How drought-proof Perth beat big dry

As sisters Ruby and Asha Casey played joyfully in the lush surrounds of their grandparents' Bicton home this week, weather experts were reaching for the record books.

Not since official monitoring began in Perth in 1876 had the period between November 1 and February 28 featured fewer than five days of rain.

Yet last night, when an inevitably long, hot summer drew to a close, a record first set in 1902-03 and matched in 1997-98 and 2010-11 was broken.

For the first time in Perth's history, there had been just three days of measurable rain. Just 2mm of rain fell over summer. The average is 35.6mm.

Such a scenario a decade ago, when the harshest of water restrictions would have been one of few options available to WA's water bosses, might have brought an end to little Asha and Ruby's days of summer fun under the sprinklers.

But in drought-proof Perth, where desalination plants have become the cornerstone of the city's water supplies and replaced all but redundant dams, it is no longer panic stations.

Sue Murphy, chief executive of the Water Corporation and the person charged with keeping the taps running, knows only too well how lucky she's got it.

"If we go back a few decades, the job of the chief executive officer of the Water Corporation was to pray for rain because that is where our water came from," she said.

"By the time I was appointed CEO in 2008, the corporation had worked hard towards climate resilience such that only one-third of our water was coming from our dams - so only one-third of my job was to pray for rain.

"Our strategy now and for the future means that in coming years, my job description will no longer have a clause in it involving prayer - our community will have security of water supply whether it rains in a particular year or not."

So just how was Perth drought-proofed?

For the answers, it is necessary to go back to 2002 when Perth endured its driest year on record and doubts were fast emerging about the reliability of the city's dams, which had until the 1970s met the city's entire drinking water needs.

As former Water Corp boss Jim Gill once noted, then premier Geoff Gallop faced an impending water crisis and "against huge scepticism" signed off on one of the world's biggest desalination plants.

The decision to build the Kwinana desalination plant would prove to be a defining moment for WA, paving the way for an even bigger, two-staged plant at Binningup.

"It saved Perth from several years of total summer bans," Dr Gill wrote in 2011.

Together, the two desalination plants have the capacity to produce 145 billion litres of drinking water a year and meet half the demand from the Integrated Water Supply Scheme - the network that takes water to 1.9 million people between Perth and the Goldfields.

Despite the rise of desalination, the Water Corp said other developments had played a crucial role in keeping the taps running.

First among them were moves to bring in restrictions under which sprinkler rosters and winter sprinkler bans became permanent - and widely accepted.

The State-owned utility said these and other savings measures reduced the amount of scheme water used every year by 100 billion litres.

Then there is WA's albeit slower embrace of recycled wastewater - a policy that reached a milestone last year when the Barnett Government gave the go-ahead for a fully fledged project to inject treated effluent into Perth's aquifers before drawing it later.

Although the initial stage will boost supplies by only seven billion litres a year, there are plans for it to eventually provide up to 20 per cent of Perth's water needs.

Rob Hammond, a former deputy director-general of the Water Department, said Perth had "done pretty bloody well" at safeguarding its drinking supplies by planning for the effects of a drier climate.

If it were not for the measures put in place, Mr Hammond said, Perth would have been hit with crippling water restrictions and its aquifers would have been depleted to plug the supply shortfall.

However, he said it still relied too heavily on its aquifers, particularly the stressed Gnangara groundwater system.

Groundwater accounts for about half of Perth's drinking water needs and Mr Hammond said the environmental consequences would be far-reaching unless the pressure was eased.

Department of Water director-general Maree De Lacey acknowledged that managing overall demand for Perth's groundwater, which included industry and backyard bore use, was one of the agency's "biggest challenges".

She said continued improvements in the way the water was used, as well as initiatives such as aquifer recharge, were helping it address the situation.

The West Australian

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