How can I find the HUC (Hydrologic Unit Code) for a stream? How can I find the name/location of a stream using the HUC?
Hydrologic Units (HUs) represent the area of the landscape that drains to a portion of the stream network. Each drainage has a unique Hydrologic Unit Code (HUC). The most current national HU dataset is the Watershed Boundary Dataset (WBD). HUCs from other sources might be out of date or differ from the WBD standards.
The WBD includes six required levels of nested HU polygons (2- to 12-digit), two optional nested levels of HU polygons (14- and 16-digit), and supporting geospatial data. 14- and 16-digit HUs only exist in a few areas of the country.
HUs and HUCs are easily found through the National Map Viewer:
- Go to The National Map Viewer (it might take a minute to fully load).
- In the green bar above the map, click on the Layers icon, which looks like a stack of paper.
- Click on the box beside "Watershed Boundary Dataset".
- Zoom in to your area of interest. As you zoom in, click on the arrow beside the Watershed Boundary Dataset box in the Layers list to toggle higher resolution layers on and off.
To view the attributes of a flowline (stream) including the Name and Reachcode, follow the above instructions to turn on the National Hydrography Dataset layer in The National Map Viewer and click on any stream to see its attributes.
The WBD is a companion to the National Hydrography Dataset (NHD), which contains information about the nation’s surface hydrography. The first 8 digits of the reachcode are equivalent to the 8-digit hydrologic unit code for the unit that the NHD feature resides within. View both WBD and NHD using The National Map Viewer or download WBD and NHD products for use with GIS software.
Learn more: Video lessons 3a-3e on using The National Map Viewer
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How often are real-time streamflow data updated?
USGS real-time streamflow data are typically recorded at 15-minute intervals, stored onsite, and then transmitted to USGS offices once every hour, depending on the data relay technique used. Recording and transmission times might be more frequent during critical events (floods, for example). Data from current sites are relayed to USGS offices via satellite, telephone, and/or radio telemetry and...
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