Winter rain figures tumble

Rainfall in the South West of WA has dropped drastically below average to its lowest levels on record in recent decades.

The Commonwealth Scientific and Industrial Research Organisation State of the Climate 2014 report, released this month, found a 17 per cent decline in average winter rainfall in the South West of Australia since 1970.

The report said while a declining trend in winter rainfall persisted in south west Australia, extreme fire weather had increased and the fire season had lengthened across big parts of the country.

According to the report, declining rainfall in the South West has come in a series of changes.

“The decline in this region has also been characterised by a lack of very wet winters, ” the report said.

Busselton-Dunsborough Environment Centre convener Alison Cassanet said while rainfall decline was a broad subject, apparent damage and decline to some tree species and vegetation could be among the impacts on the region.

“We’ve had calls this summer from people inquiring about declines in the eucalyptus rudis or red gums, some hybertia hypercoides or yellow buttercups appear to be dying and there appeared to be damage to peppermint trees from the Cape to the forests, ” Ms Cassanet said. “Things are changing and it is possible these changes could be associated with declining rainfall levels.”

Murdoch University professor of environmental science Tom Lyons said the biggest indicator of rainfall decline was in significantly reduced flow into dams.

“It is due both to large-scale changes in the climate system and land use changes like wide scale clearing for agriculture, ” he said.

Department of Water figures showed the 2013 rainfall of 873mm was above the 745mm average for the Busselton catchment area.

“This produced more than double the flow in the Carbunup River in 2013 at 41,240 million litres compared to the flow in 2012 which was 17,720 million litres, ” department spokesman Peter Collins said.

The average annual flow for the Carbunup River is 31,000 million litres but in 2010 the river recorded its lowest annual flow on record with 10,670 million litres.