Banking water in aquifers during wet years for long-term storage then recovering it in drought is an application of managed aquifer recharge (MAR) that minimises evaporation losses. This requires a suitable aquifer for long-term storage of banked water and occasional periods when entitlements to surface water are available and affordable. This has been widely practised in Arizona and California but thus far not in Australia, in spite of severe impacts on agriculture, society, and the environment during recent droughts in the Murray–Darling Basin. This preliminary study based on a simple area exclusion analysis using six variables, some on a 90 m grid, over the 1 million km2 basin produced a first estimate of the order of 2–4 × 109 m3 of additional aquifer storage potential in surficial aquifers close to rivers. For 6 of the 23 catchments evaluated, banking capacity exceeded an average water depth of 0.3 m for the irrigated area. At one prospective site in the Macquarie River catchment in New South Wales, water banking operations at various scales were simulated using 55 years of historical monthly hydrologic data, with recharge and recovery triggered by dam storage levels. This showed that the estimated 300 × 106 m3 additional local aquifer capacity could be fully utilised with a recharge and recovery capacity of 6 × 106 m3/month, and recharge occurred in 67% of months and recovery in 7% of months. A novel simulation of water banking with recharge and recovery triggered by water trading prices using 11 years of data gave a benefit cost ratio of ≈ 2. Data showed that water availability for recharge was a tighter constraint on water banking than aquifer storage capacity at this location. The analysis reveals that water banking merits further consideration in the Murray–Darling Basin. Firstly, management across hydrologically connected systems requires accounting for surface water and groundwater entitlements and allocations at the appropriate scale, as well as developing equitable economic and regulatory arrangements. Of course, site-specific assessment of water availability and hydrogeological suitability would be needed prior to construction of demonstration projects to support full-scale implementation.
Managed aquifer recharge (MAR) is the intentional recharge of water to aquifers for subsequent recovery or environmental benefit. MAR can potentially increase security of water in drought more economically than new dams, can augment existing dams with higher efficiency storage (less evaporation), augment brackish groundwater desalination schemes, and facilitate conjunctive use of surface and groundwater resources. In Australia in 2023, there are currently 10 known operational MAR schemes used to increase agricultural activity in varying stages of development, providing a total capacity of ∼ 70 × 106 m3/year. A review of these Australian MAR schemes identified several general principles which are more likely to lead to successful implementation, including: an ongoing demand for water for high value agriculture; availability of water for recharge; a suitable aquifer for storage with the capacity to store water for recovery and use; a suitable location for the MAR scheme typically in areas of low topographic relief; and the organisational capability, institutional arrangements and supportive policies to operate the scheme sustainably and economically. If MAR schemes are to be developed to support agricultural activity in Australia, site identification, project design, economic viability, and community and regulator consultation within an investment prospectus will be required. Operational demonstration schemes in a variety of agricultural settings will encourage wider adoption. Supportive policy development is required to ensure sustainable and equitable ongoing operation of MAR to support irrigated agriculture and for drought resilience.
Water availability and quality issues will only gain importance in the future, with climate change impacts putting increasing pressure on global water resources. Dealing with these challenges requires drawing on all available water management tools, including Managed Aquifer Recharge (MAR). Although MAR has seen increasing global implementation during the last half a century, it is still often overlooked as a management tool. While technical, bio-physical, and hydrogeological aspects of MAR are well researched, this cannot be said for socio-economic and other governance factors. Where information is available, this study seeks to understand the conditions necessary for MAR success. We apply fuzzy-set Qualitative Comparative Analysis on 313 world MAR applications, and also model separately for high- and low-middle-income countries. Results show that sophisticated hydrogeological site understanding and scheme operation is paramount for MAR success, as is utilizing natural water sources for high value end uses. High-income country MAR schemes tend to be large and utilize natural water sources and sophisticated water injection and treatment methods to augment potable water supply; while low-middle-income country schemes are not large, older than 20 years, and use gravity infiltration methods and (limited) no water treatment. These findings will help inform the future suitability of MAR application design and its likely success within various contexts.
Abstract Wastewater reuse coupled to managed aquifer recharge (MAR) provides a means to store and reuse treated wastewater (TWW) year-round. Determining the fate of nutrients in the subsurface during MAR remains challenging for environmental regulation due to the interaction of the MAR source water with site specific aquifer conditions. To facilitate the understanding of natural treatment processes, this study uses operational monitoring data from a full-scale aquifer storage and recovery (ASR) scheme using TWW to assess nutrient (N and P) transformation and fate. Analysis of median water quality injected into and recovered from the ASR wells for two complete ASR cycles (June 2014 to March 2016) was used to describe the removal of nutrients in an anoxic carbonate aquifer. Total nitrogen (TN) removal was dominated by redox processes, with median removal of 40 to 60% for TN and nitrate (the dominant N species) and higher removal of ammonia (95%) and total Kjeldahl nitrogen (TKN) (70%). Total phosphorous (TP) removal was also observed (~ 90%) due to sorption (filterable reactive phosphorous median removal of ~ 80%). A 40% increase in median salinity was evident within each ASR cycle due to recovery of the entire volume of injected water each year (ambient groundwater is 200% higher in TDS, on average). A reduction in salinity of the recovered water could be achieved by leaving a residual of source water in the aquifer to create a buffer zone between the ambient groundwater and the fresher source water.
Managed aquifer recharge (MAR) is used worldwide in urban environments to replenish groundwater to provide a secure and sustainable supply of potable and non-potable water. It relies on natural treatment processes within aquifers (i.e., filtration, sorption, and degradation), and in some cases involves infiltration through the unsaturated zone to polish the given source water, e.g., treated wastewater, stormwater, or rainwater, to the desired quality prior to reuse. Whilst MAR in its early forms has occurred for millennia, large-scale schemes to replenish groundwater with advanced treated reclaimed water have come to the fore in cities such as Perth, Western Australia, Monterey, California, and Changwon, South Korea, as water managers consider provision for projected population growth in a drying climate. An additional bonus for implementing MAR in coastal aquifers is assisting in the prevention of seawater intrusion. This review begins with the rationale for large-scale MAR schemes in an Australian urban context, reflecting on the current status; describes the unique benefits of several common MAR types; and provides examples from around the world. It then explores several scientific challenges, ranging from quantifying aquifer removal for various groundwater contaminants to assessing risks to human health and the environment, and avoiding adverse outcomes from biogeochemical changes induced by aquifer storage. Scientific developments in the areas of water quality assessments, which include molecular detection methods for microbial pathogens and high resolution analytical chemistry methods for detecting trace chemicals, give unprecedented insight into the “polishing” offered by natural treatment. This provides opportunities for setting of compliance targets for mitigating risks to human health and maintaining high performance MAR schemes.
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