Climate change impacts on hydrological processes and water demand scenario in the weyib river basin, Southeastern Ethiopia

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The main objective of this study was to investigate the spatiotemporal variation of current and projected hydrological processes, water demand and water availability under changing climate and increasing population in the Weyib River basin in Ethiopia. The impact of climate change on the temperatures and rainfall characteristics of the basin has been investigated using GFDL-ESM2M, CanESM2, and GFDLESM2G models output for the RCP2.6, RCP4.5, and RCP8.5 scenarios from coupled model intercomparison project 5 (CMIP5). The SDSM calibrated and validated using the observed daily data of twelve meteorological stations was used to generate the future scenarios. The ArcSWAT hydrologic model calibrated and validated using the observed daily streamflow data for historical time period was employed to projected future hydrological processes and hence to evaluate water availability. Current and projected population of the basin is considered to estimate the annual water demand thereby status of water resources need of the basin was estimated based on water stress index analysis.Results revealed that the mean annual maximum and minimum temperature, and rainfall have shown statistically significant (at 5% significant level) increasing trend in all the nine ESM-RCP scenarios in the 2020s 2050s and 2080s time slices. The variability of both temperatures and rainfall is higher in all ESMs of RCP8.5 than RCP4.5 and RCP2.6. The mean annual actual evapotranspiration, ground water contribution to the streamflow (baseflow), percolation, soil water content and water availability in the stream have been found to increase for all the nine ESMs-RCP scenarios in the entire basin and in all the sub-basins. However, surface runoff and potential evapotranspiration have shown a decreasing trend. The future (mean of 3 ESMs) total annual water availability in the basin is observed to increase ranging from 15.04 to 21.61%, 20.08 to 23.34% and 16.21 to 39.53% by the 2020s, 2050s and 2080s time slice respectively from the available water resources (2333.39 Mm3) of the base period.
Supervisor: Arup Kumar Sarma