FIGURE 2. Schematic diagram of the recharge and recovery phases of ASR for a typical south Florida system. The relatively symmetric spread of fresh water away from the well shown assumes a fairly homogeneous, isotropic aquifer with negligible regional flow relative to the flow rates induced by pumping during recharge or recovery. The actual configuration of the storage bubble may be considerably more complex. SOURCE: NRC, 2001.

ASR has advantages and disadvantages compared to surface storage. ASR systems generally take up less land and may avoid water losses due to seepage and evapotranspiration (USACE, 1999). This is of particular importance in south Florida, where land acquisition costs are high and flat topography coupled with a shallow water table place constraints on surface reservoir construction. Additional advantages cited for this strategy are that ASR wells can be located in areas of greatest need, thus reducing water distribution costs, and that ASR permits recovery of large volumes of water during severe, multi-year droughts to augment deficient surface water supplies.

Potential disadvantages of ASR wells include low recharge and recovery rates relative to surface storage, which limit capture rates of excess water, and losses due to mixing within brackish or saline aquifers (USACE, 1999). While slightly brackish water may be acceptable for drinking water, increases in salinity, and other water quality changes resulting from inputs of ASR water to surface ecosystems, may have unknown ecological effects. Operations and maintenance costs may also be higher for ASR, largely due to high energy requirements. Because of the complementary strengths of ASR and surface storage, these two storage options may be used in tandem.

PREVIOUS RECOMMENDATIONS CONCERNING ASR

While ASR technology has been employed successfully in Florida since 1983 (Pyne, 1995), with individual well clusters having capacities up to about ten million gpd (38,000



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