International Osoyoos Lake Board of Control

Lake Level Status and Trends


For real-time Osoyoos Lake water levels plotted against the IJC rule curve, please click on the following link:

For past plots of Osoyoos Lake water levels plotted against the IJC rule curve, please click on the following link:

For current and past water level data for Osoyoos Lake, please click on the following link:


October 5, 2017: Osoyoos Lake level slowly dropping towards normal low winter level. 

Osoyoos Lake levels have declining since mid-September, are within the allowable elevation range stipulated in the IJC Order.  Lake level will continue to slowly decline towards a more stable winter elevation of around 909.5 ft.  To manage a gradual decline in lake levels, the operator of Zosel Dam (Oroville, WA) are adjusting gate settings on the dam as required, to account for upstream Okanagan river inflows to Osoyoos Lake and downstream flow requirements.


June 30, 2017: Osoyoos Lake levels are higher than usual this summer.

Water Levels on Osoyoos Lake are expected to be higher than usual this summer.  This is due to high inflows into Osoyoos Lake from the Okanagan River, which in turn is experiencing high flow rates as the upstream water levels on Okanagan Lake slowly decline from the record peak lake levels seen in early June.  Given the forecast high summer releases from Okanagan Lake, it is expected that the current high inflows and water levels on Osoyoos Lake will extend through July and into August.  Therefore, Osoyoos Lake will likely remain slightly above the normal summer-period high-water level of 912 ft, as identified in the IJC rule curve for Osoyoos Lake (click here for real-time water level plot), rather than the normal summer operating level, which is closer to 911.5 ft.  

Zosel Dam, which can control the outflow of water from Osoyoos Lake, remains fully open and allowing as much water as possible to pass through the dam.  Zosel Dam is not contributing to high water level conditions on Osoyoos Lake but is operating to maximize outflow from the lake, to help lake levels return to a normal level (within the bounds of the IJC rule curve) as quickly as inflow conditions will allow.  

The IJC Osoyoos Lake Board of Control will continue to monitor conditions and provides updates as conditions change.


May 19, 2017: Osoyoos Lake levels are rising!  Onset of 2017 freshet.

With melting snow and extended periods of rain resulting in increasing flows in the Okanagan and Similkameen River systems, water levels on Osoyoos Lake have been increasing significantly over the past week. For more information, see Ecology News Release

The level of Osoyoos Lake has been rising rapidly and is expected to continue to rise over the coming days and weeks.

The flow control gates on Zosel Dam have been fully open as of April 26, to allow as much outflow from Osoyoos Lake as possible.

The rate of rise and level reached by Osoyoos Lake will be dependent upon the weather (i.e., temperatures and precipitation) during this period and is difficult to predict, but lake-shore residents, property owners and others who might typically be impacted by higher spring lake levels should take precautions to reduce the risk of impacts due to high water levels on Osoyoos Lake at this time.  

For a comparison of water levels in 2017 with past water level ranges on Osoyoos Lake, please see the following plots:

Plot of current water levels (2017) vs. 1985-2016 period of record (since current dam operational, with IJC Orders)

Plot of current water levels (2017) vs. 1944-2016 period of record (full period of IJC Orders for Osoyoos Lake)

Plot of Exceedance Probability for Osoyoos Lake Water Levels (for both 1985-2016 and 1944-2016 periods) 

(Plots last updated: June 5, 2017) 

Additional updates on conditions will be provided throughout freshet as appropriate. 

In the meantime, in addition to the real-time Osoyoos Lake water level information provided at the top of this page, the following websites provide additional information:

BC River Forecast Centre

Town of Osoyoos

NOAA Northwest River Forecast Center

Regional District of Okanagan-Similkameen

Washington State Department of Ecology – Zosel Dam


May 5, 2017: Drought Criteria not met in 2017

The International Osoyoos Lake Board of Control (Board) has reviewed the criteria for drought conditions in the Okanagan Valley per Condition 8 of the International Joint Commission’s 2013 Supplementary Order of Approval. Based on water-supply forecasts as of early April, the Board has decided that the criteria for a drought to be declared were not met in 2017.

The Order states that for drought conditions to be declared, criteria (a) and either (b i) or (b ii) have to be met:

(a) the volume of flow in the Similkameen River at Nighthawk, Washington for the period April through July as calculated or forecasted by United States authorities is less than 1.0 million acre-feet; and

(b i) the net inflow to Okanagan Lake for the period April through July as calculated or forecasted by Canadian authorities is less than 195,000 acre-feet; or

(b ii) the level of Okanagan Lake fails to or is forecasted by Canadian authorities to fail to reach during June or July elevation 1122.6 feet Canadian Geodetic Survey Datum.

Recent forecasts exceeded each of criteria (a), (b i), and (b ii), in early April and early May 2017. The NOAA Northwest River Forecast Center forecasted a water supply of 1.514 million acre-feet at the Similkameen River at Nighthawk for April through July at the 50% exceedance level. The British Columbia (BC) River Forecast Centre forecasted a net inflow to Okanagan Lake for the period April through July of 449,136 acre-feet, and the Canadian system operator forecasts that Okanagan Lake levels will reach 1,123.7 feet in June or July.

The Board will continue to monitor the hydrologic flow and lake-level projections and will issue notification should there be any change in its assessment of the drought criteria.




Archived updates: