Logging in Melbourne's Water Catchments!

Logging threatens water supply and quality

Towering Mountain Ash in the Central Highlands. Photo: Ern Mainka

Within the spectacular giant mountain ash forests of the Central Highlands lie Melbourne’s water catchments, which provide drinking water to over 3 million Victorians. Five of these catchments, which supply 40 per cent of Melbourne’s drinking water are open to clearfell logging.

Several independent studies, including a technical report published in December 2000, have found that clearing and regeneration of these forests has a dramatic effect on water yield.

Research has shown logged areas to suffer a 50 per cent reduced water yield (shown in graph). Young regrowth trees need more water to grow, thus releasing less water into river catchments. It takes 150 years for water yields to regain their pre-logged status.

It is breathtaking that in this time of severe drought our most precious resource is jeopardised by logging and that the Government continues to see fit to threaten the little water we have left.

Further studies have shown that logging adversely effects water quality through increased sediment entering rivers as a result of landslides, soil erosion and turbitity. Roading in catchment areas can add 90 tonnes of sediment per hectare, per annum into catchment rivers.

Thomson catchment with logged areas behind Central Highlands, Vic. Photo: Ern Mainka

A policy of no logging in water catchments would not only result in greater water yields and less sedimentation in rivers, but protection of these areas would also be a financial benefit. An economic study undertaken in the Thomson catchment, which supplies Melbourne, found that when comparing the value of water versus that of timber extraction, a no logging policy would have a financial benefit of $147 million to the Victorian community.

It is clear that logging in the Central Highlands’ native forests is not only having a catastrophic effect on the water, but also on all aspects of forest and stream ecology.

Last year The Wilderness Society stopped logging in Cement Creek catchment through a successful community campaign. Despite this success, three of Melbourne’s water catchments will be logged this year; Armstrong, Starvation and the Thomson. Combined, these catchments supply 40 per cent of Melbourne’s drinking water.

Melbourne’s pristine drinking water is the envy of the world, however, the source of that water is being devastated by an intense logging regime. It’s time the Government protected our water supplies.