One idea that’s cropped up occasionally recently is water banking. The basic idea is that you take water in flood years and set it aside for use in drought years. Simple enough, and a compelling concept given the increased variability and boom-bust-ness of our rainfall as the climate changes. What makes it a very interesting idea for Australia is that the logical place to bank it is not surface dams, which is historically what we’ve relied on, but underground. We have huge evaporation rates – enough to empty a swimming pool in a year even in misty Melbourne – which makes it harder to store large quantities of water long term on the surface. However, underground, there’s no evaporation. Australia has a lot of aquifers with a high carrying capacity, including directly under several of our major cities. This means we could potentially “bank” a very large amount of water, drought-proofing both key agricultural areas and large segments of the Australian population. The people who’ve been talking about this are from the National Centre for Groundwater Research and Training, the director of which, Professor Craig Simmons, is a finalist for this year’s Eureka Prize in Science Leadership. Water banking is one of their various irons in the research fire.
Water banking isn’t vapour-tech – it’s already well used in California, and is in use in parts of Queensland. It’s well enough understood to be implemented here, though there’s room to increase our understanding and develop internationally-saleable expertise. What makes underground water banking complicated is mostly the social and economic aspects. Currently our water laws don’t generally allow people to retain rights over water once they’ve put it in the ground, so setting up a “banking” system would mean setting up a mechanism for allowable “withdrawals”. That would have to allow for both normal irrigation access in an ordinarily dry season, and increased water access during drought. There’s also the question of how to integrate water banking with our existing entitlements arrangements, and the question of whether farmers and others with water entitlements would accept the process. A recent survey by the NCGRT talked to farmers in the Namoi region, which withdraws the largest total amount of water from the Murray-Darling Basin. Two thirds of farmers surveyed were positive about the concept, and even dead keen. The remaining third were mostly cautious about possible environmental effects and whether we understand those well enough. And that’s a fair call – it’s predicted that environmental effects will be usually positive if systems are put in and managed correctly, but each local system would have to be looked at and researched on its own merits. The need for each local system’s needs and effects to be considered is what would help develop Australia’s water banking expertise and useful technology, which the NCGRT sees as potential export material. So even that caution is potentially a positive thing.
Groundwater recharge is already being trialled and/or used in some of our cities – notably Perth and Adelaide. But in these cases the recharge is from urban wastewater, either stormwater runoff from roads and roofs that’s had some minimal treatment, or used-and-recycled grey/blackwater that’s been cleaned up to drinking-water-standard. Capturing floodwaters in agricultural areas is something that is just starting to enter the conversation as a serious possibility, a way of mitigating our boom-and-bust water cycle and evening out foodbowl expectations.
More information
The article abstract from the Australasian Journal of Environmental Management journal article on the farmer survey and overview of water banking issues
The National Centre for Groundwater Research and Training’s main website. The National Centre for Groundwater Research and Training is an Australian Government initiative, supported by the Australian Research Council and the National Water Commission.
AgriTapestry 