A Method of Analyzing Transient Fluid Flow in Multilayered Aquifers

A new approach to transient fluid flow in multilayered aquifers has been developed using the finite element method. This is a numeric technique in which an initial boundary value problem is converted to a variational problem and applied to a descretized system of elements. Details for the case of isotropic systems have been presented elsewhere. This paper extends the treatment to anisotropic systems. The method has been used to investigate potential distributions in multilayered aquifers of finite radial extent being pumped at constant rate using completely penetrating wells. An analysis of two‐layer systems with permeability contrasts of up to 100:1 indicates that at early time the drawdown behavior can vary significantly from the Theis solution, depending on where observations are made. As time increases, however, the results eventually converge on the Theis solution regardless of the permeability contrast. A 13‐layer aquifer containing either isotropic or anisotropic layers has been examined, and the results are in general agreement with the behavior for two‐layer systems.