A Method for Integrating Delayed Recharge Flux Through Unsaturated Zones into Analytical and Numerical Groundwater Flow Modeling

The temporal delay in the water table's response to precipitation is a common phenomenon. Using a mathematical model, we developed a function that represents the recharge flux through unsaturated zones of varying thickness to model the delayed response of groundwater level due to precipitation. The recharge flux from the developed function was integrated into the analytical and numerical models to estimate the actual groundwater levels in the unsaturated zone. The analytical and numerical models accurately determined the actual groundwater levels. Additionally, calibrated hydraulic parameters from numerical estimates reflected the values measured in the actual aquifer, thereby highlighting the potential application of the developed function to wide‐ranging groundwater problems. Based on the recharge function, a recharge module can be developed for existing flow simulators to enhance groundwater modeling. Plain Language Summary The delay (ranging from minutes to months) in the change in the groundwater level due to precipitation is common. If this delay is neglected, then erroneous estimates of the groundwater flow and solute transport are inevitable. Most of the models on ground water estimation are incapable of assessing delayed groundwater response (practically evaluated with great difficulty). To overcome these limitations, in this study, a statistical function representing the delayed recharge flux through the unsaturated zone is derived. To validate the function, delayed recharge fluxes were obtained by calibrating the developed function using actual groundwater level data of a few locations. Then, the fluxes were applied to analytical and numerical models for groundwater level estimation. The results reasonably reflected the actual groundwater levels and aquifer hydraulic properties, indicating that the developed function is useful in resolving real‐world problems. Key Points A function representing the delayed recharge flux through unsaturated zones of varying thickness was derived The recharge flux from the function was integrated into analytical and numerical models, producing consistent results The function can be combined with existing models to simulate more realistic groundwater flow and solute transport