Far and away, the larger of the two rivers at this confluence is the Thompson River, the Nicoamen River flowing into it from the east. It flows westward from the interior toward the western edge of the Thompson Plateau. Consisting of several tributaries, its main tributary is about 30 to 40 kilometers in length, at most.
The
Thompson River, joins the Fraser about 15 kilometres southwest of here. The South Thompson, though only 55 km. long, is a large river as it originates at Little Shuswap Lake at the town of Chase, which is fed by many mountain streams to the north and east, draining a fairly large area of 18,000 square kilometres. Its average flow is about 292 cubic metres per second, while its maximum flow is around 1,610 cubic metres per second.
The North Thompson drains a somewhat larger area than the South Thompson, having an average flow of about 427 cubic metres per second, while its maximum flow is around 2,740 cubic metres per second. Together, as the Thompson River, they become the largest tributary of the Fraser River, meeting at the town of Lytton in the Fraser Canyon.
In the photo below the Nicoamen River flows under a Canadian National Railway bridge, then meets the Thompson, which flows from right to left.