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ASSESSMENT OF CLIMATE CHANGE IMPACT ON INFLOWS TO KOKA RESERVOIR IN UPPER AWASH SUB BASIN

SALIH DURI ABDULAHI


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<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:creator>SALIH DURI ABDULAHI</dc:creator>
  <dc:date>2019-12-19</dc:date>
  <dc:description>Climate change impact and its variability on stream flows are now becoming one of
the significant challenges. Hence evaluation of the impact and the trends of the change
is very important at watershed level. The aim of this study was to evaluate the impacts
of climate change on inflows to Koka reservoir in upper awash sub basin using HBV
model. The climate model variables (precipitation and temperature) were obtained
from Coordinated Regional Downscaling Experiment (CORDEX) from Regional
Atmospheric Climate Model Version2.2 (RACMO22T) under representative
concentration pathway (RCP4.5) and (RCP8.5) scenarios. Bias correction was applied
to climate variables before transferred to hydrological model (HBV) to simulate
discharge. For model performance evaluation; Coefficient of determination (R2), Nash
Sutcliffe Efficiency (NSE) and percent bias (PBIAS) were used during calibration (2002-
2010) and validated (2011-2015) period. The result of calibration and validation (R2,
NSE and PBIAS) are 0.88, 0.78 and -6.72 and 0.88, 0.83 and -12.51 respectively. Stream
flow was simulated for two consecutive periods (2021–2040) and (2041–2060) for both
scenarios and compared with the base period (1996–2015) to explore impact of climate
change on inflows. The result obtained shows that overall mean annual flow is projected
to decrease by 11.7 and 18.1% under RCP4.5 and RCP8.5 scenarios respectively. For
the period (2021-2040) flow expected increase in October under both scenarios. The
increment will be 113.2% and 115.5% under RCP4.5 and RCP8.5 respectively while the
maximum reduction will be expected in March (84.6%) under RCP4.5 and in January
(69.5%) under RCP8.5. Similarly for the period of (2041-2060) the maximum increment
will be in October under both scenarios while the maximum reduction projected in
January under both scenarios. Flow duration curves indicate that, the probability of
occurrence of high flow (Q5) and median flow (Q50) are likely to be more in the future
under both scenarios. However, low flow (Q95) is predicted to decrease under both
scenarios. High flow (Q5) will be vary from (35.6% to 55.9%) and median flow (Q50) vary
from (37.2% to 85.8%). Low flow (Q95) expected to decrease by 78.3% under RCP4.5
and 71.8% under RCP8.5. The monthly and seasonal variations are expected to be
more relative to annual variations. During summer and autumn season, flow expected
to increase while decrease in winter and spring in the study area under both scenarios.
As the result of high increment in flow in certain months and high reduction in the
other months, flood and drought may be expected in future in the basin. Overall there
will be a variations of flow month to month and season to season. Therefore, it is
important to consider this variation of flows to Koka reservoir to frame appropriate
guidelines for planning and management
 </dc:description>
  <dc:identifier>https://nadre.ethernet.edu.et/record/4451</dc:identifier>
  <dc:identifier>10.20372/nadre/4451</dc:identifier>
  <dc:language>eng</dc:language>
  <dc:relation>doi:10.20372/nadre/4450</dc:relation>
  <dc:relation>url:https://nadre.ethernet.edu.et/communities/aastu</dc:relation>
  <dc:relation>url:https://nadre.ethernet.edu.et/communities/nadre</dc:relation>
  <dc:rights>info:eu-repo/semantics/openAccess</dc:rights>
  <dc:rights>http://www.opendefinition.org/licenses/cc-by</dc:rights>
  <dc:subject>HBV  RCM  Climate model  Bias correction  Climate Change Discharge</dc:subject>
  <dc:title>ASSESSMENT OF CLIMATE CHANGE IMPACT ON INFLOWS TO KOKA RESERVOIR IN UPPER AWASH SUB BASIN</dc:title>
  <dc:type>info:eu-repo/semantics/doctoralThesis</dc:type>
  <dc:type>publication-thesis</dc:type>
</oai_dc:dc>
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