Wellhead Protection Area Delineation Methods and the Influence of Heterogeneity, Anisotropy, and Aquifer Surface Recharge

The decisive parameter for a wellhead protection area (WHPA) is attributed to a time of travel value. The available analytical methods that define the time of travel are based on simplistic assumptions of reality. These methods assume a one layer aquifer to be homogeneous and isotropic and the layered aquifer to be equivalent to a homogeneous and anisotropic one layer aquifer. In the absence of surface recharge for an aquifer, Chenaf, Boukemidja, and Kettab (Chenaf et al. 2013) have shown that it is important to consider the anisotropy and heterogeneity of the aquifer as naturally encountered. They have shown, in particular, that the calculated times of travel for the equivalent models dangerously underestimate the WHPA. In this article, the influence of the heterogeneity and the horizontal and the vertical anisotropies on the time of travel in an aquifer is examined when a surface recharge exists. It is found that the time of travel and therefore the WHPA are affected by the surface recharge beyond a certain distance from the pumping well, in all aquifer configurations.