Increasing Freshwater Recovery upon Aquifer Storage: A field and modelling study of dedicated aquifer storage and recovery configurations in brackish-saline aquifers

“The subsurface may provide opportunities for robust, effective, sustainable, and cost-efficient freshwater management solutions. For instance, via aquifer storage and recovery (ASR; Pyne, 2005): “the storage of water in a suitable aquifer through a well during times when water is available, and the recovery of water from the same well during times when it is needed”. This can be successful in storing and recovering both potable and irrigation water. ASR is attractive due to the limited space requirements above ground and the generally successful conservation of water quality (Maliva and Missimer, 2010).
The recovery efficiency (RE) of ASR is defined as the part of the injected water that can be recovered with a satisfying quality. Several factors can limit the RE during ASR in brackish-saline aquifers, such as the simultaneous abstraction of injected freshwater and ambient, more saline groundwater. This can be a result of ‘bubble drift’, which happens when the infiltrated bubble is transported away from the ASR well by the local or regional hydraulic gradient. However, the RE can be particularly limited in brackish–saline aquifers by the density difference between the injected freshwater and ambient brackish or saline groundwater. This is because this density difference causes the freshwater to float upwards in the aquifer (‘buoyancy effect’), while denser saline water is recovered by lower parts of the well (Esmail and Kimbler, 1967; Merritt, 1986; Ward et al., 2007). Both water types are thus blended in the ASR well to produce a brackish, generally unsuitable water quality.
Freshwater availability is more and more stressed in coastal areas, where brackish and saline groundwater is commonly present. Therefore, the ability to increase the RE of ASR systems provides a true benefit because it would significantly amplify the potential of freshwater management. The general objective of this study is therefore to quantify and increase the performance (indicated by RE) of relatively small-scale ASR systems in areas with brackish-saline groundwater, taking into account recently developed well configurations for performance optimization.”

(Citaat: Zuurbier, K.G. – Increasing Freshwater Recovery upon Aquifer Storage: A field and modelling study of dedicated aquifer storage and recovery configurations in brackish-saline aquifers)