Delineation of the wellhead protection area in an unconfined aquifer with variable vertical hydraulic conductivity.

Abstract

Delineation of wellhead protection areas is an important component of groundwater contamination protection programs. However, the calculations to determine these areas assume that the medium is homogeneous, when in fact it is not. In this paper we compared different analytic variants used to calculate the areas of sanitary protection, with the VisualModflow numeric model, which offers greater precision. The results show the importance of aquifer heterogeneity in the delimitation of wellhead protection areas. The causes of the discrepancies in the results were discussed, and we propose an adaptation to the analytic variants that improve their results more than 30% for the analyzed conditions. This adaptation allows to use the maximum value of the hydraulic conductivity of the aquifer for heterogeneous media.