UP TO eight Sydney Harbours' worth water could be stored in the Murray-Darling Basin's underground aquifers, new CSIRO research has revealed.
Managed aquifer recharging - also know as underground water banking - is being investigated as a drought mitigation strategy, given it is vastly less expensive than building a dam and prevents evaporation or algae blooms.
The study identified potential water banks in the regions around the Warrego River, Condamine-Culgoa Rivers, Darling River, Macquarie-Bogan Rivers and Namoi River.
Each has the potential to store more than 200 gigalitres each, or the equivalent up to 16 per cent of the basin's above ground storage.
Study co-author Declan Page said the recent announcement of a La Nina weather pattern - indicating a higher likelihood of rainfall - was a timely reminder to regional communities they had an opportunity to secure more water before the next drought.
"Often people look at drought measures once we're already in drought - by then it's too late and there aren't many options," Dr Page.
"For now, we've got a bit of breathing room to make decisions.
"Recharging aquifers at times of higher rainfall, storing the water, and discharging them during droughts is a cost-effective way to manage regional water security."
Although the CSIRO has developed the science behind the concept, it's up to governments, communities and industries to make it a reality.
"It needs community support and a local champion of sorts to shepherd the concept through the various levels of government," Dr Page said.
So far there has been a "fair bit of interest", and the CSIRO has started conversations with local governments in NSW, including Dubbo, Orange, Parkes and Moree.
"It could even been industry, such as an irrigation company that has seen its water allocations decline and might want to invest in its own water bank," Dr Page said.
The CSIRO study investigated the economic case for water banking in the Dubbo region, and proposed a solution where water was purchased from the water market at lower rates when it was plentiful.
The water is then stored underground - where it does not evaporate - until needed, such as in a drought when water prices increase.
"This method of buying low and selling high is a way to fund the sustainable long-term operations of water banking schemes to enhance water security," Dr Page said.
"Dams and more recently water desalination are often seen to be the main option for increasing water security.
"However, in areas where the topography, climate or environmental impacts don't make dams suitable, or towns are too far away from the ocean for desalination, water banking can be a cost-effective opportunity for regional towns.
"Water banking allows communities and their industries to potentially limit the economic impacts of a drought, operating at far less restrictive levels, for far longer."
There are a number of methods to get the water into the aquifer, which vary depending on how deep it is. The cheapest way is to use a big holding pond above a shallow sandy aquifer and let it naturally soak in.
For the deeper limestone aquifers, the water has to be injected under pressure through a well or pump.
Retrieval is as simple as pumping it back out through a bore.
The CSIRO is interested in working with any communities and industries interested in progressing the idea of an underground water bank.
The story Basin underground aquifers could bank eight Sydney Harbours: CSIRO first appeared on Farm Online.