Williamson Lake in Revelstoke is clear of algal toxins according to test results from B.C. environment. The "cautionary advisory" the city of Revelstoke and Interior Health had for a "potential algae bloom" was lifted on July 20.

"The water is clear; there is no sign of an algae bloom." Interior Health communication specialist Susan Duncan wrote in an email on Friday, July 21 to tell reporters the advisory was lifted.

Interior Health put up the advisory on July 8. The city of Revelstoke put up signs around the lake warning people not to swim in it.

The city and Interior Health would not do interviews with StokeFM but said they were waiting for water sample test results, and they gave an information page about algae.

Signs at Williamson Lake warning people about a potential algae bloom. Photo by Meagan Deuling

On July 15 Duncan emailed to say that Interior Health and the city were working together to monitor the lake water. A test from July 15 showed "an absence of toxin," the email said.

Algae is natural and present in many waterways. Algae blooms are also natural and healthy, according to Hamish Kassa, the Environmental Services Coordinator with the Columbia Shuswap Regional District.

Blooms occur when algae is fed by nutrients. These can come in the form of soil or sediment in the water from the high, late snowpack this spring. Water is still high and snow is still melting.

Plus the pollen bloomed late and all at once, filling the air and creating streams of yellow and white on the top of water.

However, Kassa said nutrients can include nitrogen or phosphorous from fertilizer runoff, although he said the source would have to be close to the water. It could also be sewer.

The city and Interior Health did not respond to questions about how the water will be monitored in the future. Kassa said that the city could make a request to B.C. ministry of environment for them to monitor.

He said the groundwater and tributaries to the lake could be sampled to try and figure out the source of the algae bloom, if toxins were found to be present.

Susan Duncan from Interior Health said in an email that the cautionary advisory was issued based on photos and information forwarded from the B.C. department of environment.

In other news, the city of Revelstoke says that the Aquatic and Community Shelter is open during "daylight hours" to act as a place to cool down.

Temperatures are supposed to reach 35 degrees Celsius and hotter this week.

According to a notice posted online, the city said that two or more days at 35 degrees or hotter, and 18 degrees at night, constitutes an extreme heat event.

The aquatic centre is at 600 Campbell Avenue downtown Revelstoke.

Click the link below to listen to the radio story which aired on July 22, 2022