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.
Delaware River At Riegelsville Nj
Millstone River At Blackwells Mills Nj
Raritan River At Manville Nj
Nb Rancocas C At Iron Works Park At Mount Holly Nj
Passaic River Below Pompton Riv At Two Bridges Nj
Crosswicks Creek At Extonville Nj
Delaware River At Frenchtown Nj
South Branch Pennsauken Creek At Cherry Hill Nj
Raccoon Creek Near Swedesboro Nj
Southwest Branch Rancocas Creek At Medford Nj
Greenwood Branch At New Lisbon Nj
Del And Rar Ca Feeder At Washington Crossing Nj
Delaware River At Marine Terminal At Trenton Nj
North Branch Rancocas Creek At Pemberton Nj
Del & Rar Canal At Landing La At New Brunswick Nj
Crosswicks Ck At Hockamik Rd Near Cookstown Nj
Manasquan River Near Allenwood Nj
Manumuskin River At Cumberland Nj
Cooper River At East State Street At Camden, Nj
Rancocas Creek At Bridgeboro Nj
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.