Aquifer Storage and Recovery Using Saline Aquifers: Hydrogeological Controls and Opportunities

Abstract

Aquifer storage and recovery (ASR) is a valuable tool for managing variations in the supply and demand of freshwater, but system performance is highly dependent upon system-specific hydrogeological conditions including the salinity of the storage-zone native groundwater. ASR systems using storage zones containing saline (>10,000 mg/L of total dissolved solids) groundwater tend to have relatively low recovery efficiencies (REs). However, the drawbacks of low REs may be offset by lesser treatment requirements and may be of secondary importance where the stored water (e.g., excess reclaimed, surface, and storm waters) would otherwise go to waste and pose disposal costs. Density-dependent, solute-transport modeling results demonstrate that the RE of ASR systems using a saline storage zone is most strongly controlled by parameters controlling free convection (e.g., horizontal hydraulic conductivity) and mixing of recharged and native groundwater (e.g., dispersivity and aquifer heterogeneity). Preferred storage zone conditions are moderate hydraulic conductivities (5 to 20 m/d), low degrees of aquifer heterogeneity, and primary porosity-dominated siliclastic and limestones lithologies with effective porosities greater than 5%. Where hydrogeological conditions are less favorable, operational options are available to improve RE, such as preferential recovery from the top of the storage zone. Injection of large volumes of excess water currently not needed into saline aquifers could create valuable water resources that could be tapped in the future during times of greater need.

Experimental observations of aquifer storage and recovery in brackish aquifers using multiple partially penetrating wells

“…During the injection and storage phases, a rotational movement of the interface between the two water types was evident and confirmed by the calculated pathlines in the particle tracking simulations. As has been found in other studies (Bakker 2010;Maliva et al 2019;van Ginkel et al 2014;Ward et al 2009), the associated thinning of the injected freshwater volume has a negative impact on the RE (max 69% if the ambient fluid was brackish water versus around 89% if the ambient fluid was freshwater for the singlecycle experiments).…”

Optimizing Multiwell Aquifer Storage and Recovery Systems for Energy Use and Recovery Efficiency

“…Factors that affect the volume of water that can be recovered from a single‐well ASR system or ASTR system have been thoroughly investigated (Khanal 1980; Merritt 1986; Yobbi 1996; Streetly 1998; Brown 2005; Lowry and Anderson 2006; Reese and Alvarez‐Zarikian 2007; Ward et al 2009; Barker et al 2016; Forghani and Peralta 2018; Maliva et al 2020). For example, in a brackish aquifer, 100% of the water volume cannot be recovered as it mixes with the ambient groundwater thereby compromising the quality of the stored freshwater (Ward et al 2009; Zuurbier et al 2013; Maliva et al 2020). Small volumes of recharged water, shorter recharge durations, and longer recovery times may also result in lower recovery efficiencies (Khanal 1980; Merritt 1986; Streetly 1998; Lowry and Anderson 2006).…”

Aquifer Storage and Recovery in Layered Saline Aquifers: Importance of Layer-Arrangements

“…During the storage phase, the well boundary is converted to a no-flow boundary and the pumping rate is zero. Such settings of the well boundary are used following Maliva et al [7] and Kang et al [31]. The solute concentration of the water entering the model by injection (left boundary) is specified as zero (i.e., C i = 0).…”

“…ASR provides a possibility to balance seasonal freshwater supply and demand without extra land acquisition or in-stream barriers, and it avoids the evaporation that occurs in surface water reservoirs [6]. Other advantages of ASR include large storage volumes, a reduced threat of contamination from natural and anthropogenic sources, less environmental impacts compared to the surface storage options, lower costs and technical resources requirements, and reduced seawater intrusion and reuse of desalinated seawater in coastal areas [7][8][9][10][11]. The performance of ASR can be impacted by clogging issues, geochemical processes, hydrogeological conditions, hydrodynamic dispersion, and wellfield design and operation parameters [12][13][14][15][16][17].…”

“…Since ASR is often implemented in brackish or saline aquifers located in coastal or semi-arid and arid areas [7,[23][24][25], RE is reduced due to density-driven free convection and mixing of saline water with freshwater. Esmail and Kimbler [26] investigated the feasibility of ASR in confined homogeneous isotropic saline aquifers by performing an analytical analysis.…”