ACT News

Ebb and flow stirs up Canberra lakes debate

Lake Burley Griffin: a fetid carp pond

A water scientist overseeing an $85 million project to clean up Canberra's polluted lakes says inflammatory comments on the putrid state of Lake Burley Griffin overlook work under way to address complex problems.

Dr Jamie Pittock wrote in Monday's Canberra Times of failures to implement aquatic species action plans, pathetic mechanical mixers on the surface and governance failures that had turned the lake into a carp-filled, poisonous waterway.

A senior lecturer at the ANU's Fenner School of Environment and Society, Dr Pittock said basic technical fixes like environmental flows and a fish passage at Scrivener Dam could achieve a modest improvement in the lake's health.

However, Professor Ross Thompson from the University of Canberra's Institute  for Applied Ecology said it was unfortunate Dr Pittock's comments, which, like all opinion pieces, sought to be inflammatory and to provoke debate, did not recognise the work under way to manage the lake.

This included the federally funded Basin Priority Project, which he was helping to oversee.

Advertisement

"The lake was designed into the city as both an ornamental or scenic feature and, in part, to manage the stormwater. The intention wasn't ever necessarily the water quality in Lake Burley Griffin would ever be fantastic. It was supposed to buffer the downstream habitats from the effects of development of the city, and, of course, it does that remarkably well," Professor Thompson said.

He said the basin project would set out a business case for solving problems not only for Canberra's lakes, but also across the Murray-Darling Basin.

It would take in work over the past 20 years on identifying sources of nutrient problems and establish a business case before beginning interventions.

Professor Thompson said institutional and governance arrangements around the lake were complex and would be reviewed and changes put forward.

"It's easy to blame the governance arrangements; I think, in general, they have been navigated reasonably well," he said.

Native migratory fish from their source, the Murrumbidgee River, had been recovering and a fish ladder would have potential but could be expensive.

"Let's just say there have been some white elephant fish ladders built around the world," Professor Thompson said.

They were an option but could cost several million dollars, which may be better spent on managing water quality issues.

The lake could continue to be stocked with native fish and leave the fish ladder to later when environmental issues had been sorted out.

Canberra ecologist Dr Bryan Pratt said a fish ladder on Scrivener Dam would enable golden perch, Murray cod and possibly silver perch to carry out their original migration, a better outcome than relying on stocking natives.

"We are buying fish from a hatchery with one particular genetic group, whereas the wild population will have varying genetic forms all moving in the system. That means better health in the fish and longer time survival at a much cheaper cost," he said.

"One of the problems we get from fish migration, when golden perch want to migrate downstream in autumn, they gather at Scrivener Dam down low, and when the gates open after rain, they all rush out and get smashed on concrete bollards down below the dam.

"So, in fact, we lose a lot of the fish without allowing to them to migrate naturally."

A National Capital Authority spokeswoman said environmental flows were not out of the question in the future, even though a constant level was maintained for ornamental reasons.

The authority was always looking at ways of improving water quality but as Dr Pittock had explained, managing the lake involved several government agencies.

"Last season, the NCA, in partnership with Greening Australia, planted macrophytes [water plants] in an effort to improve quality," the spokeswoman said. 

Advertisement

4 comments

Comment are now closed