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.
Pottsburg Crk At Us90 Nr S. Jacksonville, Fl
Sw 122 Ave Canal At Sw 202Nd St Nr Goulds, Fl
Minam River At Minam, Or
Madison River At Kirby Ranch Nr Cameron Mt
Mongaup R Below Swinging Bridge Reservoir Ny
Johnson Creek At Milwaukie, Or
Sixes River At Sixes, Or
Rock Creek Ab Hwy 30/93 Xing At Twin Falls Id
Row River Above Pitcher Creek, Near Dorena, Or
John Day River Near John Day, Or
Tenmile River At Tusten Ny
Irondequoit Cr Above Blossom Rd Near Rochester Ny
Crystal Springs Creek At Bybee St, Portland, Or
St. Johns River At Jacksonville, Fl
Lake Champlain At Port Henry Ny
Eagle River At Price Lane Bridge Near Gypsum, Co
Anchor R Nr Anchor Point Ak
Warm Springs Creek At Warm Springs Mt
Unnamed Trib To Bertrand Cr Nr H St Nr Lynden, Wa
Stony Brook Unnamed Trib 2 Nr Weston Station
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.