Modelling the impact of historical and future Land Use Land Cover changes on the hydrological response of an Ethiopian watershed

Abstract

Land Use Land Cover (LULC) is generally considered one of the key factors influencing the hydrological processes and sediment output in arid and semi-arid watersheds. Focusing on the Ethiopian Fincha watershed, the current study applies the Soil & Water Assessment Tool (SWAT) model to evaluate how LULC changes affect the watershed hydrological dynamics. Utilizing the available stream flow time series data acquired from 1986 to 2008, the model was calibrated and validated based on past conditions. At the same time, future scenarios were simulated by means of the Land Change Modeler (LCM) model using historical trends. To investigate the effect of LULC changes on watershed hydrology, six LULC maps have been produced to account for historical (1989, 2004, 2019) and future (2030, 2040, 2050) conditions. The results show an increase in surface runoff in the past, while a similar tendency is expected for the next three decades if no specific mitigation measures will be implemented soon. On the other hand, lateral flow and groundwater flow are generally decreasing. The present analysis shows that the ongoing LULC transformation, which involves an expansion of agricultural land, urban areas, and intermittent logging of forest cover, may be the reason for the increment in surface runoff, and the decline in groundwater and lateral flow.