Runoff's heavy sediment flow draws line in Kalamalka Lake

Sediment draws line in lake

Kalamalka Lake may not be flooding, but the effects of a heavy spring runoff are very visible.

Much of the "lake of many colours" is currently a muddy brownish colour as sediment is washed into the lake from Coldstream Creek.

Coldstream Coun. Simone Runyan, president of the Society for the Protection of Kalamalka Lake, says the north end of the lake is grey-brown from the sediment.

"On Thursday, looking down from Kalamalka Lakeview Drive, I noticed the sediment from Coldstream Creek had spread south past Rattlesnake Point," says Runyan.

"The sediment extent appears to be more than in past years, even when creek levels were similar. This occurred after only a few days of heat and high melt water in Coldstream Creek."

On Friday, Greater Vernon Water turned off its Kal Lake water intake due to increased turbidity. The sediment makes it difficult to adequately treat drinking water.

Runyan, a registered biologist, says it also contains nutrients such as phosphorus and can contribute to algae blooms and weed growth.

Runyan's photos show suspended sediment hugging the west shore of the lake and a distinct line in the water extending south from Rattlesnake Point in Kalamalka Lake Provincial Park.

Much of the east side of the lake was still clear.

Runyan notes that prior to the late 1940s, Coldstream Creek flowed through a large marsh that occupied the Kalavista area and acted as a filter, allowing the water to slow and drop sediment.

"However, the creek was channelized when the subdivision was built, causing the creek to deliver sediment directly into the lake."

Similar events have been documented in the past, with records showing a 1969 sedimentation event took years to fully settle.

More recently, a 2019 study showed that sediment is disturbed by motor boats in water as deep as eight metres, which is why no-wake speed zones are encouraged near shore.

The turbidity is caused by clay and silt particles washed into the lake during spring freshet.

Conversely, it is the minerals in Kal Lake's water, swept down from the Monashee Mountains, that give the lake its nickname, lake of many colours, as they swirl in the current.

Known as 'marl' lake, the colours are caused by suspended limestone crystals in the water.

They also have the unique effect of changing the lake's colour to a solid green in the summer heat.

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