Unconfined aquifer recharge from water table configuration modeling

Abstract

The potential of estimating steady recharge to deep unconfined aquifers by comparing observed water levels to the water levels produced by a series of simulated cases was examined. Finite-element simulations were performed on an idealized region to examine the sensitivity of the water table position to anisotropy, recharge, grid density, horizontal layering, and region geometry. The position of the water table was found to be particularly sensitive to region geometry, medium heterogeneity and anisotropy. A graphical method based on comparison of water levels at three observation points to simulated water levels produced a good estimate of dimensionless recharge and the anisotropy ratio. Determination of the absolute value of recharge requires accurate determination of region geometry and hydraulic conductivity so that computer simulations are representative. An analytical solution to the Boussinesq equation was found to give a poor estimate of water table position and hence recharge for this case.