Modeling of Low-Velocity Non-Darcian Flow With Nonlinear Consolidation in a Leaky Aquifer System Induced by a Fully Penetrating Confined Well

Abstract

Existing groundwater flow models for leaky aquifer systems rarely consider the consolidation effects of aquitards. Neglecting these effects can significantly impact the accuracy of groundwater flow simulations within such systems. To address this issue, this paper develops a model that describes unsteady flow within a leaky aquifer system incorporating nonlinear consolidation. The flow in both unconfined and confined aquifers is radial one-dimensional Darcian flow, whereas the flow in the aquitard is vertical one-dimensional non-Darcian flow, considering nonlinear consolidation. The finite difference method is used to solve the model, and the difference between the results obtained with and without considering consolidation effects is examined. The findings indicate that the groundwater head in the confined aquifer, when considering the effects of consolidation, is higher than that in the confined aquifer without consolidation effects. Initially, this difference in confined groundwater head increases rapidly with time, and then progressively decreases. The magnitude of this difference is positively correlated with the aquitard's compressibility index and permeability index, as well as with the pumping rate. Conversely, it is negatively correlated with the aquitard's threshold hydraulic gradient and initial void ratio, the confined aquifer's hydraulic conductivity and specific storage, and the unconfined aquifer's hydraulic conductivity and specific yield. During the early period of pumping, the difference is positively correlated with the aquitard's initial vertical hydraulic conductivity; however, this correlation reverses in the late period of pumping. Finally, a case study is employed to validate the effectiveness of the developed model.