Thesis Open Access

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

SALIH DURI ABDULAHI


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  <identifier identifierType="DOI">10.20372/nadre/4451</identifier>
  <creators>
    <creator>
      <creatorName>SALIH DURI ABDULAHI</creatorName>
      <affiliation>ADDIS ABABA SCIENCE AND TECHNOLOGY UNIVERSITY</affiliation>
    </creator>
  </creators>
  <titles>
    <title>ASSESSMENT OF CLIMATE CHANGE IMPACT ON INFLOWS TO KOKA RESERVOIR IN UPPER AWASH SUB BASIN</title>
  </titles>
  <publisher>National Academic Digital Repository of Ethiopia</publisher>
  <publicationYear>2019</publicationYear>
  <subjects>
    <subject>HBV  RCM  Climate model  Bias correction  Climate Change Discharge</subject>
  </subjects>
  <contributors>
    <contributor contributorType="Supervisor">
      <contributorName>Brook Abate (PhD)</contributorName>
      <affiliation>ADDIS ABABA SCIENCE AND TECHNOLOGY UNIVERSITY</affiliation>
    </contributor>
  </contributors>
  <dates>
    <date dateType="Issued">2019-12-19</date>
  </dates>
  <language>en</language>
  <resourceType resourceTypeGeneral="Text">Thesis</resourceType>
  <alternateIdentifiers>
    <alternateIdentifier alternateIdentifierType="url">https://nadre.ethernet.edu.et/record/4451</alternateIdentifier>
  </alternateIdentifiers>
  <relatedIdentifiers>
    <relatedIdentifier relatedIdentifierType="DOI" relationType="IsVersionOf">10.20372/nadre/4450</relatedIdentifier>
    <relatedIdentifier relatedIdentifierType="URL" relationType="IsPartOf">https://nadre.ethernet.edu.et/communities/aastu</relatedIdentifier>
    <relatedIdentifier relatedIdentifierType="URL" relationType="IsPartOf">https://nadre.ethernet.edu.et/communities/nadre</relatedIdentifier>
  </relatedIdentifiers>
  <rightsList>
    <rights rightsURI="http://www.opendefinition.org/licenses/cc-by">Creative Commons Attribution</rights>
    <rights rightsURI="info:eu-repo/semantics/openAccess">Open Access</rights>
  </rightsList>
  <descriptions>
    <description descriptionType="Abstract">&lt;p&gt;Climate change impact and its variability on stream flows are now becoming one of&lt;br&gt;
the significant challenges. Hence evaluation of the impact and the trends of the change&lt;br&gt;
is very important at watershed level. The aim of this study was to evaluate the impacts&lt;br&gt;
of climate change on inflows to Koka reservoir in upper awash sub basin using HBV&lt;br&gt;
model. The climate model variables (precipitation and temperature) were obtained&lt;br&gt;
from Coordinated Regional Downscaling Experiment (CORDEX) from Regional&lt;br&gt;
Atmospheric Climate Model Version2.2 (RACMO22T) under representative&lt;br&gt;
concentration pathway (RCP4.5) and (RCP8.5) scenarios. Bias correction was applied&lt;br&gt;
to climate variables before transferred to hydrological model (HBV) to simulate&lt;br&gt;
discharge. For model performance evaluation; Coefficient of determination (R2), Nash&lt;br&gt;
Sutcliffe Efficiency (NSE) and percent bias (PBIAS) were used during calibration (2002-&lt;br&gt;
2010) and validated (2011-2015) period. The result of calibration and validation (R2,&lt;br&gt;
NSE and PBIAS) are 0.88, 0.78 and -6.72 and 0.88, 0.83 and -12.51 respectively. Stream&lt;br&gt;
flow was simulated for two consecutive periods (2021&amp;ndash;2040) and (2041&amp;ndash;2060) for both&lt;br&gt;
scenarios and compared with the base period (1996&amp;ndash;2015) to explore impact of climate&lt;br&gt;
change on inflows. The result obtained shows that overall mean annual flow is projected&lt;br&gt;
to decrease by 11.7 and 18.1% under RCP4.5 and RCP8.5 scenarios respectively. For&lt;br&gt;
the period (2021-2040) flow expected increase in October under both scenarios. The&lt;br&gt;
increment will be 113.2% and 115.5% under RCP4.5 and RCP8.5 respectively while the&lt;br&gt;
maximum reduction will be expected in March (84.6%) under RCP4.5 and in January&lt;br&gt;
(69.5%) under RCP8.5. Similarly for the period of (2041-2060) the maximum increment&lt;br&gt;
will be in October under both scenarios while the maximum reduction projected in&lt;br&gt;
January under both scenarios. Flow duration curves indicate that, the probability of&lt;br&gt;
occurrence of high flow (Q5) and median flow (Q50) are likely to be more in the future&lt;br&gt;
under both scenarios. However, low flow (Q95) is predicted to decrease under both&lt;br&gt;
scenarios. High flow (Q5) will be vary from (35.6% to 55.9%) and median flow (Q50) vary&lt;br&gt;
from (37.2% to 85.8%). Low flow (Q95) expected to decrease by 78.3% under RCP4.5&lt;br&gt;
and 71.8% under RCP8.5. The monthly and seasonal variations are expected to be&lt;br&gt;
more relative to annual variations. During summer and autumn season, flow expected&lt;br&gt;
to increase while decrease in winter and spring in the study area under both scenarios.&lt;br&gt;
As the result of high increment in flow in certain months and high reduction in the&lt;br&gt;
other months, flood and drought may be expected in future in the basin. Overall there&lt;br&gt;
will be a variations of flow month to month and season to season. Therefore, it is&lt;br&gt;
important to consider this variation of flows to Koka reservoir to frame appropriate&lt;br&gt;
guidelines for planning and management&lt;br&gt;
&amp;nbsp;&lt;/p&gt;</description>
  </descriptions>
</resource>
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