A day after the Murray Regional Algal Co-ordinating Committee said testing was being done on a green scum found at the lake it was announced moderate “amber” levels of a potentially toxic variety of blue-green algae had been detected.

The committee’s chairwoman Natasha Ryan said the torrent of water flowing into the lake over recent weeks had brought in more nutrients from bare land.

Those nutrients have fed the algae which has also been encouraged by recent humid weather.

“At these levels, the water is still safe for recreational activities such as swimming, sailing and fishing; however, people are advised not to drink untreated water and that boiling the water does not inactivate algal toxins,” Ms Ryan said.

“Many species of blue-green algae are potentially toxic and may cause gastroenteritis in humans if consumed and skin and eye irritations after contact.”

Ms Ryan urged water users to be wary when entering the lake and avoid any water that appears bright green, where obvious green scums are present, or a distinctive odour is noticeable.

Lake Hume Tourist Park co-owner Kevin Downie said it was disappointing blue-green algae had appeared when the dam was full for the first time in years.

“It is frustrating,” Mr Downie said.

“After the positive press we’ve had it leaves a bit of a sour taste.

“I’d like to have the water clear and not have any worries about it, that’s the ideal situation.”

The algal committee will continue to assess the outbreak but Ms Rayn could not say when the bloom may disperse.

“Monitoring across Hume Dam will continue and the Murray RACC will notify the public with any changes,” Ms Ryan said.

Cattle owners should check stock water supplies for blue-green algae and remove stock from foreshores where surface scum is visible or algae suspected.