Stream Depletion from Pumping a Semiconfined Aquifer in a Two-Layer Leaky Aquifer System

We consider the case of pumping a semiconfined aquifer overlain by a phreatic aquifer hydraulically connected to an infinitely long and straight stream. The hydraulics of the system are described by a linearized model in which it is assumed that flow in the aquifers is essentially horizontal, and that drawdown in the phreatic aquifer is small enough to allow the water table to be sufficiently well described by the Theis equation. Fourier-Laplace transforms of drawdown are obtained and numerically inverted. Comparisons are made with another well-known analytic model of Hunt, who considered a single aquifer/aquitard system. It is observed that while both models may have excellent agreement during the initial phase of pumping, the longer-term consequences of sustained pumping are quite distinct.