Spring Freshet Update for Osoyoos Lake and Similkameen River
The level of Osoyoos Lake reached 913 feet (278.3 meters) on June 23 in response to runoff within the Okanagan/Okanogan and Similkameen basins during the spring freshet (Figure 1).
At this elevation of Osoyoos Lake, some beaches along the shoreline are inundated and wind or boat-generated waves may impact lakeside infrastructure such as docks and swimming areas. The International Osoyoos Lake Board of Control recommends that lake shore residents take necessary steps to protect their property and infrastructure.
Figure 1: 2022 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)
Moderately elevated discharge of the Similkameen River as of June 23 (10,500 cubic feet per second [cfs] or 297.3 cubic meters per second [cms]) is expected to marginally increase or remain stable due to limited remaining snowpack in the contributing Similkameen basin (Figure 2).
Figure 2: 2022 Similkameen River near Nighthawk (solid blue)
At this discharge, the stage of the Similkameen marginally limits outflow from Osoyoos Lake, while gates at Zosel Dam remain fully open. However, spring runoff in the Okanagan basin has resulted in above-normal water levels in Okanagan Lake (1,124.07 feet or 342.62 meters as of June 22; Figure 3). Osoyoos Lake inflows, as measured on June 22 at the Okanagan River at Oliver, British Columbia (2,990 cfs or 84.7 cms), will likely start decreasing as tributary contributions downstream of Okanagan Lake begin to decline.
Figure 3: 2022 Okanagan Lake at Kelowna level (solid green), International Joint Commission Orders of Approval Drought Criteria (dashed red) and BC Ministry of Forests target Full Pool Okanagan lake elevation (dashed black)
As a result, Osoyoos Lake levels are expected to start dropping over the next few days or week, with the lake returning to its normal summer levels by or before mid-July.
Please monitor this site for further snowmelt and river conditions updates as the temperatures ramp up and freshet continues. Real-time Osoyoos Lake levels from the US Geological Survey are available on the IOLBC’s website at ijc.org/olbc/watershed/levels.
The International Osoyoos Lake Board of Control ensures that ouflows from Osoyoos Lake are regulated in accordance with the International Joint Commission’s (IJC) orders of approval.
The International Joint Commission was established under the Boundary Waters Treaty of 1909 to help the United States and Canada prevent and resolve disputes over the use of the waters the two countries share. Its responsibilities include investigating and reporting on issues of concern when asked by the governments of the two countries.