June 5, 2020: Spring freshet update - Osoyoos Lake level is dropping!
With flow of the Similkameen River declining since its recent peak on June 1, the backwater effect of the Similkameen River on the Okanogan River is decreasing. This allows for increased outflow from Osoyoos Lake and a corresponding drop in its level. Osoyoos Lake crested at 913.65 ft. (278.481 m) on June 2, and is now 913.26 ft. (278.423 m) at 06:45 June 5. The rate of Osoyoos Lake’s water-level decline will depend on the rate of decrease in Similkameen River flow, inflow rates from the Okanagan River system, and the potential for runoff from precipitation and snowmelt to the Okanagan and Similkameen River.
Outflow at Okanagan Lake Dam was increased by 250 cfs (7.1 cms) on June 2 because Okanagan Lake was above full pool levels, but appears to be cresting (June 5 level is 1,123.97 ft. (342.587 m). The release from Okanagan Lake resulted in inflow of about 2,900 cfs (82.1 cms) into Osoyoos Lake by June 3. The Okanagan Lake release was delayed until after the backwater effect of the Similkameen River decreased and outflow from Osoyoos Lake increased. Zosel Dam will continue to maintain all flow control gates fully open during this time, until the lake level drops below the upper limit of the IJC rule curve for Osoyoos Lake (912 ft.).