The challenge
Managed aquifer recharge (MAR) to improve water security for urban and agricultural water supply
MAR can improve water security by using aquifers to store water when it is abundant until it is required for use. Storage periods can be short-term to augment dry season water supply or longer term to provide strategic drought protection (i.e. water banking).
MAR can also provide water quality treatment which increases the use of seasonal alternative water sources, such as urban stormwater, recycled water or mining treated wastewater or recycled water or mining surplus water.
The use of MAR has grown in the past 60 years due to growing confidence in the safety of using aquifers to store and treat water. MAR investigation provides knowledge of subsurface processes and supports sustainable and economical water security solutions.
Our response
Risk-based assessment of MAR feasibility
We provide science to manage health and environmental risks during MAR scheme development and operation.
Our scientific contribution is documented in the Australian MAR Guidelines, the only international example of risk-based guidelines to manage both water quantity (that is, impacts on other groundwater users or groundwater dependent ecosystems) and quality (salinity of water available for use).
Desktop, laboratory and field investigations conducted in partnership with operators, water managers and regulators have demonstrated feasibility of significant urban water security solutions. For example, urban stormwater MAR in Salisbury, South Australia provides 2.5 GL/y non-potable urban water supply and Perth's recycled water Groundwater Replenishment Scheme provides 14 GL/y with expansion underway.
Detailed scheme-scale technical feasibility assessments involve aquifer and recharge source water characterisation for assessment of solute transport including mixing between the source of water for recharge and the ambient groundwater, impacts on other groundwater users or groundwater dependent ecosystem, changes in groundwater levels or aquifer pressures, water quality in relation to suitability for intended end use, geochemical reactions and energy requirements.
We also develop new approaches to gain understanding of subsurface processes that can be applied to individual MAR operations in different hydrogeological settings. For example, by providing standardised methods to quantify natural or passive treatment using available recharge source and recovered water quality data, or the potential impact and management of clogging in laboratory column studies.
Importantly we bring together scientific teams to assess technical feasibility, from a health, environmental and operational perspective, alongside the important aspects of social and economic feasibility.
The results
Confidence in MAR schemes across Australia
MAR schemes have been investigated in every sate and terriorty across Australia. For example, the City of Salisbury, South Australia now stores approximately 3.5 GL/y urban stormwater (around 20% of annual runoff) in confined limestone aquifers to provide 2.5 GL/y non-potable urban water supply.
A long-term research partnership with the City of Salisbury and other sectors of government and private industry has assisted the development of a sustainable alternative water supply which reduces stormwater discharge and pollutant loads to the marine environment, whilst ensuring flood protection.
This research at Salisbury has provided valuable insight into the use of alternative water sources, including the potential for urban stormwater use as drinking water supply, the reliability of urban stormwater supply under variable climate and of the potential for natural treatment of pathogens, nutrients and organic chemicals in the aquifer to reduce the need for engineered water quality treatment.
These investigations of pathogen risks in stormwater were the first to evaluate the safety of stormwater harvesting for three different levels of human exposure; public open space irrigation and third pipe non-potable supply (both current uses at Salisbury) and drinking water supply (not a current use in Salisbury). The required levels of treatment for harvested stormwater were calculated for various uses with different levels of human exposure. For example, aquifer treatment, if validated, may be used in conjunction with disinfection with UV and chlorination for drinking water supply.
This research develops the use of hybrid natural and traditonal engineered systems to minimise costs and maximise benefits of using alternative water sources.