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The water turns green every once in a while and it gets murky when everyone is playing in it. The lake even has the word ‘die’ in it, for crying out loud. So how dangerous is the water at Dierkes Lake?
Put simply, the water at Dierkes Lake is safe for swimming. And to ensure this, the City of Twin Falls tests the water regularly during the busy swimming season and even when there is the suspicion of toxins in the lake.
The popular swimming spot receives up to 500 visitors a day during warmer months, so the City wants to ensure it’s safe to swim in. To do that, the City partners with the Department of Environmental Quality to test the water for toxins including e. coli and cyanotoxins. The City sets an extremely low threshold of 126/100mL for e. coli as opposed to the national threshold of 235/100mL to further ensure public safety.
Social media posts suggesting the water is stagnant and dangerous are not accurate. Although it may not appear so, Dierkes Lake continuously cycles fresh water from springs in the west part of the lake through fissures on the east side near Shoshone Falls.
The confusion created by the social media posts caused some people to swim in less safe waters not intended for swimming.
Most emergency response calls to Dierkes Lake are for diving accidents or accidental drownings. The City doesn’t have a record of any reported illnesses from swimming in the water at Dierkes Lake. But that doesn’t mean toxins are never present in the lake. During late summer when temperatures increase and less fresh water is flowing into the lake, there is an increased chance for algae blooms or other toxins.
That’s why the City of Twin Falls Parks Department, Water Department and Department of Environmental Quality all work together to regularly monitor and test the lake’s waters. And an important reminder to swimmers to always follow posted signs indicating water that is unsafe for swimming.
If toxins are suspected of being present in the lake, the City will post signs declaring the waters are ‘Unsafe to Swim In. Do Not Swim.’
For more information about the Dierkes Lake water quality testing, please visit TFID.ORG