Soil and Water Assessment Tool (SWAT Model) for Estimating Groundwater Recharge in Sokoto-Rima River Basin, Northwestern Nigeria
Publication Date : 01/06/2022
This research was undertaken to provide a procedure to improve existing approaches to the estimations of groundwater recharge and compute values for other hydrological parameters at sub-basin level and monthly intervals. Using the distributed hydrological model ''Soil and Water Assessment Tool'' (SWAT), the groundwater recharge was 2 estimated for the entire Sokoto-Rima River Basin, covering 72,498.711km . The procedure involved model calibration and validation based on measured river discharges, and statistical quantification of the goodness-of-fit using SWAT-CUP, a semi-automated approach (SUFI-2) for sensitivity analysis. The SWAT model was calibrated (2006-2010) and validated (2011-2014) at Kende for the entire Sokoto-Rima River Basin. The simulated river 3 3 discharge yielded a mean monthly discharge of 96.25m /s at calibration and 95.65m /s at Validation. The estimated groundwater recharge was 182.10mm, which is 18% of the mean annual rainfall of 1019mm. The computed mean annual potential evapotranspiration, actual evapotranspiration, and surface runoff were 1600m, 500mm, and 236.53mm respectively. A comparison of observed and simulated monthly river discharges showed a coefficient of 2 2 determination (R ) of 68.3% and Nash-Sutcliffe efficiency (NSE) of 98% for calibration and R of 65.7% and NSE of 84% for validation periods respectively. Although the modeling proved successful and was applied in estimating groundwater recharge and other hydrological parameters, there are, however, two limitations in the Sokoto-Rima basin model: (1) there were just 2 river discharge measuring points in the entire watershed, and (2) SWAT capabilities were also affected by limited data on available reservoir/impoundments and agricultural management information.
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