Why might USGS streamflow data be revised?

Real-time USGS streamflow data are PROVISIONAL, meaning that the data have not been reviewed or edited. These data might be subject to significant change and are not official until reviewed and approved by the USGS.

Real-time streamflow data can be affected by:

  • backwater from ice or debris such as log jams
  • algae and aquatic growth in the stream
  • sediment movement
  • malfunction of recording equipment

Data are reviewed periodically to ensure accuracy. Each station record is considered PROVISIONAL until the data are published. The data are usually published within 6 months of the end of the water year.

Data users are cautioned to consider the provisional nature of the information before using it for decisions that concern personal or public safety or for business that involves substantial monetary or operational consequences.

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Is there a way to get alerts about streamflow conditions?

Yes! The USGS offers two services: WaterAlert - automated emails or text messages are sent to you whenever certain parameters (that you define) are exceeded at one of our gaging stations. WaterNow - Send an email or text message to WaterNow@usgs.gov containing the USGS Site Number of the gage you want to query (optionally add parameter codes to...

How can I obtain river forecasts (flood forecasts)?

River forecasts (flood forecasts) are made by the National Weather Service River Forecast Centers and released through local Weather Service Offices. The NOAA website has a map showing the location of the forecast centers, their areas of responsibility, and the location of the gages they use. The vast majority of current streamflow data used for...

Does "stage" tell you how much water is flowing in a stream?

Not directly. You cannot say that because a stream rises (doubles) from a 10-foot stage to a 20-foot stage that the amount of flowing water also doubles. Think of a cereal bowl with a rounded bottom. Pour one inch of milk in it. It doesn't take much milk to make it up to the one inch level because the bowl is at its narrowest near the bottom. Now...

Why are there sometimes differences between USGS and National Weather Service river stages?

At some USGS stream-gage installations, NOAA’s National Weather Service (NWS) maintains a separate stage sensor that is serviced by NWS technicians. Calibration of any sensing device can occasionally drift from a "true" value, so there might be differences between USGS and NWS data reports. USGS personnel visit installations on an interval of 6...

What does the term "stream stage" mean?

Stream stage is an important concept when analyzing how much water is moving in a stream at any given moment. "Stage" is the water level above some arbitrary point in the river and is commonly measured in feet. For example, on a normal day when no rain has fallen for a while, a river might have a stage of 2 feet. If a big storm hits, the river...

What is a rating curve? Why does it change over time?

In order to convert water height (or “stage”, usually expressed as feet) into a volume of water (or “discharge”, usually expressed as cubic feet per second), USGS hydrographers must establish a relationship between them. This stage-discharge relationship is called a rating curve. It’s developed by making frequent direct discharge measurements at...

Sometimes the USGS real-time stage data seems too high (or too low). Are the USGS data inaccurate?

There can be occasional equipment or database problems where erroneous data are reported for short periods of time until corrections can be made. This is why it is important to look at a record of streamflow (like the 7-day hydrograph plots) rather than a single point in time. However, most of the time the USGS has a high level of confidence in...

Where can I get real-time and historical streamflow information?

The best starting point for USGS streamflow data is the interactive National Water Information System (NWIS): Mapper website. Zoom in to your area of interest or use the search options in the left navigation window. The map displays active surface-water sites by default, but you can change the type of water site (surface-water, groundwater,...

Why do some real-time streamgaging stations stop transmitting data for extended periods of time?

The USGS usually corrects any equipment or station problems at our streamgages within a few days of their occurrence. Occasionally, replacement parts or equipment might not be readily available, or a station might be inaccessible due to weather conditions. Most USGS streamgaging stations are operated in cooperation with other agencies. At some...

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...
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Date published: February 1, 2017

The Vital Nature of Streamgaging

Gary Moore spent the last three days of 2015 stacking hefty bags of sand in front of a fellow church member’s brick home. With only 1,000 feet between the house and the swelling Mississippi and Meramec Rivers, Moore and other volunteers worked quickly, in frigid temperatures, to assemble a 10-foot high, 1,000-foot-long sandbag wall to ward off floodwaters.

Date published: August 22, 2016

Fighting the Floods

The USGS response to the Louisiana floods is part of the larger USGS flood science mission...

Date published: March 22, 2016

Follow Your Stream to Learn About Water

Explore America's streams and rivers from your computer or mobile device.

Filter Total Items: 10
Snowmibiles needed to get to Blackrock Creek streamgage
January 4, 2018

Snowmibiles needed to get to Blackrock Creek streamgage

Snowmibiles needed to get to Blackrock Creek streamgage

A USGS streamgage in Puerto Rico damaged by Hurricane Maria.
December 31, 2017

A USGS streamgage in Puerto Rico damaged by Hurricane Maria

This USGS streamgage, located on the Río Gurabo in Gurabo, Puerto Rico, was one of the 94 USGS gauges damaged by Hurricane Maria. Days after the storm past, USGS crews were able to repair the gauge and get it up and running again. USGS Photo.

Image shows a USGS scientist in a PFD servicing a streamgage
August 29, 2017

Servicing a Streamgage at Barker Reservoir Following Hurricane Harvey

USGS scientist Tom Pistillo wades through the waters of Barker Reservoir to ensure accurate reservoir water-level data are being measured, which are critical for helping the U.S. Army Corps of Engineers and Harris County Flood Control District make informed reservoir operation decisions.

Ice jam at Ponca Creek at Verdel, NE, February 15, 2017
February 15, 2017

Ice jam at Ponca Creek at Verdel, NE, February 15, 2017

USGS Nebraska Water Science Center hydrologic technician, Nathan Shultz, collecting depth and velocity data at the USGS streamgaging station 06453600 Ponca Creek at Verdel, Nebraska during an ice jam on February 15, 2017. 

Ray Dupuis, U.S. Geological Survey hydrologic technician, begins to repair a USGS streamgage in Homosassa Springs State Park, Fl
September 2, 2016

Repairing a streamgage

Ray Dupuis, U.S. Geological Survey hydrologic technician, begins to repair a USGS streamgage in Homosassa Springs State Park, Florida, that was damaged by storm surges brought by Hurricane Hermine. Photo by Don Hampton, USGS. 

Image: Flooded Streamgage on the Gasconade River
December 29, 2015

Flooded Streamgage on the Gasconade River

Why did that USGS streamgage go down?! Well, because it got flooded, most likely. As floodwaters rise, sometimes they inundate our streamgages. We repair them as quickly as possible so they get their data back up and running.

In fact, in some instances, we have enough lead time to get the instrumentation in the streamgage as high as possible to prevent it from being

Attribution: Natural Hazards
Image: Ice Jam Remnants
April 28, 2015

Ice Jam Remnants

On April 29, hydrologic technicians Anthony Underwood and Jeremiah Pomerleau visited the USGS gaging station on the St. John River at Ninemile Bridge and found a sea of broken up, dirty ice left behind by a recent ice jam.

According to Anthony, photos don't do the size and scale of the ice chunks any justice.

December 11, 2012

Streamflow Gaging Station and Measurement on San Pedro River, AZ

USGS employee, Hanna Coy, talks about stream gauging.

October 14, 2009

Streamgages: The Silent Superhero

Whether you drink water from your tap, use electricity or canoe down your local river, chances are you benefit from USGS streamgage information. So what is a streamgage and what does it do for you? This CoreCast episode gives you the inside scoop on your silent superhero.

Transcript and captions available soon.