Understanding the Impact of Land Use and Land Cover Change on Local Hydrology: Implications for Long-Term Planning in the Sore and Geba Watersheds, Southwestern Ethiopia

This study aims to evaluate the impacts of land use and land cover change on surface runoff in the Sore and Geba watersheds, the upper Baro-river basin covering an area of about 6551 km2 located in East Africa. Landsat images were used to analyze the land use and land cover change trends for the periods of three decades (1987-2015). Land use and land cover maps were produced using the maximum likelihood algorithms based on supervised classification. Trends of land use and land cover change showed that cultivated land has increased by 16.55% within the periods between 1987 and 2015 with annual expansion by 36.15 km2 at the expense of other land use types such as open forest, dense forest and wood land. The impacts of land use and land cover change on surface runoff were evaluated using the Soil and Water Assessment Tool (SWAT) model. Nine sensitive flow control parameters were identified and used for calibration of the model. Good performance was obtained in both calibration and validation periods. Results show that between 1987 and 2015, a 16.5% cultivated land expansion was observed which may explain an increase of about 6.65 m3/s annual surface runoff. In general, significant influences of land use and land cover change were reflected in changes to the region’s hydrologic system during the study period, with important management implications for this region as well as other similar regions in Africa.