Probabilistic delineation of groundwater protection zones in fractured-rock aquifers

Abstract

Groundwater protection zones in fractured-rock aquifers are delineated with a hybrid method that combines discrete fracture network (DFN) models and equivalent continuum models. The method, known as the Statistical Continuum Method (SCM), relies on statistics of movement of particles in a local-scale DFN followed by the use of those statistics to mimic movement in a catchment-scale continuum model. Because the method is based in a Monte-Carlo procedure, it is possible to delineate probability contours for protection zones. The method is implemented in a catchment-scale synthetic case study that uses MODFLOW as the continuum groundwater flow model. Reverse particle tracking is conducted and the locations of the particles at time t are used to create probability contours of the t-isochrone protection zone. The computational needs for upscaling from local to regional scale are not heavy and probability contours of protection zones can be easily computed.