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.
Catawba River At Nc Highway 16 Nr Millersville, Nc
Cheoah River Nr Bearpen Gap Nr Tapoco, Nc
Catawba River Bl Lookout Shoals Dam Nr Sharon, Nc
Pee Dee R At Hwy731 Bl Lk Tillery Nr Norwood, Nc
French Broad River At Asheville, Nc
Catawba R Nr Pleasant Gardens, Nc
Pigeon R Bl Power Plant Nr Waterville, Nc
Neuse River Near Fort Barnwell, Nc
Catawba River At Rhodhiss, Nc
French Broad River Near Fletcher, Nc
Roanoke River At Halifax, Nc
Pigeon River Near Canton, Nc
Lake Mattamuskeet W Of Nc Hwy 94 Nr Fairfield, Nc
Catawba River Dnstrm Deck Mtn Is Dam Nr Mtn Is, Nc
Pee Dee River Above Jones Creek Near Cordova, Nc
Lake Mattamuskeet E Of Nc Hwy 94 Nr Fairfield, Nc
Pee Dee River Below Powerhouse Dam Nr Pee Dee, Nc
Oconaluftee River At Birdtown, Nc
French Broad River At Haywood Rd At Asheville, Nc
Catawba R At Rr Bridge Ab Nc 73 At Cowans Ford, Nc
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.