UN book showcases ways to store water for a not-so-rainy day
There is an ever-increasing demand on the world’s traditional water resources. A growing population and climate variability means we to improve water security and resilience by preparing for a greater variability in water availability.
To help prepare for the future, United Nations Educational, Scientific and Cultural Organization (UNESCO) has published a new book that showcases 28 examples of an emerging solution in improving water security: managed aquifer recharge (MAR).
MAR is intentional groundwater replenishment. MAR uses aquifers to store water when it’s abundant, until it’s required for use or for environmental benefit. When MAR is coupled with water recycling, it can increase the productive use of urban stormwater and wastewater, which reduces the pressure on traditional water sources (surface water and groundwater).
Managed aquifer recharge in Australia
In the past 60 years, there has been considerable growth in MAR. The volume of water added to aquifers in MAR schemes is now approximately 10 billion cubic metres per year, globally. MAR uptake is still relatively small: MAR or groundwater replenishment is only around 2.4 per cent of groundwater extraction across the countries with MAR schemes.
In Australia, the amount of water intentionally recharged is approximately 410 million cubic metres per year. This represents 8.3 per cent of Australia’s yearly groundwater extraction. MAR schemes operate or have been investigated in each state and territory of Australia. They store available water from many sources, and this MAR water is often used for urban and agricultural water supply, or to sustain groundwater dependent ecosystems.
The number of MAR schemes in Australia is growing. The increase in volume of water added to aquifers through MAR in Australia (3.6 per cent per year) is slightly below the global average (4.9 per cent per year). There is potential for greater uptake of MAR in Australia, to harvest available surface water, urban stormwater, recycled water and groundwater for use, or to provide environmental benefit (sustaining rivers and groundwater dependent ecosystems, for example).
MAR can also help to replenish over-exploited groundwater systems, in conjunction with demand management. Another emerging application of MAR is its use in longer-term water banking for droughts.
Assisting successful expansion of MAR
There are several perceived barriers to the uptake of MAR. Uncertainty remains around: the technical feasibility of MAR in various hydrogeological settings; the compatibility with water resources management policies, and; MAR’s economic viability. CSIRO’s research has addressed these barriers, in turn.
1. Showcase exemplary MAR schemes around the world, and in Australia
Showcasing MAR schemes can help to address uncertainty around the technical feasibility of MAR. Two Australian MAR schemes are showcased in a book published by UNESCO (accessible through https://unesdoc.unesco.org/). The book “Managing Aquifer Recharge: A Showcase for Resilience and Sustainability” profiles 28 international examples of sustainable and economic MAR. The two Australian schemes featured are Salisbury’s stormwater MAR and Perth’s groundwater replenishment scheme.
Salisbury Water’s scheme is a multi-site urban stormwater MAR for suburban non-potable water supply. Over two decades, CSIRO research has supported Salisbury to operate and expand their scheme safely and sustainably.
We’ve researched where water moves in the aquifer, how stormwater and groundwater interact, the water quality of recovered water, and the suitability of the water for different end uses. The Salisbury scheme currently has nine stormwater harvesting wetlands, stores 3.0 million cubic metres of stormwater per year and provides 2.5 million cubic metres of non-potable urban and industrial water supply per year by over 150 km ‘purple pipe’.
Perth’s groundwater replenishment scheme uses recycled water to increase security of urban drinking water supplies. CSIRO played a key role in extensive trials to develop this novel application of MAR for drinking water supply in Australia.
We’ve researched many facets of the scheme, including the intensive characterisation of the recharged aquifers, fate of contaminants and groundwater modelling. Groundwater replenishment with recycled water has a current capacity of 14 million cubic metres per year that is being expanded to 28 million cubic meters per year. Future expansion is being investigated amongst a suite of options to meet Perth’s future water demand.
2. Use guidelines for health and environmental protection
Australia is currently the only nation to adopt guidelines for risk-based management of MAR that address water quality and quantity aspects, to ensure any MAR scheme provides adequate protection of human health and the environment.
The ‘Australian Guidelines for Water Recycling: Managed Aquifer Recharge’ can be applied to any source of water for recharge, aquifer, recharge method and end use of the stored water and addresses management of water quality and quantity. The guidelines are underpinned by pragmatic scientific understanding gained through decades of research and investigations, led by CSIRO, that occurred during the development of Australia’s MAR capacity.
The UNESCO book applied standardised approaches to economic and sustainability assessment, which means these tools could be applied to vastly different MAR schemes, regardless of the scheme type, the water source or the hydrogeological setting.
Both Salisbury’s stormwater MAR and Perth’s groundwater replenishment scheme were found to perform well in the global assessment of sustainability. This was largely because they adopted the unique Australian MAR Guidelines approach.
3. Dollars and cents: Assessing the costs and benefits of MAR operations
CSIRO has previously assessed the benefits and costs of a number of Australian MAR projects to understand the relative economic benefits and their costs relative to alternative solutions. The two Australian projects independently assessed in the UNESCO book had benefit-cost ratios of 2.5 and 1.5 for Salisbury and Perth.
The levelised cost, which is the present value cost per cubic metre, derived by assessing costs over the life of the project, was found to be significantly lower than the marginal cost of water from alternative sources.
The future of managed aquifer recharge
Case studies demonstrate a large variety of ways to harness conventional and alternative water sources using MAR to develop resilient supplies for both potable and non-potable uses.
Investigations and collaboration between private industry, government and research organisations were integral to development of the Perth and Salisbury schemes.
Over the past 20 years, research partnerships have addressed multiple facets of MAR scheme development in Australia. For example, targeted investigations have addressed:
- Aquifer characterisation and migration and fate of the recharged water
- The extent of mixing and its impact on recovery efficiency;
- Source water quality and reliability
- Biogeochemical processes and their impact on water quality including natural treatment of pathogens, organic chemicals and nutrients and the potential for mobilisation of geogenic species (e.g. arsenic) from the aquifer
- Aquifer microbial ecology and thermal impacts of MAR operations
- Operational trigger values for use in risk-management
- Management to prevent and remediate clogging of recharge wells and basins
- Potential for biofilm and sediment formation in pipe material receiving stormwater
- Methods for mapping aquifer suitability for MAR
- Economics of MAR, including water banking
We will continue to meet the demand for innovation in methods to investigate and apply MAR to improve water security for towns and agricultural industries around Australia.
This work is connected to CSIRO’s broader work in drought resilience. With the aim of improving regional water security, CSIRO’s Drought Resilience Mission is developing projects to demonstrate MAR technologies in drought-affected communities.
“Managing Aquifer Recharge: A Showcase for Resilience and Sustainability” is published by UNESCO, and can be found here. The book was jointly initiated UNESCO, the International Association of Hydrogeologists Commission on Managing Aquifer Recharge (IAH-MAR) and Groundwater Solutions Initiative for Policy and Practice (GRIPP).
You can also watch the World Water Day Webinar on Managed Aquifer Recharge here.