Posted on January, 17 2002

Sydney, Australia - Cold water released from large dams is a major threat to Australia�s rivers, and Federal and State Governments must take urgent action to establish standard national protocols to control the problem says WWF Australia and the Inland Rivers Network.

�All big rivers in an arc between Moree to Bendigo are polluted by cold water discharge from dams each spring and summer. Over 2,500km of major rivers in New South Wales are estimated to be seriously affected by thermal pollution, and in Victoria, the Yarra, Loddon, Campaspe and Goulburn rivers are also affected, �said Greg Williams, Inland Rivers Network coordinator.

�Loss of native fish species is one of the most obvious critical effects as cold water pollution can kill fish eggs and larvae, reduce reproduction, inhibit growth and cause localised extinction of some species. But this is not just a conservation issue � many rural towns depend on the recreational amenity of rivers as a tourist asset and cold water pollution directly affects rural economies. �

Philippa Walsh, WWF Australia�s South East Program Manager said there was an urgent need to develop a national strategy to asses the extent of cold water pollution throughout Australia.

�We need to review the operation of dams and weirs and investigate new management methods,� she said.

�Cold water pollution is a relatively simple problem that can be fixed but ultimately, State and Federal governments must take a leadership role in developing solutions to deal with the problem. It must become a high priority and resources must be invested to ensure dams are modified or managed correctly.�

IRN and WWF have released Australia�s first comprehensive compilation of expert papers on thermal pollution throughout rivers in the Murray Darling Basin. The scientific papers were presented at a forum attended by over 70 ecologists, engineers and water resource managers.

Greg Williams said members of the forum had agreed that evidence for the impact of thermal pollution was �conclusive and compelling.� Many of the problems could be mitigated quickly by a simple review of dam management and operations, he said.

Cold water pollution occurs when water is released from valves at the bottom of major dams to meet downstream agricultural, industrial and domestic usage. Studies show that thermal pollution can occur for up to 300km downstream from dams, with temperatures frequently as much as 15 degrees below natural temperatures.

In spring and summer, water stored in deep dams forms layers, with a surface layer warmed by the sun overlaying a cold bottom layer. Lack of turbulence in the water means that these layers do not mix and when water is released from the dam � usually by valves located at the base of the dam wall � a slug of unnaturally cold water is released, affecting river ecosystems for hundreds of kilomteres.

For further information:
Rosslyn Beeby, WWF Australia Media email: rbeeby@wwf.org.au