Estimation of potential groundwater recharge by a drywell in sandy clay soil

Abstract

We estimated the potential groundwater recharge (Rpot) of a drywell that receives, temporarily stores, and infiltrates direct surface runoff from a contribution area (180.5 m2) comprising a roof and a cemented floor. The Rpot for traditional rainwater management and for similar contribution area but covered with grass was also estimated for comparison. Our methodology involved the use of water budget equation, monitoring of rainfall and soil water content up to 1.92 m depth, estimation of drywell overflow using the modified Puls model, and determination of actual evapotranspiration using water stress coefficient in 2017 and 2018. Results revealed that the Rpot for drywell was 83.3% of the precipitated volume, 2.22 times higher than that of the grass-covered area (37.6%) given the increased area for evapotranspiration in the latter. In turn, the traditional urban drainage system did not demonstrate potential of groundwater recharge. Therefore, the drywell contributes significantly to groundwater recharge apart from serving as local flood control.