Ingénierie des systèmes d’irrigation et de drainage

Modeling Surface Water Potential of Somodo Watershed

Abstract

Etefa Tilahun Ashine

The availability of freshwater is likely to decrease due to population growth, industrialization, land use and climate change; unfortunately demand for water increases across the world. Quantifying the water resources of a watershed is essential for providing the strategic information needed for long-term planning of water security. Thus this study was initiated with an objective to determine the surface water resources potential of Somodo watershed. GPS, GIS, SWAT, and SWAT-CUP software were the materials used. Secondary data namely DEM, land use/land cover map, soil map, stream flow and meteorological data were collected from responsible organizations. Sensitivity analysis, calibration and validation of the model were done to check performance of the model. The result reveals that Surface runoff and base flow were the most sensitive parameters of the stream flow in Somodo watershed. The statistical results for the model performance displayed satisfactory (R² of 0.795 and NSE of 0.68) between the simulated and observed flow, respectively for calibration and there was also a very good agreement between the observed and simulated stream flow with R² value of 0.821 and NSE value of 0.7 for validation. From total watershed area of 19860 ha, a total of 56.75MCM surface runoff was generated by the model from the catchment annually. Construction of water harvesting structures at the upstream of the watershed is useful to increase the water potential and to use the water during the dry period and is recommended from this study.