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Iconic sinkhole turns green

Posted on October 30, 2009, 8:08am and updated on October 30, 2009 at 11:37 am

Little Blue LakeA Mount Gambier local has told The Border Watch he was shocked when he saw the state of the Little Blue Lake this week.

Although often green, the water body suddenly turned a stronger shade than normal recently.

“I couldn’t believe it when I saw it,” Chris McGowan said.

“It is a major concern that an icon of the district has gone that way.”

He said people viewing the lake could usually see rock formations clearly to a depth of around five metres.

“Now you can’t see anything but this incredible turquoise,” he said.

Mr McGowan said the lake provided a window into underground water resources, which were linked and was concerned about potential for pollutants to have also reached other sinkholes and caves if they were to blame for the colour change.

“It could easily happen to all other sinkholes, which wouldn’t be good for the tourist industry and sustainability of Mount Gambier’s water supply,” he said.

Department of Environment and Heritage spokesperson Steve Bourne said he hoped to visit the Little Blue Lake this week, which divers and rangers had told him had turned a vivid green colour.

“It is possibly due extra run off this year from fertiliser, but until testing is done that is only guesswork,” he said.

Mr Bourne said pollutants may have stimulated an outbreak of blue green algae and there was potential for work in future to reduce farm run-off as contamination of the site had long been a problem.

Grant District Council environmental health officer Bob Dunstone said the issue had been identified since 2005 and testing over the years had identified different algae each time.

He said recent tests showed nitrate levels were low, but phosphate analysis was continuing.

However, he said the main concern for the public was the algae could cause irritation to people with sensitive skin or lesions.

“The underlying message is don’t swim in this water,” he said.

Diving enthusiast Ian Lewis, who is undertaking a doctorate study on the geology of Naracoorte’s caves after previously completing an honours paper on South East sinkholes, said he was shocked by the state of the lake.

“I was horrified when I walked over to the edge and looked at it,” he said.

“I’ve been involved in studying the regions cave features for decades, but in all my life I’ve never seen it that colour.”

He said the only time he had seen a sinkhole in the region turn a similar colour was when dozens of carcases were dumped in a water feature, but he did not believe deliberate interference was to blame for the recent phenomenon at the Little Blue Lake.

Mr Lewis said agriculture run-off was also not common at the site as water only drained into the sinkhole from a neighbouring road, where phosphate may have been deposited during cartage and ended up in the water.

He said it was unlikely contaminants would flow from the sinkhole to other water bodies as studies showed the flow between features was slow and filtered by limestone.

JASON WALLACE

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Comments

2 Responses to “Iconic sinkhole turns green”

  1. Shorty on October 30th, 2009 3:55 pm 1

    My god the best swimming hole in the south east gone. Thank heavens that I got to enjoy the little blue when the water 12 feet deeper and the colour of the sky.
    Sad for the Mount that the once pristine water supply is turning to crap.
    Where are people meant to swim now? please dont say at the pool.
    Remember the old days during summer, get all the mates together and ride our pushies down to the little blue for a swim then call into the valley lakes for another swim on the way home.
    Ahh the good old days, to bad there gone, now the kids will just have to hang around the mount and get into mischief.

  2. Mr Mat on October 30th, 2009 6:07 pm 2

    Yep, the south east is full of people interested in making money and not looking at a sustainable agriculture system. FARMERS should be paying to remove the nutrient added to the water table.. and don’t get me started on the valley lakes that’s just sad, they still allow boats the No 1 pollutant makers of the lake, how are our lakes and underground waters suppose to recover from self-centred money making idiots…or maybe its just plain old ignorance.

    Of corse there’s no pressure from governments and banks locking people into debt forcing / causing these issues.

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