Abstract We consider a single pumping well within a two-dimensional heterogeneous aquifer, in the presence of a mean uniform background gradient. We analyse the uncertainty associated with the location of the stagnation point which is generated downstream of the well and the maximum lateral extent of the well recharge area. The study is relevant for risk assessment practice, since it allows one to estimate the maximum width of the region contributing to the well and to properly locate regions of inversion of the flow direction. The problem is approached within a numerical Monte Carlo framework and the dependence of the main statistics of the quantities of interest on the moments of the log-conductivity field is studied. An assessment of the impact of one conductivity datum at the pumping location is performed.

Keywords conditioning; stagnation point; stochastic; well-catchments; width of catchments