In case of budget constraints, it would be preferable to do more detailed studies with enhanced monitoring at a reduced number of sites or with a reduced number of ASR wells, rather than more limited studies using the currently planned number of exploratory wells. Important elements that should be considered in design of the pilot tests are listed below. . These should be a high priority at each pilot ASR site for purposes of delineating bubble geometry, potential preferential flow paths, and the extent of mixing between recharged and ambient water. Tests designed to compare effects of short and long sections of open borehole on well performance. These would be particularly useful for optimizing design of ASR wells. .
Hydrologic models indicate that continuous recharge is likely to be required for multi-year periods.
The pilot projects are also lacking studies to help assess the appropriate water quality standards for discharge of recovered water to ecosystems. With an improved understanding of ASR systems that will result from these studies, it should be possible to develop ASR system designs that then can be compared to other storage options in terms of overall performance, including storage capacity and cost effectiveness. These include performance of surface and subsurface storage, a comparison of losses from surface evaporation and subsurface storage, the number and distribution of wells required for a regional ASR system, and estimates of energy costs for operation over the anticipated project life.