GIS Supported Irrlqable  land  and Water  Resource  Potential  Investigation  for  Irrigation  (The  Case  of  Hare  River Watershed
Creators: name: ABEL TADESSE
Publisher: name: National Academic Digital Repository of Ethiopia
Year: 2005

description: ater  resources  development  and  utilization  is  usually  not  integrated  with 
Ethiopia's  overall  socio-economic  development  objectives.  In  the  above 
regard ,  one  of  the  actions  included  in  the  strategy  encourages  to  undertake 
assessment  and  development  of  the  country's  surface  water  resources  by, 
among  others,  making  inventory  of  the  available  surface  water  in  the  country 
both  in  quantity  and  quality  and  applying  suitable  methodologies  to  assess 
the  available  surface water both  in  time  and  space. 
As  integrated  development  of  water  resources  begin  with  an  inventory  of 
available  surface  water,  this  paper  in  particular  is  focusing  on  the 
investigation  of  availability  of  water  for  irrigation  by  implementing  modern 
tools  like  the  Geographic  Information  System  (GIS)  and  Watershed  Modeling 
Software  (HEC-HMS)  considering  the  Hare  river  watershed  as  representative 
of  the  study. 
The  watershed  area  of  Hare  River  is  situated  in  the  southern  region  of 
Ethiopia  (SNNP) .  It  is  wi th  a  size  of  162  Km
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lies  northeasterly  from  the  Kulfo 
river  basin  and  is  located  between  6°03'  N  and  6°18'  N  latitude  and  37°27'E 
and  37°37'E  longitude.  Four  sub-basins  (namely  upper  Harrere,  Lower 
Harrere,  Gina  and  Lower  Hare)  were  identified  for  these  study  based  on  the 
threshold  of  their  contribution  to  flow.  The  flow  which  will  be  generated  from 
these  sub-basins  will  be  one  set  of  decision  parameter  weather  the  area  at 
the  outlets  of the  sub-basins  can  benefit from  the  use  of  irrigation. 
From  the  result  of  the  analysis  of  suitable  irrigable  land ,  Lower  Hare  sub 
basin  contributes  to  most of  the  irrigable  land  (about  63%  of  sub-basin  extent) 
followed  by  the  Gina  sub-basin  (about  47%  of  sub-basin  extent).  The 
combined  lower  and  upper  Har(o/e  sub-basins  contribute  much  less  (about 
43%  of  combined  sub-basin  extent)  as  compared  to  the  separate  land 
contributed  by  the  other  two  sub-basins .  Moreover,  the  soil  dominating  these 
sub-basins  is  clay  in  texture  and  due  to  being  mountainous  it  is  constantly 
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subjected  to  erosion.  As  a  result  of  this  irrigation  demand  assessment 
focuses  primarily  on  crops  cultivated  on  the  Gina  and  Lower  Hare  Sub­ 
basins. 
From  the  farmers  experience  adapted  in  the  two  selected  sub  basins  crops 
cultivated  in  the  Gina  sub  basin  include  maize,  wheat,  sweet  potato  and 
beans  and  crops  cultivated  in  the  lower  Hare  sub  basin  include  maize  (II), 
cotton,  sweet  potato,  peas,  cabbage  and  banana  .  These  crops  were taken  as 
representative  crops  for  assessment of  irrigation  water need. 
Assisted  by  the  CROPWAT  software,  the  requirements  of  the  different  crops 
in  the  respective  sub-basins  were  made.  It  was  observed  that  the  Gina  sub 
basin  doesn't  require  any  sort  of  diversion  from  the  Gina  River  as  the  natural 
rainfall  is  sufficient  to  fulfill  the  crop  water  requirement  while  the  scenario  is 
quite the  opposite for the  lower  Hare sub-basin. 
The  runoff  from  Gina,  Lower  Hare  and  Upper/Lower  Ha&amp;.e  was  generated 
using  the  HEC-HMS  package.  The  runoff  generated  from  the  upper two  sub­ 
basins  (i.e.  Gina  and  Harrere)  was  routed  through  to  the  outlets  at  Lower 
Hare.  It  was  observed  that  much  of  the  contribution  of  the  runoff  at  the  lower 
Hare  area  comes  from  the  Gina sub-basin. 
Finally,  a  comparison  was  made  between  the  water  supply  from  the  main 
river  and  the  irrigation  water  demand  with  in  the  adopted  frame  of  refe 
for  the  Lower  Hare  sub  basin  where  water  stress  is  obvious.  There  was  a 
deficit  zone  observed  in  the  period  of  analysis.  This  deficit  zone  during  the 
critical  crop  growth  stage  represents  55%  of  the  total  time  of  analysis  which 
means that  for  more  than  half of  the  crop  duration,  the  crops  are  subjected  to 
water  stress.  This  result  was  helpful  to  conclude  that  this  shortage  needs  to 
be  compensated  by  means  of  irrigation  applications.  Also  with  in  the  year 
though  twice  harvesting  was  possible,  there  are  moments  observed  where 
water  stress  exists  and  need  to  be  compensated  if  desired  crop  production 
level  is  not  meant to  reduce.