Climate Change Impact Assessment on  Water  Resources of  the  Gumara Watershed, Upper Blue Nile  River Basin
Creators: name: Hanibal Lemma Geberkidan
Publisher: name: National Academic Digital Repository of Ethiopia
Year: 2010

description: Recently,  there  is  growth  in  scientific  evidence  that  global  climate  has  changed ,  is 
changing  and  will continue  to  change.  and  Climate  change  is  al so  expected  to  aggravate 
current  stresses  on  water  resources  availabilit y  clue  to  rapid  population  growth  and 
economic  deve lopment.  The  major  uncertainty  in  water  resources  management  is  the 
variability  of water supply  and  demand  pertaining to  changes  in  climatic  variables  and  in 
dynamics  or  river  basins.  Therefore.  the  water  s upply  potential  of  a  river  basin  is 
sensitive  to  land  use  and  climate  changes.  Hence,  in  many  river  basins  steady  climatic 
(stationary)  conditions  are  no  longer  considered  a  valid  assumption  for  sustainable  water 
resources  management.  The  aim  of  the  study  is  to  assess  the  potential  impact  of  climate 
change  on  the  water  resources  of  Gumara  watershed  using  reliability ,  resilience  and 
vulnerability  indices. 
Although  quantitative  estimation  of  effects  of  climate  change  water  resources  are 
essential  for  understanding  and  solving  the  potential  water  resource  management 
problems  associated  with  agriculture,  power  generation  and  water  resource  planning  and 
management;  the  coarser  resolution  of  General  Circulation  Models  (GCMs)  does  not 
provide  reliable estimates  of meteorological  variables at  the  appropriate  scale  required  for 
regional  impact  assessments.  Hence  more  reliable  meteorological  variables 
corresponding  to  future  climate  scenarios  can  be  derived  from  GCMs  outputs  using  the 
so-called  downscaling  techniques.  In  the  study  area,  there  is  better  access  to  data  from 
1971  to  2000,  which  is  taken  as  a  standard  of 30-years  base  period  for  downscaling using 
Statistical  downscaling  model  (SDSM).  AR(l)  and  LARS-WG  were  used  for  fil ling  in 
. miss i ng data  and  to  extend  records  at  Woreta  station  respectively.  I n  th i s  study  SDSM  is 
used  to  downscale  the  HadCM3  GCM  outputs,  and  dynamically  downscaled  RegCM3 
scenario  outputs  are  collected  from  IWMI  to  generate  the  possible  future  scenarios  in  the 
Gumara  wat ershed .  After  setting  up  and  calibrating  H E C -H MS  hydrologica l  model,  the 
downscaled  meteorological  variables  were  subsequentl y  used  as  input  to  the  model  to 
si m ulate  th e  co rresponding  current  and  future  stream  n o w.  CROPW.t \T  is  used  to 
esti mate  future  I rrigation  requirement .  F inally ,  the  cli m ate  change  i mp act  is  assessed 
using the  Re liabi l ity ,  R esilience and  Vulnerabilit y  indices . 
Generally  the  S DSM  projected  max imum  and  minimum temperature  shows  an  increasing 
trend  for  the  next  century ,  but  the  precipitation  shows  decrease  trend.  I t  is  also  observed 
that  the  reliabilit y  inde x  for  all  climate  scenarios  reveal  above  91% , resi l ience  inde x  of 
above  96%  and  Vu l nerab i lity  of  less  than  3 0 %.  Hence,  it  is  concluded  that  it  has  high 
capabilit y to  meet  the  required  target  demand  in  2 0 3 0s ,  and  also  it  recover s  q uic k ly  from 
a  fa ilure  to  meet  t he  de mand  to  satisfying  the  targe t  draft.  Based  on  t he  result  of 
performance  i nd ices .  the  decision  makers,  concerned  persons  or  an y  w.uer  u s ers  in  the 
area  can  be  as s ured  that  the  proposed  irrigation  proj ect  has  very  good  potenti a  I  to  irrig a t e 
the  re q uired  area  under 2 0 30 s  cli m atic condition