Freshet Update: Okanagan/Okanogan and Similkameen Basins


Spring freshet has largely concluded and the Osoyoos Lake level has reached its 2024 peak. 

The snowpack in the Okanagan/Okanogan and Similkameen basins was extremely low throughout the 2023-2024 winter. Since January 1, 2024, the British Columbia Snow Survey and Water Supply Bulletin has reported the snowpack in the Okanagan and Similkameen basins varied between 49-86 percent and 32-62 percent of normal conditions, respectively. Lower elevation stations were fully melted about one month earlier than the gauged record. However, the snowpack remained longer at higher elevations due to cooler temperatures recorded in May. 

​Water in Osoyoos Lake peaked at 912.44 feet on May 22, remaining within the limits outlined in Condition 8 of the 2013 International Joint Commission Osoyoos Lake Order of Approval which requires dam operators to operate under drought conditions. As of June 16, the Osoyoos Lake elevation is 912.18 feet (278.03 meters) and is at 53 percent of normal for the 1987-2023 period of record for this time of year (Figure 1).  


Figure 1: 2024 Osoyoos Lake Levels (bright green) and allowable range under the normal rule curve (solid black) and drought rule curve (dashed red) defined by the International Joint Commission Orders of Approval for Osoyoos Lake.  For the period of record from 1987-2023, the mean daily lake level is shown as a dotted black line, and the historical gauged minimum, 10th, 25th, 75th, 90th and historical gauged maximum lake levels are shaded gray (USGS, 2024). 


To mitigate the impacts of persisting drought conditions, lake operators will likely hold the Osoyoos Lake level close to the Condition 8 maximum allowable level of 912.5 feet for as long as possible. 

Quick Facts  

  • The International Osoyoos Lake Board of Control oversees the operation of Zosel Dam to manage water levels in Osoyoos Lake, which crosses the British Columbia-Washington State border.   
  • In April 2024, the International Osoyoos Lake Board of Control notified the Washington Department of Ecology that Osoyoos Lake can be operated under the drought rule curve as defined by the 2013 Order. The drought rule curve will remain in place until November 1, 2024, or until the board determines the conditions no longer meet the criteria of a drought year.   
  • This year’s public meeting will be held on Thursday, October 3, 2024, in Oroville, Washington, from 6:30-8 p.m. Please check the board website closer to the date for more detailed information.  
  • To contact the board by email, click “Contact” under “Contact Us” at the bottom of the webpage here.  
  • Stay in touch and subscribe to receive email news updates from the Osoyoos board.  



Sarah Dunn, US Secretary  

Martin Suchy, Canadian Secretary 


International Osoyoos Lake Board of Control