Estimation Of Water Balance In Chemoga Watershed Using Swat Model, Abay Basin, Ethiopia

Abstract

Water resource development is the basic and critical infrastructure for a nation’s sustainable development .To use water resource in optimum and effective way, it is necessary to understand the quantity or the distribution in space and time through different researches. Hence this study were conducted on hydrological process using SWAT model on Chemoga watershed located in Abbay basin. In this study calibration and validation of simulated versus measured flows of Chemoga river and estimation of Waterbalnce in the watershed were conducted after sensitivity of hydrologic parameters had been identified using SWAT-CUP model tool. Sequential uncertainly fitting algorithm (SUFI-2) of SWAT-CUP (Calibration and uncertainty program) were used with sets of hydrologic parameters. From those parameters, Evaporation Compensation factor (ESCO) is the most sensitive parameter in the watershed. The hydrological simulation performance evaluation using SWAT-CUP were achieved with the objective function of calibration (R2=0.72 and NS =0.65) and Validation (R2=0.82 and NS =0.71).This model evaluation was performed at monthly levels. The daily model evaluation performance did not fit with objective function due to poor model performance in daily levels of (R2 =0.54 and NS =0.42).The change in soil water or Waterbalnce of the watershed is 24.5mm in the calibration period. The surface and subsurface flow contributions at the outlet of the watershed were resulted in the simulation from which 68% of the total yield of water from the watershed is base flow (ground water contribution).