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.
Arkansas R. At St Charles Mesa Diver. At Pueblo,Co
Colorado River Near Kremmling, Co
Colorado R Blw South Canyon Cr Nr Glenwood Spgs Co
Arkansas River Below Moffat Street At Pueblo, Co
Lake Fork At Gateview, Co.
Eagle River At Price Lane Bridge Near Gypsum, Co
South Platte R At 64Th Ave. Commerce City, Co.
White River Above Coal Creek Near Meeker, Co
Colorado R Abv Roaring Fork R At Glenwood Spgs, Co
San Juan River At Four Corners, Co
Fountain Creek Bl 8Th St., At Colo. Springs, Co.
Arkansas River At Granite, Co.
Arkansas River Near Avondale, Co.
Colorado R. Abv Gunnison R. At Grand Junction, Co
Gunnison River Near Gunnison, Co.
Colorado River At Windy Gap, Near Granby, Co.
Colorado River Near Colorado-Utah State Line
San Juan River Near Co Rd 119 At Pagosa Springs Co
Monument Cr Abv Woodmen Rd At Colorado Springs, Co
Cimarron River Blw Cimarron Creek At Cimarron, Co
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.