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.
C-1 Channel Abv Mouth Nr Henderson, Nv
Hunter Ck Nr Reno, Nv
Cleve Ck Nr Ely, Nv
Walker Rv Blw Mason Vly Wma At Rr Xing Nr Wabuska
Henderson Ck Blw Vinnini Ck Nr Eureka, Nv
Warm Spgs Confl At Iverson Flume Nr Moapa, Nv
Franktown Ck Nr Carson City, Nv
L Currant Ck Nr Currant, Nv
Walker Rv Abv Little Dam Nr Schurz, Nv
S Fk Humboldt Rv Abv Tenmile Ck Nr Elko, Nv
Rock Ck Nr Battle Mountain, Nv
Sloan Channel At Charleston Blvd Nr Las Vegas, Nv
Galena Ck At Galena Ck State Park, Nv
E Walker Rv Nr Mason, Nv
Maggie Ck At Carlin, Nv
Preston Big Sprg Nr Preston, Nv
S Fk L Humboldt Rv Nr Paradise Valley, Nv
C-1 Channel Nr Warm Spgs Rd At Henderson, Nv
Las Vegas Wash Overflow At Lake Las Vegas Inlet
Steamboat Ck At Short Ln At Reno, Nv
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.