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.
Poesta Ck At Beeville, Tx
Guadalupe Rv At Third Crossing Nr Sattler, Tx
Indian Ck At Sh 78 Nr Farmersville, Tx
W Nueces Rv Nr Brackettville, Tx
Sandy Ck Nr Kingsland, Tx
Clear Ck At Mykawa St Nr Pearland, Tx
Blanco Rv At Fischer Store Rd Nr Fischer, Tx
Middle Verde Ck At Sh 173 Nr Bandera, Tx
Walnut Ck At Webberville Rd, Austin, Tx
Clear Fk Brazos Rv At Fm 3116 Nr Anson, Tx
Goose Ck At Baytown, Tx
Nueces Rv At Calallen, Tx
Medina Rv Nr Somerset, Tx
Brazos Rv Nr Glen Rose, Tx
E Fk San Jacinto Rv Nr Cleveland, Tx
Manadas Ck At Laredo, Tx
Big Cypress Bayou Nr Jefferson, Tx
N Fk Guadalupe Rv Nr Hunt, Tx
Pecan Ck Nr San Angelo, Tx
Leon Rv At Gatesville, Tx
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.