Acidity spikes high then low in Anglesea River

IN THE past two weeks, acidity in the Anglesea River has spiked at the highest level since monthly water sampling began in 2008 then dropped to the lowest level since 2019.

The variation is the result of heavy rains that first washed record quantities of acid into the estuary but then forced the normally closed river to open naturally to the ocean allowing saline flows back into the system, Estuary Watch member Dick O’Hanlan said.

“The two creeks – Salt and Marshy – that feed the estuary are permanently acidic, so the more water you put in, the more acidic it becomes.

“When we did the Estuary Watch readings (October 19) it was the lowest pH that Estuary Watch has ever recorded.
“These pH values remained extremely low until they jumped markedly on [October] the 28th… the jump seems to coincide with very high spring tides.”

Averaging between 4.0-4.5 pH over the last year, the readings on October 19 were between 2.8-3.0pH, but by the end of the month they were about 7.0pH.

It is a welcome reprieve for the system, which until last week was in its third year of permanent acidity at levels that have rendered it uninhabitable for fish and most aquatic life and prompted the Surf Coast Shire to re-establish warning signs about potential health risks to humans.

“We don’t know how long it will stay like this, the river mouth will close up again… but it’s certainly a welcome surprise,” Mr O’Hanlan said.

“Fish will almost certainly have swum in from the ocean, but I suspect they’ll be found belly-up if the pH drops again.”

Mr O’Hanlan and fellow members of the Friends of Anglesea River (FOAR) have been campaigning for action on the estuary’s health for years, believing that Alcoa’s decades of pumping water from an aquifer beneath the town is linked to the system’s poor health.

 

In June, the shire called for an “urgent investigation into the health of the Anglesea River”, including the impacts of historic and present groundwater extraction, land use and climate change on its catchment.

Three months later, Alcoa was denied a short-term extension of its groundwater licence the company has been using to fill its former mine.

The Department of Environment, Land, Water and Planning has initiated a process to look into remediation of acidity in the estuary, but has resisted calls to examine what is causing it.

“They’re buying a whole lot of buckets, but they’re not trying to fix the leak,” FOAR member Keith Shipton said of the process.