Consequences and mitigation of saltwater intrusion induced by short-circuiting during aquifer storage and recovery in a coastal subsurface

Abstract

Abstract. Coastal aquifers and the deeper subsurface are increasingly exploited. The accompanying perforation of the subsurface for those purposes has increased the risk of shortcircuiting of originally separated aquifers. This study shows how this short-circuiting negatively impacts the freshwater recovery efficiency (RE) during aquifer storage and recovery (ASR) in coastal aquifers. ASR was applied in a shallow saltwater aquifer overlying a deeper, confined saltwater aquifer, which was targeted for seasonal aquifer thermal energy storage (ATES). Although both aquifers were considered properly separated (i.e., a continuous clay layer prevented rapid groundwater flow between both aquifers), intrusion of deeper saltwater into the shallower aquifer quickly terminated the freshwater recovery. The presumable pathway was a nearby ATES borehole. This finding was supported by field measurements, hydrochemical analyses, and variable-density solute transport modeling (SEAWAT version 4; Langevin et al., 2007). The potentially rapid short-circuiting during storage and recovery can reduce the RE of ASR to null. When limited mixing with ambient groundwater is allowed, a linear RE decrease by short-circuiting with increasing distance from the ASR well within the radius of the injected ASR bubble was observed. Interception of deep short-circuiting water can mitigate the observed RE decrease, although complete compensation of the RE decrease will generally be unattainable. Brackish water upconing from the underlying aquitard towards the shallow recovery wells of the ASR system with multiple partially penetrating wells (MPPW-ASR) was observed. This "leakage" may lead to a lower recovery efficiency than based on current ASR performance estimations.

Spectroscopic Determination of Water Salinity in Brackish Surface Water in Nandoni Dam, at Vhembe District, Limpopo Province, South Africa

“…Other than estuaries, the elevated groundwater salinity can be observed in the regions where groundwater is in contact with evaporates formations, or mixed with high mineralized and deeper aquifers [8,9]. The discharges from industrial effluents containing dissolved salts, leachates of saline soils and the runoff of salt deposits such as halite or gypsum that is present in the sedimentary rocks also increase the amounts of total dissolved salts and thus lead to the formation of brackish water [10][11][12]. However, the primary contributing source of brackish surface water (e.g., brackish dam water) is the mixing of the saline water from the open wells and the fresh water as well as the flow from the saline aquifer sourced from pumping wells to the surface water [13].…”

“…Other than estuaries, the elevated groundwater salinity can be observed in the regions where groundwater is in contact with evaporates formations, or mixed with high mineralized and deeper aquifers [9,10]. The discharges from industrial effluents containing dissolved salts, leachates of saline soils and the runoff of salt deposits such as halite or gypsum that is present in the sedimentary rocks also increase the amounts of total dissolved salts and thus lead to the formation of brackish water [11][12][13].…”

Application of social identity models of collective action to facilitate participation in groundwater aquifer storage and recovery management

“…ASR, as an approach to water storage ( Smith et al, 2017 ), is an inexpensive solution to increase water storage, to remove pollution ( Stuyfzand and Osma, 2019 ), to reduce aquifer salinity ( Ghaffour et al, 2013 ; Gibson et al, 2018 ; Sathish and Mohamed, 2018 ), and to improve aquifer quality ( Smith et al, 2017 ; Ghose et al, 2018 ). This method has advantages such as evaporation decrease, no need for large land areas for implementation, low cost of implementation ( Bouwer, 2002 ; Khan et al, 2008 ; National Research Council, 2008 ; Maliva and Missimer, 2010 ; Forghani and Peralta, 2018 ; Wasif and Hasan, 2020 ), potentiality for being used in different aquifers and climates ( Maliva et al, 2011 ; Jeong et al, 2018 ), and prevention of the progression of the salinity ( Pyne, 2005 ; Zuurbier and Stuyfzand, 2017 ).…”

Using geographic distribution of well-screen depths and hydrogeologic conditions to identify areas of concern for contaminant migration through inactive supply wells

“…Contaminant migration through inactive supply wells can negatively affect groundwater quality (Landon et al 2009;Mayo 2010;Jurgens et al 2014;Zuurbier and Stuyfzand 2017; see Gailey 2017 for a detailed literature review). With the exception of Clark et al (2008), studies on wells that act as conduits for contaminant migration address single wells; however, the combined effects of groups of wells may cause greater impacts (Gailey 2017).…”