Managed Aquifer Recharge (MAR): Has the greatest international use; less common in this country. The original definition referred to intentional banking and treatment of water in aquifers.
Managed Underground Storage of Recoverable Water (MUS): Introduced in 2008 by NRC’s Committee on Sustainable Underground Storage of Recoverable Water to define “purposeful recharge of water into an aquifer system for intended recovery and use as an element of longterm water resource management.” Southwest Hydrology is using the broad definition of ASR."
Since, no clear consensus exists regarding an exact definition, the term ASR throughout most of this website will refer to the injection and recovery of water via wells, irrespective of the number of wells, provided that such wells directly access the storage aquifer; in addition, injected and recovered water is used as a water resource management tool and for aquifer restoration purposes. Thus, this definition puts parameters on the hydrogeologic conditions required for an ASR scheme to be deemed feasible and for the development of such projects to be used primarily for the purpose of boosting water supply and/or enhancing overdeveloped aquifers.
For a general overview of the basics of ASR and the importance of groundwater, please view the following presentation:
So, what is Aquifer Storage and Recovery (ASR)?
Unconfined Aquifer and ASR
In an unconfined aquifer (a), injected water mounds near the injection well. Injection occurs during high flow periods and when complete, injected water eventually propagates throughout the aquifer and an increase in the height of the water table is observed. Water is then stored until the summer when demand is high. During recovery, a cone of depression forms until recovery seizes and a lowering of the water table is observed, until the cycle begins again during winter months. If boundary conditions exist such that stored water increases water levels, the water is retrievable when needed.
Confined Aquifer and ASR
Injecting water into a confined aquifer (b) temporarily increases pressure within the aquifer; however, if a density difference in native groundwater exists (i.e. brackish water), injected water will form a “bubble” around the injection well and remain until recovery occurs, at which time the bubble shrinks. Injection typically occurs during winter months and recovery during summer months. If injected water is of similar quality, maintaining a storage bubble is unnessary.