A new water strategy for the Sydney basin says the New South Wales government needs to look urgently at investing in alternative sources of water, including more desalination plants and large-scale recycling of wastewater.
But the state’s minister for water, Kevin Anderson, skirted around the most contentious part of the report: the consideration of large-scale recycling into the drinking-water system.
Anderson instead emphasised the less contentious option of using recycled water for watering gardens and for “greening and cooling”.
The new report from the NSW Department of Planning and the Environment said if Sydney takes this approach, its rollout would be limited to new housing developments because it requires a second set of pipes.
According to the report, 93% of water in Sydney is currently used once and is then put out to sea with only partial treatment.
The report called for the government to build a demonstration plant to show the public how large-scale recycling technology works and to initially use the water for greening and cooling projects, such as waterways and environmental flows.
But it said the government needed to consider purified recycled water projects for drinking, as many other cities now do.
“Compared to other Australian cities, Sydney has a low level of rainfall-independent water supply, making our city vulnerable to rapid onset and prolonged drought,” the report said.
It said while a “very substantial” network of dams existed, “meeting the demand for water from a growing population means that we can’t rely solely on these dams and the Sydney desalination plant to meet all our future water needs.”
“Our forecast sustainable supply level is between 515 and 540GL per year – and modelling suggests this may be about 40 to 70 GL a year less than we need under a mid-case demand forecast in the short-term”, the report said.
“While this does not create an immediate risk for greater Sydney because dams are currently full and we have time to plan and act, we need to progress a range of responses in the short term to support growth and enhance resilience.”
The strategy said 49GL a year can be obtained through water conservation projects at relatively low cost. A further 20GL could be achieved by changing the approach to operation of the Sydney desalination plant to enable flexible and continuous operation.
But it says planning and investing for new sources of water will be needed in the next 5-10 years, and again in 2040 and 2060, and that there should be “a range of rainfall-independent supply options such as desalination and purified recycled water”.
More dams have been ruled out as an option, because the climate crisis will mean that the halving of inflows into the catchments experienced in the last drought is likely to be repeated in the future.
The strategy suggests more desalination plants is one option, which could deliver between 70-250GL a year depending on the number and size.
But the report also flags the twin problem of dealing with ageing wastewater and stormwater systems and the need to restore environmental flows.
“Despite the success of major recycled water schemes in some suburbs such as Rouse Hill, only about 7% of wastewater in Greater Sydney is recycled,” the report said.
A demonstration plant would highlight the safety of recycled water as a proven technology, as well as its range of beneficial uses, the report said.
“Purified recycled water involves releasing highly purified wastewater into an ‘environmental buffer’, such as a river or underground aquifer, before re-extracting and treating the water for drinking.”
On other contentious water projects, such as raising the wall of Warragamba dam, the strategy said that it would not increase water supply.
It warned that an alternative plan to store less water in Warragamba dam and use the extra capacity as a flood buffer would result in a less resilient water supply for Sydney.
