Soil and water assessment tool (swat) model based Runoff and sediment yield prediction of dura river Sub basin, abay basin, ethiopia

Abstract

Long term planning in water resource development requires full information about the water resource and the amount sediment which affects amount and availability of water. For this the soil and water assessment tool (SWAT) model was applied to simulate runoff, the sediment yield and associated uncertainty with the simulated output from the Dura River sub basin (area 545 km2 ), located in North-Western Amhara Regional State, Ethiopia. The SWAT model was calibrated for the period of 1985 to 1994 and validated for the period of 1995-2004 based on nine parameters identified during sensitivity analysis for both flow and sediment for which GW_DELAY for flow and Curve number for sediment were the most sensitive ones with their t-stat and p-values. The uncertainty analysis was done by using SUFI-2 which is package for a SWAT –CUP. The calibration and validation of the model was found satisfactory as performance rating criteria value of coefficient of correlation (R2 ) and Nash-Sutcliffe simulation efficiency (NSE) is found to be 0.85 and 0.82 during calibration and 0.83 and 0.81 during validation for flow and 0.8 and 0.73 during calibration and 0.78 and 0.72 during validation for sediment yield prediction respectively. In the same order from the model uncertainties analysis the percentage of the observed data within the uncertainty bound is 88% during calibration and 77% during validation for flow and 80% during calibration and 70% during validation for sediment yield prediction. The water and sediment yield of Dura sub basin was quantified and also the most sediment yielding part of the basin was identified. Accordingly, annual average flow of Dura River was estimated to be 18.8M 3 /sec. and annual average sediment yield of the sub basin was estimated to be 10.9 ton per hectare. Substantial sediment contributing sub basins were sub basin 1 (73.36 ton ha-1 yr -1 ), sub basin 6 (78.33 ton ha-1 yr -1 ) and sub basin 9 (96.5ton ha-1 yr - 1 ) identified as severe condition of extent. In conclusion, the SWAT model could be effectively used to predict runoff and sediment yield in order to effectively design and plan water related development in absence of gauged information.