Earth and Atmospheric Sciences, Department of


Date of this Version



Published in Water Resources Research (June 2005) v. 41, 6 p. W06022, doi:10.1029/2004WR003716. Copyright 2005, the American Geophysical Union. Used by permission.


The effects of an aquitard on drawdown in an overlying unconfined aquifer can be represented by a drainage-type term at the aquitard-aquifer interface. The functional form of this boundary condition is similar to the Boulton-Neuman boundary condition used for water table aquifers except the kernel contains an inverse square root of time instead of a negative exponential. Type curves using the new boundary condition were obtained in semianalytical form. Examples for several representative conditions show that the effect of the underlying aquitard can contribute to the type curve at early and intermediate times, but the effect becomes negligible at late times.