River Murray faces potential toxic blue-green algal blooms, blackwater and acid drainage over next year

THE River Murray is at risk of acid drainage, blackwater events, and blue-green algal blooms over the next year, the Murray-Darling Basin Authority has warned.

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THE River Murray is at risk from acid drainage, blackwater and blue-green algal blooms over the coming year, the Murray-Darling Basin Authority has warned.

In its operating plan for 2018-19, the authority says in four of six scenarios, ranging from extremely dry to moderate conditions, acid and blackwater could be problems.

There is risk of a “significant” blackwater event if conditions are near average or wet.

Algal blooms are a potential threat in all scenarios.

The plan takes into account factors including the amount of water in storage and the climate outlook.

Acid drainage occurs when acid sulfate soils dry out, producing sulfuric acid. That is eventually flushed through to the river, affecting water quality.

These acid “plumes” can contaminate water supplies, erode metal, and are toxic to marine and freshwater plants and animals.

A golden perch and a carp swim in blackwater in the River Murray.

Blackwater events are when decaying organic matter washing into the system uses up the oxygen in the water, turning it black. That can affect fish including Murray cod.

Algal blooms are generally worse in drier years; once formed, they are hard to stop. They can be toxic to humans, livestock and wildlife.

The authority says the water flows to SA will depend on a range of factors. If it’s extremely dry, there will be less environmental water but if it’s wet, there could be significant floods along the river.

An aerial view of the River Murray, just upstream from Murray Bridge, in January 2010.

… and a year later, showing the change in colour of River Murray water, during a ‘blackwater’ event.

Executive river management director Andrew Reynolds said the annual plan canvassed a range of conditions.

“Our hope is that the plan provides a useful indication to states and stakeholders about the breadth of potential river operations in the 2018-19 water year,” he said.

“We experienced relatively dry conditions last year resulting in low inflows to the River Murray system, and while there is a strong possibility that dry conditions will persist into the coming season, the MDBA plans for the full range of scenarios from extreme dry to wet.”

Mr Reynolds said the authority planned how to manage water shortages in peak irrigation times, how to deliver water most effectively, and how to make sure states had maximum water available.