Thompson

Geography

The South Thompson originates at the outlet of Little Shuswap Lake at the town of Chase and flows approximately 55 kilometres (34 mi) southwest through a wide valley to Kamloops where it joins the North Thompson. Highway 1, the Trans-Canada Highway and the mainline of the Canadian Pacific Railway parallel the river. Little Shuswap Lake is fed by the Little River, which drains Shuswap Lake, which is fed by several rivers and creeks.

The North Thompson originates at the toe of the Thompson Glacier in the Cariboo Mountains west of the community of Valemount and flows generally south towards Kamloops and the confluence with the South Thompson. For most of its length, the river is paralleled by Highway 5 and the Canadian National Railway (both of which cross the river a couple times).

History

The Interior region of British Columbia was first populated after the retreat of the continental ice sheets of the last ice age. The ice moved out of the Thompson River region approximately 11,000 BCE, and migration by the ancestors of the Nlaka'pamux and Secwepemc people is thought to have occurred soon after. Some of the older archaeological sites on the lower Thompson include the Drynoch Slide site, near Spences Bridge, with artifacts dating to about 7350 BCE, and the Landels site, near Ashcroft, which dates to older than 8000 BCE. Archaeologists theorize early settlers lived in small groups, beginning with nomadic bands hunting ungulates on the plateaus around the river, who then established more permanent dwellings along the river benches as their fishing techniques developed.

Ecology

The Thompson River supports 24 fish species, including two considered endangered. It also hosts carp, which are not native to the watershed. The river is home to large populations of Pacific salmon, including coho, sockeye, pink and chinook. Through its tributary, the Adams River, the Thompson has one of the largest sockeye salmon runs in the world. Pink salmon spawn mostly below Kamloops Lake, while coho spawning beds are found in 40 of the Thompson watershed's streams and rivers. Coastal rainbow trout (Oncorhynchus mykiss irideus), including an anadromous variety called steelhead, are found in the river along with a local strain the Kamloops rainbow trout which occurs in Kamloops Lake at the Thompson River headwaters and other nearby lakes.

Geology

The Thompson River valley has existed in some form for at least 50 million years; however, for much of its history, it did not drain to the southwest into the Pacific Ocean as it does today. Geologists believe water from the river flowed northward, through the Cariboo region, eventually entering what is the modern-day Peace River drainage basin and ending up in the Arctic Ocean.