Water temperatures in the Willamette River have been rising over the past decade due to drought, decreased snow pack, and changed flows. The trend of increased water temperature threatens species of fish in the basin such as Chinook salmon and steelhead trout. Salmon and steelhead are coldwater fishes and require water temperatures in the range of 8-15ºC (45-60ºF) for optimal survival and reproduction. As temperatures rise, salmon and steelhead become stressed and are more susceptible to disease, increasing the risk of pre-spawning mortality.

This indicator measures the attainment of water temperatures required for salmon and steelhead health.

Remaining areas of cold water have become havens for temperature sensitive fish like trout and salmon. Photo courtesy of Dave Herasimischuk (Freshwaters Illustrated).