Modelling the effects of land cover and climate change on watershed hydrology in south-western Ethiopia

Sammanfattning: Degradation of the hydrological regime is a pressing issue in the Ethiopian Highlands. It is one of the most rapidly degrading landscapes due to its topography and large amounts of annual precipitation. This problem has been exacerbated through anthropogenic influence from land use/land cover (LULC) and climate change. This paper presents the effect on the hydrological cycle caused by these changes through modelling the observed and projected changes between 1989-2079 in a watershed in South-Western Ethiopia. The Soil & Water Assessment Tool (SWAT) was used to quantify the changes in water quality and quantity. The model output showed a general increase in precipitation and temperature throughout the whole study period with an intensification of the secondary wet season. This caused an overall increase in the fluxes of the hydrological cycle and sediment yields for observed and projected years. The climactic changes to the watershed were accompanied by a strong anthropogenic influence on the LULC, which resulted in large increases to both surface runoff and sediment yield. The changes in LULC were shown have far greater impact on the hydrological regime than climate change alone. These findings indicate a need for intervention on a local scale to diminish further deterioration of the watershed.