Resource Management 74 IDA J OURNAL | S ECOND Q UARTER 2010 WWW. IDADESAL . ORG Copyright © 2010 by IDA and AWWA. All rights reserved. oday, water availability and security are critical, particularly in the Middle East and other arid areas. Cost-effective integration of two proven technologies, desalination and aquifer storage and recov- ery (ASR), can secure a reliable, sustainable, high-quality freshwater supply for the Gulf States and other parts of the world. Power generation facilities that meet existing and pro- jected needs typically operate at or close to peak-design capacity during summer months but have spare capacity during off-peak times. Using this spare power generation capacity to desalinate seawater with electrically driven de- salination processes can produce cost-effective additional potable water during several months of the year. To con- vert a seasonally available supply to a reliable, year-round water supply requires storage. A combination of advanced water reuse using membrane technologies and ASR can se- cure a sustainable, recoverable water supply, which can be safely injected into natural or artificial aquifers to provide economical storage and solutions for seawater intrusion. The advantages of ASR are compelling. Large vol- umes of water can be stored underground at a fraction of the cost of other storage options, such as aboveg- round storage tanks and surface reservoirs. ASR systems also do not experience the evaporative losses of surface water reservoirs, have minimal surface footprints and land requirements, and are less vulnerable to intentional and unintentional contamination from surface activities. However, ASR is not a panacea for water resource management. ASR systems do not work everywhere and vary in their hydrologic benefits. In addition, ASR may have regulatory and operational challenges, which reduce usefulness and economic value to system owners and operators. ASR Definitions Pyne (1995) defined ASR as “the storage of water in a suitable aquifer through a well during times when water is available, and the recovery of water from the same well during times when it is needed.” Pyne’s definition has two components: water is injected, stored, and recovered for beneficial use and injection and recovery are performed using the same well (Figure 1). Pyne’s definition has been adopted by the US Environmental Protection Agency (USEPA, 1999). In addition, USEPA (1999) considers an aquifer recharge well to be used only to replenish the water in an aquifer. In most instances, injection and recovery from the same well is the preferred option for economic reasons. It is typically less expensive to construct one dual-use well than dedicated injection and recovery wells. How- ever, from an operational perspective, it may be more T In the face of increasing populations and global climate change, communities in many parts of the world face difficulties in obtaining a sustainable, long-term supply of freshwater. Aquifer storage and recovery (ASR) is increasingly being viewed as a way to provide large storage capacity to capture seasonally or intermittently available excess water for later beneficial use. Potential stored waters include desalted and reclaimed water (treated sewage effluent) surplus produced during low-demand periods. ASR is a proven technology, but its implementation has problems. ASR systems vary in their hydrologic value (i.e., the degree to which they achieve useful storage) and, in some instances, have not met expectations or have failed entirely. It is now clear that ASR hydrogeology systems are more complex than originally envisioned. Excessive regulatory requirements unnecessarily increase project costs and adversely impact economic viability. However, the advantages of ASR as a water resource management tool are still compelling. The challenge is to take advantage of lessons learned from recent growth in ASR system construction and research to improve all aspects of ASR implementation and regulation. Aquifer Storage and Recovery: Developing Sustainable Water Supplies Robert G. Maliva and Thomas M. Missimer