Second-order shallow flow equation for anisotropic aquifers

Transient unconfined ground-water flow is described using the well-known Boussinesq equation, in which the Dupuit assumptions are implicit. When these assumptions fail, one must recur to the next level of approximation, which is the second-order theory for shallow flow in porous media, developed by Dagan (1967) for isotropic aquifers. When the soil is highly anisotropic Dagan's second-order theory can become invalid. Here we present the generalized second order theory that account for anisotropy. An analytical solution for the second-order theory with anisotropy is presented for the linearized equation that is used to illustrate this effect on the bank storage problem. (C) 2013 Elsevier B.V. All rights reserved.