Induced infiltration in aquifers with ambient flow

Well water quality depends on the relative amounts of water drawn from the pumped aquifer and nearby surface water bodies, such as streams, lakes, and wetlands. Although a surface water body may normally gain water from the aquifer, pumping can reverse gradients, causing it to lose water near the well. Surface water then enters the well by induced infiltration. Two‐dimensional vertically integrated models of induced infiltration are developed for various combinations of aquifer geometry and sources of recharge. The models, which have applications in wellhead protection, aquifer pollution characterization, and aquifer remediation, are presented graphically. They show that the propensity for and rate of induced infiltration are enhanced by higher pumping rates, proximity of the well to the stream, and the presence of nearby barrier boundaries. The propensity and rate are reduced by the presence of other surface water bodies. Ambient groundwater discharge rate to the surface water body also plays a role, but not its source, whether it is from local vertical recharge, lateral inflow, or both. The results are also largely indifferent to whether the aquifer transmissivity is assumed to be a constant, or a function of water table elevation. Finally, if the well is close enough to the surface water body, say, less than 5% of the aquifer width, then the aquifer acts as if it were semi‐infinite.