Evaluation of hydrological impacts of land use/land cover changes of Holota Watershed, Upper Awash Sub-basin, Ethiopia

Land use and land cover change (LULCC) has a significant impact on hydrological processes. Studying the effects of LULCC on hydrological processes may lead to a better understanding of the phenomenon to be able to make better decisions. The purpose of this study was to assess the hydrological impact of LULCC of the Holota watershed in the Upper Awash sub-basin of Ethiopia. Agricultural land was found to account for the largest proportion of the study area in the three periods. Using this result, fluxes were analyzed using the Soil and Water Assessment Tool (SWAT) hydrological model to assess the hydrological response to LULCC. The SWAT model successfully simulated flows for both calibration and validation using the coefficient of determination (R2) and the Nash–Sutcliffe (NS) efficiency coefficient. Flow analysis showed that in the dry season both LULCC 2001–2009 and LULCC 2009–2017 decreased by 6.1% and 6.2% respectively, but increased by 1.85% and 1.78%, respectively, in the wet season. Runoff decreased by 6.4% between 2001 and 2009 and by 15.9% between 2009 and 2017. This results in reduced water yield by 3.1% between 2001 and 2009 and by 7.4% between 2009 and 2017. Potential evapotranspiration did not change significantly under either scenario. However, lateral flow increased by 23.6% between 2001 and 2009 and by 22.4% between 2009 and 2017. LULCC is not the only factor affecting watershed hydrology, but other factors, such as climate change, can also affect their combined impacts on rivers, but were not considered in this study.