The lake is primarily fed by snow runoff from nearby Mount Washington and the surrounding areas.

The lake is also fed by two small creeks, which may dry up seasonally, along with Great Spring, the source of the McKenzie River.

Clear Lake is the headwaters of the McKenzie River, which is the sole source of drinking water for Eugene.

[1] Clear Lake is reported to be one of the most exceptional freshwater dive spots in Oregon.

The trees are remarkably preserved due to the cold year-round water temperatures of between 35–43 °F (1.6–6 °C).