Heavy rain fails to refill dams

The parched earth around Perth's dams has sucked up most of the rain this year, leaving the city's reservoirs almost no better off despite record downpours in recent weeks.

The Water Corporation moved yesterday to dispel any notion a wet end to winter and start to spring had replenished dams, saying they were just 34 per cent full as of last Thursday.

Storage levels were almost identical to reserves held at the same time last year and included the significant desalinated and groundwater supplies stored in the reservoirs.

Ben Jarvis, the corporation's water efficiency manager, said 28 billion litres had flowed into the dams this year compared with the long-term annual average of more than 100 billion litres.

In contrast, Perth and other towns connected to the South West water grid used about 300 billion litres of drinking water a year.

Mr Jarvis said run-off had been subdued because dam catchments were historically dry at the start of winter from years of dwindling rainfall. He said there had been an unprecedented 10m fall in groundwater levels under the Perth Hills since the 1970s.

Although dismissing any suggestion households would become complacent in light of the rain, he urged people to leave their sprinklers off while the wet weather continued.

"We've really caught up with the rain of late but it still hasn't put us in an amazing position," Mr Jarvis said.

"Our catchments are just so much drier than they used to be because of decades and decades of below average rainfall.

"It's like a sponge. When we started this year it was a sponge that was completely empty and if you pour water in it's going to take a while before water starts coming out again, whereas in previous years that sponge was already full so water going in meant water coming out."

The Weather Bureau said Perth had had its wettest start to September in 16 years.

But this year Perth had received 684.6mm of rain until 9am yesterday, still well short of the long-term annual average of 848.3mm.