Perth’s sprinkler rules responding to climate change

Perth’s sprinkler rules responding to climate change

Perth is about to encounter its first “significant and important response to climate change.” It achieves this by changing the use of drinkable water in suburban gardens. From Thursday, 1 September, the end of the winter sprinkler ban, garden bore owners will lose their third day of watering. They will have to align with the two-days-per-week sprinkler roster for scheme water users in Perth and Mandurah.

This will save up to 30 billion litres per year of water. It is one of the three major pillars of a water use reduction strategy eight years in the making. This new element is aimed at arresting a steep decline in the aquifer now supplying 40 per cent of Perth’s drinking water.

There are 120,000-180,000 Perth and Mandurah households using bores. They pump about 22 per cent of all the groundwater taken annually, about 90 billion litres, according to government estimates.

No infringements will be issued for the first 12 months, focusing on education to help people adapt.

“It’s the first time we’ve seen a significant and important response to climate change,” Department of Water and Environment Regulation director-general Michelle Andrews said.

She was one of a group of senior government water experts appearing before a budget estimates hearing on Wednesday. They said with climate change driving a 15-20 per cent drop in rainfall for Perth over the past 100 years, rainwater runoff captured in dams could now supply only about 10 per cent of Perth’s needs. The remainder of Perth’s water needs would come from two desalination plants and groundwater.

Sprinklers use more water than people realise

The water people saw in dams, they said, was mostly desalinated water piped in for storage.

The most important groundwater source is the Gnangara Mound, a system of underground aquifers beneath Perth’s northern suburbs that contain about 20 trillion litres of water. It has lost 1 trillion since 1979, with a more rapid decline from 2000.

The 30 wetlands and lakes reliant on it have also suffered from declining water levels. There have also been flow-on effects on plant and animal species.

The new Gnangara groundwater management plan was released in June and took tangible effect on households on September 1. It aims to arrest the decline in water levels and environmental health. About 275 billion litres annually go to greater Perth’s agricultural, commercial and residential uses.

New plan will save water

The new plan means a 54-billion-litre reduction in annual water use by 2028. Perth and Mandurah garden bore users, reducing their sprinkler days to two will save up to 30 gigalitres a year.

The Water Corporation itself will have to reduce the water used for its public supply system by 27 per cent by 2028, and licensed water users who take water directly – for example, agricultural users – will have to reduce their take by 10 per cent by 2028.

The plan will marginally improve the situation for a few lakes and wetlands. Further decline is expected, and the focus is on minimising this.

It is expected a new desalination plant will come online by 2028. It will be energy-hungry and expensive, and the population will be growing all the while.

Department science and planning executive director Jason Moynihan said there had been an 80 per cent reduction in dam runoff.

Wetlands disappearing, sprinkler use must be eased

“Over the past 200 years, we’ve probably seen around 80 per cent of wetlands lost across the Swan Coastal Plain,” he said.

“We must balance the industry’s interests in arriving at some of these allocations, together with the environment and other general water users. It’s something of a balancing act.”

He said government support measures included Waterwise initiatives for homes and support for farmers. There has also been an expansion of a current $600,000 water efficiency project from North Wanneroo into other areas. A $4 million package has helped local governments use less water in their green spaces. There was also funding to expand the Water Corporation’s sprinkler roster compliance monitoring.

He said there were few other options other than significant investments in desalination. It raised difficult questions regarding who bore the costs, given the high needs of industry and agriculture.

“It will be up to the likes of you and I as water users to try to find improved water efficiency measures,” he said.

“The only thing we’re very confident about is that there’s going to be reduced rain falling in coming years and less water available.”

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