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Physical Features

Osoyoos Lake lies in the southern end of a great valley, both deep and wide, with sand or gravel beaches, cultivated sloping land, and bare rounded mountains cut with sharp gullies. These creeks carry only a short spring run-off.

The bedrock of the valley is hundreds of millions of years old. It can be seen wherever solid rock seems to poke up though the thin earth cover.

The last glacial age, the Pleistocene, lasted for about a million years, and the advances and retreats of the great masses of ice in geologically recent times provided the features we see today. The great ice-sheet, 7,000 feet thick above the valley floor, melted first on the uplands, and the tongues of ice in the valley, scouring out deeper and deeper channels, were the last to go.

The river flowing through the valley before the Pleistocene age was very large, filling the whole width of the meadows at the head of the lake. After the melting of the glaciers gradually silted up its channel, it carried much less water. The present river is very small. Osoyoos Lake was once a huge section of stagnant ice, trapped by deposits laid across at the south end from the side-hill creeks (in the United States). The rolling terraces or benches on both sides of the lake were formed between the glacier and the hillside, and such deposits as are seen in the gravel pit north of Osoyoos on the highway were carried along and then dropped by the melt-water against the remains of the ice. The rapid melting cut sharp gullies, and the boulders and finer material brought down settled into alluvial fans where the creeks emerged on to a less steep slope.

One very odd feature in Osoyoos is a number of roundish steep-sided ponds. These are technically called "kettles" and were formed by a brig block of ice becoming caught against some obstacle. Gradually they were covered with sand and gravel. When the ice finally melted the hollows were left as pot-holes or kettles.

Since the valley is part of a great north-south system, in summer air from the desert regions of the south moves northward, bringing hot dry weather, while in winter polar air moves southward, bringing cold dry days. These weather conditions are moderated by the effect of the large bodies of water in the lakes.

Osoyoos Lake is at an altitude of 912 feet and has a position unique in Canada for dryness and heat, the rainfall being 7 to 10 inches annually, and the widest swings of temperature going from -16 degrees to 110 degrees Fahrenheit. Thus the fauna and flora are of great interest, as they are of necessity adapted to these conditions. Here is part of the Osoyoos Arid Biotic Zone, a small area which reaches nearly to Penticton, and includes the lower Similkameen.