GIS Supported  Irrigable  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: Water  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  thesis  in  particular focuses  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. 
Within  the  Hare  watershed,  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  whether  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  Harrere  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.  As  a  result  of  this  irrigation  demand 
assessment  focuses  primarily  on  crops  cultivated  on  the  Gina  and  Lower 
Hare  Sub-basins. 
Assisted  by  the  CROPWAT  software,  the  irrigation  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 
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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  Harrere  was  generated 
using  the  HEC-HMS  package  (version  2.1.3).  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  within  the  adopted  frame  of  reference 
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  more  than  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 
within  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.