Osoyoos Lake Freshet Update 


The spring freshet in the Okanagan/Okanogan and Similkameen basins has come to an early end as snowpacks have been depleted and levels on both Okanagan and Osoyoos lakes have peaked and begun to decrease.

Osoyoos Lake peaked at 912.10 feet (278.01 meters) on May 8 in response to runoff within the Okanagan/Okanogan and Similkameen basins during the spring freshet. The Zosel Dam operator remained in compliance with a 2013 IJC Order even though lake levels exceed 912 feet (277.98 meters), as all gates were open on the dam during that time. 

freshet june 7 2023 osoyoos

Figure 1: 2023 Osoyoos Lake Levels (solid green) and allowable range under the normal rule curve defined by the International Joint Commission Orders of Approval for Osoyoos Lake (solid black). 


Mid- to high-elevation snow monitoring stations in both the Okanagan/Okanogan (Mission Creek, 1,780 meters (5,840 feet)) and Similkameen (Blackwall Peak, 1,940 meters (6,365 feet)) basins have now dropped to zero millimeters Snow Water Equivalent (SWE). Okanagan snowpack melted about two to three weeks earlier than normal, while those in the Similkameen melted almost one month before normal. 

freshet june 7 2023 osoyoos

Figure 2: 2023 Mission Creek and Blackwall Peak snow pillow station. Orange lines illustrate the Snow Water Equivalent (SWE) for the current year (BC River Forecast Center, 2023)   

Currently, lower-than-normal discharge in the Similkameen River at Nighthawk as of June 4 (3,240 cubic feet per second, 91.7 cubic meters per second) is expected to continue decreasing due to the depleted snowpack.

Meanwhile, spring runoff to Okanagan Lake has resulted in an earlier-than-normal and rapid rise in lake level, which as of June 5 is 1,123.05 feet (342.31 m) and a near-normal peak. This has resulted in elevated outflows from the lake as measured on June 5 at the Okanagan River at Penticton (1,497 cubic feet per second, 42.4 cubic meters per second), which peaked about one month prior to normal. The contributions from the Okanagan basin are likely to remain higher-than-normal in the coming week(s) and may cause Osoyoos Lake levels to increase slightly but are not expected to rise above 912 feet (277.98 meters). 

Please monitor this site for further snowmelt and river condition updates. Real-time Osoyoos Lake levels are available on the International Osoyoos Lake Board of Control's website

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