Logging must stop in Melbourne’s biggest water supply catchment

Abstract

Continued logging in Melbourne’s water catchments could reduce the city’s water supply by the equivalent of 600,000 people’s annual water use every year by 2050, according to our analysis.

We calculated water lost due to logging in the Thomson Catchment, which is the city’s largest and most important water supply catchment. Around 60% of Melbourne’s water is stored here.

Since the 1940s, 45% of the catchment’s ash forests (including mountain and alpine ash forest) have been logged. There are plans to log up to a further 17% of these forests under the VicForest’s existing logging plan.

Past logging in the ash forests has reduced the Thomson Catchment’s water yield, which is the amount of water that flows through the catchment, by 15,000 megalitres (a megalitre is a million litres) each year. This equates to around 9% of water yield from ash forests across the catchment.

By 2050, continued logging in these forests at the current rates could increase this loss to 35,000 megalitres each year, or 20% of water yield. This will be equal to the water use of around 600,000 people every year, based on estimated water use of 161 litres per person each day.