Steady-state semianalytical solutions for assessing the two-dimensional hydraulic head distribution induced by an underground dam in a sloping aquifer with artificial aquifer recharge and pumping

Abstract

Underground dams are a technology for artificially increasing existing groundwater resources. They modify the natural groundwater flow in aquifers and, typically, cause hydraulic heads to rise upstream and fall downstream of the dam. However, such modifications must be defined to forecast their environmental, economic and/or social impacts. A steady-state semianalytical solution is proposed for evaluating the two-dimensional distribution of hydraulic head caused by an underground dam fully penetrating a homogeneous and inclined aquifer. The dam is impermeable, of rectangular shape, and its length concerns a limited part of the aquifer width. The developed solution is based on the method of fundamental solutions. Analysis of the semianalytical solution included sensitivity tests and a satisfactory comparison with numerical modelling. Dimensionless graphs relating the dam geometry to maximum hydraulic-head variations upstream and downstream of the dam are given. The proposed solution was applied at two field sites, giving satisfactory results. A semianalytical solution is also developed for an artificial recharge area and/or a pumping well near the underground dam. Interestingly, in the case of highly permeable aquifers, the increase in hydraulic head created by the dam may be much higher than that created by managed aquifer recharge (MAR), despite high injected flux. These semianalytical solutions will be useful applications for assessing the long-term spatial distribution of hydraulic head induced by underground dams, or for testing the combination of dams with pumping wells or MAR technology. They are intended to guide the design of such structures, especially to quickly test various configurations.