Overall Health Index
The Willamette River report card compares 15 indicators (water quality index, toxics, temperature, native fish, non-native fish, juvenile chinook, bald eagle, channel complexity, floodplain forest, flow targets, peak flows, fish consumption advisories, tribal fisheries, fecal bacteria, harmful algal blooms) to scientifically derived thresholds or goals. These individual indicators were averaged to calculate scores for each of the five categories, for the upper, middle, and lower Willamette. These five categories were then combined into an Overall Health Index for each reach of the river. The overall grade for the river is the average of these three reach scores.