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Big dry hits wetlands hard
Parched: Robert and Kathy Macleod at lake Nowerup. Picture: Sharon Smith/The West Australian

Lakes and wetlands in Perth's northern suburbs are drying out at an alarming rate, according to the worst ever results returned in an audit of monitoring wells on the Gnangara mound.

As the Weather Bureau noted Perth had not had meaningful rain for 85 days, the Department of Water released a report laying bare the extent to which the city's groundwater levels have plummeted.

The department said 17 out of 30 of its monitoring bores on the Gnangara mound - one of Perth's most important drinking water sources - were unacceptably low.

Water levels in the Jandakot mound in Perth's south were generally higher, although almost a quarter of wells were also "non-compliant".

Taken from the 2012-13 financial year, the results were the worst since regular audits began and came during a time in which Perth had less than two-thirds of its average rainfall.

The department attributed the decline to a drying climate, "unsustainable" water use and pine plantations which sucked up billions of litres.

"The department's primary approach to non-compliance is to manage abstraction more stringently in environmentally sensitive areas," the report said.

Rob Hammond, a former deputy director-general of the department, said the Gnangara mound was "buggered" in many places from years of over- pumping and dwindling rainfall.

He said Perth had relied heavily on the aquifer for too long and the drying climate now meant it would be almost impossible to avoid permanent damage to it.

"I'm concerned it's a one-way street unless something dramatic changes," Mr Hammond said.

Edith Cowan University ecology professor Pierre Horwitz, who has been heavily involved in monitoring the Gnangara mound for the department, was more optimistic.

Professor Horwitz said 2012-13 was a low point and he expected results from this year, after a wet end to last year, would show an improvement.

He said many parts of the Gnangara had not suffered "irreversible" decline and could bounce back, although this relied on government action and wetter weather to a big degree.

Kathy Macleod, who has lived next to Lake Nowergup in Perth's north for more than 20 years, said she had seen it "dry out before my eyes" to the extent that wildlife was no longer returning.

She questioned what authorities were doing to protect the mound and its lakes, saying there appeared to be ever- increasing amounts of water being pumped for industry.