Semi-Distributed Modeling Of A Large Scale Hydrological System Using SWAT Model

This work aims to contribute to water resource management in one of the main Moroccan rivers using the SWAT model. Physically-based modeling aims to represent the interactions between the external factors (rainfall and temperature) and internal factors in the catchment (landuse, soil and groundwater). In this matter, the SWAT agro-hydrological model is operated at a monthly time step over the period 1990-2014 in the Ouergha catchment. The modeling was carried out on a period of 24 years including 7 years as warm-up period, 9 years for calibration and 8 years for validation. A spatial calibration approach has been applied to optimize the sensitive parameters in each sub-basin. The results indicated that NSE were between 0.60 and 0.85 in calibration, and was between 0.60 and 0.75 in validation period. This study shows a good agreement between simulated and observed monthly flow except for two stations where flows have been undervalued or overvalued. Overestimation and underestimation are due to river's overexploitation by irrigation and flooding in 2009 and 2010 respectively. Using the optimized parameter sets, the calibrated and validated SWAT model allowed us to establish the water balance of the Ouergha basin. It shows a dominance of evapotranspiration which represents 54% of rainfall, while surface runoff is 29%, lateral flow is 10% and total aquifer recharge is 8%.