Stochastic delineation of wellhead protection area in fractured aquifers and parametric sensitivity study

In many countries, the setup of protection areas around every drinking wate r well was instituted at a national level in order to preserve the quality of water as well as the perennially of the resource. Wellhead protection su rfaces have been defined using capture zones showing the area influenced by a well within a certain time. A stochastic method is developed for delinea ting time-related capture zones in fractured aquifers characterised by a lo w porosity and a high degree of fracturing. The flow velocity within the fr actures is determined statistically depending on the distribution of the fr acture features and the mass transfer solution is obtained through a partic le tracking algorithm. Probabilistic capture zone curves are obtained as a function of the travel time of particles to the well and the percentage of particles apt to be extracted up to this time. A sensitivity study of fract ure network parameters leads to the conclusion that orientations and apertu re distribution of the fracture sets are of primary importance to the wellh ead protection delineation.