A lot of Perth’s drinking water supply comes from the Gnangara groundwater mound. Rainfall across Australia has been decreasing in the last few years and Western Australia is no exception. In some places in the eastern states of Australian, you’re not allowed to water your garden (unless you have your own rainwater tank), while in Perth we only have our water use restricted to two days per week when each household is allowed to turn on reticulation. The Gnangara Mound also supplies irrigation for horticulture, agriculture and parks and private garden bores in and around Perth.
local wetlands were drying out, soil was acidifying and some species had died as Gnangara’s water levels continued to drop.
The WA Water Resources Minister John Kobelke said
planning for the Gnangara Mound was flawed because it was based on rainfall predictions that never eventuated. What we have really… is that climate change has impacted and impacted quite severely on the south-west of WA
Western Australia’s state government is currently trying to find solutions to decreasing water availability. Professor Jorg Imberger from the Centre for Water Research at the University of Western Australia said on an ABC radio program
the Yarragadee aquifer is the best source for the state’s next new water supply.
Minister Kobelke believes that extraction from the Yarragadee aquifer will be planned around lower rainfall and so the problems occurring with the Gnangara Mound will not occur with the Yarragadee. The government is investigating a number of options, including:
recharging the aquifer with treated wastewater and burning off natural bushland to cut water intake. [Clearing] the large government pine plantations that cover parts of the mound…The plantation timber is worth millions of dollars.
The Yarragadee Community Action Site discusses the possible effects of drawing water from the Yarragadee aquifer, including:
changes in the level of biodiversity in Scott River Plains, which includes Scott National Park, and the future of the Honey Possum in that region.
The swamps on the Scott River Plains may be sensitive to even a slight change in groundwater levels, which could occur if water is extracted from the Yarragadee aquifer.
Another solution put forward to increase available water in Perth is
A desalination plant in Cockburn Sound just south of Fremantle.
Desalination is not a solution because it’s unsustainable and could have devastating environmental impacts on Cockburn Sound.
Professor Imberger also said,
My first preference has always been for demand management and recycling of water.
This is the most sensible option. We use way too much water, not just on our public and private lawns, but everywhere. I use some water saving methods in my house eg. a dual flush toilet, reusing grey water from my washing machine on my garden and a water-efficient showerhead, but there is still so much more I could do. There’s a lot of recycling of water that can be done in buildings, but it’s more difficult if it isn’t built into the design. Flushing a toilet doesn’t need drinking-quality water, but that’s what occurs unless it’s designed otherwise.
But household use of water is a small part of overall water use. There are many more wasteful commercial uses of water. Mundaring Weir, east of Perth, collects rainwater. Perth uses some of this for drinking water but it’s also pumped 600km to Kalgoorlie, where it’s used in gold processing. I don’t know much about this, but Michael often tells me what a waste of water it is. Building sites reduce wind-blown dust by spraying the site with water. Public parks and ovals have pristine lawn, even in the middle of summer. The second could easily be done using recycled water. The latter uses ground water, but this still adds to the decrease in the Gnangara Mound.
We all need to decrease our water use and ensure new buildings are designed to recycle water and also collect rainwater for use within the building and surrounds.