Influence of infiltration and evaporation on aquifer recharge using a vadose zone infiltration well

Vadose-zone infiltration well is an efficient way to achieve groundwater recharge for the area where sufficiently permeable soils or sufficient land areas for surface infiltration systems are not available. Several mathematical models have been developed for the infiltration well in the vadose zone. However, such models usually ignore the infiltration and evaporation on the ground surface, which may cause errors in recharge evaluation and prediction. This study takes these two processes into consideration with the purpose of understanding their influences on the hydrodynamics of unsaturated flow and recharge efficiency. A three-dimensional governing equation is used to describe the groundwater flow in the saturated zone and a linearized three-dimensional Richards' equation is used for the flow in the unsaturated zone. Laplace-Hankel transforms are applied to derive the solutions for the hydraulic head and recharge rate. Then the semianalytical solutions are compared with the finite-element numerical solution built with COMSOL for accuracy. Sensitivity tests are analyzed to assess the influences of infiltration and evaporation on the artificial recharge.