Water levels on Kootenay Lake remain within the limits established under the International Joint Commission’s (IJC) 1938 Order of Approval, according to the International Kootenay Lake Board of Control.
An extended period of warmer-than-average temperatures and below-average precipitation across the Kootenay basin has reduced runoff, resulting in lower lake levels and weaker inflows than are typical for this time of year.
Water flowing into Kootenay Lake reached a seasonal peak of 86,100 cubic feet per second (2,438 cubic metres per second) on May 28. By July 28, inflows had declined to 20,300 cubic feet per second (575 cubic metres per second). Outflows peaked at 61,300 cubic feet per second (1,736 cubic metres per second) on June 2 before falling to 18,100 cubic feet per second (513 cubic metres per second) by July 28. Water leaving the lake is regulated through Corra Linn Dam or passes naturally through the constriction at Grohman Narrows.
The lake reached its highest elevation this year on June 1, measuring 1,748.16 feet (532.8 metres) at the Queens Bay gauge. As of July 28, the level had fallen to 1,743.6 feet (531.45 metres) at Queens Bay and 1,743.3 feet (531.36 metres) at the Nelson gauge.
Under the 1938 Order of Approval, once the lake level at the Nelson gauge drops below 1,743.32 feet (531.36 metres), it must remain below that elevation until Aug. 31. The Nelson gauge fell below that threshold on July 8 and is required to remain below it through the end of August.
The allowable operating level will increase on Sept. 1, when the rule curve rises to 1,745.32 feet (531.97 metres), based on measurements at the Queens Bay gauge.
