River faces pressure of pollution
THE Swan River is in better condition than many assume, but there is still work to be done, Swan River Trust acting general-manager Mark Cugley says.
“Overall, it’s in good condition, based on the fact that people can continue to swim along it, the amount of fish and it supporting a vibrant dolphin population,” he said.
The Trust works to control excess nutrients reaching the river, including a $3 million project at the Bayswater Brook main drain, about 7km from the Perth CBD, where 150,000 riverbank plants may stop 1.3t of nitrogen reaching the river each year.
Nitrogen and phosphates from fertilisers can create toxic algae blooms in hot weather, so the Trust’s Midland and Wilson plants pump oxygen into the water to provide refuges from the blooms for fish in the rivers’ upper reaches.
Ellen Brook, about 10km north of the Midland plant, is the worst tributary for the pollution, breaching short- and long-term reduction targets in the past four years.
Mr Cugley said 14 other Swan River catchments were meeting 20-year targets and that work would continue with the catchments’ councils, farmers, golf courses and landscapers to reduce fertilisers, while other State Government agencies would enforce the Swan and Canning Rivers Management Act .
He said the rivers would continue to be affected by a growing population and a drying climate, so the Trust would continue to educate the public about the threats.
Downstream, three screens will block any plumes during dredging for a boating basin soon to begin at Elizabeth Quay in the Perth CBD.
Trust statutory assessment manager Jenifer Stritzke said monitoring had not indicated any inflow of contamination from historic dumps among which the Quay was being excavated.
She said much of what came out from the large main drain adjacent to the Quay and into the Swan would have flowed from Lake Monger, 4km north-west, which itself was fed by smaller drains taking road run-off from places as far away as Shenton Park.
Mark Cugley (top left), acting general manager of the Swan River Trust, says that the river, while in pretty good condition, will face additional pollution pressures as the city becomes more developed.