Watershed hydrological responses to land use land cover changes at Bilata watershed, Rift Valley Basin, southern Ethiopia

Abstract

Most anthropogenic activities have a profound effect on land cover that affects the water cycle and, ultimately, the availability of water in the watershed. The idea of this study was to evaluate the hydrological response to land use and land cover change in the Bilata watershed. To achieve this objective, supervised land use land cover classification was applied for the years 2000, 2010, and 2020 using ERDAS IMAGINE 2015. The watershed underwent significant land use and land cover changes from 2000 to 2020. There was an abrupt expansion of agricultural land and a reduction of forest. The SWAT model was applied to evaluate the impact of land use and land cover change on hydrological processes. The calibration and validation of the SWAT model showed that the model has performed well in simulating the hydrology of the watershed with a coefficient of determination, Nash–Sutcliffe efficiency, and per cent of bias greater than 0.6 for both calibration and validation. Due to intensive agricultural expansion and settlement, the surface runoff increased from 172 to 259.5 and 265.0 mm in 2000, 2010, and 2020, respectively. The average streamflow increased from 132 to 134 and 150 m3/s between 2000, 2010, and 2020.