Sediment yield responses to land use land cover change and developing best management practices in the upper Gidabo dam watershed

Water resources that can be used for different purposes have persistently been affected by both temporal and spatial land use land cover (LULC) changes. However, quantifying the impact of LULC on water resources and developing best management practices (BMPs) is very important for the sustainable use of these resources. The broad objective of this study was to investigate the potential impacts of LULC change on sediment yield and developing the BMPs that have been paramount to alleviate sedimentation in the upper Gidabo dam watershed. In this study, the Soil and Water Assessment Tool (SWAT) model was used to examine the effects of LULC change on sediment yield. The LULC change analyses for three periods (1990, 2005, and 2019) were performed using ERDAS Imagine 2014 and ArcGIS 10.4. During the study periods, agricultural land has increased by 8.9%, while forest land and shrub-land have been declined by 7.11% and 7.53%, respectively. Due to LULC changes, average annual sediment yield was increased up to 3.45 t/ha/yr (44%) and 7.06 t/ha/yr (47.38%) for the period 1990–2005 and 2005–2019 respectively. The result of model performance indicators such as coefficient of determination (R2), Nash-Sutcliff efficiency (NSE), and percentage bias (PBIAS) in simulating sediment yield indicates a good agreements between simulated and observed values during calibration and validation periods. Based on the simulated average annual sediment yield using 2019 LULC, the 10 critical sub-watersheds above the tolerable limit were prioritized for effective watershed management. Hence, three BMPs, namely filter strips, terracing and reforestation were developed for critical sub-watersheds to reduce the sediment yield delivered to the Gidabo dam reservoir. The result revealed the terracing management option reduce the sediment yield up to 64.02%. Implementing filter strips with 5 m, 3 m, and 1 m wide indicates 59.12%, 55.97%, and 50.73% reduction, respectively, whereas reforestation has given the least reduction that is 40.98%. Therefore, applying terracing in critical sub-basins is the most effective practice for reducing sediment yield in upper Gidabo dam watershed.