Wellhead Protection Area Delineation Using the Analytic Element Method of Ground‐Water Modeling

Abstract

AbstractThe Analytic Element Method (AEM) of ground‐water modeling was used to delineate wellhead protection areas (WHPAs) for existing and proposed wells in Brooklyn Park, Minnesota by simulating steady‐state flow in two aquifers: the water‐table aquifer (in glacial outwash) and the Franconia‐Ironton‐Galesville bedrock aquifer. Ground‐water time‐of‐travel was used as the delineation criterion. Ground‐water flow is significantly affected by a buried bedrock valley underneath the City. Transmissivity values for the water‐table aquifer are much higher in the buried bedrock valley and the hydraulic connection between the water‐table and the Franconia‐Ironton‐Galesville aquifers is more pronounced. The Analytic Element Method does not utilize a grid mesh and incorporates both regional‐scale and more detailed, local‐scale features in the same solution. This feature of AEM provided for the simulation of the city wells in the context of the regional flow field. Separate models, encompassing an area of approximately 500 square miles, were developed and calibrated for each aquifer using the Single Layer Analytic Element Model (SLAEM) and then linked together using the Multi‐Layer Analytic Element Model (MLAEM). Ground‐water travel‐time zones and WHPAs were delineated for the existing wells using reverse particle tracking.