US Water Quality Index
Our composite Water Quality Score combines temperature, reservoir levels, and flow rates to rate conditions for swimming, fishing, and recreation.
How We Calculate Water Quality Score (0–100)
Maximum points when water temp is near ideal 71.5°F (22°C) for most recreational activities.
Full points when reservoir is at or near full pool capacity. Low levels reduce score.
Moderate, stable flow (100–5,000 cfs) earns full points. Extreme highs or lows reduce score.
Lookout Point Dam Tailwater Near Lowell, Or
Foster Dam Tailwater At Foster, Or
Klamath River Below Keno Dam, At Keno, Or
Coquille River At Coquille, Or
Middle Santiam R Blw Green Peter Dam Nr Foster, Or
Klamath River At Miller Island, Near Midland, Or
Big Cliff Dam Tailwater Near Niagara, Or
Hills Creek Dam Tailwater Near Oakridge, Or
Green Peter Dam Tailwater Near Foster, Or
Prowell Springs Diversion Pool, Near Bend, Or
Keno Reservoir At Keno, Or
Cougar Dam Tailwater Near Rainbow, Or
Detroit Dam Tailwater Near Detroit, Or
Dexter Dam Tailwater At Dexter, Or
Wapato Canal At Pump House, At Gaston, Or
Scoggins Creek Near Sw Old Hwy 47, Near Gaston, Or
Columbia River Below Bonneville Dam, Or
Blue River Below Tidbits Creek, Nr Blue River, Or
Ef Dairy Cr Abv Murtaugh Cr Nr Meacham Corner, Or
South Fork Bull Run River Near Bull Run, Or
Understanding the Water Quality Index
The US Water Quality Index is a composite score designed to give anglers, swimmers, boaters, and outdoor enthusiasts a quick, at-a-glance assessment of water body conditions. Unlike traditional water quality indices that focus on chemical pollutants (which require laboratory analysis), our index uses real-time USGS sensor data to reflect physical conditions relevant to recreation.
Temperature Component (40 points)
Water temperature is the most important factor for recreational fishing, swimming, and wildlife activity. The ideal range for most activities — comfortable for swimming, optimal for bass and walleye fishing — is approximately 65–78°F (18–26°C). Our scoring peaks at 71.5°F and decreases proportionally as temperature moves away from this ideal.
Reservoir Level Component (30 points)
Reservoir levels (measured as a percentage of full pool) reflect drought conditions, drought recovery, flood risk, and overall ecosystem health. A reservoir at full pool (100%) scores maximum points. Severely depleted reservoirs — common during drought — score fewer points. This metric is particularly relevant in western states where water storage is critical.
Flow Rate Component (30 points)
River discharge (measured in cubic feet per second, cfs) indicates safe boating, wading, and kayaking conditions. Moderate, stable flow rates between 100–5,000 cfs are typically ideal for most recreation. Extremely high flows indicate flood risk, while extremely low flows suggest drought stress and limited habitat for fish.