Map
Layers
- River Gauge
Categories Major Flood23Moderate Flood520Minor Flood3056Action7451No Flood63441645Flood Category Not Defined34470No Forecast Available00Low Water Threshold200Data Not Current6060Out of Service1810
National Water Model Layer
Official NWS streamflow forecasts are produced by NWS hydrologic forecasters for specific river gauge locations using hydrologic models that are calibrated to that location. This process considers additional guidance and information from other available sources, including local expertise and experience, to produce the best forecast possible. This NWM layer provides access to National Water Model streamflow guidance, available for approximately 2.7 million stream reaches.
Use of the NWM Layer
The streamflow network on the NWM layer is shown in the color chosen when the layer is enabled. As one zooms in, more
of the network will be disclosed. At river gauge locations where there is an official NWS gauge (denoted by a square
and/or circle marker), selecting the marker provides access to the official hydrograph (“Official” tab) for that gauge
and a supplemental hydrograph (“National Water Model Guidance” tab) for the river reach that contains the gauge. This
supplemental “National Water Model Guidance” hydrograph displays the NWM model output in addition to the official hydrograph.
Selecting a section of river with no gauge marker (no official forecast) will provide the NWM guidance hydrograph for
that river section.
The NWM is currently undergoing extensive validation and verification to identify where scientific updates to the model can make the most improvement, and new versions are planned for release on a regular basis. The NWM output provides supplemental guidance to NWS forecasters and should not be considered an official NWS river forecast.
Flood Inundation Layers (EXPERIMENTAL)
These services are considered experimental and are undergoing testing for an area that covers 30% of the U.S. population. Testing of these experimental services will expand to cover 60% of the U.S. population in September 2025 and then 100% of the U.S. population in September 2026.
The experimental flood inundation maps represent the National Weather Service's best approximation of inundation extent based upon modeled river discharge. These maps are derived from the official River Forecast Center forecasts and National Water Model analyses and forecast guidance. Flood inundation maps will display upon zooming in where river flow information depicts flooding or flow exceeds regionally derived high water thresholds.
Please visit https://www.weather.gov/owp/operations for more information about the experimental National Water Center Visualization services and the experimental Flood Inundation Mapping services. Services can be accessed directly by visiting https://maps.water.noaa.gov/server.
