Assessment of hydrology and optimal water allocation under changing climate conditions: the case of Megech river sub bas
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ORIGINAL ARTICLE
Assessment of hydrology and optimal water allocation under changing climate conditions: the case of Megech river sub basin reservoir, Upper Blue Nile Basin, Ethiopia Asimamaw Nigusie Asitatikie1 · Wondimagegn Zerihun Gebeyehu2 Received: 22 June 2020 / Accepted: 17 October 2020 © Springer Nature Switzerland AG 2020
Abstract The main aim of this study was to assess climate change impact on hydrology and water allocation of Megech river sub basin reservoir, Upper Blue Nile Basin, Ethiopia by integrating rainfall runoff HBV-light and Water Evaluation and Planning (WEAP21) model. GCM of the CMIP5 output for RCP2.6, RCP4.5 and RCP8.5 scenarios were obtained from CORDEXAfrica database. The HBV-light model was calibrated and validated to simulate upcoming Megech Reservoir inflow volume and had good performance. WEAP21 was used to assess the water demand requirements, supplied delivered, unmet demand and prepare rule curves for demand sites. The results indicated that the basin average temperature, potential evaporation and open water evaporation would all have increasing trends with pronounced increment in RCP8.5 than RCP4.5 and RCP2.6. However, the inflow volume to the upcoming Megech Reservoir would have decreasing and increasing trend and consistent with precipitation patterns. The total annual water demand requirement was 147.18 Mm3, 179.14 M m3and 300.44 M m3 for 3 baseline, lower and higher growth scenarios, respectively. The supply delivered would be 146.92 Mm for baseline period and maximum 155.49 Mm3 and minimum 143.77 Mm3 for 2055–2090 under RCP2.6 and RCP8.5, respectively. The annual sum of Megech reservoir capacity under baseline year was 1045.54 Mm3. But it reduced to 570.1955 Mm3, 570.66 Mm3 and 587.59 Mm3 for 2019–2054 period. And also reduced to 448.31 Mm3, 395.88 Mm3 and 383.61 Mm3 for 20552090 demand projection periods under RCP2.6, RCP4.5 and RCP8.5 emission scenarios, respectively. So, in order to guarantee the water resource development project further studies should incorporate impact of land use, sedimentation, adaptation option of climate change, find other supply preference and use crops which have low water requirements. Keywords Climate change · Water allocation · HBV-light · RCP · WEAP21
Introduction Climate change refers to a change in the state of the climate that can be identified by changes in the mean and/ or the variability of its properties and that persists for an extended period, typically decade or more (IPCC 2007). Climate model projections show an increase in the global * Asimamaw Nigusie Asitatikie [email protected] Wondimagegn Zerihun Gebeyehu [email protected] 1
Department of Hydraulic and Water Resources Engineering, Debre Tabor University, Debre Tabor, Ethiopia
Department of Engineering Hydrology, Amhara Reginal State Water Resources Buereau, Bahir Dar, Ethiopia
2
mean near-surface air temperature (IPCC 2001). It is now widely acknowledged that climate change will have impacts on water resource availability and management throughout th
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