Canning River breathes easy via new plant

A $1 million oxygenation plant completed this month on the Canning River is expected to double the level of oxygen relief in the water 2.2km upstream of the Kent Street Weir.

Since 1998 two older oxygenation plants have been servicing 2.3km of the Canning River.

However, Swan River Trust River system manager Mark Cugley says the plants only oxygenate half of the stretch needed upstream of the weir.

"This next plant finishes the whole area that we can feasibly influence," he says.

Oxygenating the river ensures it can process nutrients in a healthy way.

"Oxygenation is really important because prior to the introduction of the two plants, there were regular blue-green algal blooms throughout the weir pool," Mr Cugley says.

"The nutrients were being released from the sediments."

He says the process works by supersaturating river water with oxygen.

"The oxygenated plants draw in water from the riverbed and introduce liquid oxygen into the water [which is] being pumped into land-based plants," he says.

"That super-saturated oxygenated water is re-introduced passively throughout the river where it mixes with poorly oxygenated water to help improve river health."

With the help of partners BOC Gases and the Department of Water, the third oxygenation plant will run in the summer and autumn months.

"In winter the flows through the Canning are sufficient enough. This means the weir pool and upper reaches of the river get a really good flush," Mr Cugley says.

"It is only when we get the weir pool static that we need to be providing additional oxygen and this mainly occurs in the summer and autumn months."

The new plant is one component of the state government's catchment to coast approach to protect and improve the health of the Swan and Canning rivers.

Other initiatives include a $4.2 million investment to build nutrient-stripping wetlands—one on the Ellen Brook and a second at the Eric Singleton Bird Sanctuary in Bayswater.

The construction of the wetland at Bayswater started in December last year and is due to be finished next month.

"By diverting about 25 per cent of the flow with a series of vegetated beds, the wetland will reduce phosphorous by 200kg, reduce nitrogen by 15 per cent, and rid 40 tonnes of sediment and rubbish that would otherwise be flowing into the Swan River," Mr Cugley says.