Numerical investigation of shallow aquifer recharge using small-diameter, low-cost wells and infiltration basins

Scarcity of potable water has become a critical issue throughout the world; there is a pressing need to overcome the common temporal imbalance between water demand and availability. As a result, aquifer storage and recovery (ASR) methods are increasingly used. Common ASR recharge methods are based on surface infiltration basins and trenches or large-diameter wells and can be quite costly to implement. A new low-cost ASR method is currently being explored. This approach uses shallow small-diameter wells installed with direct-push (DP) technology and recharge via gravity; installation and operation costs can be very low. A numerical modeling investigation, which was carried out to explore the potential of the approach, will be described here. This investigation found the expected dependence of infiltration capacities on subsurface parameters. For sites in unconsolidated settings, DP technology provides an excellent means for carrying out the detailed subsurface characterization required at proposed ASR sites. The modeling results also demonstrate the advantages of small-diameter wells over a surface infiltration basin. For example, a small number of 2“ shallow wells can be used to recharge water at the same infiltration rate as a 60 m² basin. Although a layer of low hydraulic conductivity (K) can significantly reduce the infiltration capacity of surface basins, this impact can be largely avoided by extending well screens below the low-K layer. A field demonstration of the approach at a site in north-central Kansas is in its early stages.