2013 UPDATE Osoyoos Lake Levels

2013 UPDATE Osoyoos Lake Levels

July 22, 2013 - Update from the International Osoyoos Lake Board of Control

Decreasing inflow to the lake from the upstream Okanagan river and tributaries has resulted in a lowering of the water level of Osoyoos lake to within the Summer period operating range of 911.0 to 912.0 ft. (re. IJC Osoyoos Lake Supplementary Order of Approval, January 2013). Lake levels are expected to remain within this range for the remainder of the summer with Zosel Dam operations aiming to maintain a mid-range lake level elevation during this summer period.

For up to date Osoyoos Lake Level information click here.

Janette Van Vianen, CMC
Director of Corporate Services
Town of Osoyoos

Update: July 2 2013; Osoyoos Lake Water Level Trends – International Osoyoos Lake Board of Control

The level of Osoyoos Lake had been rising over the past week, reaching a peak lake level elevation of 912.73 ft. on June 29^th and the lake level is now beginning to fall (lake level elevation was 912.67 ft. on July 1^st). The rise in lake level was primarily due to increased flows in the Okanagan River due to heavy rainfall over the past two weeks which led to increased discharge from Okanagan Lake and tributary streams. Flows in the Similkameen River had also been increasing early last week, with a peak of 9660 cfs (cubic feet per second) on June 25^th, but have been receding to lower flow rates since (e.g. 7170 cfs on July 1^st). At these flow rates, a backwater effect on Okanogan River discharge (downstream of Zosel Dam) from the Similkameen River is considered a minor possible influence on Osoyoos Lake levels compared to the high inflows to Osoyoos Lake from the Okanagan River. The trend of receding tributary inflows is expected to continue over the next two weeks with the result that Osoyoos Lake levels are expected to fall into the normal summer operating range of 911.0-912.0 ft. by mid-July.

Zosel Dam continues to operate with gates fully open and is in compliance with the IJC Orders for Osoyoos Lake.

Update: June 21 Osoyoos Lake Water Level Trends - International Osoyoos Lake Board of Control 

The Okanagan has received significant rainfall over the last few days.  As result, stream flows and lake levels have been rising, including Okanagan Lake.  In response, the release of water from Okanagan Lake has been progressively increased over the past 3 days.  This increase in release from Okanagan Lake, combined with the increasing tributary stream flows are causing the Okanagan River inflows to Osoyoos Lake to rise as well.  These higher inflows are expected to cause the level of  Osoyoos Lake to rise to an elevation slightly above 912.0 ft, possibly as high as 912.3 ft, over the next day or two.  In anticipation of rising lake levels, the flow-control gates on Zosel dam (at the outlet of Osoyoos Lake) have remained fully open in order to pass as much water as possible and will stay fully open until the lake level returns to the normal summer controlled operating range of 911.0 to 912.0 ft, as required under the International Joint Commission’s (IJC) 2013 Supplementary Order of Approval for Osoyoos Lake.  At this time the water levels in the Similkameen River are not influencing or expected to influence the amount of rise in the level of Osoyoos Lake (i.e. no Similkameen River backwater effect).  Given the natural conditions that are causing water levels to exceed the IJC rule curve for Osoyoos Lake, the operation of the Zosel Dam is in compliance with the IJC Orders.