Groundwater Responses to Tidal Oscillations in a Coastal Plain Overlying a Sloping Semiconfined Aquifer System

In a coastal aquifer, the interaction of tides and groundwater has a crucial impact on marine ecosystems. The model in this study consists of a semiconfined coastal aquifer overlying a sloping impermeable base in the presence of tidal waves. The groundwater flow was represented by a nonlinear Boussinesq equation, which was further solved analytically by converting it into a linearized form using a suitable technique. To assess the validity of the linearization technique, a numerical solution was obtained from the corresponding nonlinear equation using a fully stable alternate direction implicit scheme. The joint effects of the aquifer and tidal parameters were considered to analyze the behavior of the water table fluctuation. The accuracy between the analytical and numerical simulation results was tested by calculating the relative percentage difference. Asymptotic cases such as zero slopes and various leakage and tidal periods are discussed. Depending on the positive, negative, or zero values of flow rate and volumetric exchange, the groundwater flow can be categorized into inflow, outflow, or steady state. It was observed from the results that slope and tidal nature have a major impact on the water table fluctuation in a semiconfined coastal aquifer.