By Don Urquhart, Times Chronicle
Osoyoos Lake levels are expected to gradually decline as the joint Canada-US board of control balances multiple demands on water flows through the Zosel Dam.
The International Osoyoos Lake Board of Control (Board of Control) said in a statement that over the last few weeks, Osoyoos Lake levels have been held just below 912.5 feet (278.13 metres), which is the upper limit of the allowed summer range during drought conditions.
The Board of Control declared drought conditions for the lake on May 12, 2026 which led it to direct operators of the Zosel Dam in Washington State to raise water levels in the lake in a bid to capture as much spring runoff as possible for what is expected to be a long hot dry summer.
Water year 2026 (bright green) and water year 2025 (dark green) Osoyoos Lake Levels, along with allowable range under the normal rule curve defined by the International Joint Commission Orders of Approval for Osoyoos Lake (solid black). Expanded drought Conditions rule curve (red dashed). For the period of record from 1987-2025, the mean daily lake level is shown as a black line, and the historical gauged minimum, 10th, 25th, 75th, 90th, and historical gauged maximum lake levels are shaded grey.
USGS, IOLBC 2026 graphic
The Board of Control is given the task of maintaining lake levels under the authority granted it by the International Joint Commission (IJC).
Lake levels reached a peak of slightly over the prescribed 912.5 feet mark on May 29 due to what it said was an “unforeseen combination of strong northerly winds, which pushed water toward the south end of the lake, and heavy rainfall, which temporarily increased inflows.”
This was quickly remedied by the Washington State Department of Ecology which operates the Zosel Dam under the auspices of the Board of Control by quickly increasing water releases thro ugh the dam to bring lake levels back within the allowable range. These maximum allowable levels have now begun to decline.
“This decrease is expected to continue as the Dept. of Ecology works to balance multiple needs: maintaining instream flows to meet water rights obligations and support fish, and storing water in the lake for later in the season,” the Board of Control said.
Lakeshore residents and recreational users on the lake should expect lake levels to keep dropping and plan accordingly, the statement read. Real-time lake level information is available on the USGS Osoyoos Lake water data page.
The Board of Control said it will continue to track Osoyoos Lake and Okanagan River conditions and provide updates as conditions change over the summer.
