La Niña won’t last forever, even if it feels like it right now.
So even as Sydney’s Warragamba Dam overflows, with communities across the state on flood watch or being evacuated, we need to focus our minds on the future of the city’s drinking water.
In a worst-case scenario, we can go from full dam to draining our drinking water supplies within four or five years. That’s what happened in the drought of 2017 to 2020, highlighting the frailty of our existing rainfall-dependent drinking water supply infrastructure. And that’s without Sydney growing— we can expect more than 1 million extra people by 2036 and a growing economy supporting more jobs and businesses.
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I’ll put it even more plainly, Sydney depends on rain for its water, and that’s a precarious thing to depend on for something so essential to life. Water is not just important for healthy communities, it’s also needed for healthy rivers and ecosystems, to help cool our sweltering city, and to give businesses the confidence to keep investing here.
But it’s not just a lack of rain that can affect water supplies – floods mean water needs more treatment to remove leaves, soil and other particulates carried down from the catchment. Bushfires bring ash, which causes a similar challenge.
As La Niña fades, the phrase you will likely hear more of in resilience discussions is “climate independent water supply”. That is, how can we increase the diversity of water supply sources, and reduce the dependence of Sydney’s water supply on rainfall.
In Singapore, drinking water security is seen as a top priority across government and the community. First, the city state ensures every drop of rainfall that lands on Singapore – a city with the same number of people as Sydney but on a land area 17 times smaller – is collected and used. Second, all wastewater and runoff is collected, recycled and combined with rainwater, desalinated water, and water from Malaysia, before being piped to residents. The Marina Barrage project that many Sydneysiders may have seen or even visited, was founded in part as a water supply project, creating a large freshwater dam where the city foreshore used to be.
Sydney does have an existing desalination plant. But servicing the vast sprawl of our city by piping water east to west would incur huge additional infrastructure costs. And we’re already sending huge volumes of wastewater the other way to be disposed of in the ocean. Put two and two together, and we have an opportunity to make better use of all that wastewater.
Unlike Singapore, we capture very little of the water that falls in Sydney itself (just 7 per cent), with most of it bouncing off hard surfaces and rushing into the nearest drain.
Slowing that water would help our drainage infrastructure cope, provide more opportunity to use water for urban cooling, and even solve some of the major park and vegetation watering that needs to be done to encourage our city to become greener. Stormwater harvesting does occur across Sydney, enabling local governments to reduce the amount of drinking water they use to keep street trees, parks and sports fields in good condition.
As Sydney grows, the demands on our primary source of drinking water, Warragamba, will also grow. Whatever happens with the dam, we urgently need to diversify the city’s water supply.
The recently released Greater Sydney Water Strategy sets out the case for purified recycled drinking water to become part of a more resilient drinking water supply for Sydney, along with reducing household demand and ramping up the existing desalination plant. But desalination uses triple the energy of recycled water, and that matters on our city’s journey to net zero.
Purified recycled water is now a core component of drinking water supplies in over 35 cities around the world, including Perth, San Francisco and Singapore. Cape Town, South Africa – a city that came within 90 days of running out of water in 2018 – is another city that has adopted purified recycled water as part of its strategy to create climate independent water supply.
But let’s be clear, any wastewater that is destined for our taps, can only do so through the most rigorous process. The process for purified recycled drinking water requires wastewater to be purified to a standard equal to or higher than that of normal drinking water. And it is also often mixed with another water source – in a river, dam, reservoir or aquifer – before being treated again to our normal drinking water standard. And research has shown that the more communities are able to engage with this technology, to understand how it works and sample the results, the quicker acceptance can grow.
Sydney Water has started construction on a new purified recycled water demonstration plant and visitor centre at Quakers Hill. The water will not be added to Sydney drinking supply just yet, rather used as a testing facility as well as an opportunity to engage the public about purified recycled water and the role it can play in Sydney’s future water security. Global experience shows building this structure, and using it to enable the community to see, touch and taste, is the most important first step. Sydney is home to diverse cultural communities, with people from more than 180 different countries in just the one local government area of Blacktown.
The next drought is a matter of when, not if. If an El Nino started tomorrow, we would not have time to build the additional infrastructure required quickly enough to bail us out. Purified recycled water could provide a quarter of Sydney’s drinking water supply by 2056, improving our climate-independent water supply.
The question is, are we going to act on that knowledge, and get on with the business of securing our drinking water supply, or wait until the dams dry up again? The choice is ours.