ASSESSMENT OF RESERVOIR SEDIMENTATION AND REDUCTION MEASURES USING SWAT MODEL: A CASE STUDY OF ARJO DIDESSA WATERSHED, ABBAY BASIN, ETHIOPIA

Abstract

The aim of this research is intended to estimate sediment yield to Arjo Didessa dam, Abbay basin, Ethiopia and identify the prone area, and developing scenarios as intervention measures in reducing sediment yield from the catchment using soil and water assessment tool (SWAT). Simulation carried out using hydro-meteorological and spatial data by dividing the watershed into 31 sub-basins with 326 HRUs. Model calibration period (2000-2010) and validation (2011-2016) for flow and calibration period (2000-2009) and validation (2010-2015) for sediment using Sequential Uncertainty Fitting (SUFI-2) within SWAT Calibration Uncertainty Program (SWAT-CUP). Model performance checked by the coefficient of determination, Nash- Sutcliff efficiency, and percent bias. Coefficient of determination (R2) 0.83 and Nash-Sutcliffe efficiency (NSE) of 0.82 for flow calibration and coefficient of determination (R2) 0.74 and Nash-Sutcliffe efficiency (NSE) of 0.74 for flow validation. Coefficient of determination (R2) 0.87 and Nash-Sutcliffe efficiency (NSE) of 0.86 for sediment calibration and coefficient of determination (R2) 0.70 and Nash-Sutcliffe efficiency (NSE) of 0.69 for sediment validation. Thus, the model indicating the good performance of evaluation in the study area. The SWAT model simulates average annual sediment yield flow to reservoir 9.85 ton/ha/year for the period (2000-2009). Spatial variation of sediment yield of sub-basins 24, 25, 26, 27,30, and