Removing salvinia from the Hawkesbury

In mid-2004 some 347 hectares of salvinia was choking the Hawkesbury and lower Nepean, stretching 88 kilometres along the rivers and their tributaries.

This was estimated to be the largest ever salvinia outbreak in temperate Australia.

The infestation of this noxious South American aquatic weed was so massive it was impossible to get a boat onto parts of the lower reaches of the rivers - an area which brings in around $100 million annually to the regional economy.

A result of the drought and resulting high nutrient levels, the salvinia outbreak disrupted the recreation industry, affecting local tour boat, water ski and caravan park businesses. Service industries and the commercial fishing industry were also hit.

Funding

A rescue effort was clearly needed.

This came in the form of a partnership between the Hawkesbury Nepean Catchment Management Authority (CMA), the Australian and State Governments, local government bodies and the community.

The Australian and New South Wales Governments contributed over $1.75 million to clean up the rivers in 2004 and 2005. Further funding of $335,000 from the Australian Government has been dedicated to a three-year program designed to improve weed control.

Activities and achievements

During 2004 and 2005 around 100,000 tonnes of salvinia were removed from the river by mechanical harvesters.

This harvest was eventually put to productive use, with a company contracted to compost the destructive weed for mulching eroded lands in the upper catchment.

Hawkesbury Nepean CMA Catchment Coordinator, Bill Dixon, said that harvesting was expensive and the region needed an ongoing program to prevent future threats to the rivers.

This includes continuing to attract various forms of funding, exploring weed control options and researching the land-based sources of weed infestation.

"We have a major project underway with the NSW Department of Primary Industries in which we're investigating biological control of salvinia at 18 sites," Bill said.

"We want to avoid herbicides if we can, and using the salvinia weevil as a control is looking quite promising.

"We're also working with the community further up the catchment to investigate 'infection' points, or weed sources located away from the river, in places like farm dams.

"This is partly an educational exercise, which aims to show that everyone can play a role in preventing weed outbreaks on our rivers."

More information

• Bill Dixon, Hawkesbury Nepean CMA Catchment Coordinator: (02) 4587 0053 or bill.dixon@cma.nsw.gov.au

Australian Government NRM Team
GPO Box 787
Canberra ACT 2601 Australia
1800 552 008 (toll-free)

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Caring for our Country is an Australian Government initiative jointly administered by the Australian Government departments of Agriculture, Fisheries and Forestry and the Environment, Water, Heritage and the Arts