The lake is composed of two bodies of water, connected by a shallow channel known locally as the Bosporus.

[1] The Boundary Commission Trail ends at the lake as the last border marker was placed there on 8 August 1874.

[2] The United States Geological Survey gives the geocoordinates of 49°03′00″N 113°54′03″W / 49.05000°N 113.90083°W / 49.05000; -113.90083 for Upper Waterton Lake.

In 1979, UNESCO established the Waterton Biosphere Reserve to protect the diverse habitats including prairie grasslands, aspen parkland, subalpine forests, alpine tundra and freshwater fens that surround the lake.

Waterton River has relatively reduced sediment concentrations due to the lakes and the reservoir acting as a sediment-settling trap.