Yang, YJ; Neil, C; Neal, J; Goodrich, JA; Simon, M; Jun, Y; Burnell, DK; Cohen, R; Schupp, D; Krishnan, R
Aquifer storage and recovery (ASR) is a widely used technical method for the storage of water in a groundwater aquifer for later withdrawal and beneficial use. ASR application and sustainability are judged by the rate of recovery, system efficiency, and benign environmental impact. Practices without intentional recovery is generally called as aquifer recharge (AR). Examples include recharge through urban green infrastructure and the subsurface injection of excess water such as treated wastewater (i.e., reclaimed water). Over the past few years, the Safe and Sustainable Water Resources (SSWR) research on ASR practice has focused on developing an ASR decision support system (DSS) for planning and assessment, design, and evaluation. The research results are contained in two reports. This report provides an overview of ASR, AR, and other subsurface activities, with a focus on the ASR technique, its principle, and technical basis. The second report will describe the DSS software and its applications. The DSS tools and methods are structured in three levels with the goal to facilitate ASR system design and related permitting. Level 1 tools and methods are focused on ASR need and feasibility as they are related to four types of data and technical information: 1) ASR regulations and permitting needs, 2) Water demand projections, 3) Climate change and water availability, and 4) ASR sites and technical information. These technical resources are useful to users in assessing water availability gaps and evaluating whether ASR can be used to address volume shortages or flow imbalances in local water supplies. For illustration, a system-scale analysis in master-planning was conducted for sustainable water supplies in Las Vegas, Nevada. The results are presented in this report. Levels 2 and 3 of the DSS can be used to assist ASR planning and assessment, design, and evaluation at specific sites. During the planning and assessment, the ASR site characterization and the analysis of water treatment needs prior to injection are two major elements of investigation. The Level 3 analysis consists of engineering design and evaluation, for which detailed hydro-geological and Geo-chemical characterization is conducted, including contaminant mobilization analysis. Together, the analyses are intended to produce technical data necessary to answer the following questions: What is the likely recovery rate of injected water? This planning question is pertinent for water storage operations that are intended to address temporal or chronic water shortages. Poor recovery rates can also negatively affect the economics of an ASR project. What hydrologist changes occur during ASR operation? Vertical hydraulic conductivity and soil-clogging in the vadose zone are important considerations for ASR operations that utilize spreading basins and soil infiltration. For ASR wells into saturated zones, aquifer permeability and near-well clogging from biological growth and inorganic precipitation are key assessment factors.?Can geo-chemical reactions between the injected water and native groundwater and/or the geological formation deteriorate the groundwater quality? During ASR operation, the injected water forms a ?bubble?by displacing the native water closest to the point of introduction and mixing with native water for somedistance away from the injection point. The point at which only native groundwater is present in pore space-defines the edge of the injection bbble. The cycle of injection-withdrawal operations will encouragement chemical reactions and, in some cases, mobilize contaminants within the bubble. Given the analysis, what type of site-specific monitoring program should be used to monitor potential water-quality changes? Water quality can be impacted by both Geo-chemical reactions and horological changes.The water quality impacts must be monitored to ensure that ASR operation is not endangering the groundwater source. Would treating the water prior to injection decrease or eliminate the likelihood of adverse Geo-chemical-interactions at an ASR site? For example, can the injected water be treated to prevent arsenic mobilization from an aquifer formation where arsenic mobilization may otherwise occur?