Aquifer storage and recovery
Aquifer storage and recovery (ASR) is the re-injection of potable water back into an aquifer for later recovery and use. ASR has been done for municipal, industry and agriculture use.
The first ASR well with a downhole control valve was installed in Highlands Ranch, CO in 1992 for Centennial Water and Sanitation District. Since then, over 40 ASR wells have been installed for many different municipalities. These wells range in depths from 1,000 ft (300 m) to 3,000 ft (910 m) below ground surface, with injection rates commonly between 100 US gal (380 l; 83 imp gal) and 500 US gal (1,900 l; 420 imp gal) per minute (gpm) per well.
The use of ASR in Florida has been examined to determine potential benefits for the Everglades and other Florida water systems under the Comprehensive Everglades Restoration Plan (CERP). An estimate of 333 ASR wells would be implemented as part of CERP and used to store, treat and supply excess surface water to the Everglades and other systems of water during dry periods.
Doubts remain about the benefit of introducing ASR in such large capacity to Florida due to a predominantly karst geography. Current or potential problems include: (1) poor recovery due to mixing of the injected fresh water with the existing brackish to saline water in the aquifer; (2) pre-existing quality of water introduced to ASR; and (3) potential risk of resulting water quality due to mixing of injected freshwater and existing aquifer.
The first agriculture ASR wells were put into service in Oregon in the autumn of 2006 and have injected well over a 3,000 acre feet (3,700,000 m3) of water during the winter and spring flood flow times using artificial recharge (AR) of flood water as their water source. This shallow recharged water is then recovered as potable water and injected into the deep basalt aquifer.
During the injection process, electrical energy can be generated by the head pressure of the water flowing back into the aquifer. This stored water is recovered during late summer and early autumn for irrigation needs.
Both of these well types use a down-hole control valve. ASR can also be used to re-inject water used by HVAC systems to maintain the ground water levels and store the thermal differences from summer time cooling for winter time heating. Industry can also capture cold winter waters and store it for summer time use and avoid the need for cooling water in the summer for industrial processes. This may also free up short supplies of summer time water for other beneficial uses. This reinjection process may also avoid the cost of surface disposal and avoid the increased thermal load to the rivers and streams during the summer air conditioning season.
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