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.
Wfk Dry Comal Ck At Schuetz Dam, New Braunfels, Tx
Clear Ck At Fm 865 Nr Pearland, Tx
Lower Keechi Ck At Ih 45 Nr Centerville, Tx
W Fk San Jacinto Rv At Fm 2854, Conroe, Tx
Colorado Rv Nr Wadsworth, Tx
Spring Branch At Sh 242 Nr Splendora, Tx
Cowhouse Ck At Old Georgetown Rd Nr Ft Hood, Tx
Sabine Rv At I-10 Nr Orange, Tx
S Fk San Gabriel Rv At Sh 1869 Nr Liberty Hill, Tx
Oyster Ck At Cr 42 Nr Rosharon, Tx
Atascosa Rv At Fm 476 Nr Pleasanton, Tx
Little Brushy Ck At Us 77 Nr Yoakum, Tx
Linnville Bayou At Fm 521 Nr Cedar Lane, Tx
Clodine Ditch At Noble Rd Nr Addicks, Tx
Devils Run Ck At Us 77 Nr Woodsboro, Tx
Cow Bayou At Ih 10 Nr Vidor, Tx
Ubc Dam 101 At O'Connor Blvd Nr Round Rock, Tx
Willow Marsh Bayou At Us 90 Nr Beaumont, Tx
W Prong Medina Rv At Carpenter Ck Rd Nr Medina, Tx
Keechi Ck At Sh 337 Nr Graford, 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.