Comparative evaluation of SWAT and WTF techniques for recharge estimation in the Vea catchment, Ghana

Comparative study of approaches debugs the uncertainty associated with recharge estimates and improves confidence in decision making toward groundwater allocation. In this study, Soil and Water Assessment Tool (SWAT) was used to develop water balance to estimate groundwater recharge of the Vea catchment with 36-year (1983–2018) climate data from 11 gridded climate stations within the catchment. The model was calibrated and validated with 2 years (2013–2014) and 1 year (2015) mean monthly continuously observed streamflow data, respectively. The most relevant and sensitive model parameters were adjusted to achieve a representative scenario. The model performance was evaluated using the Nash–Sutcliffe Efficiency (NSE) and Coefficient of determination ( R 2 ), which were 88.8% and 96.0%, respectively. Annual Recharge coefficient in the catchment ranged 0.6–20.4% (mean = 10.26%) of rainfall amount ranging between 747.1 and 1174.4 mm/year (mean = 963 mm/year) and the monthly mean recharge coefficient was 8.1%. The results of the water table fluctuation (WTF) technique (36.7–178.1 mm/year representing 6.1–16.5% of annual rainfall) confirmed the recharge estimates and proven reliable. Recharge and precipitation are found to have a strong exponential relationship with R 2 of 98%. The model was within 95% predictive uncertainty and could be useful to forecast future recharge for known rainfall events. In addition, actual evapotranspiration and runoff were intense at an average rate of 71% and 24%, respectively, of the annual mean precipitation. The findings could be applied for decision making, policy formulation and watershed scenario planning for sustainable management of groundwater resources in the catchment and within similar terrain.