Water Stewardship Information Sources
| ID | 1029 |
|---|---|
| Citation | Josephy, A. 2011. An investigation of method for including ecosystem requirements in order of approval (Study 5). Prepared for International Joint Commission. |
| Organization | International Joint Commission |
| URL | http://ijc.org/rel/boards/osoyoos/Study%205%20Final%2020110208.pdf |
| Abstract/Description or Keywords | Osoyoos Lake is one of several glacial-relic lakes in the bottom of the Okanagan Valley. These lakes help support regional biodiversity by mitigating annual temperature fluctuations and providing unique habitats, particularly riparian areas, adjacent to the lake and wetlands above and below the lake. There are three major categories of species that need to be considered in managing the Osoyoos Lake basin. They are: o Invasive species in the lake and surrounding wetlands o Protected, endangered or declining native species using the riparian and wetland areas adjacent to the lake o Salmonids using the lake and the stream channel below the Zosel dam spillway. The geographic distribution of these groups of species requires that considerations for determining lake level and discharge take into account impact on the lake, riparian areas and their associated wetlands, and the downstream in-channel habitat in the reach of the Okanogan River between the outflow of Zosel dam and the confluence with the Similkameen River. When lake level rises above 912.5 ft (278.1 m), waterfront property, beaches and riparian wetlands can be flooded. Periodic and gradual flooding of wetlands can be beneficial for some wetland species; however rapid changes in lake level and sustained high levels that cause shoreline erosion are not favorable for most riparian and wetland plants in need of protection. Discharge from Lake Zosel is critical to salmonid populations downstream of the lake. Because there is little evidence of significant populations of shoreline spawning salmonids in Osoyoos Lake, discharge, and not lake level, is the most important criteria for maintaining healthy salmonid populations in the lake. Downstream of Zosel dam, water releases have the most impact on habitat in the reach between the dam spillway and the confluence with the Similkameen River. Below the confluence, the in-stream discharge is dominated by outflow from the Similkameen. Because salmonid spawning and incubation occurs in this reach during most of the year, discharge from the dam needs to be maintained year-round at a minimum level to support salmon redds. Under current conditions this discharge is close to the recommendations made by the Washington Department of Ecology of ~300 cfs (8.5 m3 /s). Additionally, discharges over 1,500 cfs (42.5 m3 /s) should be avoided to prevent harmful shoreline erosion. |
| Information Type | report |
| Regional Watershed | Okanagan |
| Sub-watershed if known | Osoyoos Lake |
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| Project status | complete |
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