Thompson River

The Thompson River is the largest tributary of the Fraser River, flowing through the south-central portion of British Columbia, Canada. The Thompson River has two main branches, the South Thompson River and the North Thompson River. The river is home to several varieties of Pacific salmon and trout. The area's geological history was heavily influenced by glaciation, and the several large glacial lakes have filled the river valley over the last 12,000 years. Archaeological evidence shows human habitation in the watershed dating back at least 8,300 years. The Thompson was named by Fraser River explorer, Simon Fraser, in honour of his friend, Columbia Basin explorer David Thompson. Recreational use of the river includes whitewater rafting and angling.

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). The North Thompson passes by several small communities, the most notable being Blue River, Clearwater and Barriere.

The North Thompson picks up the Clearwater River at the town of Clearwater. The Clearwater, the North Thompson's largest tributary, drains much of Wells Gray Provincial Park.

A notable feature along the North Thompson is Little Hells Gate, a mini-replica of the much larger rapid on the Fraser downstream from the mouth of the Thompson. About 17.4 kilometres (10.8 mi) upstream from the small town of Avola, the river is forced through a narrow chute only about 30 feet (9.1 m) wide creating a rapid that resembles the Fraser's famous rapid.

At Kamloops, the combined Thompson River flows 15 kilometres (9.3 mi) from the confluence of the North and South Thompson Rivers before reaching Kamloops Lake, which is roughly 30 kilometres (19 mi) in length, ending at the town of Savona. From there it flows in a meandering course westwards through a broad valley area. At Ashcroft, the Thompson Canyon begins and the river turns southwestward to its confluence with the Fraser. The river is paralleled by the Trans-Canada Highway, the Canadian Pacific Railway and the Canadian National Railway.

From Ashcroft to Lytton, the river is completely confined within Thompson Canyon, making for spectacular scenery. The Thompson River joins the Fraser River in Lytton. There is a striking stretch of dark black cliffside just downstream from Ashcroft and visible from the Logan Lake-Ashcroft highway is officially named the Black Canyon. Just below the town of Spences Bridge was the site of a major rail disaster in the early 20th century. Communities along this section are Bighorn, Shaw Springs, and Goldpan.

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. This flow direction is estimated to have ended approximately 2 million years ago, as the Pleistocene era of heavy glaciation began.