Climate change measured in the Murray Hotham catchment
Released 25 Mar 2009
Results from the study suggest that a reduction in rainfall since 1975 has been accompanied by an even larger reduction in streamflow – meaning less water into dams.
The results of the Department of Water study were presented this week by the Bureau of Meteorology at the Greenhouse Climate Change and Resources 2009 conference at Burswood Convention Centre.
This reduction flow is a nationwide trend and the study is helping scientists and water resource managers better understand how to reduce the impact on total available water resources.
Projected climate change is expected to have major consequences for available water resources and the results from this study have provided valuable information to the strategic water management capabilities of the Department of Water.
According to the department's water resource management director John Ruprecht, the dramatic reduction demonstrates the extreme sensitivity of streamflow to changes in rainfall, soil storage deficits, and the threshold of rainfall runoff production.
"Part of this study was to investigate how projected changes in climate characteristics may influence catchment processes – particularly how they relate to streamflow and salinity," Mr Ruprecht said.
"For the period 2035-2064 rainfall is projected to decrease by around 13 per cent with a corresponding 49 per cent decrease in streamflow.
"Rainfall and streamflow data were compared before and after 1975 – when step changes were observed in the south-west of Western Australia.
"A 10 to 17 per cent reduction in mean annual rainfall was observed in the southwest, with fewer wet years after 1975.
"The step change was accompanied by a seasonal shift in rainfall, with a large decrease in autumn and early winter rains, and a much smaller increase in spring and summer rains.
"The reduction in rainfall caused a much larger reduction in annual streamflow – from 42 to 70 per cent at two gauging stations."
The study was jointly funded by the State and Australian Governments through the South West Catchments Council.
Contact: Peter Collins
Phone: (08) 6364 6848 / 0434 603 441