Models for wellhead protection in regional unconfined aquifers and stratified aquifers

Mathematical concepts are used for the development of wellhead protection and zoning methodologies, based on analytical solutions and on groundwater flow and particle tracking finite differences. Wellhead protection limits are a function of the local geology, of the aquifer parameters and the regional hydraulic characteristics of the aquifer, and of the extraction rates or of the productivity of the aquifer. In the vertical dimension the analysis was performed using an axisymmetric flow model, assuming that groundwater flow into the well is radial. The radial axisymmetric mathematical tools were robust and user friendly, facilitating the application of the new Portuguese legislation regarding groundwater protection. The methodology is exemplified in two case studies, one for the coastal aquifer of the Bardez, Goa State, India and the other in Ramalhal, Portugal.