 
crops  will  give 
The  bAnana   plant  is  of   low   salt  toler ance  and   reduction 
+he  EC  of  saturat ed  extract  1s  greater  than  1.0  mmhos/ cm. of  yie lds  may  occur  if 
-    14   -Field electrical conductivity values  were  determined  on  a l:l  soil/wat er 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  comp aring l:1 soil water  EC   with  saturated extract  is  to multiply the  l:1 results  by  a  factor of 2.0. 
By  checking  the  EC   of   infiltrat ion sites before  and  after the  test an  indication of  the  leaching effect can  be  obtained.    Results  below  show  that  the EC   of the 
l:1  soil/water mixture  in  the  top  25   cm   of  the  soil profile was   reduced  after 
8  hrs  as  follows: -
SITE 
EC    l:1 (Top  25   cm) 
EC   AFTER INFILTRATION 
(Top  25   cm) 
(mmhos/cm) 
DRH   6 
DRH   23 
10.2 
6.5 
3.7 
2.1 
6.6 
8.7 
8.4 
(mmhos/ cm) 
6.8 
DRH   21 
AIP   10 
DRH   24 
DRH   5 
DRH   7 
3.1 
I.6 
0.46 
5.6 
3.2 
5.3 
Average  EC 
values  of  saturated  extract  for  the 
Me lka Sadi  area  are  shown  below: 
SOIL 
LE VEL 
Topsoils 
Upper   subsoi ls Subsoils 
Deep   sub-soils ()  150   cm   deep) 
AVERAGE  EC 
(mhos/ em) 
2.24 2.94 3.12 3.22 
RAN GE  OF  EC  VALUES 
(mmhos / cm) 
6.0 -   0.98 8.5  -   0.72 
8.1  -   0.16 
9.5  -   0.68 
High  EC    values  were   found   during  field  tests  on   the 
areas, for  examp le  at  DRH   2  where  the  EC 
of  the  top  soil  was   22.0   mmho s /cm  at 
top-soi ls  of  the 
ab  andoned 
clays ,  as    me  asured  within  the  5  m deep  bores.     At   one  site its  value  was  as  high as   60   mhos / cm,  as  can  be  seen  from  an  inspection  of  Table  2. 
The   re sults  of  chemical  anlayses  are  shown   in  Annex   3. 
3- 10   cm   depth.    High  EC    values  were  also  found   in  the  weathered  tuffs  and 
6.3.2 
Exchange ab le  Sodium  Percent age   (ESP) 
A high  concentration  of   exchange able sodium  causes  break  down   of  the  soil structure.  which   results  in  reduced   permeability, aeration  and   workability.    The amount   of   exch ange able sodium  present  is  expressed  as   ESP   which  is  determined 
fr om   the  extracted  cations  less  soluble  cations  to  give  the  sodium  absorbtion ratio,  sAR,  which  may  be  deternined  as  follows : -
-   15  -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 
although  higher  ESP 
vertisol  such  as   those  found  in  the 
or  less  is  considered   acceptab le for  a  non-a lkaline soil, values  can  be   tolerated  if the  soil  is  a  fine  textured 
north  of  the  Me lka  Sadi  area. 
A high  value 
for  exch  ange able 
sodium  can  have  an  effect  on  plant  growth  and   some   authoritieg 
quote  a  figure  of  3 
the  upper  limit  of  a   non-a lkaline soil. 
milli-equivalents  of  exchange ab le  sodium  per  100   g  soil  as 
ESP 
values  for  the  Me lka  Sadi  area  are 
given   below: 
ESP   VALUE S   OF   NON   SALINE   NON   ALKALINE   SOILS 
(EC  less  than  4.0  mmhos/cm  and  ESP  less  than  15) 
SOIL  LEVEL 
Topsoils 
Upper  sub-soils 
Subsoils 
Deep  sub-soils 
(greater  than  150  cm  deep) 
ESP 
2.76 
4.36 
4.36 
4.68 
ESP   VALUE S  FOR   SALINE 
ALKALINE   SOILS 
(EC  greater  than  4.0  mmhos 
SOIL  LE VEL 
Topsoils 
Upper  sub-soils 
Sub-soils 
Deep  sub-soils 
(greater  than  150  cm  deep) 
and  ESP   greater  than  15) 
ESP 
7.13 12.70 24.20 38.65 
The   high  ESP 
weather ing  tuffs  and   clays , 
values  in  the  deep  sub-soils  are   gener ally associated  with 
as  are  the  high  EC    values  nentioned  above. 
6.3.3 
pH   Values   (Saturated Extract) 
The    aver age  pH    values  for  all  samples  was   7.55  with  the  range  between  7.15  and 9.6. 
A PH   value  greater  than  8.5  1s   8enerally  regarded  as   indicating  an   ESP   greater than  15.     High   pH    values  coincided  with  high  ESP     values. 
-   16  -6.3.4 
Soluble  Anions 
Traces  of  S04  were   pres ent  in  half  the  samples,  and  of  the  remainder  high,  and often  very  high  values  of  S04  were  obtained  indicat ing  the  presence  of  gyp sum (Caso4),  an   import ant  factor associated with  high  sodium  levels .    In  many   cases high  levels of SO4  were  present  in the samples  with  large amounts  of 
exchange ab le sodium, 
7.       HYDRAULIC   CONDUCT IVITY 
7.1    Pour  in Tests 
Pour  in  tests  following  the  USBT   method,  were  carried  out  in  soil profiles  above the  water   tab le, 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 
Cm. 
When   swelling  clays  (vertisols)  or  loose  sands  were  encountered  a   filler of 
radius  giving  a  wetted  area  of  1963  sq 
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 
envelope  was   saturated .      Water  used  in  the  test  was   taken 
from  an  ad iacent  cana1 
surrounding  soil 
metres/ day  and   are  reproduced  in  Table  4. 7.2    Pump   out  Tests 
or  from  the  main  canal  within  the  farm  area. 
Results  were  expressed  in 
Pump   out  tests, 
on   the  soil  profiles  below  the  water  table. 
following  the  "Auger  hole  method"   of  Hooghoudt   et   al, were  made 
textures  of  many   profiles  Wide  variations  in 
Owing   to  the  laminated  variable 
site.   Where   sightly  confined  water  was 
found  in  coarse  textured  aquifers, 
results  were  obtained  from   site  to 
particularly  high  values  were  recorded. 
Results  are  again  reproduced  in 
10   cm   were  run  for  a   minimum  of  8    hours. 
Table  4. 
7.3    Infiltration tests Infiltration  tests  using  3  sets  of 
double  rings  per  site  and  a  water 
depth  of 
hand  but  at  others it was 
back  of  a  vehicle  to 
drive  the  rings  into  the  soil. 
necessary  to  use  a    hydrau lic jack 
At   many   sites  the  rings  were   set  in  by 
On    the  finer  textured  soi ls 
springing  from   the 
with  a  strong deep 
allow  the  clay  to  swell  sufficiently  to  hold  water  in  the  rings. 
cracking  pattern  initial wetting  of  the  soil  was 
the 
results  from   each  of   the  three  rings  was   calculated  and  is  reproduced   for 
The prolonged  to 
me  an  of 
each  site  in  Table  4. 
8 
WATER   QUALITY 
The   quality  of   irrigation water 
(particularly  sodium),  its nature, 
is  dependent  on   the   tot al   salt  content 
the  ratio  of  calcium  and   magnesium   to  bicarbonates. 
the  ratio  of  sodium  to  the  other  cations,  and 
Total  salt  content  is  related  to 
recorded  at  Melka  Sadi  Farm  was 
0.28   amhos/ cm corresponding  to  l60  ppm   salts. 
electrical conductivity. 
A typical  value  of  Ec 
-    17 -TABLE   4 
Results  of   Hydrau lic Conductivity  and Infiltration Tests 
1. 
POUR    IN   TESTS 
SITE 
Hydraulic  Conductivity  "K"   (m/day) Depth  below  ground  level 
Infiltration  (m/day) 
0- 60  cm 
60- 120  cm 
120   -   180  cm 
DRH  1 
| DRH   2 
| DRH   3 
|DRH  4 
| DRH   6 
| DRH   7 
DRH   20 
DRH    21 
| DRH   22 
| DRH   23 
| DRH    24 
DRH  25 
DRH   26 
|DRH  27 
I DRH   28 
DRH   29 
DRH   30 
| DRH    31 
DRH   32 
DRH   33 
|  DRH  34 
DRH   35 
0.048 0.059 0.09 
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 
| DRH   360.041 
| DRH  37  0.0156 
DRH  38     0.06 
| DRH    39     0.019 
I DRH    40        0.103 
0.116 
0.016 0.50 
0.25 
0.102 
0.144 
| 
0.028     0.43 
|0.07 
0.122 
0.0337 
0.108 0.083 0.12 0.036 0.0024 0.04 0.3217 
0.039 
0.072 
0.072 
| DRH   41 
0.054 
|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 
|0.08 
DRH   42 
DRH   44 
DRH   45 
0.067 
|0.34 | 
0.63 
0.13 
|0.14 
0.73 
0.31 |0.72 
0.42 0.61 0.50 0.78 0.64 0.60 0.54 0.75 0.30 0.43 
0.10 
0.35 
0.57 
0.71 
0.08 
0.53 
0.53 
0.53 
|0.69 
0.96 
DRH  46 
DRH  47 
0.109 
0.194 
|0.102 
0.09 
-
DRH  48 
0.062 
| DRH  49 
|DRH  50 
0.06 
0.052 
0.063 
DRH   51 
| DRH  52 | DRH  53 | P1l 
0.045 
0.216,0.212 0.120 
0.06 
0.103 
|0.0296 
0.118 
0.02 
0.061 
0.0346 
0.083 
0.033 
|0.06 
0.130 
0.06 
0.072 
0.08 
|1.71 |1.86 
1-18 0.69 0.61 
0.33 
0.50 
0.58 
|1.75 
0.04 
-   18  -TABLE   4  (Cont inued) 
2. 
PUMP    OUT   TESTS 
SITE 
Depth (m) 
Hydrau lic Conductivity "K" 
(m/day) 
Infiltration (m/day ) 
DRH   1 
DRH     2 
|DRH  4 
| DRH   20 
| DRH   20 
| DRH   21 
DRH   23 
DRH   23 
2.23 
|3.41 
| 4.05 
4.89 
| 3.79 
|1.78 
1.83 
2. 32 
| 2.52 
|0.63 
0.43 
| 
0.31 
0.42 
-
| DRH   24 
DRH    24 
| DRH  28 
DRH  30 
| DRH   25 
| 2.36 
2.58 
| 3.00 
DRH   32 
|3.70 
| 3.03 
DRH   32 
4.10 
DRH   33 
DRH  34 
DRH  34 
|3.75 
| DRH  35 
DRH  37 
| DRH   40 
| DRH 39 
DRH   40 
|7.31 
|7.52 
2.35 
1.73 
|0.85 
1.0 
DRH   41 
|1.07 
DRH   41 
|1.35 
|1.64 
DRH   42 
1.35 
DRH   45 
1.64 
DRH   46 
3.46 
DRH   47 
2.75 
DRH   48 
1.86 
DRH   48 
2.75 
0.61 
| 
0.50 
0.60 
0.76 
0.43 
0.10 
0.35 
0.57 
0.08 |0.53 
|1.10 
|0.69 
0.96 
|.86 
| 
|1.18 0.69 
DRH   51 
DRH   54 
|1.08 
2.37 
|0.884 
0.969 
|0.0379 
|0.0326 
|0.9915 
0.198 
0.154 
|   4.30 
|  1.46 
|  4.43 
0.4 
|1.62 
|  2.23 
|  1.35 
|0.874 
|0.171 
|0.924 
|  5.0 
|0.837 
|0.683 
|1.44 
1.87 
|0.28 
2.90 
| 10.5 
|4.85 
|0.358 
|  2.41 
1.62 
0.065 
|1.90 
0.406 
0.89 
0.50 
-   19   -Sodium  percentage  is  the  percent age  of 
sodium  cations  in  the  total cations 
expressed  in milli-equivalents  per  litre. 
carbonate  CO3   plus  bicarbonate  HC03    less  the  calcium  plus  magnesium  all expressed  in Meq/litre. 
Res idual  sodium  bicarbonate  is 
The  wat er  from   the  Awash   river var ies  in 
periods  of  low   flows  there  is  usually  an   increase  in  disolved  salts  and   thus  a 
quality  throu ghou t   the  ye ar. 
During 
lowering  in quality.    The   USDA   guide  for  water 
quality  shows   the  Awash  water  to 
be   of  C1Sj   quality  meaning  low   s odium,  low 
the  quality may   drop  to  CST, which  indicates  low  sodium  hazard  but  medium 
salinity hazard,  but  during  low   flows 
salinity hazard. 
Both  sodium  percentages  and  amounts  of 
those  required  for  first  quality water,  the  upper  limits  for  which   are  6.5Z  and 
residual  sdium bicarbonate  are  below 
1.25  Mg/litre  respectively. 
Nevertheless  it must  be  stated  that  water  of  first quality contains  soluble 
salts  in  appreciable  quantities. 
concentration related  to  an  EC    of  0.35    mmhos/ cm,  will  add   200   kg   of  salt  to  each 
Water  containing  200   ppm   of  disolved  salts,  a 
hectare  each  year  when   the  water  is  applied  at  the 
rate  of  lm per  year. 
Resu lts  of  the    analys is 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  increased.  in  the  soil  SOme and  of 
thus  the  relative  proportion of 
s odium in  the  soil  water  is 
the  sodium  will  be 
absorbed  into  the 
soil colloids  which  will  affect  the 
physical  structure  of  the 
level  of  sodium  in  the  soil  which   in   turn  is  toxic  to  pl ants. 
soil,  reducing  its   perne ability and   creating  a  high 
waters  were  selected  on   the  basis 
In   Sir   Willi am   Halcrow  & Partaers'   Hydr opedol ogical Report,  dated  1975,  two 
of  highest  SAR   Values ,   one  of  which  was   that 
for  Melka  Sadi  having  a  SAR   Of   2.0. 
then  calculated  us ing  various  values  for  the   leaching  requirement. 
The   expected  SAR   of  the  drainage  water  was 
The 
hazard  unless  the  amount   of  water 
resu lts obtained  indicated  that  there  is  not  likely  to  be   an   alkalinity 
percolatin8  beloW   the  rootzone  is  reduced  to 
less  than 
5   of  the  applied  water,  taking 
the  critical  1leve l of  the  SAR   of  the 
exchangeable  sodium  in  the  soil  colloid  comp lex  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  haruful  to  the  crop, each  of  which  has   its  own   level  of  tolerance.    Such   r emoval can  prove difficult if  there  is  a   shallow  galine  water  table  present. 
During  the   irrigat i on 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    dis solved salts  towards   the  soil  surface.     If there  is  a  shallow water  table the  upward  capillary movement   is  maintained  from  that  water  table,  also 
drainage  water  as  15. 
to  be  in  the  range  of 
Melka  Sadi  farm  deep  percolation  losses  are  expected 15  At -   20}  and   thus  the  prob lem   of  excessive quantities  of 
20  -(Meg/1itres) 
Residual Nac03 
SAR       | 
| 
Boron     (ppm) SO4+ 
|1.21        |0.24 0.76      0.56      |      0.82 0.00 
1.92      1.6   |1.96        |1.36 |1.57  2.00 
| 
nil nil  |0.1 nil nil |nil |0.41  0.1  nil 
0.01 0.01 nil 
| 
FROM 
WEIR 
D 
DETERMINE 
0.40      nil 
| 
0.42  0.45 
0.43| 
|0.45 
| 
DIVERSION 
nil 
nil 
| 
0.88 nil  nil  nil 
AS 
WATER SADI 
TABLE       MELKA 
| 
2.90 30    1.70 0.40 3.00 2.85 3. 
17| 
RIVER 
0.19 0.10       0.18 |0.18 
| 
| 
20 
| 
AT 
K 
Nat  | 
| 
l.40 |0.65   1.65 |1.61 
| 
AWASH TAKEN 
l.45 
0. 
| 
| 
0. 
| 
1.70 
1.33 |1.36|1.28           0.56 |1.12|0.24                |      |1.25|0.15          0.25 
| 
| 
| 
OF 
ANALYSIS 
SAMPLES 
Cat+       Mgt+        | 
Acidity            | | (pH)      I 
|1.33 
| 
|1.20 
| 
|1.24 
|8.1 7.7  8.0 8.5  7.7  |7.8 
EC 
|(mhos/            cm) 
31/12/         70   |0.27 |0.28  0.32 |0.33  0.33 0.32 
Stamped 
5/1/71  3/1/71         I 
24/1/71  19/2/71 
6/2/71 
Date 
| 
21 containing dissolved  salts, 
or    ne   ar  the  surface  of  the   soil.   This  is  generally  referred  to  as 
le ading   to  increas ing  amounts  of  salts 
deposited  at secondary 
salinisation. 
If  there  is 
can  be  kept  at   a   suitable  level  by  drainage  then  there  is  little 
a   large  volume  of  water  passing  through  the  soil  and   the  water  table 
risk of build 
up 
of  salt  in  the  soil  profile. 
However   irrigation water  is  usually  limited  and 
the  adopted 
amount   of  land  lost 
drainage  system will  be   dictated  partly  by   cost,  partly  by   the 
used),  and   part ly   by 
to  drains,  (particularly where  a  sur face drainage  system  is 
the  physical  condition of  the   soils. 
Hence  several  factors 
may   dictate  the  depth  or 
to  be  arrived  at  which  will  allow  the  water  table  to  be  controlled  at  an 
effectiveness  of  the  drains  and   a  compromise  often  has 
toler ance  limit  of  the  crop. 
In  order  to  ensure  the  removal  of  the 
accept ab le  depth  and  the  dissolved  salt  content  of  the  soil  water  kept  below  the 
the  drainage  syst em   a  proportion  of  the  irrigation water must  move 
dissolved  salts  fr om    the  soil profile  into 
thr ough   the 
soil  to  the  drains. 
This  proportion  is  referred  to  as   the  leaching 
requir enent 
and   is  usually  expressed  as  a    percent age   of  the  total  applied 
irrigation water 
together  with  any  effective 
rainfa1l  amounts. 
The   leaching  requirement  (LREC)   is  deternined  by   the  following  equation: -
LRgC 
ECi 
ECdw 
X 
Where    EC;      is  the  EC   of  the  irrigation water, 
ECA        is  the  EC    of  the  water  below  the  root  zone. 
and   f   is  the  leaching  efficiency 
Leaching  efficiency  is  dependent  on  a  unl form  movement  of  wat er  through  the  soil 
profile. 
The  medium  to  light  textured  sOils  of  the 
Me lka Sadi  farm  are  expected 
to  have  a   leaching efficiency 
around  0.6,  While   the 
fine  textured  cracking  clavs 
will  have  a   lower  value  around  0. 4   as 
the  cracks  causing  uneven  water  distIlbution  in  the  s oil profi le. 
a   result  of  the  concentration  of  water  in 
With  a  value  for  EC; 
efficiency  factor  of  0.6,  the  leaching  requirement   will  be: 
of  0.28  mmhos/ Cm,    a  value  for  ECdu   of  4.0  mmhos/ cm   and   an 
LRgC 
0.28 4.0 
The   calcu lated  water  requirement  for 
every  fifteen  days   and  allows  for  a   leaching  requirenent  of  10%. 
11.7%  of  the applied water 
ban ana at  Melka  Sadi  fam  ie  10  om 
applied 
The   Fine  textured  soils  have  a  lower   leaching  efficiency  factor  of  0.4  and   their leaching  requirement  will   be: 
LREC 
0.28  X 
4 
17.5% 
0.4 
mhie   bioher reguirement  on  the  fine  textured soils is the  same  as  the  caleulated Field percolation  losses,  assumlng  an   irrigation efficiency  of  65% 
-    22  -By   growing  a more  salt toler ant crop  such  as  cotton,  the  ECdw  can  be  raised  to 12.0  mmhos/cm,   gíving  a  LRpEC      of: 
0.28 12 
5.8% 
This  is  consider ab ly less  than  the calculated field percolat ion  losses  o£  17.5%. 
11,    RECLAMATION   OF   SALINE   SOILS 
It is recommended  that  the water  tab le within the Melka  Sadi  farn be  lowered  by me ans  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  confirn  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. 3 
Satisfactory  infiltration  and  perme ability 
Removal   of  excess  salts  by   leaching 
4.       Careful  soil  and 
water  management 
The  minimum  water 
the   irrigation  system  being  used.     For  Me lka  Sadi 
table  depth  required  for  leaching is 
farm,  where  banana  is 
dependent  on   the  crop  and 
year, the  minimum  water  table  depth  below  ground  level  required  is  1.8  m. 
irrigat ed   by   the  application  of 
10   cm   of  water  once  every  l5  days   throughout  the 
The   infiltration  and 
a reduction  of 
perme ability during  and   after  le aching 
perme ability rates  recorded  are  satis factory  and   at  present 
Nevertheless  soil   perme ability shou ld  be 
monitored 
dur ing  the  drainage  and 
is  not  expected. 
leaching trials. 
Removal  of  excess  salts 
initial 
stages .     The   present  water  distribution  system  at  Melka  Sadi  faru  is 
r equires large  amounts  of  water  to  be   applied during  the 
considered   cap ab le  of  supplying  this  water  in  addition  to  that  for  normal 
irrigation  needs. 
salt  balance,  to  ensure  that  there  is  no 
Care ful management   of  the  leached  land  is  required  to   maint ain a  satisfactory 
syst em    and   consequently  raise  the  water 
table,  and 
over   water ing to  overload  the  drainage 
nutrients,  while  at  the 
s ame  time  sufficient  water  for 
to  avoid  leaching  out  plant 
provided. 
crop  growth  must   be 
The   char acter istics  of  the 
drainage  are as  follows: - (a)    Root   System 
banana  plant  related  to   the  problems  of  sa linity  and 
The   vertical rooting  of  the  banana  plant  is  between  65   and   75   cm    in  depth.     The 
roots  of  a  vegetat ively  propogated    pl ant    are  adventitious  roots  and 
40   cm   are  produced  by   each  plant,   spread ing  lat er  al ly  to   s one   4.5  metres.    The 
upwards  of 
majority  of 
these  roots  are  found   in  the  top  75-65   cm   of  the  soil  profile 
-   23  -8.0,  but 
forming  a  dense mat. 
(b)    pH   and   Salinity  (soluble salts) Banana will  tolerate  a  wide  range  of  soil 
can  be   expected.    The  average  pH   at  the 
outside  the  range  of  pH 
reaction,  between  about  pH   4.5  and 6.0-7.2  some   problems  of  nutrient  absorption 
Melka  Sadi  farm  is  7.0. 
Soluble  galts  in  excess  of  500  ppa  are  toxic  to  the  banana   plant. 
approximately  corresponds  to  an  EC   value  of 
0.78   mmhos/  cm. 
This  leve l The  EC    of  the 
soluble  salts  of  around  190  ppm. 
irrigation  supply  is  nomally  in  the  range  0.2-0.3 
The   difference  between  the  EC    of  the 
mmhos/  cm   which  corresponds  to 
irrigation supply  and 
the  toxic  level  is 
therefore  small  and   it  is  vital  to  keep 
60-75   cm   of  the  soil  profile. 
(c)    Water  Requirements 
The  ideal water  requirement  wou ld  be  2.5  cm  of rainfall  per  week  throughout  the 
the  soluble  salt  content 
below  the  500  ppa   level,   particular ly   in  the  top 
year,  which  is  equivalent  to  1.3  m  per 
an num. 
This  wou ld  ensure  uniform  growth 
which  is  important  if high  yields 
application  is  10   cm   every  15   days ,  which  is  equivalent  to  2.43  metres  per  annum 
are  to  be   obtained. 
The  proposed  water 
and  a1lows   for  a  10%   leaching  requirement, efficiency. 
as suming  a  65%   irrigation 
It  is  recomnended  that  the 
dainage  trials  be   carried  out  initially  on   some   15% 
of  the  saline  area  within  the 
is  described  in  section II  following. 
Melka  Sadi  farm  and  the  loction  of  this  first  area 
Section  II  also  includes   rec  Ommendations 
for  improvement  of  drainage  in  the 
remainder  of  the  farm  area. 
-    24   -ISTRY     O 
PART   A  (CONTINUED) 
MELKA  SADI  AREA,  MELKA  SADI  FARM 
SOIL  AND  SALINITY  STUDY  AND  DRAINAGE  DESIEN 
BRARY AND 
SERVIC 
SECTION   II:  DRAINAGE   DESIGN 
l.    INTRODUCTION 
The  existing drainage  system  of  the  Melka  Sadi  farn  area  has  proved  inadequate, and   the   inplement  ation of  a drainage  programme  is now  required to  lower  the water  tab le  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  inevit ab ly  lead  to  severe  restr ictions on  the  land 
Use. 
A system  of  draiFage  based  on  the  results  of  the  field studies  described  in 
Section 
implement  at ion  of   the  work  has  also been   prepar ed  together  with  an   estimate of 
I   has  been  determined  and  is  outlined  below.     A suggested  progr amme   for 
costs  and   likely benefits  arising  from   increased  crop  yie lds. 
2 
DRAINAGE   REQUIREME NTS 
The  present  main  crop  in  the  Melka  Sadi  area  is 
deep  rooted  plant  with  roots 
extending  down   to  about  1.2 m.      Of   the  other 
ban ana, which  is  a  moder at ely 
sorghum,  have  roots  extending  to  about  1.8  m. 
So   as   not  to  preclude  the  growing  of  these  crops,  drainage  design  has  been 
likely  to  be   growa     the  deep-rooted  ones   such  as   alfalfa,  cotton,  maize 
and crops 
considered  on   the  basis  of 
possible.    However  where  the 
lower ing   the  water  table  to  a  depth  of  1.8    m where 
to  obtain  a  water   tab le  at  this 
permeable  soil  layer  is  shallow  and  drain  spacing 
on   drawing  the  water  table  down 
depth 
some   25%   of   the  irrigated  area. 
to  l.5 m depth.    The  area  so  affected  comprises 
wou ld  be   very  close,  design  has  been  based 
After  each 
soil  to 
a   level   depend an t  on   the  amount   of  deep  percolation  and   the  porosity  of 
application  of  irrigation water,  the  water  table rises within  the 
the  soil, 
minimum  depth  to  the  water  table  is 
The  acceptable  limit  for  this  rise  has  been  set  at  0.3  m  and   thus  the 
soil). 
1.5  m,       (1.2  m in  areas  of  shallow  perme  ab le 
water  has   to  be   applied  at  the  surface  such   that 
In  order  to  remove   the  salts  in  the  soil  within  the  rooting  zone,  sufficient 
for  this  leaching  requirement. 
deep  percolation  is  adequate 
The   minimum  amounts   for   leaching  on   clay  and   medium   textured  soils  have  been determ ined to  be   10%    and   17.57  of   field  application  respectively.    Since  losses 
to  deep   percolation  for  furrow  and   basin  irrigation  (as  practised  at  Amibara) 
are  estimated  to   be   20%    and   25% 
requirenents are more  than  satisfied. 
3.      DRAINABLE   EXCESS 
of  field  application  respectively,  the    le aching 
The   drainable  excess  within  the  area  (other  than 
seepage  losses  from   the   cana ls ,  percolation  losses rainfall         from   the runoff)       fields comprises             and   surface runoff, 
-    25  -This 
The    pe   ak  gross 
field  application  is  l00  mn   every  l5   days   for   ban  an as. 
represents  70%   of 
the  diverted water  into  the  area, 
some   207  having  been  lost  by 
seepage  from 
distribution  channe ls,  10%   by   spill age  onto 
banks  and  evaporat ion . 
The   seepage  losses  are 
(100  x  20)/70  =  28.5  mm    per  irrigat ion. 
In-fie ld 
losses  to  deep  percolation 
application of  100  n 
amount   to  25%   of  the  irrigation  application 
for   bas in irrigation,  and   for  an is  to  be  drained. 
some   25       m per  irrigation 
Surface  runoff  losses  are  10%   of  field  application,  or  10       n per irrigation. 
4. 
DRAIN   SPACING   EQUATIONS 
The   various 
methods  of  calculating 
drain  spacing  fr om   details  of  the  soi ls 
characteristics  fall  into  two  main 
categories  -   steady-state  and   non 
ste ady 
state. 
Since  the  time  interval  between  each 
irrigation  application  is  large, 
the  method 
chosen  for  the 
table  is  assumed  to  reach  the  highest  pemitted  level 
calculations  is  the  non 
steady-state  type  by  Glover 
immediately  prec eding the 
Dumm      where   the  water 
subsequent  irrigation,   The   formula  is: 
L 
where  L K d 
ho 
modified  value  of  the  depth 
16 he ho) drain  spacing  (m) hydraulic  conductivity of 
the  soil  (m/day ) 
from   the  drain  water  level  to  the 
impervious  layer 
from   Hooghoudt    (m) 
soil  porosity 
(expressed  as 
a  decimal) 
maximum  height  of 
water  table  above  drain  water  level  (m) 
above  drain  water  level  after  time 
and 
d 
des ired  height  of water  table t  days  (m) 
15   days 
D 
1+ 8D   ln  D 
where  D Or 
actual  depth  from  drain 
wetted  perimeter  of  the 
Tro  where  ro  is  effective   r adius  (pipe  drains)  (u) 
wat er  level  to  the  impervious  layer  (m) drain  (open  drains )  (m) 
1 
ILRI Pub lication  No   16   "Drainage  Principles  and   Applications" 
26  -5 
DATA   FROM   FIELD  OBSERVATIONS 
The  measured  values  of hydrau lic conduc tivity  (K,   expressed in m/day)  of the soils essentially split the area into five parts  as  showa  on Figure  5.    For  the purpose  of  the  drain spacing calculations ,  K values of 0.4,  0.8,  1.85  and  2.5 n/ day have  been  used  (the  1.8  and  1.9 areas  being  taken  toge ther with   aver age  K of 1.85). 
The  depth (D)  from  designed  drain  water level  to  the  impervious  layer  is caleulated  from  the  difference between  observed  perneable  soil depth  and required drain depth.    Contours  of  depth  to  the  relatively imperme ab le  layer  are plotted on  Figure 5. 
Although  not  directly measured,  the  porosity  (4)  can  be  deduced  from  the hydrau lic conduct ivity of  the  soil  from   the  general  relationship  according  to 
the   USBR2, 
Since  sand   layers  form  part  of  the  soil mass  where  greater  values  of 
hydr aulic  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 
(n/ day) 
0.4 
0.8 
l.85 
2.5 
(uS BR) 
0.08 
0.12 
0.16 
0.18 
(u's ed   in  calculations) 0.08 
0.10 
0.12 
0.14 
6 The 
FIELD  DRAIN   DESIGN 
application. 
in-field drainage  requirement  has  been  shown   to  be  25   mm    for  each  irrigat ion 
sp acings  for 
each  value  of  K were   found   to  be  most   significant ly  affected  by   the 
For  this  depth  of  recharge  to  the  water  table,   fie ld   drain 
depth  of   perme ab   le 
the  large  range  of 
soil  for  a  given  water  table,  and 
hence  drain  depth. 
From 
for  each  area  of 
dr ains 
being required. 
hydr aulic conductivity  with  a  total  of  8  different  types  of 
spacings  and   depths  possible,  a   compr omise  was   decided  upon 
drains  and   the  areas  to  which   the 
These  are 
listed  in  Table  6  as  options  for  open  or  tile 
7.  The   northern  area  (9)   shown   on 
type  numbers   refer  are  shown  on  Figures5  and 
below   the  739.75   cont our   as   shown   on   Figure  6  and  was   found   to  be   too  low 
Figure  5  as   'Not  drainable  at  present'  lies 
relative  to  the 
drain  as   it 
exists. 
expected  level  of  water  (from  irrigation losses) 
Deepening  and 
widening  of  this  drain  from   the  Melka   Sadi 
in  the  prinary 
area  for 
possible  to  drain  this  area  (9) 
considered  to  be   a practicable  option.          adequately,  unless  of  course  pumping  is  later 
some   considerab le  dist ance  wou ld  be 
necess ary before it wou ld  be 
2 
US BR    -  Drainage  Manual.     Figure  2.5 
between  specific  yield  and   hydrau lic conductivity". 
"Curve  showing  general  relationship 
-    27    -730d 
O.20     74|   741.10       DRAIN        PRIMARY 
G 
boundary       wlth 
DRAIN 90m 50m   75m  m   35 2Om   30m   m   35 m   45 
SPACING 
present 
to 
(K) 
oreos    hypes. 
of   depth        Conlours          oImpervious                     loyer  permeability            between        differAnt 
DRAIN      DEPTH     m   2.3 2.3m    m   2.3 2.3m    2.0m    2.0m     2.0m m   2.3 
Boundary          of 
of 
drainable 
Soil 
drons 
LEGEND 
TYPE 
Not 
9 
9 
02 4Q9 
\K    2.6 
=0.4 K 
FARM          MELKA             SADI 
0.5 Km Scole 
Y  AGENC    II PROJECT 
HIOPIA 
NT    LOPME            DEVE 
DRAINAGE                   IN-FIELD 
REQUIREMENTS 
ET    OF     GOVERNMENT 
HIVER 
SH AWA 
IRRIGATION 
VALLEY               JAWASH 
AMIBARA 
Sir   Williom   Haicrow   & Partners. 3hsoo 
20   1OCo       741 
DRAIN         PRIHARY 
-738.50 
FIGURE  6 
De 
to 
Formed           by   Enlarging 
Road 
Drains Existing           Main       and 
Collector             Droins 
under 
Tile     Block        Drains 
soz 
DRAIN 
under 
Drop       Temporary          Drain        on   Structure         Consiructed                 SD2 Phase         I 
Block 
Existing           Droins 
LEGEND Open 
Clvert Bridgs 
CI 
I /PH SE 
RAIN 
-743 
742.50 
DRAIN            SD 
2  AIN 
TD 
DR 
743.50 744.50 
NON  SALINE 
NE     UCEK 
PHA 
tpHASE 
PASTURE 
AD5  DRAIN 
5  H SE 
0.5 Km 
MELKA             FARM          SADI 
Scole 
NON 
SALINE 
AGENCY      I 
ETHIOPIA DEVELOPMENT 
PROJECT 
PHASING                CONSTRUCTION 
IRRIGATION GOVERNMENT                          OF               DRAIN 
RIVE        WASH          A 
VALLEY 
AMIBARA 
SH 
AWA 
29 
Wliom  Holcrow   &  Portners G 
o 750 20   IAO 
10 741 
I0 741 
Non-Sollne                ki  Bonana   Moderote/      Moderate              Aban        doned 
Type 
Pilot       droingge 
Abandoned                   Saline Droln 
Low      Sollnity 
No./ 
Drain        Secondary Primary            Canal     Primary           Droln     Droins          Other 
Other        Conal 
oreo 
Pasture     nLucarne            Banana    Solinity 
TTTT        Dyke 
ND     LEGE 
Area Structure 
Phoss 1/3 H.70 
997//8      768 
9.45      1/7 2/7 
12.04 
8.88 
9.60 
I0.05 
2.12 
12.20 
8.79760 8.6%12    II.   50 
V32 
9.40 
10.0/8      9.30 
9.002 
00 
D.72, 
I0.644/6 
9 
8.85 
2/8 2/7 9.55 
8.65 
1/3 
490 
775 
7.60/       59   5 
I1.30,K           930     9.5/211       9.55/ 10.29 
2/3 
.69/2 
II.70 
2/2 
.2/2/2 
7.60 
9 45 
$90 
2/1 1.95 
4/6 h416   |.08 
2/3 9.30 
I|.26 8.J0 
3/6 9.55 
4/6  965 
||2/3 
Iu60A 
2/3 I075, 
4/4 
2/4 8.60 360 
12.I0 
8.30 
3/3 
3/2 
I0   00 
I7.90 
I|25 3/2 
3/6 7.6 
3/6 6.73 I5.40 
5/5 
3/2 3r2 9.30 
I520 90 
3/3  /4 17.20 
4/4 
955 4/6 13.60 3/6 12.55 
|3.50 
4/4 
I0   60 
/4 
14.60 B/5 
3/2 I1.50 I0   70 
3/3 69q 
s/5 
1259 
3/3 
3/4 3/3\000  .9 
y30, 4/4 
9/4 
3/2 
510 
K3/3 3/3 
650 
I2   0 3/4 14.50 5/4 
940 12.0  3/3 
3/3 
5/4 7.1B       5/4 5/4 I6.50 
U.5 
Km 
9.75 
5/5 
Scale 
3/3 
5/4 15.00 
MELKA             SADI        FARM 
5/4 
AGENCY       II 
TYPE 
3/1 9.00 l2.57 
9.30 3/1 
3/1 
PROJECT 
6/4 3/1 13./0 
1430 5/4 
7.50 
GOVERNMENT                          ETHIOPIA                 OF 
LOPMENT 
LOCATION                    BY     FIELD 
J0. 
33/1    IL.00 
DEVE 
DRAIN IGATION 
AND 
RIVE        AWASH 
VALLEY       IRR No. AMIBARA           PHASE 
AWASH 
William  Holcrow  &  Partners Drain     Type 
|+ 
|5 
|4 
2 
3       |1   |6 
2 
| 
of (m) Depth        to 
invert 
Pipe 
1.9  2.2  1.9   2.2  2.25 2.25 2.25 1.95 
2.25 
0ption 
REQUIREMENTS Dr 
Gravel 
Surround 
ain 
(m) 
0.175 0.175 0.175 0.175 
0.25 0.25  0.25  0.25  0.25 
Pipe 
Side      Pipe      |   Diam        Slope|       (m)     1.5:1        |0.1 |0.1      1.5:1 |0.1      1.5:1 0.1     | 1.5:1  1.5:1        0.15      |      |0.15        1.5:1 0.15      | 1.5:1 |0.15        1.5:1 o.15      | 1.5:1 
5 Figure 
DRAIN TILE 
| (m) 
AND 
OPEN TABLE            6 
OF 
ARISON 
Drain         Open        0ption 
Bed 
width 
(m)       Nil  Nil   Nil Nil  0.3   0.3 0.3  0.3  0.3 
to also 
Refer + 
Depth        to invert 
(m)       2.0 2.3 2.0   2.3 2.3  2.3 |2.3 |2.0 2.3 
| 
| 
| 
| 
COMP 
Spacing            | 
(m) 
DETAILS 
| 
50  | 1.5 
| 
Drain        | 
20   | |1.2 
35      35   | |1.2 
45 
75   | 1.5   90   | 1.5   30   | 1.2 |50     1.5 
table 
Min 
| (m) 
| 1.5 | 
| 
1.5 
DRAIN  Depth          to   | 
| 
| 
Water Design 
FIELD 
(m)      2.5|      1.5 2.5|      1.8    Ig.e.*   3.0     |1.5 3.01.8     3.0     |1.8 1.8   4.0|1.8     2.5     | 1.5  2.5     1.8 
Depth         to   | 
Impervious 
(m)     | 
| Conductivity 
Layer          | 
|l.t* 
4.0   | 
to Ig.e. |1.t.  |3.0 8.e. 
|1.t 
|1.t. 
I8.e. 
to equal 
or than 
| 
than       less greater 
Hydr       lic    au 
day)      (n/    | 
0.4  |0.4 0.8 |0.8 |1.85  |1.85  |1.85 2.5  2.5 
*1,t. 8.e. 
| 
| 
| 
3 Table  6  lists  design  data  for  the  alternatives  of  adopting  either  tile drains  or open  drains,  The  advantages  and  dis advant ages  of  each  type  may  be  summ  ar ised  as follows: 
(a)    Advantages  of Tile  Drains 
Consider ab ly   less  irrigable  area  wou ld  be  taken  up   by   the  pres ence of permanent  drainage works, 
Maintenance  wou ld  be   less  costly  as   there  wou ld  be  no   requirem ent  for continual  excavation  of  accumulated silt  and  weed   from  open   drains, Tile  drains  would  not  be  in  danger  of   bec oming clogged  with  wind-bourne debris  as  wou ld  open  drains 
Difficulties  of  access  throughout  the  area  wou ld  not  be  compounded Tile  drains  would  be   che aper  to  install 
The    progr ammed   time  for  completion  of  the  works   wou ld  be  cons iderab ly shorter. 
(5)    Advant ages    of   0pen    Drains 
There  wou ld  be   no   need   to  import  sophisticated  pipe  laying  equipment difficulties  in  effect ing  timely  fabr icat ion  of  tiles  and 
procurement  of  filter material. 
There  may   be 
Consideration  has  bee given  to  each 
alternative  and   cost  estimates  and  a 
programme  prepared  for  both  tile  and  open 
drains. 
The    re sults of  these  studies 
have  concluded  quite  clear ly in 
in-fie ld  drains  and   als0  perimeter  block 
favour  of  the  use  of  tile drains  for  the 
Where  however  open  collectors  are  already  in  exist ance 
drains  where  none  are   alre ady  existing. 
form   the  block  drains  by   enlarging  them  into  deep  open  drains  to  carry  the 
it would  be  preferab le  to 
required  discharge. 
A  decision  on  whether  to  proceed  with  tile 
drains,  perhaps  only  for  the 
drains  or  revert  to  a    syst em of  open 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    ch   ange  Will  aot  be  necesary  and  with not  be  recOrnmended. 
present  knowledge  wou ld 
7 
INTERCEPTOR   DRAINS 
Convey ance   losses  have  been  shown   to  be    s ome    28.5  mm    per  irrigation  at  a  field 
application rate  of  100  an  each  15  days.    It has  been  caleulated  that  this  would amount   to  a total of  100  1/sec  for  a typical  10  ha  field,  which  wou ld  normal ly be drained  by  percolation  to  the  in-field drains,   particular ly where  these  are closely  spaced.    However,   for  the  wider  spaced  drains,   intercept or  drains constructed parallel to  the  cana ls  at  about  30  n 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  showa  on  Figure  6 1s,  by  1nspection,  an  area where   probl ems  may 
Occur.     It is  recommended  that  the water  table be  monitored  in a  number  of areas after  the  construction of  drains  1n  Phase  I  and  action taken  as  necessary shou ld 
-   32  -interceptor drains  be  found  to  be  required. 
8           BLOCK   DRAINS 
mm 
Block  drains  are  required  to  convey  percolat ion  and  run  off  los ses  avay  from  the 
fields.  It has  been  assumed  that  the  irrigation losses  by  surface  runoff  of  10 
per  irrigation  are  drained  in  24  hours  at  an  average  rate  of  0,4 mn/hr,  and 
capacity  for 
for  a typical  10  ha  block  this  wou ld  anount  to  some  12  1/s.   Total  block  dra in 
would  be   depth  2.15  m or  2.45  m to  suit  in-field drains,  bed  width  0.5  n  and minimum  bed  slope  0.00015.    The   depth  of  flow  for  this  design   wou ld 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  wou ld  have  to  be   cap ab le  of  discharging  the  sums   of  the  flows   from  each field  drain  entering upstream.     Requir ements for  slope  and  diameter  shou ld  be calculated  again  as suming  a total  capacity  of  16   1/ sec  at  the  dowas tre am   end of a  l0 ha fie ld.    The   locations  of  each  type  of  block drain  are  showa  on Figure  6. 
COLLECTOR   DRAIN   DESIGN 
10   ha   wou ld be   about  16   l/s,  and   an   adequate  design  for  open  drains 
The  overall  losses  each  l5   days  are  field 
convey ance   losses  of  28.5  mm,    and   for  the  irrigated  ara 
application  losses  of  25   mm    and 
ha   (excluding  the 
northern  area),  amount   to  some   0.5 ms.  Drain  SDl   has   been 
of  approximately  1l000 
des igned  for 
a  flow  of  0.4 m/s  and   drain  SD2   Eor  0.l m/s at  their  lower  ends . 
has  been  calculated  that the 
Outflow  from   the  area  is  limited  by   the  capacity  of  the  Primary  Drain,  and  it 
rate  of  0.5  m/s. 
It has  been  assumed   that  no    signific ant backing  up   effects 
depth  of  flow  in  this  drain  is  0.58  m  for  a   flow 
occur  as  a  result  of  drainage  of  are as   downstree am    of  the  Me lka  S adi   farm, 
This  depth  of  Elow 
739.75  m contour. 
Since  the  ground  slope  through  which   the  Primary  Drain  flows 
effectively  limits  the   drainab le area  to   land  lying  above  the 
is   small, 
kilometres  wou  ld   be   necessary 
considerable  enlarging  of 
be fore affecting  the  drain water 
the  drain  for  a  distance  of  several 
not  considered  that  this  would  be  cost  effective  at  this  time, 
level,     It is 
and   it  is 
recomnended   that  alterations  to  the  Primary  Drain  be  carried  out  as   part  of  the normal  malntenance  programne, 
Figures  9 and   10   show   the   longitudinal  sections  of   the  collector drains  for  the area  and   typical  cross  sections  of  drain  SD2. 
-   33   -required) Pipe 
drain     Clay    tile 
surroUnd       Filter 
1 
1.5 
outlet 
Tertiary      canal. 
canal      Field 
(no 
protection 
SECTION  A-A 
Scale 50   1: 
0.5m 
(SHOWING TYPICAL 
1.5 
TYPE 
34 
1:2000      Scale    DRAINS 
FIELD 
8 
175mm    pipe    material            cover  min    Filter     to  -
clay  tile  100   dia    mm excavator             hydraulic       machine trench        suit     or  Width      to of 
DRAINAGE WITHIN 
LAYOUT         10 
trenching 
level, field    Nor    mal 
F 
ha 
Tile drains to  follow ground 
slope at  const ant  depth  of  20m 
FIELD) 
A 
A   Scale     1:50 
SECTION   B-B 
25m 
B 
10m 
-Field      drain 
Tile 
drains 
drain  Open collector 
at 
35n 
CRS 
Existing          drain field 
or 
FIGURE   8 
block 3U91 VISED           RE    DRAIN 
-EXISTING               DRAIN           SECTION SECTION 
6 
745     744      743    742                  740  -739  -738   737 
o0| 
7387 737-44 
736-86 
0G.L       739     79 
iv, 
2h: 
SLOPES  BED  WIDTH  4m 
SLIDE 
|7390 
REVISED 
FFL 
GROUND           LEVEL 
923= SLIDE          SLOPES 
WIDTH            BED       I0m 
73779 
|737-45 
WATERLEVEL            LEVEL 15h:       lv, 
NO3S 
|738-4| 
738-07 
-ose 
73764  Km  t900  3 
REVISED           BED 
WIDTH
07m 
738-29 
741-3545 
TION 
SEC 
LONGITUDINAL 
74150)4-8        BED 
739-40 
739-07 
EXISTING                FFL 
lv, 
I5h: SLOPES 
SIDE 
SECTIONS 
SDI-
CROSS 
DRAIN 
741:59 
DRAIN            REVISED               SECTION 
|7450leo   Km     CHAINAGE 90  742 
WTR     FOR      LEVEL       IRRIGATION 
259 
DRAIN            -EXISTING                  SECTION 0.GL.        74250 
-
SD2 DRAIN 
GROUNO LEVEL    DESIGN 
LOSS         ONLY 
BED       LEVEL VISED 
743     -742 
41 
740    739    738      737 
7eOB25 
737-44 
736-86 
REVISED               FFL 
5-0 
SECTION 
neC 
cONSTRICTED 
5m 
O WIDTH 
LONGITUDINAL 
39 
4036    Km     I+400 
979 
737-96 
737-64 
-05 
EXISTING          BED     LEVEL 
GROUND          LEVEL 
REVISED          BED     LEVEL 
FFL       EXISTING 
SD2-
DRAIN 
BED 
lv, 
5h: 
| SLOPES 
74|49 -I25 
WATER        LEVEL 
SIDE 
ETHIOPIA                 OF     GOVERNMENT 
SECTIONS            SECTIONS 
AGENCY               DEVELOPMENT                      AMIBARA                  IRRIGATION 
74036 
CHAWAGE                  Km                    DESIGNWTR                 FOR       LEVEL        IRRIGATION 
BED       LEVEL LOSS         ONLY 
GROUND LEVEL 
REVISED 
VALLEY               AWASH   PROJECT                II  SD2-LONG CROSS 
SD!, SD2 DRANS       DRAINS DEVELOPMENT               eAWASH            VALLEY LONGITUDINAL                 DRAINS              SECTIONS          AMIBARA      OF 
GOVERNMENT                ETHIOPIA OF IRRIGATION                 TD.I, 
ID2, 
T.D3, 
PROJECT 
T. 
D.4, 
droins 
For 
NOTE: 
localion 
see 
Fiqure 
9 Choinoge Km    3 
2:0 
DRAIN       T.O2 
of 
O-5m       I5h:ly      b.w.    siopes    Side 
these 
2 
Constont 242 Depth    m be  o 
a 
TD.5. 
AGENCY 
I 
Culvert C4 
g737·45  -738 
739 
740 
741 
742 
743 
level    Bed 
irrigotion        only     loss      Woler       level for 
Ground     level    Choinoge Km 
Choinoge Km 
741- 29 
741-   49 
744-20 
2-2 
DRAIN       TD4. 
bw  Side 
slopes   O 
5 
0.5   bw.    Side     m 
DRAIN     T.D. 5. 
739-97 
740-25 
742-5 
t 
m 
I5 
h:lv 
slopes 
I5 
h:ly 
constont    242m Depth be   lo 
738-87     739-20   741-  30      0-0 
Culvert  C6 
-738 
-739 
-740                      741 
-742 
743 
744 
745 
lo-0 
740        G740-88 
742 
-743 
-744 
-745 
746 
level    Bed 
irrigot1on         only      loss 
| 
Woler      level for 
Ground    level   Chainage Km 
DRAIN      TO.I. 
Choinoge Km 
740 22  740-55  742-60  3-8 
740-00  740-32  742-531 
T.O. 
BW. O75m 
I5h:l      slopes    Side 
b.w.  O5  Side  m 
slopes hilv. 
DRAIN         TD.3. 
05m    widh   Bed 
level    Revised         bed 
level  Woler 
5 
constont 2·42 Depth    m be   lo 
739 
L740 
741 
AF742   Culver   C5 
Groung 
p738-08 
743 
737-57  737-91|p 
736 97  737:55|739-5  o:6 
Level 
Side 
0-5m Widih -738 
Red 
9741 |o 
736 
737 
739 
740 
Joins Droin S.D.1. -742 
743 10      PHAS ING  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 invo lved  in  cons truc tion,  and  is ordered  such  that  the  relative cost per  hectare of  construction  incre ases from  phase  1 to  phase  5 as  shon below: 
Phase 
Area  to  be Drained 
2 
|3 
210  ha 219  ha 
|252 ha 
Estimat  ed   Cost per hectare (Birr) 
| 2,200 
| 2,350 
| 2,420 
Notes 
| 
I Not  including non-saline area | 
Not  including non-saline area | 
5 
The 
| 192  ha 
| 145  ha 
| 2,890 
|3,400 
Not 
including  lucerne  area 
Not 
including  pasture  area 
from  which  it  can  be  seen  that  the  activity  limiting  rapid  progress  is  the 
progr amme   rec ommended  for  construction of  the  works  is  shown  in Figure  11, 
working  either  double  shift,  or  single  shift 
enlargement  of  the  existing  open  col lector  and  secondary  drains.    It is  intended that  excavation will  take  place  using  one  back-acting  hydr aulic excavator 
excavation  by   hand,   throughout  the  full  three  year  period  of   implement  at ion. 
supplemented  by 
a  team 
engaged  on 
It  is  further  recommended   that  a  pilot  drainage  area  be  est ablished  first  in  the area shown  on  Figure  7.    The   purpose  of  this  pilot  area  wi11  be   twofold. 
Firstly  it will  be  necessary  to 
designs  desCribed  in  this  report.    The   soil 
are    bas ed    were  of  necessity  determined  from  relatively               par  ame ters on   small   which   volumes      these of designs         soil  in 
verify  the  assumptions  used  as   a   basis  for  the 
pilot  plots  to  verify  the   as sumptions made. 
the  auger  hole  method,   and  consequently  it  would  be   sensible  to  make  use  of  the 
future  phases  could  then  be  made   if necessary . 
Modifications  to  the  design  of 
The  second  point  concerns  the  progr amme   shown  on  Figure  11.      Rather  than awaiting  delivery  of  suitab le  tile laying  equipment  before  comencing  the  wor ks , 
it would  be 
it  would  be    advant ageous  to 
preferab le   to  commence  right  away   using  alternative 
install  the  field  drains  in  a  clearly  defined  area 
equi pment, and 
where  development  costs are  least.   The  tile  drains  could  be   laid  us ing  a 
back-acting  hydraulic 
the walls of  the  exc avation.    In  this  way   the  eed  for  a  sophisticated  tile 
exc avat or  perhaps  trailing  a  travelling shutter  to  support 
laying machine,  which  although  thought  at  present  to  be  essential  and   is included  in  the  programme   and   cost  estimates,  could  be   confirmed. 
A  schedu le  of  equipment  required  for  the  trials  on   the  pilot  drainage  area, rogether  with  that  required  for  further  studies  within  the  Amibara  and   Me    lka Sadi  areas ,  is shown  as  Tab le  7. 
-   37  -1 26    25  24     23 
21   20   19   18   17   16   15    14    13    12   11   10 
7      6 
4 
ITEM        NO 
structures             Construct for Enlarge         Lay     tile   Construct structures                Enlarge          Lay     Construct  for 
Enlarge 
Lay 
Monitor/ 
Lay 
Construct Enlarge         Construct Enlarge Delivery          Test   trenching            Procure            machine   Review   Construct            Leach            Enlarge         Lay     Procure       Mobilise,    / 
Lay 
ACTIVITY 
tile 
drains 
tile 
tile 
tile 
and 
open 
open 
drains 
structures 
open 
drains 
of 
and 
salts 
drains 
drains open    Review 
structures structures 
commission 
open 
tile 
secondary 
dra    Fabricat     prepare 
drains 
drains 
drains 
for   drains 
drains 
trenching 
for 
for 
for 
results remainder 
for 
ins 
for 
Phase 
for 
for Phase   4 
for 
Phase 
for 
remainder 
trenching machine 
for 
structures        and revise 
monitor desiqns 
dra 
working  e 
clay 
for 
for 
for 
for 
Phase  5 
Phase 
5 
Phase 
Phase 
for 
remainder 
tiles 
5 
Phase   3 Phase 
3 
Phases 
3  Phase 
reSults 
Phase   2 of 
pilot 
area 
for drawings 
in 
remainder 
4 
4 
of  machine 
if 
necessary 
Phase     2 
pilot 
area 
1& 2 
Phase of 
of 
pilot 
area 
PROGRAMME 
Phase 
2  Phase 
1 
1 
1, 
and 
set 
out 
59,700m 19,300 62,400m           m 6 35,350        96,650mhand             55,70Om            m  ncher   Tre 
8 No 
No 
6 No 
46,70Om          Trencher        No     83,450m          5 
28,200m   7 
54,80OmExcavator           No 
1 No 
266     m  k |OUANTITYlOF 
600m   2 13, 800m   1, No 
AMIBARA 
FOR 
Trencher 
hand 
vator       Exca    1 
+ 
Trencher 
Excavator  1 
hand 
" 
1Excavator 
1Excavator +  Trencher        + 
hand 
hand 
Excavator  1 offshore  Local or Excavator  1 
EXECUTION     METHOD DRAINAGE 
IRRIGATION 
Completion                38      area     pilot                                                                                                                                                                                                                                                                 1982 
MASoNDDFMA            AsoNDF MA 
|J 
WORKS WITHIN PROJ 
1983 
Phostion   Com 
1 
LCompletion 
Phase  2 
ECT 
MAESO FARM 
AREA 
II 
MJAsoNDJFMAMJJAsO ND  1984 
Completion         Phase   3 
LCompletion           Phase   4 
Completion          Phase   5 
1985 
FIGURE   | TABLE   7 
SCHE DULE   OF   EQUIPMENT   REQUIRED   FOR 
TRAILS  ON  PILOT  DRAINAGE  AREA  AND  FURTHER  SALINITY  STUDIES 
Item 
1 
2 
3 
4 
5 
6 
7 
1 
9 
10 
11 
12 
13 
14 
15 
16 
17 
18 
19 
20 
Deseription 
Discharge  récorders  for  attachment  to drain outlets Calibrated buckets  and  stopwatches  for  measur ement  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   s ampler to  recover  samples  from  within observation well  tubes  and  below water  level 
Water  s ound ing  tape with electric indicator Auger  hole kit  (Eijkelkamp  -  Holland) 
Evaporation  pan,   comp  lete  with  gauge   and   cover,  Class  A Soil moisture  probes  -   wa lking  stick  type 
Top   pan  balance  500   gm   cap acity 
Soil  s ample   rings  with  plastic  caps  and  carrying  case Rung   holder  for  above,   samp ling above  the  water  table Ditto  for  samp ling  below  water  t ab le  (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  diame ter Screw  type auger  head  25   mm   di ameter 
4-wheel  drive  pick-up 
Quantity 
2 
1 
1 
6 
1 
4 
1 
24 
1 
2 400  m 
50 
50 
100  m 
(Total  CIF  Cost  for  budget  purposes  approxinately  Birr  50,000) 
-  39 moderate ly  high  salinity which has  been  abandoned  is  ine luded. 
Within  each  phase  of  development,  including  the  pilot  area,  an  area  of  high  or 
trials shou ld be  performed  on  small  sections  of  such  areas  within  each  phase, the  results  from  which  may   affect  the  design  or   inplement at ion  of  the  remainder 
Further  leaching 
of  the  drains  for  the area. 
For   this   reas on  the  main  inclusion  of  the  saline 
areas  is  towards  the  end  of  the   implement at ion  period  for  the  drainage  system  as a  whole,  as   is  shown   below: -
Phase 
Abandoned  Area of Saline Soil (ha) 
Notes 
60 
2 
Total  Area (ha) 
|  210 219 
For  le aching trails  on soils of K 0.8  and  2.5 
For leaching trial on soil  of  K 0.4  as  mainly   | included in Phases  4 & 5| 
3 
4 
50 
|   252 
) 
| 137                                        192 
Main  inclus ion of drainage  of  saline areas 
TOTALS 
|82 
|338 
145 |1018 
The  locations of  ab andoned  areas of both moderate  and  more  severe salinity are shown  on  Map   No   5,  bound  separately. 
11.     QU ANT ITIES AND   COST  ESTIMATE S 
The  quantities,  tabled  for  each  phase  of  construction,  include all major  items of work required  to  implement  the  syst em,    and   are  included  in  the  form  of  priced bills as  Tables  8-12.    These  t ab les  follow  the detailed analys is  of  exc avat ion rates  and  costs  given  over leaf. 
Since  the  longitudinal  and  cross   sectional  det ails of  all existing drains  other than  drain  SD2   and  the  primary  drain  are  not  available,  a reduc tion has  been made   for  the  existing  excavat ion  within  the  proposed  revised  design  cross 
section  for  drains  SDl   and  TDl   to  TD5   based  on   the  known  drain  detai l..    In  the case  of  open  block  drains  a   reduction  of  4.5   m  per  m run  has  been  made  where 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   l, 2 and     3 is 
ha   and 
the  overall  cost  of  providing  the  drainage  works  described  for  Phases 
approximate ly  Birr  2300  per 
to  5  is  estimated  as   Birr  2600   per  ha. 
I 
-   40  -COST   ESTIMATES 
11.1 DE  TERMINATION OF   RATE   FOR  TILE  DRAINS 
11.1.0       GENERAL 
Tile drains  may  be  layed  using  a back  acting hydrau lic excavator with  a 
travell ing shutter  following  close  behind  within  the  excavation  to  support  its ne ar  vertical walls.   Such  a  method  is envisaged  for  laying tile drains  in the pilot area  as  it is  recomnended  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  as sump t ion  that  a trenchless  or  trenching machine  will  be    imp orted  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 
somet imes trailing 
costs of  each  type  are  similar  but  it is  thought  that  a machine  of  the 
a   shield  to  supoprt  the walls  of  the  excavation.    The   capital 
be   found  which  is  capable  of  laying  tiles  as  deep  as   2.3  m. 
trenchless  plough  type  wou ld 
be    prefer able for  use  at  Amibara,  providing  one  c an 
is  approaching  the  limit  of  most  trenchless  machines  and  a   trencher/ ladder 
However,   this  depth 
excavator  type  may  be  necessary  as  a  result. 
11.1.2  MACHINE   DESCRIPTION 
Fully  tracked  trenchless  or 
n wide   tr acks. 
trenching machine  with  250   hp   diesel  drive,  twin  500 
1l.1.3 
OPERATIONAL   LIFE 
A   reas onab le  assump tion  for  rate  of  use  is 
1ife  of  10    ye ars.    Dur ing  this  period  the  machine  will  be  assumed   to  be 
1750  hrs  per  year with  an  economic 
available  for  60%   of  the  time,  40%   being  taken  up   in   mech an  ical  maintenance, 
awaiting  setting out  and  other  instructions  and  moving  to  location. 
Depreciation  is 
interest  charges  are  omitted. 
11.1.4  RATES  OF  OUTPUT  AND  PROGRESS 
taken  as  linear  over  the  operationa1  life  of  the  machine  and 
The   total  area  to  be  drained  within  the  MAESCO   farm  is 
length  of  tile drains  required  for  this  area  is  266,300  m. Tot  al   output  is  estimated  as  200  m per  oper ational  hour,  or 
1018  ha,  and  the  total 
200   x  1750  x0.6/1000  =  210   km 
the  MAESCO   area  is  therefore 
266.3/210  =  l.3 ye ars or  l6  months. 
per  year.    Total  time  required  for   comp letion  of 
The    aver age  density  of  drains  is  266,300/ 1018  = 
rate  of   progress  to  be  expected  from   the  machine  in  terms  of  area would  be 
262  m per  ha, 
and 
a  reasonable 
210.000/262  =   appr oximately 800   ha   per  ye ar. 
11.1.5 
SP ARE   PARTS 
The  cost  of  spare  parts  is  assumed  to  be   70%   of  the  total  machine   cost. (including  deivery),  spread  equally  over   its  operational  life. 
-   41  -11.1.6       FUEL  AND   LUBRICANTS 
Rate of useage  of fuel is  assumed  to  be  5   gall per  hour.     Rate  of   consump tion of lubricant s is assumed  to  be  7}%  of that  for  fuel. 
1.1.7 
Assumne 
LABOUR 
1  operator full  tine, 
1 relief  operator/bank sm an  full  time, 2  mechanics  for  2.5  months  per  year, 4  labourers  full  time, 
1 surveyor  full  time, 
2 chainmen  full  time, 
1 supervis ing  engineer  full  time. 
11.1,8       ASSISTANCE  WITH  COMMISSIONING  OF   TRENCHING  MACHINE   FROM   EXPATRIATE TECHNICIAN 
It is  expected that one   technici an  from  the supplier of  the  trenching machine will visit the site for  two  month6  directly after it is delivered for  the purpose  of  tr ans ferring knowledge  in its operation and  maintenance  to  local staff and operatives. 
11.1.9       DRAINAGE   PIPES 
These  will either be  clay  tiles manufac tured  locally or   alternative ly perforat  ed PVC  plastic  tubing procurred offshore  and  despatched at the  same  time  as   the trenching machine.    It is  thought  that  the costs wil1 be  simi l ar   whichever option is  ch0s en. 
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  availab le locally. 
-   42  -11.2  COST   ESTIMATE   FOR   TILE  DRAINS 
Capital   Annual 
11.2.1 
MACHINE   COSTS 
Basic  Cost  of  Trenching  Machine: 
Delivery: 
Costs  Associated  with  Provision  of Technician 
for  Comnissioning  and   Training: 
Av  Depreciation  over  each  year  of  Operat ional  Life: 
Av    use age  of Spare Par ts: 
(Birr)* 
370,000 48,100   | 
50,000 
468,000 
46,800 
Recurrent (Birr)* 
Fuel  (5   x 
@ Birr 8.2/gall): 
11.2.2       LABOUR   COSTS 
Machine  Operat or  (1  No  for  12  months  @ 
Lubricants 
1750  x  0.6  gall  @ Birr 5.2/gall): (0.075  x 5 x 1750  x 0.6  gall 
Relief   Operat or/ Banksman 
(1   No    for  12  months 
Birr  720/month): 
Mechanics   (2   No    for  2.5  months   @ 
Birr  600/month): Surveyor   (1   No    for   l2  months  @ Birr   800/mon th): 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): 
@ Birr  720/month): 
40%    on-cost  on   each  of  above 
tr ansportat ion etc: 
for  administration, 
TOTALS   OF   MACHINE   COSTS   AND    LABOUR: 
BAS IC  ANNUAL  MACHINE  AND  LABOUR  COSTS: 
46,800 
29,300 |  27,300 
3,200 
8,600 
8,600 
3,000 9,600 
7,200 7,200 
9,000 
21,300 
134,300 
Birr  181,100 
An   exchange  rate  of 
deternination  of 
machine  capital  costs  and   costs  of 
Estg  l.0  =  Birr  3.70  has  been  taken  in  the 
spare  parts. 
Output  has   been  estimated  at  210   km/year. 
-   43  -SUMMARY   OF    1l.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 Add   contingencies  at  10% 
Birr  0.86/m. 
TOTAL 
Birr 2.1/m 
Birr 3.40m 
Birr  6.36/m 
Birr  0.64/m 
Birr  7.00/m 
-   44  -11.3  DETE RMINATION  OF   RATE    FOR   EXCAVATION   USING   BACK-ACTING   HYDRAULIC 
EXCAVATOR 
11.3.1 
TYPICAL  EXCAVATOR  CHARACTERISTICS 
Gross Weight  :   11 tons 
Engine  Horespower  :  90  bhp  at  2,200 rpa 
Size of  Bucket  :  5/8 cu  yd 
Range  o£  Boom  Lengths:  4-6  m (two  piece  or   monob loc) 
Range  of  Dipper  Arm   lengths  :   2-4.5  m 
Typipcal  Reach   :   9.5  n 
11.3.2       OPERATIONAL  LIFE 
A reasonab le  as sump tion for rate of use  on   this  type  of work  wou ld  be  1,750 hrs per   ye   ar   and  an  economic  life of 8   ye ars.    Dur  ing this  period  the  excavator will be  assumed  to be   avai lab le  for  excavation   80     of  the  time,  20%   being taken up  in mechanical maintenance,  movimg  to  location  and  avaiting setting out. 
11.3.3       EXCAVATOR   OUTPUT 
As sumptions: 
5/8 cu  yd  bucket 
50  minute   wor  king  hour 
25  sec  cycle  time  for  l80°  swing 
90%    bucket  factor 
803  operator  efficiency  (This  is  lov  since drains  are snall) 157   allowance  for  bulking  of ill 
Output  is  therefore  (5/8  x (50/60)  x  (3600/25 ) x 0.9  x 0.8)/1.15 47   ydloperat ional  hour 
or  36m/operational  hour 
and  annual   out put  is  36  x  l750  x 0.8     50,400 n3 
11.3.4 
SPARE   PARTS 
The  cost  of  spare  parts  is  assumed  to  equal  70%   of  the  total machine  cost (including  delivery)   spre ad 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   con sumpti on   of lubricant s is   as sumed to  be   7}%   of  chat  for  fuel. 
l1.3.6 
As sumne  : 
LABOUR 
1 Operat or  full  time 
1 Relief operator/banksman  fu ll time 
2 Mechanics  each  for   2 ontha  per   ye    ar 1  Labourer  full  tine 
45   -1l.4 COST  ESTIMATE   FOR  EXCAVATION  WORKS 
Capital    l Annual 
1l,4.1  MACHINE  COSTS 
Basic Cost of Machine: 
Delivery: 
Av  Depreciation over each ye ar  of  Operat  ional Life: 
Av      Use  age  of  Spare  Parts: 
Fuel  (2  x 1750  x 0.8 gall @ Birr 5.2/gall): 
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  @ Bi|r 120/month): 
40%  on-cost  on  each  of the above  for administrat ion, transport  etc: 
BAS IC CosT  PER  M3    (based  on  output  of  50,400  mlyear ): 
(Birr) 
255,000 
33,100 
288,100 
36,000 
Recurrent (Birr) 
36,000 
25,200 
| 14,600 
|  1,700 
8,200 
|  8,200 
|  2,400 
| 1,400 
8,100 69,800 
TOTAL   : 
0.71    +     1.39 Birr  2.1/m3 
-   46  -TABLE   8 
MELKA   SADI  DRAINAGE   -   PHASE   I BILL  OF   QUANTITIES 
|Item     Description 
Unit    | Quantity   Rate     Amount 
|1.1 
| 
|1.2 
|1.3 
|1.4 
|1.5 
|l.6 
|1.7 
|1.8 
|1.9 
|1.10 
|1.11 
|1.12 
Gonstruct  Type    1 drains  (90m  c/c,  2.3m nominal  depth)  in fie lds of area of 38.90 ha 
Construct Type  2 drains  (5Om  c/c,  2.3m nominal  depth)  in fields  of area of 59.21  ha 
Construct Type  3 drains  (75m  c/c,   2.  3ra nomin al depth)  in fields  of area of 
41.25  ha 
Construct Type  7  dr  ains  (35m  c/c,  2.Oun nominal  depth)  in fields  of  area of 
9.97  ha 
| lin m| 4,400     |7.0 
lin m  | 11,900 | lin m      5,500 
1in  m  2,900 
|7.0 
|7.0 
|7.0 
30,800 83,300 | 38,500  | 20, 300 
Construct Type  8 drains  (4Sm  c/c, 2.3m| nominal  depth)  in fields of area of 
60.96  ha 
Construct  tile block drains  of  2.3 m nominal depth 
lin m |13,600 
lin m  |  3,500 
Enlarge existing open  blockdrains  to 
2.45  m nominal  depth  side  slopes 
1.5h:lv, bed  width  0.5  m (cut  to  spoil)  | m Excavate  drain  SDI   (cut  to  spoil)  from 
km   0+000   (at  Primary  Drain)  to  km 
17,300 
2+500 
Excavate   dr   ain  SD2   (cut  to  spoil)  fromn km   5+215   (at  Primary  Drain)   to  km 
3+900 
Excavate  drain  TD2   (cut  to  spoil)  from km   0+000  to  km   2+000 
Construct  man   holes  at  junctions | between  tile block  dr ains Construct Culvert  C1 
m3             22500 m5             1800 
|7.0| 95,200 |8.0| 28,000  | 
|2.1  |  36,330 | 2.1  |  47,250 
m 
15000 
| 2.1    | 2.1 
3,780 
31,500 | 
|1.13  Construct Culvert C2 
No 
No              1 No 
7000  28,000| 
4000  4,000 | 
4000  4,000  | 
-   47   -TABLE   8     (Cont inued) 
ME LKA   SADI   DRAINAGE   -    PHASE    1 BILL  OF   QUANTITIES   (Continued) 
Item      Description 
|1.14     Construct  Culvert  C3 
|1.15     Construct  Culvert  C4 
1.16        Construct   Tempor  ary  Drop  structure on   Drain  SD2 
! 
Unit 
Quantity   | Rate  | Amount 
No                                       4000 
4,000 | 
No 
| No 
4000  |     4,000 
1 
| 2500  | 
2,500 | 
TOTAL 
|461,460 
-   48 TABLE    9 
MELKA   SADI  DRAINAGE BILL  OF   QUANTITIES 
Item   Description 
PHASE    2 
T Uait   |Quantity  | Rate  | Amount 
2.1        Construct Type  1 dr ains  (90mc/c,   2.3m nominal  depth)  in  fields  of  area 
11.3  ha 
2.2 
| Construct  Type  2 drains  (5Omc/c,  2.3am nominal  depth)  in  fields  of  area 
42.95  ha 
2.3       Construct  Type  3  drains  (75mc/c,   2.3m nominal  depth)  in  fields  of   area 
67.55  ha 
2.4 
|7.0 
I7.0 
|7.0 
|7.0 
9,100  | 60,200  | 63,000| 17,500 
2.5 
| Construct  Type  4  drains  (35me/c,   2.3m nominal  depth)  in  fields  of  area 
8.8  ha 
Construct  Type   7  dr ains  (35mc/c,   2.0 nominal  depth)  in  fields  of  area 
|47.9  ha 
2.6 
| Construct  Type  8 
nominal  depth)  in  fields  of  area 
drains  (45mc/c,  2.3 
2.7 
|1.5h:lv,  bed  width  0.5  m (Cut 
52.1  ha 
| Enlarge  existing  open  block  drains  to | 2.45  m nominal  depth,  side  slopes 
|lin n    1300 
lin m    8600 
| lin   m 9000 
1in m     2500 lin   m |13700 
1in  m      11600 
|7.0    |  95,900 I 7.0       81,200 
to  spoil) m5 
| 46850 
2.1 
98,385  | 
2.8      |Excavate   dr   ain  SD1 
|Erom  km  2  +  500  to Excavate  drain  TDl 
fr om   kn  0   +  000  to 
(cut  to  spoil ) 
km   3  +  400 
(cut  to  spoi1) km    2  +  800 
n3          5100 
| 2.9 
| 
| 2.10 
| 2.11 
| 2.12 
| Excav ate  dr ain  TD3 
fr om    km   0   +  000   to  kn   (cut 1  + to 500   spoil) Construct  culvert  C5 
2.1  |  10,710| 
2.1  42,525| 
m3 
No 
20250 |11250 
2.1 
23,625 I 
Construct  culverts  on   open  block dr ains  for  access  requir ements (Proviional ) 
4000  |     4,000 
No 
4 
| 2000 
TOTAL 
8,000 | 514,145 
-    49  -TABLE   10 
MELKA  SADI   DRAINAGE   -   PHASE   3 BILL  OF   QUANTITIES 
Item 3.1 
|3.2 
|3.3 
|3.4 
| 3.5 
|3.6 
Description 
Construct Type  l  drains  (90m  c/c,  2.3m nominal  depth)  in fields of area 
78.64n  ha 
| Construct Type  2 drains  (5Om  c/c,  2.3m I nominal depth)  in fields  of area 
| 72.5  ha 
T Construct Type  3  drains  (75m  c/c,  2.3m | nominal depth)  in fields of area 
102.6  ha 
|  Construct Type  4  drains  (35m  c/c,  2.3m I nominal  depth)  in fields  of area 
| 22.4  ha 
Construct Type  6   dr ains  (3Om   c/c,  2.Om nominal  depth)  in  fie lds  of area 
36.43  ha 
Unit 
Quantity  | Rate 
Amount 
lin m 
8800 
| lin  m 14500 | lin m | 13800 | 1in m  6400 
| lin  m  12200 
7.0    |  61,600 7.0     | 101,500 | 
|7.0  |  96,600 | 
7.0   |44,800 7.0       85,400 
Enlarge  existing open  block drains  to 
2.45  m nominal  depth,  side  sl opes 
1.5h:lv, bed  width 0:5 m (Cut  to  spoil )  m3 
28 200 
2.1 
59,220 
| 3.7 
| 3.8 
| 3.9 
I Enlarge existing open  block drains  to | 2.15  m nominal  depth,  side slopes 
|1.5h: lv, bed  width  0.5 m (Cut  to spoil) 
m3 
| 2.1 
22,050 
| 
Excavate  drain  SDl   (cut  to spoil)  from km   3+900  to  km   8+000 
Excavate  drain TD4   (cut  to spoil)  from km   0+000  to  kn  l+900 
I m3 
10500. 28300 
14250 
| 2.1 
| 
59,430 | 
3 
| 2.1 
| 
29,925  | 
|3.10 
Excavate  drain TD5    (eut  to spoil)  from 
| ka 0+000  to  km  2+050  15400 
3.11  Construct Culvert  C6 
3.12  | Construct  Culvert  C7 
I No 
2.1    |   32,340  | 4000  |    4,000 
|No         1                         4000 
|3.13 
Construct  Cu lvert  C8 
3.14  Construct  Culverts  on  Block  Drains  for 
|access requirements  (Provisional) 
No 
No  3 
4000 
| 2000 
TOTAL 
4,000 
4,000 
6,000 
| 610,865  | 
50  -TABLE   11 
MELKA  SADI  DRAINAGE        PHASE   4 BILL   OF    QUANTITIES 
|Item 
4.1 
Description 
Construct Type  4 drains  (35m  c/c,  2.3m nominal  depth)  in fields of  area 
119.6  ha 
Unit   Quantity  | Rate    Amount    | 
4.2       Construct  Type        dr ains (30m   c/c,  2.Om nomin al  depth)  in  fieldg  of  area 
72.38  ha 
4.3       Construct  tile block drains  of  2.3  m nominal  depth 
4.4       Construct  tile block  drains  of   2.0  m nominal  depth 
4.5       Enlarge  existing open  block drains  to 2.15  nominal  depth,  side  slopes  l.5:lv, bed  width  0.5  m  (Cut  to  spoil) 
1in m  34200 
| lin m | 24200 | lin m | 3000 | lin  m 1000 
7.0      239,400 |7.0   | 169,400 
8.0| 24,000 
8.0 
8,000 
| 
m3 
8700 
2.1     |  18,270 
4.6       Excavate  drain  SD2    (cut  to  spoil)  from 
km   3+900  to  km   l+400                                                             15000 
|4.7 
Excavate  drain  TDl   (cut  to  spoil)  fr om km   2+800   to  km   4+050 
m3              9400 
4.8  Excavate  drain  TD4  (cut  to  spoil)  from 
km   1+900   to  km    2+200 
4.9       Construct  manholes  at   junctions between  block  drains 
m 
2250 
| 2.1 
2.1 
2.1 
|5.0 
|5.1 
Construct culverts  on  Block  Drains  for access  requirements  (Provisiona l ) Allow  for   lowering  of  invert  level 
of  drain  under  Bridge 
No  1  7000 
No  2000 
Lump 
Sum 
31,500 19,740 
4,725 7,000 | 8,000 
25,000 
TOTAL 
555,035 
-   51  -TABLE   12 
MELKA  SADI  DRAINAGE   -   PHASE   5 BILL  OF   QUANTITIES 
Item 
5.1 
Description 
Gonstruct Type  4 drain8  (35m  clc,  2.3m 
Unit 
Quantity  | Rate  Amount 
nominal depth) 
83.2 ha Construct  Type 
in fields  of area 
5.2 
nominal  depth) 
5 drains  (20m  c/c,  2.Om 
in  fields of area 
5.3 
5,4 
63.45  ha 
| Construct  tile 
block  drains  of  2.3  m 
nomina l  depth Construct  tile 
16,800 
block  draing  of  2,0  m 
nominal  depth 
lin m  23800 
| lin m    31800 lin m    2100 
|lin  m  2000 
7.0  166,600  | 
7.0  222,600  | 
8.0 
| 
8.0    |   16,000| 
5.5 
Enlarge  existing  open  block  drains  of 
2.3 m nomin al depth,  side slopes 
1.5h:lv,  bed  width  0.5  m (Cut  to  spoil) |m3 
19300        |2.1   | 40,530 
5.6 
5.7 
Construct  man   holes  at   junctions between  block  drains 
Construct  culverts  on  Block  Drains  for access  requir ements (Provisional) 
No              3 
7000   |  21,000 
No                                           2000 
10,000 
TOTAL 
493,530 
-   52  -12. 
ESTIMATES  OF  BENEFI TS 
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  bene fits 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  con ce rned, the area would be progressively abandoned during the next eight years.    The programe 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 
30  t/ha.     These have      commen   steadily          ced in  1971     declined       (GC), mainly         yields were       with reportedly               increasing over 
salinity, but  also  under  an   increasing nematode  problem. the  following  yields  are  reported  by  MSFD: 
Since  1975, 
Year  (GC) 
1975 
1976 
1977 
1978 
1979 
1980 
1981  (provisional1) 
Yield 
t/ha 
23.8 
21.7 
15.4 
l4.8 
14.5 
12.1 
12.1 
On    the  basis  that  the  47   ha  remaining  non- saline is still 
30   t/ha,  the  average  yields  in  usable  salinized  area  have  now   fallen 
yielding 
to  10.9  t/ha  (Figure  12). 
Al though  neither  soi1, soil-water,  nor  climate is  ideal  for  ban anas, 
and    cons equently high  comercial  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 
and nematodicides. 
Budget  yields  on  non-saline  land  have  been  projected 
fertilizer,  pest  control 
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 Bírr 520/t.   A recent  export   cons ignment   fetched  US$    35O/t  fob  Asab, 
but  after  allowing  transport, handling  and  port  charges,  the  price  ex-fara is virtually the same. 
-53 TABLE   13 
ETHIOPIA 
ME LKA  SADI  AGRICULTURAL  ENTE RP RISE Rationalisation of Areas 
Present 
1981 1/ 
Programe 
Reclaim 
Non-saline                                                               47 
Potential 
1,065 
bananas 
(47) 
Low /moderate salinity                                  845 
680 
165 
bananas other  crops fallow 
Abandoned  area emp ty 
(653) 
(160) 
(32) 
390 
338 
52 
lucerne /pas ture  trials                            46                                                                 46 
Totals (Cropped) 
1,382 (906) 
1,018 
1,328 
(1,276) 
1/ 
Cropping  (1981) 
bananas capsicua onions 
lucerne /pas ture 
700 
130 
30 
46 
906 
-54 TABLE   14 
C 
1989 R/P 
1988 
R/P 
C 1987 
R/P 
47 
32 
1,065 
1,065 
1,065 
1,065 
(5) (52) 
(5) (52) 
(5) (52) (5) (52) 
1,065 
47 
1,065 
1,065 
1,065 
1,065 
1,065 
47 
1986 R/P 
28 
(hectares) 
RI ENTERP 
SE 
C 
1985 
R/P 
19  92 (964) 126 161 32 (882)  208 
243 
32  (800) 290 325 32 (718) 372 
1,065  (5) (52) 
257 
Area 
219     337 
CULTURAL 
ETIIOPlA ana 
Ban NELKA            AGRI         SADI 
of 
C 
1984 R/P 
337 
407 32   (636) 454                  728     91 (32)  (271) 
337    065     l, 471    728 
91  210  348 
412  59          471 
lopment 
C 
47      489 32      (554) 536                 257  S03 (32) ((30) 
503 
nCLivities. 
Deve 
1983 
R/P2/ 
1982 Present 
1981 
571 32   (472) 618 653  (390) 
700 
210 150          210 653 (32) (390) 
550 
65o2/ 
of 
47 
47 
32 
47 
(Prograume) 
(32) (390) 
653 
47  b03 
47  653 
Without            Project          (simulated) 
saline         Low/nod Non-salinc 
zone 
salinity 
700 harvested 
nhandoned                zone 
Project 
lou/oderate                   ty   Balini 
low/mod 
ncement 
coDe re-plonted         during 
turbed or 
reclaimed       dis 
Total        bananas 
at  declining              plhase   nt   inproving              phase area 
Cropping              C- area 
Drainaçe 
Non-saline 
New       planted            areas 
med      Reclai           area which 
Abonloued 
ilarvest            area:        ed 
yield       nt   full 
Abandoncd Pallow 
banana 
Totol 
as alloved 
Arca 
th 
Wi 
Fallow 
ol 
R/P 
27 
la 
B. 
S0 
3/ 
- 55 Figure  12 
ETHIOPIA 
Marketed Production of  Bananas  by Me lka Sadi  Agricultural Enterprise 
(tonnes  per ha) 
35 
30 
Projected Potential 
Assumed  actual yield in non-saline  area  (47  ha) 
25 
(23. 8) Marketed              Production                  (t/ha) 
(21.7) 
20 
15 
(15.4) 
average  yield (14.8) 
(14.5) 
Assumed   average  yield  in 
(12.1)       (12.1) 
10 
usable salinised area  (10.9  t/ha) 
5 
1975 
1976 
1977 
1978 
1979 
1980 
1981 
Harvest Year  (GC) 
Source:  Horticultural  Department,  Ministry  of  State Farms  Development. 
-56 Estimates of  production  costs  are  based  on  MSFD's  own  cos ts, modified 
as  explained  above.     These have been calculated for each of the average situations and  are presented in Table 15. 
Inves tment  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     allowan ce  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 
substantial  increase  in  working  capital  have  been  absorbed,   the  cash 
temorarily  reduced  production  and 
the 
flow  indicates  a   strong position.    In  relation  to  this  cash  flow,  the establishmen t loan  required  would  be  relatively small,  and  would 
mostly  comprise working  capital. 
No   attempt  has  been made   to 
would  be  borrowed,   and   a  simple  cash  flow  has  been  calculated 
speculate  on  the  source  of  funds  which 
to 
(Tab le 16)      This 
government  would  be 
indicates  that  the  financial  return over  10  years 
Or 
any   other charges  made 
in  the order  of 
for  supplying 
36%   before  finance  charges 
original  land 
be  sensitive  to  the  achievement  of  the  projected  output  (yields  or  price) 
development  costs. 
This  financial  rate  of  return would 
irrigation water  or recovering 
at  a  drop   in average  yields  (on non-saline  land)   fr om  30  to  24 
which  would  reduce  the  calculated  rate  of  retum  to  10%. 
t/ha, 
As   a  State Farm  operation  using 
project  would 
It  is  emphasised  that 
yield  a  higher  rate  of  return  than  indicated  above. 
borrowed  capital  paid  for at  l07, 
the 
have 
relatively little impact  on   the  projected  costs which  are  dominated 
the  projected  costs  of 
the 
by 
the 
increasing  production  costs  and   the  as sociated  increased  need   for 
drainage  programme   itself 
working 
capital. 
12.5   Economic  Benefits 
The   cash  flow  has  been 
have  been  converted  at  the  official  rate  (Birr  2.07  =  US$   1.00),  and  non 
product  value, 
inves tment  and 
converted  into 
operating  costs. 
accounting  values  by 
Foreign  exch 
adjusting  the 
tradeable  items 
have  been  converted  at  the standard  conversion  factor 
ange  costs 
given by  the  DP SA at 
0.75.    The  only  exception  to  this  is  the value  of 
1/   Costs   in  Section  II  are 
for  price  escalation has  been  built  in. 
given  at 
1981 
levels,  and  no   contingency 
-57 TABLE   1s 
Full      Devalopment                (non-saline                   arean) 
30 
15,600 
S40 145 340 
2,853 
42     1,739    264    5,923     814 591 40 500 
1,947 7,870   354 610 8,834 6,766 
areag 
drainnge) 
Improving after 
25 Birr/ha 
13,000 
500 120 340   2,377   42    1,713    264  5,356    814 591 
2        1,911 7,267    327 610   8,204 4,796 
464 
Costs 
ENTBRPRISE  Production 
yenr (first 
(salinised                areas) 
and AGRICULTURAL 
ETIIOPIA 
Returns 
Bstimated SADI 
HEIKA Bananas 
Present 
12 
6,240 
303 
1,141     42    1,581    264 
3,331 
814 591 40  286 2 
1,733 5,064    229 610 
5,903 
337 
343 798 
Management,                     administration,                          medical costs 
TAX CAIARGES 
published estimates 
data project 
on Based 
and Source: 
(declining)" 
'present 
for 
Enterprise  Development". 
Agricultural "Full 
and 
Sadi  "Improving" Melka 
by for 
520/tonne) 
/ha     tonne         s 
Small        tools,         sundries 
Vehicles              and    transport 
costs 
production              capital 
WATER 
MARKETABLE                         PRODUCTION 
Birr 
TOTAI.            PRODUCTION                       COSTS 
PRODUCTION                        COSTS 
Nematode                control Pest      control    rental          Crate 
Total        variable             costs 
Otlier         Direct          Costs   Permanent                 labour 
(at 
Misce1laneous direct 
direct WOrking 
LLAND, 
Variable            Cost6  Fertilizers 
Machinery                costs Casual          labour 
Sales 
Packaging 
Land       tax   other 
Depreciation 
BEFORE 
Yicld 
total   on 
Total 
Finance 
ToLal 
PROFIT 
Sub 
-58 Pinancial 
ROR 
TABLE  16 
5,777 
NPV 
(at    10% 
10 
discount) 16,614 
66,114 
16,614 
16,614 
8,382 
8,382 
8,382 
8,382 
8,382 
8,382 
8,809 7,805 
9 
16,614 
Birr) 
(1981 Analysis       6 
16,614 
16,614 
Birr       C00 
8,382 427 8,382 427 8,382 27 8,382 427 8,382 
13,196 
7,805 
16,614 
16,614 
16,614 
16,614 
A27 
sh 
l1,357  4,381 15,738                                     203 
Ca 
203 
8,382 427 
8,809 7,805  7,805 8,809 7,  805 349  7,456 
7,359 809     8,     7,805  446 
8,809 7,805  434 7,371 9,012 6,726  531 6,195 
ETIIIOPIA : 
Unit ana Ban 
4,009 6,123 10,132 
(378)   897    519    71 2,273        1,463 2,863     5,730 2,449 8,179 472  11,469          8,619 (1,337) (1,752) 511     13 
733 568 2,730 4,031                   724   724     99 
2,286 
2,022    461 3,423 5,906 427 
88)       (5,099) 
Sadi 
Melka  2 
(4,5 
I8c. 
733 3,139  3,872 
733 3,763  4,496 
733 4,075  4,808 
644    644    44 1,019 1,707 
370 
2,547 
1,526 
4,443 
427   6,577     704     b07 (2, 
705)     (3,312)   of 
yeara 
756 121    877 
(253) 624 
370 3,054    3,424 427   4,475 21 
(683) 
1981 
370  3,307    3,677 427    4,104 704 704 
3 
11. 
atter 
6ection value 
residual     in 
included 
4,705,000) 
(B capital 
equipncnt)               machinery, 
works 
2/ drainage        (residual)             capital 
HARGES 
50% 
nt.ion given 
depreci 
tor excova 
out 
lieu      replaccments.                     of 
non-saline                  trom        areas declining                from       areas    mproving                areas        from 
Sales 
VALIE           TOTAL            SAIES 
xpenscs           operating               e     total       drainage            Sub vorking 
bananas 
non-saline                  in  areas       Production                   COBts          Total 
in  arcas        declining             in  improving                 areas 
FINANCP 
Lments            inves         Total Production                 Costs 
(faru       Depreciation 
PIT 
and 
cutting 
Banana 
of Value 
in 
XPENDI             TURE          E tracnt 
Lnves 
tal Replanting           Incremen 
OUT  TOTAL.  CASII  BEFORE 
CP 
BALAN 
balance           v Iduct   B2PE 
NET 
Trencher AÍter 
SIHPU 
2/ 
En 
3/ 
59 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  adjus ted cash  flow  stronger than in the financia 
return       exceeding                 analysis,  50%.       and  indicates          The  project's       an  internal        sensitivity       economic    would rate  be of  reduced, and  should  show  a l0%  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 
value  of  the  drainage  project with 
previous  investment  as  sunk  costs. 
alternative  crops,  (b)   the  incremental 
nematode  control  and   (c)  assume  all 
-60 PART   B 
AMIBARA   AREA 
SOIL  AND  SALINITY  STUDY 
-   61    -PART  B 
AMIBARA AREA 
SOIL  AND  SALINITY  STUDY 
CONTENTS 
PAGE  NO 
1. 
2. 
3. 
4. 
5. 
6. 
Sumary 
Background 
Geo logy   and   Hydrogeology 
Soils  of  the  Amibara  Area 
Infiltration  and   Perne ability Test  Results 
Drainage 
63 
63 
63 
64 
64 
65 
Schedule  of  Tables 
Table  17    Amibara  Area,  Observation  Well  Records 
Table  18  Depth  to  Imperne able  or  Slowly  Perme ab le  Layers 
Table  19 
Groundwat er Levels  and  Electrical  Conductivity  of   Groundwat er 
Table  20    Rates  of  Soil  Infiltration  and  Perme ability 
Schedule  of  Annexes,   (Bound   Separ ate ly) 
Annex  5  AIP  Obs ervation Well  Records,  August  1980  - November  1981 
66 
67 
68 
69 
Annex   6 
Soil Profile Descriptions,  Pits  and   5n   Bores 
Schedule  of  Maps,   (Bound    Separ ately) 
Map   7 
Location  of  Test  Sites,  Depth   to    Groundwat er ,  EC   of Groundwater,  Depth  to   Iaperme able  Layer  and   Soil  EC    Values 
62  -PART   B 
AMIBARA  AREA 
SOIL  AND   SALINITY  STUDY 
1.      SUMMARY 
Dur ing the  soil  salinity study  at  Melka  Sadi  farm  it was   agreed  that  the  study should  be   extended  to  include  the  remainder  of  the  Me lka Sadi  area  and   the  whole of  the  Amibara  area,  the  field work  to  be  started directly after the  Me lka  Sadi farm    study.     This  field work  was   co   include  investigation of  the  results  from  a minimum  of  30   soil   perme ab ility and  infiltration tests,  toge ther with  5 m deep borehole  sites approximate ly  2   km   apart  over  the whole  area.    The  me thods  and equipment  used  were  the  same  as  for  the Me lka  Sadi  farm  study .      Field  work commenced  on  29  September  1981  and  was  completed  by  9   December  1981.    28   soil pits  were  described  and    s amp led for  chemical analysis. 
2 
BACKGROUND 
The  Amibara  area was   studied by  Italconsu lt dur ing  their surveys  of  1969  and 1971, and   later  in  1975  Hunting  Technical  Services  commissioned  a  hydro 
pedo logical study of  the Melka  Sadi  and  Amibara  areas.    In 1980  the Amibara Irrigation Project  authority  instal led  a network  of  27  observation  wells,  which 
have  been  in  operat ion  since  late  1980.      The  area covers  some  7250  ha of which 3056  have  been under  irrigation for  some  years.    The early deve lopment  was  alOng the  south  bank  of  the  Awash  with  irrigat ion  water  supplied by  diesel pumps   to a number  of separate  farms.     In  1981  1800  ha of new  area was  supplied  by   gr avity from  the Melka  Sadi  he adworks. 
The   principal  erop  is  cott on but  there  are  also  some  areas  planted  to  banana, citrus  and   t omato .    In  addition  there  is  approximate ly 60  ha  of irrigated pasture  in  the  settlement  area.    The Institute of Agricultural Research 
maint ains  a research  farn of  300  ha  which  is  also supplied  by  gravity  from  the Me lka  Sadi   headwor ks. 
3. 
GE OLOGY    AND    HYDROGE OLOGY 
3.1   Geology 
The   description  of  the  Melka  Sadi   area  in  Section  I   also  applies  to  the   Amibar a are a.    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    fr  om      Do fan. 
North  of  the  developed  area  is  a  series  of  warn  springs  in  the  valley  floor which  form  the  Billen  swamp.     The  water  is alkali with  an  EC   of + 1.0  mmhos/ cm and   pobably  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   observat ions  were started in August  l980.    The  recharge  of  this  aquifer is supplied  in  part  by infiltration upwards  from  the  under ly ing  confined  aquifers originat ing  in  the Alledeghi plain.   The  Awash  river, especially at  tines of high  flow,  also contributes  to  this  aquifer.     A third  possible contribution is  the very  saline groundwater  associated with  the  volanic  cones  and  feat ures ,   as  at  Amibara  and 
Ambash.  whích  are  found within  2.5  m of  the  surface  at  borehole site  DRH   71,  1 
Km    north-west  of  Amibara  hill, 
-63 The  deep  aquifer  is  now  also  receiving  some  water  fron  the  re lat ive ly  shallow, normally  non-saline,  aquifer  which  has   deve loped since  the   introduc tion of 
drainage  towards 
irrigation  and this will 
the  Billen  swamp 
cont inue to  cause  the  aquifer  to  rise since  the  natural 
is  extreme ly  slow. 
The  second,  and  shal low,   aquifer  is  gener al ly  of  low  salinity  and  is  confined  to 
rising in level.   At   some   sites it is  extreme ly saline, particularly where  the natur ally  saline  groundwater  was   already  close  to  the  surface  as   at  Amib ar a and Ambash. 
The   depth  of  the  groundwater  table  as  measured  in  November   and  December  1981 
toge ther with  the  salinity of  the  water  (EC)   are  shown   in  Table l2. 
The   shallow  aquifer  and   the  deep  aquifer  are   separ at   ed  by   a  variab le  thickness of  very  slowly  perme able  or  possibly  imperme ab le  clays  and   silty  clays .     The 
Or 
aear  the  presently  irrigated  areas,  and   this  shallow  aquifer  is  gradually 
depth  at  which  such  a   layer  or  series  of  layers  was   found  while 
bores  is  shown   in  Table 
making  5  m deep 
14   shows   the  salinity of  the 
3   together  with  the  depth  of  the goun dwater.     Table 
fall  of  its  level, 
groundwater ,   together  with  cOmments   on  the  rise  or 
4.      SOILS   OF   THE    AMIBARA    ARE   A 
The   l: 20,000  scale  map   produced  by   Italconsult  in  1969   shows 
area  in detail,   The   earlier  irrigation   deve lopment  is  on  soil  units  3   and  6, 
the  soils  of  the 
"vertisols  on   recent 
grain size".   The   present 
alluviu"  and  "recent  alluvium  with  frequent   alter ations  in 
"hydromor phic  vertisols",  and   soil  unit  6. 
deve lopment   area  is  mainly  on   soil  unit  5, 
A  feature  of  all  the  vertisols  is  the 
and   fine  sandy   lo ams   in  the  deep  subsoil,  the  thickness  of   the 
presence  of  stratified silts,  silt  loams 
from  50 
alluvium" 
cm   to  3   metres.    Soil  unit  4   "non-calcereous  vertisols  on  recent 
vertisol  varying 
example, due  to  the 
became    calc areous  following  irrigation,  as  shown   at  DRH    73   £or 
calcium carbonate  content  of  the  AWash   river   water. 
Another  feature  of  the  vertisols  is 
prismat ic  structure,  With 
p ads  up   to  50   cm   high  and  25 
the  very   comp  act  B 
of  fine  cracks,  and 
to  soil  unit  5   "hydr omorphic  vertiso ls"  and 
also  with  pores  or  root  channels. 
1-1.5  km   wide  adjacent  to  the  primary  canal. 
generally  occurred  in  a  strip  about 
horiz on   with  a  strong 
cm   across   almost  devoid These  soils  were  confined 
Dremature  ripening  of  the  cotton  was 
a   good   indicator  of  these  soil  conditions. 
Uneven   and 
stunted  growth  with 
as  at  DRH   81,82,  84,  89,  91  and  92. 
Some   of  the  soil  unit  6  sites  were  very  saline,  for   examp le  as   at  DRH 
damp   saline patches on  the soil surface.    Otherwise  the  soils  were   found gener ally 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    satur ated  extr act. 
74,  with 
to  be 
5 
INFILTRAT ION   AND   PERME ABILITY  TEST   RESULT'S 
Results  of  the  infiltration  and    perme ability tests ,  both  "pour-in"  and 
"pump-out"  are shown   in Table  15. 
The  methods  used  are  the   s ame as  for  the  Melka  Sadi  farm  study .   Water  used  in the  tests was   taken  from  the  primary  canal. 
64  -When  testing the  vertiso ls  it was  necessary  to  pack  the  bores  with  a filter of vo lc an ic 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.    Perme ability tests were  run  for at  least 6  hours  and  infiltration tests were  run for  8  hours. 
The  re sults obtained were  much  as  expected.    The   recent  alluvial  soils  (soil unit  6)  had  satisfactory infiltration rates  and   perme ability rat es.    The vertisols had  rather  low   perne ability 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  par ts of  the  earlier deve lopment  area  which  have  shallow,  often saline groundwaters .    These  areas  are  gener ally located around  the vo lc anic features  of Amibara  and  Ambash,   as  shown  on  Map   6. 
To determine  the  extent  and  cont inuity of  these  shallow  groundwaters  it will  be neces sary  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 inter va ls ,   l site per  50  ha,  in  the  first  inst ance  should be  a  sufficient density of observat ion.   As   a  guide all those  are as  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  alre ady very  high  and  there  has 
been  a  slow  but  gr adual  rise  in  the  groundwater  level  which  c an   only  be 
acceler at ed   by   further  irrigation  deve lopment .     To  esure that  there is  an  ear ly warning  of  ris ing  groundwaters  throughout  the  area  and   to  provide  a  me  an s of estimating probable  drainage  needs  in  the  future,  the  number  of  observation 
wells  should  be   increased  so  as  to  have  one   observat ion well  located  halfway 
new   wells  should  be   installed to  the  depth  of  the  first  water  table  which  may   be far  less  deep  than  indicated  by  the  observattion  wells ,   where  the  salinities  are often  higher  as  was   shown  at  the  Me lka  Sadi  farm. 
In  conc lusion  it  is  considered  that  tile drainage will  eventually  be   required within  the  Amibara  area. 
levels  and    s alinities  as   described              There  is above         a cont in  inu order        ing  need   to  establish               to  monitor the   groundwater              timing  and extent  of  the  drainage  facilities  required,  but  on   the   informat ion  presently available  it  is  not  expected  that  a   progr ane  for  instal lat ion  of  a  tile drainage  network  should  be  comnenced  before  perhaps  5 years,  and  it is  quite probable  that  the  drainage  prograne  cou ld  be   delayed  even  further. 
between  each  of  the  existing observation wells,  at  present  26   in  number. 
These 
-   65   -TABLE    17 
AMIBARA  AREA,  OBSERVATION. WELL  RECORDS 
Depth  to    Water  Table  in  Metres  and Salinity Expressed  in  EC   - November  1981 
SITE  NO 
|32 
33 
34 
35 
36 
|37 
|38 
39 
41 
42 
| 44 
|45 
46 
47 
48 
49 
|50 
51 
52 
|53 
| 54 
| 55 
57 
| P9 
P2 
PP5 
DEPTH   TO   WATER   TABLE 
(m) 
6.03 
8.53 
8.71 
9.27 
7.46 
|8.21 
| 4.36 
|1.96 
|  7.00 
|12.46 
|8.44 
|  2.81 
14.71 
13.78 
|   6.15 
|  6.79 
|11.78 
| 13.65 
12.89 
| 13.00 
| 15.48 
|  5.92 
| 14.68 
(mhos/ca) 
7.7 
1.7 
0.0 
9.2 
3.5 
2.1 
1,4 
2.0 
3.0 
|> 10.0 
|> 10.0 
1.3 
|>  10.0 
|>  10.0 
1.6 
)   10.0 
6.3 
28.0 
|>  10.0 
6.6 
3.9 
1.8 
3.5  (June  1981) 
8.7 
3.5 
2.2 
ELECTRICAL  CONDUCTIVITY 
(EC) 
| 8.93 
8.24 
8.36 
-   66  -TABLE   18 
DEPTH  TO  IMPERME ABLE  OR  SLOWLY  PERME ABLE  LAYERS 
| Site  No | DRH   59 
Depth  to 
Depth  to  slowly  l Depth  to 
% of  Amibara  Area 
imperme ab le  1layer    perme ab le layer 
(m) 
|0- 2 
77         |0- 2 
| (m) 
|1.8 |1.6 |2.5 |2.1 
2.0 
2.1 
2.2 
2.8 
2.8 
2.6 2.7 2.5 
3.5 3.3 
|3.2 3.3 3.0 
3.9 3.5 3.1 
| 3.0 | 3.2 | 3.1 
|3.9 |4.3 |4.0 |4.8 |4.2 | -
| 
|5.1 | 
|> 
water  table (m) 
5.0 
DRH  57 60 66 71 72 73 75 76 78 79 
DRH   55 58 
61 63 68 69 70 74 81 82 84 85 
DRH  56 
64 
| 2  -   3 
|2 -  3 
2   -    3 
2   -    3 
2   -    3 
2  -   3 
5.1 
3.6 
6.25 
|>  13.0 12.9 
2.5 
|> 
5.0 
2.1 
2 
3 
2   -   3 
|2 -   3 
|2 -  3 
|3 -  4 
|3 -   4 
|3 -  4 
|3 -  4 
|3 -   4 
|3 -   4 
|3 -  4 
|3 -  4 
|3 -   4 
|3 -   4 
|3 -   4 
|3 -   4 
|4 -   5 
|>   5.0 
5.0 
13.0 
|> 11.0 
31.25 
|> 
|> 
7.8 
5.0 
5.0 
|>   5.5 
|>   3.5 
8.9 
6.8 
1.5 
2.7 
3.8 
37.5 
|> 
3.1 
5.9 
8.5 
67         |4- 5 
|4 
5 
|>   5.0 
12.5 
80 
DRH  62 65 83 86 
|4 -
>5 
|> 5 
|> 5 
|> 5 
15.48 >    5.0 
14.71 
|>   5.0 
11.8 
5.9 
12.5 |TOTAL 100  % 
-  67 TABLE   19 
GROUNDWATER  LEVELS  AND  ELECTRICAL  CONDUCTIVITY OF  GROUNDWATER 
SITE 
DRH  AIP 
No  No 
Depth  to imperaeab le layer  (a) 
Depth  to 
groundwaterIgroundwater 
EC   of 
Reaarks 
(m 
| (mhos/ca) 
S9 
77 
| 57 
| 60 
66 
71 
-
38   m | 45 
72        P2  nr 
73 75 76 7: 79 
| 55 58 
| 61 63 
| 
32 | 51 I 53 
S 
| 36 -
|  43 
-
68 
69  P9 
70  |49 
74  39 
Close  to main  drain  agd riaary canal 
AIP   38  GHL   4.36,  EC   1.4,  rose  1.2 m May-Nov ember  1981 GWL   rose from  3.61  to  1.88  Eolloving  irrigation end September  1981 
GWL    ro8e  30    ca  in  past  year 
GWL    Eose   20   ca  in  15   montho 
Ne ar  Amibara  volanics     Saline area EC   top soil 1: 1 30.0 aahos/cm 
P2  GWL   8.24 m,  EC   3.5 mhos/cn 
GWL   in bore  2.4 a,  rose to 2.1  after 6 hra 
GWL   vas  3.25  March  1981.    Irrigated Pasture Trial GWL    Cose   l.16      in  May   and   fell  again  and   rose  50    cm 
Septem ber-Novenber  1981 
GWL    rose   1  m  in   15   months 
No   records availab le 
GWL    rose  1.5  m  in  15    months 
Close  to  secondary  drain 
AIP   43   Dry   bore  in  rock 
Ternite  nest  at  4.0  m 
Near   Am ib ara  Volanics 
GLW   rose  3.2  m   June-Nov ember  1981,   high  civer  floods? EC   fel1  from  >  10-8.7 
GWL    rose  1.87  n  May-November  1981 
Near  Amibara  volc anics 
folloving  irrigation. 
81 
82 
34 
| 
85  S5 
1.8 1.6 
2.50 
2.10 
2.00 
2.15 
2.20 
2.80 
2.80 
2.60 
2.70 2.50 
3.50 3.30 3.25 3.30 3.00 3.90 3.50 3.15 
3.00 3.20 3.10 3.90 
5.0 |>  5.0o 
1.98 |> 13.0 
12.89 2.50 
|>  5.0 2.10 6.03 
15.65 
13.0 
)   11.0 
7.84 
5.0 
5.0 
5.5 
3.52 
8.93 
6.79 1.85 
2.2 
13.0 
14.8 
36.0 
1.2 
7.7 
28.0 6.6 
3.5 
|> 
|> 
2.75 
3.8 
3. 10 
5.92 
16.4 8.7 
40.0 
13.2 
0.86 
2.0 
56      44 64        - 67    54 80 
62       46 65 
83       50 
4.30 4.00 4.80 4.20 
|> 5.0 
|> 5.0 
|5.10 
|> 5.0 
8.48 |> 5.0 |   15.48 
|>  5.1 14.71 
5.0 11.78 
9.27 
8.53 8.20 
4.36 7.00 
12.46 
6.15 
8.24 
8.36 
14.68 
36.4 3.9 
86 
35 
AIP  33          N/A AIP   37 
AIP  38 AIP  4l AIP  42 AIP  48 
P     2 
PP   5 
AIP   57 
18.0 6.3 
9.2 1.70 
2.1 1.4 
3.0 
>  10.0 
1.6 
3.5 2.2 3.5 
EC     AIP   392.0  GWL    rOse   2m     fol lowing  irrigation  June-Sept ember 1981.    Saline  area  nearby   (EC   topsoil  > 40.0  nhos/cm) 
GWL    AIP   34  8.71  and   EC    0.88.    Level  rose  65   cm    in   14   months Too   hard  to  auger  below   3.8 
Too  hard  to  auger belov 3.1 m 
GWL    rose  1.8        May -November  1981    (High   river  leve ls  + irrigation) 
GWL    £luctuates  slight ly  vith  irrigat ion 
GWL   rose  30   ca  ia  15   moaths 
Near   volc anic  out  crop 
GHL   roge  40  cm    in  past  year 
GWL    rises  and  falls 
GWL    Eose   30    cm   in  past   through       year   60   ca  folloving  irrigation GHL   rose  1  m  in  15   months 
GWL    F1luctuates   in  response  to  irrigat ion 
GWL    rose  l  m following  irrigation  March-Noven ber  1981 
GWL    rose  54   ca  in   15    months |GHL   rose  23   ca  1n   past  y 
year 
"Stone"  ac    12.5  a   vhen  drilled.    GWL    rose  1.5  n   in  15 
months 
|GWL  rose  62    cm     June-Nov ember . 
Re ad ing  for  September  and  November   1981   only 
High  river  ilovs ? 
3.8   km    east  of   project  boundary  GWL    rose   17    Cm     October  80   - November  81   due   to  discharge  of    drainvat er? 
68  -TABLE   20 
RATES   OF   SOIL  INFILTRATION  AND    PERME ABILITY 
I site  | Infiltrat ion  | Rate  of  Perne ab ility (m/ day ) 
Depth   (m) 
No 
|Rate 
| "Pour  in"  Method 
(mm/hour) 
| Depth 
0-60 
Cm 
Depth 60 120cm 
Depth 120 180 cm 
Depth 180 
240cm 
Rate of 
| Perneability "Pump  out" Method 
(n/ day) 
| 55 | 56 
57 
|58 
| 59 
|60 
|61 
|62 
| 63 |66 
|67 
|68 
| 69 
| 70 
| 71 
| 72 
| 73 
| 74 
| 75 
|76 
| 77 
| 78 
| 79 
| 80 
| 81 
| 82 
|83 
| 84 |85 
|17.3 
| 13.0 
20.7 
3.4 
| 24.6 
| 22.3 
| 17.6 
| 23.6 
| ll.0 
| 20.7 
22.7 
17.0 
26.0 
| 22.7 
| 21.7 
| 23.7 
| 11.7 
| 14.7 
| 15.0 
17.4 
| 24.0 
| 14.0 
19.4 
16.0 
12.4 
| 13.0 
|0.079 
|0.168 
|0.108 
0.152 
0.123 
0.225 
0.88 
0.160  -
0.156  | 
|0.047 
|0.032 
|0.130 
T0.072 
|0.168 
0.124 
0.018 
0.052 
0.012 
0.041    0.26 
| 2.75  n 
0.014 
0.021 
0.050 
0.022 
|0.3422 
0.191 
|0.04l 
|0.040 
|0.139 
| 0.167 
0.097 
|0.163 
0.l17 
|0.118 
0.217 
0.105 0.01 
0.186 
0.206 
0.127 
0.004 
0.190 
0.043  I 
0.1 
0.033    | 
0.222 
0.067  | 
0.098  | -
0.098 
0.039 
0.098 
0.039 
0.296  | 
0.081  | 
0.028 
0.036 
0.058 
0.136 
0.108      0.22 
0.021 
0.098 
0.135 
|0.204 
0.216 
|0.061 
0.194 
0.218 
0.120 
0.190 
0.041 
0.207 
0.102  |0.60 0.1664.26 
0.570 
0.012    | 
3.63 
2.51 
| 2.26 
0.20 
0.141 
0.181 
0.144 
0.197 
0.190 
0.118 
0.195 
0.028 
0.206 
0.128 
0.058 
|0.232 
|0.100 
0.244 
0.196 
0.181 
0.060 
0.201 
|0.037 
0.220 
0.004 
0.008 
|2.78 
|0.614 
2.52 
2.69 
|0.205 
|0.128 
0.217 
0.025 
0.294 
0.151 
0.168 
|0.291 
0.301 
0.116 
0.180 
0.217  | -
-   69  -PART  C 
ME LKA   SADI   AREA 
STATE   FARMS    I   AND    II SOIL  AND    SALINITY  STUDY 
-   70  -PART  C 
MELKA  SADI  AREA STATE  FARMSI  AND   II 
CONTENTS 
PAGE   NO 
1, 
2. 
3. 
Summary Soils Drainage 
72 
72 
72 
Schedule  of   Annexes,  (Bound   Separ ately ) Annex  8      Results  of  Soil Chemical  Analys is 
-    71    -PART  C 
MELKA   SADI  AREA 
STATE   FARMS   I   AND   II 
SOIL  AND   SALINITY  STUDY 
1.       SUMMARY 
The  Me lka Sadi  area covers  s Ome  4, 240 ha  of which  l,330 ha  are  occupied  by  the 
Melka  Sadi  farm  and  600  ha  by   new ly developed  irrigated cotton. 
The  rema in ing 
2.310  ha  are to  be    deve loped  for  irrigated cotton under  the  current  progr ame. The   total area  of  2,910  ha forns   Me lka 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  alluviu".   These vertiso ls  are often up  to   3 metres  deep and  have  low   perme ab i  l ity and  infiltration values .     There is  a   smalI  area on units   1 and   2,   "soils  on  veIY  recent  alluvium". 
About  half  the  area  of  State Farn  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  sal ine  areas will require careful leaching be fore 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  mnhos/ cm,   and  one   hor izon only  at  180-200  cm. 
At 
AIP   7  the  soil  was   saline with  an   EC of  saturated  extract  of  9.5  amhos/cm. 
The  soils  in  unit  6 have  slight ly 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  infiltrat ion  and  perme ability rates  are  satisfactory , 
and   as   the  groundwater  table  is  relat ive ly  deep  over  most  of  the  area,  with  the exception  of  the  area  close  to  Me lka  Sadi  farn,  no   immediate   probl ems   are expected  following   irrigat ion.    The   area  clOse  to  the  farm,    alongs ide  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   drain age shou ld  then  be  extended  northwards  in  step  with the  expected  rise  in  water  levels.    On   soil unit  3,   vertiso ls, the present 
groundwat er   levels  are  deep  and  the  water  is  saline  or  very  saline. 
Infiltration results  are  satisfactory for  cotton while   perme abil ity rates are Iather  low,      Deep  ripping,  cultivation and  the  cotton roots will help  improve the  situation.    Dr ainage to control  the  water   tab le 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  plant ing  by  March  1983  a closer pattern of  observat ion  wells  is required,  and  these  shou ld be  sited between  the  exist ing  AIP  wells  and  extend 
down  to  the  present  water  table.  Once  the  whole  area has  been  irrigat ed  for  2 or  3  seaons  the  expected rate of rise can  then  be  estima ted with  some  accur acy to obtain  the  probab le date by  which  drainage wil1  be  needed. 
-     72   -In 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  networ k. 
Groundwat er levels,  salinity of  groun dwater,  depth  to  imper vious  or  slowly pervious  layers  and  observation well  sites are  shown  in  Map  Nos   l-4. 
As   with  the  Amibara  area  the  tining of  the  requirement  for  drainage  within State Farms  I  and  II has  not  been  identified  clear ly, and  continued monitoring of groundwater   leve ls and  Salinities is necessary  to establish this. 
-    73  -BIBLIOGRAPHY 
Brady N C Currey  DT 
FAO 
FAO 
Foraky  S  A 
International  Institute  for 
Land  Reclamation  and  Improvement 
International  Ins titute  for 
Land   Reclamation  and   Improvement Italconsu lt 
The  nature  and  properties  of  soils ,   8th  Ed 
New   York,   1974 
Informal  technical  report  No    l4, 
UNDP/FAO/ETH/ 72/006,  May   1973 
Irrigation  and    Drain age  papers  Nos    l,  9  and 16 
Guide l ines  for soil descript ions 
AIP  site investigat ions  report. 1975 
Bruxelles, 
Italconsult 
Morton  B   A 
Sir  William  Halcrow  & Partners 
Sir  William  Halcrow  & Partnes 
United  States  Dept  of  the Interior 
Wilson  E   M 
Drainage  Principles and  Applications, 
Vols  I  -   IV.      Wagen  ingen,  1974 
The   Auger  hole  method.    Wageningen,   1971 
Melka   Sadi  -  Amibara  proposed  Irrigation Project.     Feas ibility study,  parts  I  and   II, Vol   I  -   IV.      Rome,   1969 
Me lka  Sadi  -  Amibara  Irrigat ion   Project, Additional  soil   s tudies.   Rome,   1971 
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Summery

Amibara Irrigation Project II - Summary

Amibara Irrigation Project II - Drainage & Salinity Study

Document Summary

1. Project Overview

This 1982 report by Sir William Halcrow & Partners for the Ethiopian government examines drainage and salinity issues in the Amibara Irrigation Project II, focusing on three areas:

Part A: Melka Sadi Farm (1,328 ha)
Part B: Amibara Area (7,250 ha)
Part C: State Farms I & II (2,910 ha)

2. Key Findings

Issue	Findings
Salinity Problems	1/3 of Melka Sadi Farm abandoned due to salinity; rising water tables observed throughout the study area
Water Table Rise	At observation well P11, water table rose 5m in 9 years to 1.8m below surface
Soil Types	Three main groups identified: saline alluvial/colluvial soils, non-saline alluvium, and vertisols
Water Quality	Awash River water classified as C₁S₁ (low sodium, low salinity hazard)

3. Drainage Recommendations

Melka Sadi Farm (Part A):

Proposed 5-phase drainage implementation (1,018 ha total)
Tile drains preferred over open drains (cheaper, less maintenance)
Estimated cost: ~Birr 2,600/ha
Projected benefits: 36% financial return over 10 years

Amibara Area (Part B):

Immediate drainage needed only near volcanic features
Full drainage system may be needed in 5+ years

State Farms (Part C):

Drainage required alongside SD2 canal by 1983
Continued groundwater monitoring recommended

4. Implementation Plan

Phase	Area (ha)	Cost (Birr/ha)	Timeline
Pilot Area	210	2,200	First
Phase 1-5	1,018	2,300-3,400	3 years

5. Key Tables & Figures

The document contains extensive technical data including:

Hydraulic conductivity test results
Water quality analyses
Drain spacing calculations
Cost estimates (Birr 461,460 - 555,035 per phase)
Projected banana yield improvements (from 12.1 to 30 t/ha)