The South Thompson River IBA site is just east of Kamloops, in the southern interior of British Columbia. It includes the South Thompson River from its origin at Little Shuswap Lake to Kamloops Lake (approximately 70 km in length). During low water levels, the river is approximately 100 m wide and is 200-300 m wide during floods. The river flows down a gentle gradient (1 m per 10 km) through a relatively broad valley. The valley bottom is about 1 km wide, with rounded hills on either side, and in many cases bounded by 50 m high glaciolacustrine silt bluffs. Some unusual herptiles occurring in the site are Great Basin Spadefoot Toad, and Western Rattlesnake, both restricted in Canada to the Thompson and Okanagan Valleys. The river is also a major migration corridor for Chinook, Sockeye, Coho and Pink Salmon.

The calm waters of the South Thompson River provide excellent foraging habitat for wintering waterfowl, while riparian vegetation along it banks, primarily black cottonwoods and ponderosa pines, provide habitat for various breeding birds. Winter surveys of this stretch of the river have revealed 100 to 400 Trumpeter Swans, which represents up to 2% of the global population. Banding studies have revealed that both the Pacific and Rocky Mountain populations of Trumpeter Swans are present here.

Up to 600 Western Tundra Swans have also been surveyed here in winter. The number of Trumpeter Swans has increased relative to the Tundra Swans in recent years. Some breeding birds of interest include 80 Ospreys, four or more Bald Eagles, Wood Ducks and Lewis' Woodpecker (nationally vulnerable).

The South Thompson River has numerous threats that could potentially occur or are occurring at present. Urbanization and land clearing are causing losses of cottonwood and shrub riparian habitat, while bank erosion is occurring in some areas due to boating activities.

The river itself and its banks to the natural boundary are crown land, while the riparian woodlands are largely private. British Columbia Parks owns a small riparian area on the north bank of the river upstream of Pritchard.