Lake Level Status and Trends
-
For real-time Osoyoos Lake water levels plotted against the IJC rule curve, please click here
-
For past plots of Osoyoos Lake water levels plotted against the IJC rule curve, please click here
-
For current and past water level data for Osoyoos Lake, please click here
May 23, 2018: Osoyoos Lake levels are dropping.
With declining flow rates on the Similkameen River (see US NWS River Forecast Center), the backwater effect at the confluence of the Similkameen River and Okanogan River is easing off, allowing for greater outflow from Osoyoos Lake and a corresponding drop in water level on Osoyoos Lake. The rate of water level decline on Osoyoos Lake will depend on the rate of decrease in Similkameen River flow, inflow rates from the Okanagan River system and the potential for weather events that could bring precipitation to the Okangan and Similkameen River Basins. 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).
May 17, 2018: 2018 freshet update. Osoyoos Lake above 916 ft. and rising again.
Despite a slight drop to water levels on Osoyoos over the past several days, the lake level is starting to rise again. With increasing melt of high elevation snowpack over the past several days and localized mid-week rainfall, the Similkameen River flow is increasing and is expected to peak by this weekend, according to the US NWS River Forecast Center.
In the near-term, Okanagan Lake outflow will be held steady at current rates to avoid increasing inflows to Osoyoos Lake, although about 60% of the Okanagan River discharge entering Osoyoos Lake is from uncontrolled tributary inflows between Okanagan Lake and Osoyoos Lake (much higher than normal). Snowpack has been reduced over the past few weeks from the annual maximum, particularly at low to mid elevations, but it is still above last year's levels in the Okanagan and Similkameen basins. At higher elevations, 60-80% of the annual snowpack remained as of mid-May. Given the current and predicted rise in Similkameen flows (with associated backwater effect restricting Osoyoos Lake discharge) and the steady input from the Okanagan River, Osoyoos Lake is beginning to rise again and will likely surpass the high water levels experienced last weekend (May 11-12), possibly approaching the 917 ft. level by the weekend. This will exacerbate current flooding around the lake until Similkameen River flows begin to recede by early next week.
May 10, 2018: 2018 freshet update. Osoyoos Lake at 916 ft. and rising!
Osoyoos Lake level continues to rise rapidly and has already surpassed last year’s maximum high water level (914.98 ft. on June 2, 2017).
Osoyoos lake level is currently at 916 ft. which exceeds previous high levels for the month of May seen in 1972 (915.79 ft. on May 31, 1972) and is expected to keep climbing through the weekend (May 12-13). The increasing water levels on Osoyoos Lake are largely due to extremely high flow rates on the Similkameen River, which flows into to the Okanogan River downstream of Osoyoos Lake, impeding outflow of water from Osoyoos Lake (backwater effect) and coupled with high inflow into Osoyoos Lake from the upstream Okanagan River. It is expected that the rate of increase on the lake will reach a peak level once the flow rate on the Similkameen River begins to drop and the backwater effect on Osoyoos Lake discharge eases off.
The flow control gates at Zosel Dam (at the outlet of Osoyoos Lake) have been fully open since March 26, allowing the dam to pass as much water as possible during this high water period.
The Town of Osoyoos has declared a State of Local Emergency due to flooding. More information: http://www.osoyoos.ca/content/bulletin-3-town-osoyoos-information-flooding-preparedness
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:
NOAA Northwest River Forecast Center
Regional District of Okanagan-Similkameen
Washington State Department of Ecology – Zosel Dam
National Weather Service – Spokane
May 6, 2018: Osoyoos Lake levels are rising! Onset of 2018 freshet.
With rapid onset of snow melt in the Okanagan and Similkameen River systems, water levels on Osoyoos Lake have been increasing significantly over the past week.
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 are fully open 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.
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:
NOAA Northwest River Forecast Center
Regional District of Okanagan-Similkameen
Washington State Department of Ecology – Zosel Dam
Archived updates: