Descriptive display bins
Below 0.5 mg/L as N0.5–1 mg/L as NAbove 1–5 mg/L as NAbove 5 mg/L as N
These colors only separate reported values for viewing. They are not drinking-water, aquatic-life, health, agricultural, impairment, treatment, or regulatory thresholds.
How to read this
Fact: each marker is a recent USGS stream-site measurement of nitrate plus nitrite, measured in situ and reported in milligrams per liter as nitrogen. The popup preserves its time-series ID, measurement time, reported unit, and approval status. Limit: this combined quantity is not nitrate alone and is not nitrate expressed as the full nitrate ion. Values can reflect local sources, hydrology, season, biological activity, and sensor context. One point does not represent an entire water body. The map infers no cause, trend, contamination, exposure, health or ecological effect, treatment need, safety, impairment, or compliance.
Source contract
USGS modern Water Data OGC API, latest-continuous, parameter 99133. Requests are anonymous, keyless, limited to stream sites in the visible bounding box and preceding 48 hours, capped at 500 features, and protected by a 60-second client cooldown. Missing, nonnumeric, negative, nonpoint, or older records are excluded. No credential, proxy, saved measurement snapshot, or proprietary GIS service is used. Source/license notes · USGS API documentation
