Assessment of the effect of climate and land use/land cover change impact on Gefersa reservoir
Creators: name: Kifle, Raji
Publisher: name: National Academic Digital Repository of Ethiopia
Year: 2020

description: Climate and land use change is one of the issues on water resource management. This study was<br> conducted to assess the climate change and land use/land cover changes on Gefersa watershed.<br> The selected scenario of RCP 4.5 and RCP 8.5 climate projection is state of the art recently<br> developed by the Max Planketon institute of Germany which focus on horn of Africa especially<br> Ethiopia with a grid coverage of 50km * 50km then Climate data was downscaled and bias<br> corrected for base period (2000 -2019) then future analysis was classified on three periods(2025-<br> 2049) short term,(2050-2074) midterm and (2075-2095) long term periods by comparing with the<br> base period by the given equation RCP 4.5 projected precipitation scenario shows an increasing<br> trend of 13.45%,6.71% and 13.24% in short, mid and long term respectively. RCP8.5 projected<br> precipitation project an increasing trend of 33.81%,19.89% and 16.39% in short(2025-2049),<br> mid(2050-2074) and long-term(2075-2095). The projected temperature max of RCP 4.5 shows an<br> increase in maximum temperature compared to based period maximum temperature is expected to<br> increase 0.990c at the end of 2095 RCP 8.5 maximum temperature projected highest increment<br> excepted on August. RCP 4.5 future evaporation loss from reservoir with a correction factor of 0.95<br> which shows increase by, 97.87 mm/y, 98.47 mm/y and 96.59 mm/y respectively and RCP 8.5 loss<br> 147.55mm/y will be excepted at the end period of projection overall the projection on precipitation,<br> temperature and evaporation loss RCP 4.5 is the most suitable scenario than RCP 8.5 for Gefersa.<br> Runoff for Hydrological the model HEC-HMS was utilized in the study area with the model<br> parameters study Deficit and constant, Clark Unit Hydrograph Transformation, and Lag methods<br> used for loss rate, transform and Routing models was used The performance of the model result<br> through calibration of NSE=0.62 and PEV=4.24% then during validation NSE=0.65 and<br> PEV=3.54% it is in a performance range. Land use cover was grouped into three categories 1998,<br> 2008 and 2018 for the analysis of land sat image using ERDSA an accuracy was done 1998 land<br> cover map show 84.8% ,84.6% and 74.28% respectively for 2008 and 2018 The land cover change<br> detection analysis of 20 years (1998-2018) indicates water body changes (28.2%), agricultural<br> activity (16.4%) and forest (28.84%) change shows decreases on the study period. The Gefersa<br> watershed has coverage of 56 km2 watershed area on 1998 water body 1.17 km2, agricultural23.17<br> km2, grassland 25.49 km2 and forest 6.17km2. Overall, the impact climate and land use land cover<br> will have effect on the water supply and water availability the main impact observed is on the<br> climate projection is increasing in temperature will led to evaporation loss has an effect on water<br> availability and Land use pattern has an increasing in urbanization and agricultural activity these<br> activities will have an effect of decreasing the reservoir storage and concern of water quality by the<br> expansion of industry and city in the watershed area