Keeping Sydney’s drinking water flowing during times of drought, fire and floods

Sydney is no stranger to droughts, floods and bushfires. Not only do they potentially lead to loss of life, damage homes and take a toll on communities, they also often impact drinking water supplies from the city’s storage dams.

So, what role has Sydney Desalination Plant played to ensure Sydney’s water supply remains uninterrupted during recent extreme weather events?

DROUGHT

It was the Millennium drought that provided the NSW Government with the impetus to build the Plant in 2007 so it could produce an average of 250 megalitres (ML) of drinking water every day – enough to fill more than 100 Olympic-sized swimming pools and meet up to 15% of Sydney’s drinking water needs.

At the time, Sydney and most of eastern and southern Australia were in the grip of the worst drought in a century. Drinking water supplies were under pressure as Sydney’s combined dam storage levels plunged to below 34 per cent.

After three years of construction, the Sydney Desalination Plant was switched on in 2010 and the city’s first desalinated drinking water supply began flowing.

The Plant operated at about full capacity producing on average about 250 ML a day until June 2012 through a plant proving period. It was then switched off and “mothballed”, as per the Sydney Desalination Plant’s original operating rules that stated it was only to be used during times of drought.

Seven years later the Plant needed to be switched back on because Sydney was in the grip of another drought. About 75,000ML of desalinated drinking water was produced up until the arrival of heavy rain in early 2020 that broke the drought and refilled dams.

FLOODS AND FIRES

But while the drought was effectively over in early 2020, the Plant, which is Sydney’s only non-rainfall dependent source of drinking water, was required to continue operating.

This was because the heavy rains that had replenished the dams had also caused flash flooding and as a result, debris such as sediment and ash left over from extreme bushfires during the summer of 2019/2020 washed into dams, including Warragamba Dam putting pressure on dam water quality.

The water quality challenges became such a material issue that Water NSW stopped using Warragamba Dam as a water source for four days in February 2020 because of the ash, sediment runoff and other debris floating on the water surface.

During that time, Sydney relied on sourcing water from its emergency supply, Prospect Reservoir and the Sydney Desalination Plant for the continued delivery of safe and clean drinking water.

CONTINUOUS OPERATION

Once the effects of the floods and fire had subsided, the Sydney Desalination Plant was requested by Sydney Water to continue to operate at various production levels based on the needs of drinking water network.

The NSW Government published the Greater Sydney Water Strategy in August 2022 that highlighted the drinking water capacity gap between what Sydney has and needs in the future.

A key recommendation of the Strategy was to utilise the assets that we already have, thus the Sydney Desalination Plant’s operating rules were officially changed in mid-2023 for continuous operation in recognition of the enhanced role it can play during extreme weather events, times of emergencies and when maintenance works are carried out on the broader water supply network.

This means the Sydney Desalination Plant no longer operates only during times of drought, but on a flexible continuous full-time basis assisting Sydney Water in delivering a resilience drinking water system for the people of Sydney.

With the prospect of more droughts, lower-than-average rainfall in the future and increased frequency of extreme weather events, the Sydney Desalination Plant can be trusted to deliver a reliable supply of high-quality drinking water every single day.