Prediction of Sediment Yeild to Lake Ziway Reservoir and Assessing Reduction methods (Using Arc-swat)

Sediment accumulation in Lake Ziway is an escalating concern driven by poor land use practices, ineffective watershedmanagement, and the absence of adequate soil and water conservationmeasures. This study aims to estimate sediment yield in the Lake Ziway watershed using the Soil and Water Assessment Tool (SWAT) integrated within ArcGIS. Themodel was calibrated and validated usingmeteorological and spatial data across 11 sub-basins and 116 hydrologic response units (HRUs), covering a calibration period from 2001 to 2009 and a validation period from 2010 to 2012. Calibration was performed using the Sequential Uncertainty Fitting version 2 (SUFI-2) algorithm within the SWAT-CUP interface.model performance was satisfactory, with coefficients of determination (R²) and Nash–Sutcliffe efficiency (NSE) values ranging from 0.72 to 0.76 for discharge and 0.72 to 0.84 for sediment yield. The average annual sediment yield was estimated at 2.69 tons/ha/year, and the gross sediment inflow into Lake Ziway was calculated at approximately 1.04million tons/year, with a deposition rate of 38.5%. Sub-basins 4 and 5 were identified as sediment hotspots, with yields exceeding 6 tons/ha/year. Three conservation scenarios were evaluated using the current watershed condition as a baseline: terracing reduced sediment yield by 72%, filter strips by 42%, and grassed waterways by 58%. These results highlight the critical role of soil and water conservation strategies in sustaining Lake Ziway’s capacity and ecosystem.