Blue-green algae advisory for Reesor Lake lifted after summer-long warning

Alberta Health Services has lifted a cyanobacteria advisory for Reesor Lake in Cypress County, ending a warning that had covered the lake and its campground and day-use areas since August.

The province's active health advisories page showed no cyanobacteria advisories in effect across any Alberta zone as of November 2026, including in the South Zone that covers southeastern Alberta.

Alberta Parks had posted the advisory on Aug. 19, 2026, warning that cyanobacteria had been identified in the water at Reesor Dock Day Use, Reesor Lake Campground and the Reesor Lake Hut ComfortCamping site. The notice told visitors to avoid contact with visible blooms, keep pets out of affected water and avoid feeding fish offal from the lake to animals. It also said people could safely eat fish fillets from the lake.

When lifting such advisories, Alberta Health Services has said cooling water temperatures reduce the health risk posed by cyanobacteria to low levels. A previous AHS release lifting a Reesor Lake advisory in November 2025 said recent weather had cooled lake and reservoir temperatures enough that cyanobacteria presented a low health risk in affected South Zone water bodies.

AHS cautions that boiling water does not remove toxins produced by cyanobacteria, and that untreated water from any recreational body of water should never be used for drinking or cooking regardless of advisory status. An alternate drinking water source should be provided for pets and livestock whenever cyanobacteria may be a concern.

The Alberta Parks page for Cypress Hills Provincial Park had not been updated to reflect the lift as of Wednesday.