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Direct well injection facilities can recharge unconfined and confined aquifers. Artificial <br />groundwater recharge through injection wells may be an option for locations where soils <br />are impermeable, land is too costly, where the vadose zone has restricting layers, or for <br />sites that have undesirable characteristics that could compromise water quality. <br />Well injection provides better control to regulate recharge. Consequently, well injection is <br />typically employed where the intent is to recover the recharged water directly on -site or at <br />a point downgradient in the aquifer. Operations where water is recharged and recovered <br />through a single well are termed "Aquifer Storage and Recovery" (ASR). Well injection, <br />recovery, and ASR operations are generally driven by higher water costs and an emphasis <br />on water reuse. Water quality, pumping rates and costs, and the potential for geochemical <br />interactions are key issues in direct well injection operations. <br />Recharge Purpose and Application <br />The most common purpose of artificial recharge is to store surplus water underground for <br />later recovery to alleviate short -term seasonal drawdown. Direct recovery of recharged <br />water is more common for potable water supplies, whereas irrigation use usually involves <br />downgradient recovery. Under some circumstances, land and water management practices <br />are implemented to contribute toward recharge as a broad aquifer replenishment benefit <br />without definite plans to recover the recharged water. <br />Injection well facilities are also used for other purposes, including operations to inhibit sea <br />water intrusion, prevent migration of contaminant plumes, dispose water or wastewater, <br />or control land subsidence caused by pumping. Although these activities can indirectly <br />effect water supply conditions, they were not addressed by this program. <br />The demonstration projects focused on using recharge for beneficial management of water <br />resources. In this context, the effective role of recharge depends on the ability to integrate <br />surface and groundwater use in balance with prevalent watershed conditions and, thereby, <br />develop more cost - effective management strategies to sustain all water resources. <br />Groundwater is an important source of new supply in states that have basins <br />where existing use is less than the sustainable yield or where it is possible to <br />store "surplus" surface water underground. The existence of underutilized <br />groundwater basins is, however, not widespread because most groundwater <br />basins are either in balance with local rivers and streams or are currently <br />overused. States will have to rely on a combination of conservation regulation <br />and supply augmentation to bring these basins into balance (WWPRAC,1998). <br />Groundwater storage through recharge has significant potential in future water resource <br />management plans. The potential for application may be restricted by the hydrogeologic <br />conditions and the current legal and administrative barriers. Nevertheless, well - planned <br />recharge facilities often have lower total costs than surface storage alternatives and can <br />also provide opportunities to incorporate environmental enhancements. <br />Program Summary Report Part I — Overview, Results, and Findings 2.13 <br />