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 its real-time stage data.

During low streamflow conditions, aquatic grasses, debris, or rocks near the gage can  produce artificial increases in water level readings. During extreme cold weather, ice can affect stage and discharge determinations at some stations. Adjustment of data for ice effects requires detailed analysis.

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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 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...

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...

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 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...

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...

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...

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 do we benefit from USGS streamgages?

Information on the flow of rivers is a vital national asset that safeguards lives, protects property, and ensures adequate water supplies for the future. The USGS is the federal agency responsible for operating a network of about 7,000 streamgages nationwide. Data from this network are used by water managers, emergency responders, utilities,...
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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.

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man in yellow slicker standing in rushing river up to his thighs, holding a stick-like instrument in the water
December 31, 2017

Measuring streamflow in fast moving floodwater.

USGS hydrographer measuring streamflow using a handheld Acoustic Doppler Velocimeter in fast moving floodwater Cajon Creek near Keenbrook, California. 

Measuring streamflow, South Fork Salmon River, Idaho
October 12, 2017

Measuring streamflow, South Fork Salmon River, Idaho

USGS hydrologic technician Pete Spatz measures streamflow on the South Fork Salmon River near Krassel Ranger Station, Idaho

A USGS Hydrologic Technician installs a new streamgage
February 23, 2017

A USGS Hydrologic Technician installs a new streamgage

U.S. Geological Survey Hydrologic Technician Patrick Anzman installs a new streamgage February 23 over the Schuylkill River in the Philadelphia neighborhood of Manayunk. Photo by Mason Manis, USGS. 

Ice jam on Little Wind River (06235500)
February 10, 2017

Ice jam on Little Wind River (06235500)

Ice jam on Little Wind River Ice jam on Little Wind River (06235500), February 2017. Streamgage destoryed soon after photo taken.

A U.S. Geological Survey hydrologic technician, uses an Acoustic Doppler Velocimeter to measure stream flow on a Florida creek.
September 2, 2016

Measuring streamflow

Neil Yobbi, U.S. Geological Survey hydrologic technician, uses an Acoustic Doppler Velocimeter to measure stream flow on Curlew Creek in Tampa, Florida. While Hurricane Hermine might have made landfall almost 200 miles away in St. Marks, Florida, a USGS rain gauge in Pinellas County, Florida, still measured more than 16 inches of total rain during the past three-day storm

Example NWIS graph of real-time streamflow monitoring
April 18, 2016

Example NWIS graph of real-time streamflow monitoring

Example NWIS graph of real-time streamflow monitoring, including historical median information.

Ice Jam at White River near Interior, SD (06446500)
February 12, 2016

Ice Jam at White River near Interior, SD (06446500)

Ice jam at White River near Interior, SD (USGS streamgage 06446500). More information on this site is available at 

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.

February 24, 2015

Under The Ice

On February 26, Nick Stasulis and Charlie Culbertson visited USGS station 01054200 Wild River at Gilead, Maine to make a streamflow measurement through the ice. For these measurements, 20-30 holes are drilled through the ice and a current meter (the spinning yellow cups) is used to measure velocity. River depths and distance across the channel are also measured. After this

December 11, 2012

Streamflow Gaging Station and Measurement on San Pedro River, AZ

USGS employee, Hanna Coy, talks about stream gauging.