Impacts of Climate and Land Use Change on Hydrological Response in Gumara Watershed, Ethiopia

Climate and land-use change affect the hydrologic cycle by altering the hydrological responses including streamflow (SF), surface runoff(SR), base-flow (BF), and evapotranspiration (ET). Several studies have addressed the separate impacts of either land-use or climate change on the watershed hydrology, but few have explored the combined impacts. In this study, the SWAT model was applied to evaluate the combined impacts of land-use and climate change on hydrological responses in Gumara watershed. This study examined four land-use scenarios that include the present and projected land-use based on the businessas-usual trend (BAU), expansion of irrigation crop (EIC), and expansion of forestland (EFL). Climate variables were simulated using Weather Research and Forecasting (WRF) model for the baseline (2005-2015) and projected period (2045-2055) under RCP4.5 and RCP8.5 scenarios. Results showed that SR increase by 5.1% under BAU scenario while BF decrease by 6.5% without altering SF and ET noticeably. On the contrary, SF decrease by 12.5% and 5.2% respectively under EIC and EFL scenarios, while ET increase by 4.8% and 8.9% respectively under EIC and EFL scenarios. The simulated SF, SR, and ET under RCP8.5 may increase significantly by 34.3%, 51.8%, and 12.2%, respectively. Similarly, the simulated SF, SR and ET may increase significantly under the combination of all three land-use and RCP8.5 scenarios. This suggested that climate change will have a greater effect on hydrologic responses than land-use change. The results of this study can be useful to decision-makers and planners in the design of adaptive measures to climate and land-use change. (C) 2020 European Regional Centre for Ecohydrology of the Polish Academy of Sciences. Published by Elsevier B.V. All rights reserved.