Regional Description

Okanagan Basin  
The Okanagan River is a tributary to the Columbia River. The Okanagan River basin runs north to south and is a major valley system found within the Interior Plateau area of British Columbia and the Columbia Plateau area of north central Washington. The main trench of the Okanagan Basin includes the Okanagan River proper and Okanagan, Skaha, and Vaseaux Lakes. The Okanagan River drainage flows into the Columbia River system at Brewster, Washington. A parallel trench located east of the main trench flows north through Duck,Wood, and Kalamalka Lakes and then south into the Vernon Arm of Okanagan Lake. The Coldstream Valley and a network of valleys that join arms of the Shuswap Basin are northern connections to the Okanagan River Basin. The Okanagan Lake / river valley bottom ranges in width from 3 – 16 kilometers with an elevation that changes from 549 meters abs to 274 meters abs. Okanagan Lake is the largest lake of the basin and has a maximum depth of approximately 232 meters. The Okanagan River basin drains an area approximately 21,600 square kilometers in size, of which approximately 16,450 square kilometers are located in Canada.

Okanagan Basin Map     
   
Sockeye Migration Maps

The Canadian portion of the Okanagan River is a 37 kilometer long river that has been significantly modified by irrigation and flood control dams, channelization, and river flow containment dykes. Channelization of the river has resulted in a loss of approximately 50% of its original length. Significant loss of critical riparian habitat is associated with works undertaken historically to channelize the river for flood control purposes. The Okanagan River supports one of the last two remaining viable sockeye salmon populations in the Columbia River system. Chinook salmon, rainbow trout, steelhead, and kokanee have also been observed in this river system.

The Canadian sections of the Okanagan River have received high profile from a number of international and Canadian outdoor organizations in recent years:

2003 – British Columbia’s Most Endangered River
         – Outdoor Recreation Council of B.C.
            Canada’s 3rd Most Endangered River
         – Earthwild International

2002 – British Columbia’s Most Endangered River
         – Outdoor Recreation Council of B.C.
            Canada’s 5th Most Endangered River
         – Earthwild International

2000 – “ among Canada’s four most endangered ecosystems”
         – Honourable David Anderson – Minister of Environment
            (Gov’t of Canada)

The Similkameen River is also part of the Okanagan River basin. It drains approximately 9300 square kilometers of the east slope of the Cascade Mountains and the Interior Plateau. The majority of the watershed is in Canada. The Similkameen River flows into the U.S. section of the Okanagan River south of Osoyoos Lake. Anadromous fish are only present in the Similkameen River downstream of Enloe Dam which is located at the historic site of ‘Coyote Falls’ just south of the Canadian border.

A combination of coniferous forests, desert-like grasslands, wetlands, and rocky cliffs make this one of the richest ecosystems in Canada. Nearly half the bird species in the country are found here, along with many plants and animals that exist nowhere else in North America or, in some cases, the world. The watersheds also act as a corridor for species migrating between the dry grasslands of the BC interior and the desert areas of the western United States.
Unfortunately, rapid urbanization and agriculture has also turned the area into one of the most endangered regions of the country. The reduction and fragmentation of habitat due to housing, agriculture and other human activities has resulted in an intense concentration of species at risk: 23 species of plants and animals currently listed as nationally threatened, endangered or of particular concern, and one-third of provincially red-listed species, make their homes here. Over half of these depend on grassland and shrub-steppe habitat, which is one of the most dramatically altered habitats.

Sheltered from the rain by the coastal mountain range, the Okanagan and Similkameen valleys have a dry climate with temperatures moderated by the open waters of the Okanagan lakes. At the cooler, higher altitudes are coniferous forests; at the hotter, lower altitudes, grassland and shrub-steppe habitat that typically receives less than 30 centimetres of rain a year. Also at these lower elevations are wetlands and a rugged terrain of sheer cliffs, boulder fields and talus slopes.

COBTWG © 2010