USGS Water Services

Overview

USGS Water Services serves real-time and historical water data from US monitoring stations — streamflow, water levels, temperature, and water quality — via the NWIS instant-values API. Keyless and free (verified live), it’s the authoritative source for US hydrology data.

Quick Start

Instant values for a site (verified live — Potomac River):

curl "https://waterservices.usgs.gov/nwis/iv/?format=json&sites=01646500&period=P1D"

{
  "value": {
    "timeSeries": [
      {
        "sourceInfo": { "siteName": "POTOMAC RIVER NEAR WASH, DC", "siteCode": [{ "value": "01646500" }] },
        "variable": { "variableName": "Streamflow, ft\u00b3/s" },
        "values": [
          { "value": [{ "value": "5120", "dateTime": "2026-08-22T04:45:00.000-04:00" }] }
        ]
      }
    ]
  }
}

Daily values (historical):

curl "https://waterservices.usgs.gov/nwis/dv/?format=json&sites=01646500&startDT=2026-08-01&endDT=2026-08-22"

Authentication

None — keyless.

Rate Limits & Notes

• Free, public US government data — no key, generous limits (bulk queries have per-IP caps).
• Endpoints: /nwis/iv/ (instantaneous), /nwis/dv/ (daily), /nwis/gwlevels/ (groundwater).
• Parameters: sites (comma-separated IDs), period=P1D/P7D/P30D, startDT/endDT (ISO dates), format=json|xml|waterml.
• Site numbers are USGS identifiers — find them via the site search or /nwis/site/ endpoint.

FAQ

Is USGS Water Services free? Yes — free, keyless, public government data.

How do I find a site ID? Use the USGS water data search, or query /nwis/site/?format=rdb&stateCd=VA.

What formats? JSON, XML, and WaterML (for hydrologic software).