For effective water and land resource management in data-scarce areas, it is imperative to investigate the spatial variability of sediment yield using a rapid, reliable, and affordable approach. The current study demonstrated the use of tools and models viz. Geographic Information System (GIS), Revised Universal Soil Loss Equation (RUSLE), and Sediment Delivery Ratio (SDR) based approach for the assessment of soil loss and sediment yield rate in Lake Hawassa Sub-basin. Input data used were soil, rainfall, digital elevation model (DEM), and land use and land cover change (LULC) maps. The result of the study showed that there was significant and widespread soil loss and sediment yield on cultivated land dominated by moderate, steep and very steep slopes with little vegetation and barren areas. An estimated mean of 16.36 t/ha/year, or 1.97 million tonnes of soil is lost annually by sheet and rill erosion across the Sub-basin. The sediment delivery ratio (SDR) at the outlet of the lake sub-basin was 0.249. Accordingly, the quantified sediment yield at the sub-basin outlet, taking into account the average-based soil loss and sediment delivery ratio, was found to be 4.07 t/ha/year. The annual siltation rate of the lake from these two forms of erosion was found to be 1.01 cm/year. Therefore, depending on the severity of the soil loss, appropriate Best Management Practices (BMP) should be applied to reduce the rate of soil loss and sediment yield to protect the lake and its ecosystem.