Data Sources

All streamflow data displayed on StreamFlowData.com is sourced from freely available U.S. government data.

USGS National Water Information System (NWIS)

The primary data source for all station readings, discharge values, gage heights, and flow statistics. USGS operates over 8,000 stream gauges nationwide and provides free API access to all data.

We use four NWIS endpoints:

  • Instantaneous Values (IV) — Real-time instantaneous readings.
    waterservices.usgs.gov/nwis/iv/?format=json¶meterCd=00060,00065
  • Daily Values (DV) — Historical mean daily discharge.
    waterservices.usgs.gov/nwis/dv/
  • Statistics (STAT) — Long-term percentile statistics by calendar day.
    waterservices.usgs.gov/nwis/stat/
  • Site Info — Station metadata (name, location, drainage area, HUC).
    waterservices.usgs.gov/nwis/site/

No API key required. USGS NWIS data is in the public domain.

Visit USGS NWIS →

USGS Parameter Codes

Two parameter codes are used for all readings:

Code Parameter Unit
00060 Discharge (stream flow) Cubic feet per second (CFS)
00065 Gage height (stage) Feet above local datum

Flood Stage Data

Flood stage thresholds (action, flood, moderate, major) are based on National Weather Service (NWS) Advanced Hydrologic Prediction Service (AHPS) data, which sets site-specific thresholds for each USGS gauge location.

Visit NOAA AHPS →

Update Frequency

Current readings: Refreshed hourly from the USGS IV service. Cached in Redis with a 1-hour TTL per station.

Daily values: Updated nightly from USGS DV service. USGS publishes final daily mean values the following day.

Flow statistics: Updated annually. Long-term percentile statistics are computed from the full period of record and change slowly over time.

Data Attribution & Disclaimer

StreamFlowData.com is an independent project and is not affiliated with the U.S. Geological Survey (USGS) or any government agency. Data is presented "as is" from public sources. While we strive for accuracy, do not rely on this site as the sole source of information for flood safety, water recreation, or emergency management decisions.

For official real-time data, visit waterdata.usgs.gov/nwis directly.