IMPACT  ASSESSMENT  OF  LAND  USE  I LAND  COVER  CHANGES  ON  SHAYA  RIVER  FLOW  USING  SWAT  (Case  Study  of  Shaya Watershed,  ln  Bale)
Creators: name: Ashenafi  Tedla Tolcha
Publisher: name: National Academic Digital Repository of Ethiopia
Year: 2009

description: In  developing  countries  like  Ethiopia  where  there  is  ever-increasing  population  pressure, 
there  is  a  continuous  LULC  changes.  The  continuous  land  cover  changes  can  have 
impacts  on  the  environment  and  the  water  resources.  Therefore,  to  safeguard  and 
minimize  environment  from  degradation,  identifying  the  impact  of  LULC  on  the 
environment  and  water  resources  are  very  crucial.  Likewise,  LULC  changes  and  their 
impacts  that  occurred  for  the  years  197'.i  to  2001  in  Shaya  watershed  of  an  area  703  . 80 
CD 
km2,  and  its  surroundings  were  monitored  using  remote  sensing  and  geographical 
information  system  (GIS)  with  field  verification. 
"  The.  a_im.  of  this  study  is  therefore,  to  utilize  a  hydrnfogic.al  model  that  can  be  used  to 
deter�ine  the  hydrologic�LrespJ;&gt;fises  of Shaya  watershed  to  the  LULC  changes.  Landsat 
images  ofMSS  1973, TM  198�  and  ETM  2001  were  classified  using  ERDAS  IMAGINE 
8.7  software  and  finally  used  for  the  extraction  of  LULC  changes.  The  hydrological 
model  that  was  used  for  determining  the  impacts  of  LULC  changes  on  the  river  Shaya 
was  SWAT.  To  use  SWAT,  different  inputs  were  used  in  the  model  and  different 
simulations  were  conducted  .In  the  first  automatic  simulation,  the  s�itivity  analysis  was 
conducted  using  the  governing  paramete�,  automatic  and  manual  calibration  was  done  in 
so  many  tries  to  confirm  the  simulated  and  the  observed  flow  fit  each  other.  During  the 
processes,  simulation  and  validation  were  conducting  under  different  periods  and 
L-- 
irrespective  of  same  data  .In  these  two  methods  of  model  testing,  the  good  fitness  of 
-��imulated  with  observed  flow  data was tested  by  statistical  model  efficiency  indicators. 
�·  From  the  image  classification,  the  LULC  change  result  indicates  that  it  did  not  show 
..  �,...co�tinuous  trend,  which  shows  both  decreasing  and  incr easing  trends.  For  impactv 
assessment,  1 4  parameters  were  identified  during  the  s�tivity  analysis.  Accordi ngly, 
the  model  efficiency  indicators,  coefficient  of determination  (r2)  greater  than  0 . 60,  Nash- 
... 
Sutcliffe  (ENS)  greater  than  0 . 5 0  and  Percent  of  difference  (D)  less  than  +25%  results 
were  obtained  in  both  calibration  and  validation  tests. 
M.Sc  Thesis  November,2009 
VI 
Impact Assessment of  Land Use I  Land Cover  Changes 011  Shaya  River Flow 
In  the  watershed  of study  area,  the  impacts  of L  ULC  were  tested  in  terms  of fl �  changes 
\.,-  and  it  was  observed  that  there  was  a  flow  change  due  jo.Jand  cover  changes.  Based  on 
this  more  than  15%  flow  variation  was  obtained  in  some  sub-watersheds  where  high  land 
cover  changes  occurred  and  less  than  15%  flow  variation  was  obtained  in  some  sub­ 
watersheds  where  less  land  cover  changes  occurred  using  land  uses  of different  periods. 
From  the  flow  variations,  it  was  identified  that  where  the  sub-watersheds  show  more  than 
15%  flow  changes,  the  sub-watersheds  are  considered  to  be  vulnerable  to  impacts  of 
L  ULC  changes. 
Generally,  the  SW  AT  was  found  to  be  very  useful  in  determining  the  impacts  of  LULC 
changes  on  stream  flow  in  Shaya  watershed  and  thus  it  can  be  promising  to  apply  in  the 
other  nearby  watersheds    (tropical)