28 May 2009
HELPING CATCHMENTS RECOVER FROM BUSHFIRE
A rigorous rehabilitation program is helping Melbourne's water supply catchments recover after the February bushfires.
Water quality to customers remains entirely unaffected by the bushfires, which impacted about 30% of Melbourne's catchments to some degree, including Maroondah and O'Shannassy.
The city's seven other reservoirs, including Thomson, Cardinia and Upper Yarra, hold the vast majority of water reserves and were not affected by bushfire.
A team of about 60 Melbourne Water staff is working with the Department of Sustainability and Environment and Parks Victoria to rehabilitate fire-affected catchments.
Manager of Water Supply, John Woodland, said the rehabilitation team had focused efforts on reducing potential for heavy rain to push bushfire debris into reservoirs by installing silt traps and repairing access roads.
"A severe bushfire followed by intense rain events is a worst case scenario for the catchments, but a combination of good planning and favourable weather has kick started the recovery," said Mr Woodland.
"More than 400 silt traps have been placed in the catchments to stop heavy rain pushing ash and sediment into reservoirs."
In Maroondah and O'Shannassy alone, teams have completed drainage works along 200 kilometres of access roads and cleaned 350 kilometres of culverts to reduce the potential for erosion on roads and reduce movement of ash and sediment.
Similar works have been completed in Tarago and the smaller catchments of Armstrong and Wallaby Creek. There will be no effect from bushfires on the reconnection of the Tarago Reservoir to Melbourne's water supply in the middle of this year.
Mr Woodland said assessments of affected catchments showed varying levels of fire damage and signs of recovery.
"There were high intensity burns in Wallaby Creek and parts of O'Shanassy and Armstrong, but in Maroondah and Tarago the burns were less intense," said Mr Woodland.
"We saw new growth in bushfire-affected catchments as early as two weeks after the fires and that has continued as we've received sporadic rain over the past three months."
Mr Woodland said Melbourne Water was also working to understand the affect of the fires on the long-term ability of the catchments to generate runoff into reservoirs.
"In the first few years after a fire, runoff into the reservoirs can actually increase because there is less demand from plants and trees. But as the trees start to regrow in earnest, runoff can fall.
"We're using our large network of rainfall and streamflow gauges, and years of research to monitor and assess the effects of regrowth on long-term water availability."
Recovery efforts in the catchments will be ongoing for up to two years.
Media Contact: Nicolas McGay (03) 9235 2278; 0438 981 836