Upstream Downstream Interaction and Impacts of  Climate Change on Water Storage Interventions in the  Abbay River Basin, Ethiopia
Creators: name: Gashaw Kebede Muluneh
Publisher: name: National Academic Digital Repository of Ethiopia
Year: 2010

description: In  the  planning  and management  of water  resource  systems  comprising  a  large number of 
water  reservoirs,  it  is  necessary  to  simulate  the  interaction  of entire  systems  rather  than  to 
consider  the  reservoirs  separately.  The  Water Evaluation  and  Planning  (WEAP)  model  is 
used  to  assess water demand  and  upstream downstream flow  interaction  of water  storages 
by  considering  the  existing  development  situation  and  future  water  resources 
development  with  and  without  climate  change  scenarios  in  the  study  area(Abbay  River 
Basin,  Ethiopia).  Three  different  development  and  climate  change  scenarios  were 
developed  to  simulate Water use  at  demand  sites  and  flow  interaction  for  46-years period 
i .e.,  i)  Current  Condition Scenario  (1995-2010) ;  ii)  Sho11  terrn development  Scenario  with 
and without Climate Change  (2010-2025); and  iii)  Long  term  development  Scenario  with 
and without  Climate Change  (2025-2040). 
Twenty  Large  Dams/Reservoirs  and/or  twenty  Seven  large  irrigation  and  hydropower 
projects  (including  dam  projects)  which  can  significantly  affect  the  flow  pattern  were 
considered  for  the  study.  Irrigation  Projects  covering  an  area  of 365,807  hectare  of land 
and  Hydropower  projects  which  can  develop  7,764MW  Power  have  been  selected  from different  sub-basins  based  on  the  basin Master  Plan  Study.  The  competing water  sectors 
were  irrigation  development,  hydropower  production  and  environmental  flow 
requirements.  Next  to  environmental  flow,  high  priority  was  given  to  hydropower 
projects  than  irrigation during  the  simulation. 
Net  evaporation  from  reservoirs,  River  headflow,  Monthly  water  demand  and  reservoirs 
physical  and  operation  data  were  the  basic  inputs  to  the  model.  Penman-Monteith  was 
used  to  estimate  evaporation  rate  from  20  large  reservoirs  and  reasonable  results  were model  simulation  results,  there  is  a  reduction  of  flow  at  the  border  for  all  different 
development  and  climate  change  scenarios.  The  current  WEAP  simulated  flow  at  the 
Sudanese  border  was  47.08BCM  per  year.  This  flow  will  reduce  to  46.48BCM  and 
45.22BCM  for  2010-2025 and  2025-2040 development periods  respectively. Considering 
Climate  Change  impacts  on  hydrology  and  reservoir  systems,  the  mean  annual 
streamflow  is  expected  to  be  46.00BCM  for  20 I 0-2025  and  44.36BCM  for  2025-2040 
scenanos. 
In  all  scenarios  and  simulation  periods  water  availability  in  the  basin  is  far  above  the 
demand  required  i.e. , demand  coverage  and  reliability of 100 was observed  in  the WEAP 
simulation  result.  Hence,  unmet  demands will  not be  the problem both  for  irrigation and 
hydropower production; keeping the minimum environmental flow to Tiss  Issat fall.