Cut trees at dams to get water: foresters
Cut trees at dams to get water: foresters

A group of foresters has called on the State Government to cut down half the trees on Perth's dam catchments, claiming the move would reap an extra 50 billion litres of drinking water a year.

Following the worst recorded year for run-off into the city's drinking water reservoirs, the WA branch of the Institute of Foresters has argued the jarrah forests which surround them are too thick and are strangling the supply of flow into the dams.

Group spokesman Don Spriggins said "thinning" the forests, which cover about 100,000ha of publicly owned land, could deliver the same amount of drinking water as the annual output from the Kwinana desalination plant.

With the Government facing a decision on Perth's next major water source as early as this year, Mr Spriggins said catchment thinning could be done for a fraction of the cost of building a new desalination plant or tapping an underground aquifer. This was because dam infrastructure was already in place.

He said there were also a number of spin-off benefits including the potential for a biomass power plant using the logged trees as feedstock and an easing of environmental pressures he claimed the forest was placing on the land.

"While rainfall up until 1975 could support existing forest densities, the decline since then means this is no longer possible," Mr Spriggins said.

"There are simply too many trees for the water available and the forest and its ecosystems are already under severe water stress."

Mr Spriggins' comments come as the Water Corporation conducts a long-term trial into the merits of thinning around Wungong Dam, south of Perth.

Under the 12-year project, the Water Corporation will spend $20 million working with various other government agencies to log trees on 7800ha of land.

A spokesman for the utility said that while modelling suggested the trial could yield an additional 2.4 billion litres of water when finished, last year's lack of rainfall and the slow progress of thinning meant it was too early to draw conclusions.

But he cast doubt on claims made by the institute, saying a broader rollout of the measure would not recover "anything like 50 (billion litres) a year".

The West Australian

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