The name ‘Osoyoos’ comes from the Native Indian word ‘Soo-yoos’ meaning ‘place where two lakes meet’. The Okanagan Valley was formed by a huge glacier during the last Ice Age. As the ice melted the glacier broke up and formed Osoyoos Lake and all the others in the valley.
The lake system starts in Armstrong and is fed by the snow packs, down through Kalamalka, Okanagan, Skaha Lake to Osoyoos Lake, into the Okanogan River in the U.S. and down to the Columbia River and into the Pacific Ocean.
Osoyoos Lake has two unique sandspits running east-west right across the lake; the first being Haynes Point and the second being a little further north on which Highway 97 and Motel Row have been built.
It is 11 miles long (6.5 miles or 10.55km in Canada) has 29.7 miles of shoreline, and 5729 square acres of water, (2036 acres in the USA and 3693 acres in Canada. Lake temperatures can reach between 26-33 C in August.
It is an international waterway, straddling the 49th parallel and controlled in Canada by the Coast Guard and patrolled by the RCMP. The water drains into the Okanogan River and thence into the Columbia River system. It varies in depth from 46 feet (near White Sands) to 208 feet (opposite the Packing House). The average level is 911.5 feet above sea level.
The lake is divided into four sections, known as the North Basin, Packinghouse (Formerly Monashee Co-op - Now Sun Fresh Cooperative Growers), Central Basin, and South Basin at the Border. Its deepest part is in the North Basin at 200 feet. It is 72 feet deep at the Border.
It is the 4th largest lake in the Okanagan River System (Canadian side).
The lake is ‘stratified’, meaning it has different layers. It has ‘epilimnion’ at the top (warm) and ‘hypolimnion’ at the bottom (cold). Twice a year, when the upper and lower temperatures are the same (about 4C), the layers of the lake actually switch places or ‘turn over’; usually late April and late October.
The lake is also classed as “eutrophic” meaning it is high in nutrients, such as phosphates and nitrates and high in plant and algae growth and low in clarity. Osoyoos Lake has more phytoplankton (microscopic plants which float free in lakes) than most of the other lakes. Consequently, its water clarity is reduced.
Lake levels are controlled by the Zosel Dam in Oroville.
Because of the lake’s condition, it was designated as ‘fragile’ by the Provincial government in 1972. In 1989, Washington State carried out tests and found DDT in the fish sampled. Thirty years ago the lake system had a healthy kokanee fish population, but by 1995 it had been reduced to six per cent of its former stock. Today the kokanee are beginning to return.
Compared to other Okanagan lakes, Osoyoos Lake is the third largest by area and third deepest but it's only the fourth largest by volume. Because of this and because of the large flow in the Okanagan River, it has the fastest flushing time of the five major lakes in the Okanagan.
The phosphate levels, which were twice the required level in our lake when the OLWQS was formed in 1990, have now been reduced to a more acceptable level. This is partly a result of sewer and treatment plant construction up the valley, and also to public education. Nitrate levels in the lake have also been reduced, though they are still a concern in the surrounding groundwater (aquifers).
In 1975 Eurasian Milfoil was introduced to the lake (probably from household aquariums )and in spite of continuing efforts to reduce this problem, we are only able to control it to a point.
The natural shoreline is gradually being replaced with concrete walls and fences, grass lawns, docks, and other artifical man-made elements. Sadly, the natural order of trees and bushes (riparian vegetation), so essential to the health of the lake system and the spawning and feeding ground for fish, is not apparently desirable to many human lake shore users.
There is virtually no shade either side of the lake, contributing to the high temperatures, which also makes it difficult for fish. The salmon hide in the depths to keep cool, 18 to 23 C being the safest.
The elimination of the oxbows and the creation of the river channel at the north end of the lake took place in the early 1950’s. Wetland areas have also disappeared: the main one remaining is just south of Haynes Point and is now owned by BC Parks.
