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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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{
  "DOI": "10.20372/nadre/4451", 
  "abstract": "<p>Climate change impact and its variability on stream flows are now becoming one of<br>\nthe significant challenges. Hence evaluation of the impact and the trends of the change<br>\nis very important at watershed level. The aim of this study was to evaluate the impacts<br>\nof climate change on inflows to Koka reservoir in upper awash sub basin using HBV<br>\nmodel. The climate model variables (precipitation and temperature) were obtained<br>\nfrom Coordinated Regional Downscaling Experiment (CORDEX) from Regional<br>\nAtmospheric Climate Model Version2.2 (RACMO22T) under representative<br>\nconcentration pathway (RCP4.5) and (RCP8.5) scenarios. Bias correction was applied<br>\nto climate variables before transferred to hydrological model (HBV) to simulate<br>\ndischarge. For model performance evaluation; Coefficient of determination (R2), Nash<br>\nSutcliffe Efficiency (NSE) and percent bias (PBIAS) were used during calibration (2002-<br>\n2010) and validated (2011-2015) period. The result of calibration and validation (R2,<br>\nNSE and PBIAS) are 0.88, 0.78 and -6.72 and 0.88, 0.83 and -12.51 respectively. Stream<br>\nflow was simulated for two consecutive periods (2021&ndash;2040) and (2041&ndash;2060) for both<br>\nscenarios and compared with the base period (1996&ndash;2015) to explore impact of climate<br>\nchange on inflows. The result obtained shows that overall mean annual flow is projected<br>\nto decrease by 11.7 and 18.1% under RCP4.5 and RCP8.5 scenarios respectively. For<br>\nthe period (2021-2040) flow expected increase in October under both scenarios. The<br>\nincrement will be 113.2% and 115.5% under RCP4.5 and RCP8.5 respectively while the<br>\nmaximum reduction will be expected in March (84.6%) under RCP4.5 and in January<br>\n(69.5%) under RCP8.5. Similarly for the period of (2041-2060) the maximum increment<br>\nwill be in October under both scenarios while the maximum reduction projected in<br>\nJanuary under both scenarios. Flow duration curves indicate that, the probability of<br>\noccurrence of high flow (Q5) and median flow (Q50) are likely to be more in the future<br>\nunder both scenarios. However, low flow (Q95) is predicted to decrease under both<br>\nscenarios. High flow (Q5) will be vary from (35.6% to 55.9%) and median flow (Q50) vary<br>\nfrom (37.2% to 85.8%). Low flow (Q95) expected to decrease by 78.3% under RCP4.5<br>\nand 71.8% under RCP8.5. The monthly and seasonal variations are expected to be<br>\nmore relative to annual variations. During summer and autumn season, flow expected<br>\nto increase while decrease in winter and spring in the study area under both scenarios.<br>\nAs the result of high increment in flow in certain months and high reduction in the<br>\nother months, flood and drought may be expected in future in the basin. Overall there<br>\nwill be a variations of flow month to month and season to season. Therefore, it is<br>\nimportant to consider this variation of flows to Koka reservoir to frame appropriate<br>\nguidelines for planning and management<br>\n&nbsp;</p>", 
  "author": [
    {
      "family": "SALIH DURI ABDULAHI"
    }
  ], 
  "id": "4451", 
  "issued": {
    "date-parts": [
      [
        2019, 
        12, 
        19
      ]
    ]
  }, 
  "language": "eng", 
  "title": "ASSESSMENT OF CLIMATE CHANGE IMPACT ON INFLOWS TO KOKA RESERVOIR IN UPPER AWASH SUB BASIN", 
  "type": "thesis"
}
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