What is a reach?

“Reach” can have slightly different meanings, depending on how it is used.

A reach is a section of a stream or river along which similar hydrologic conditions exist, such as discharge, depth, area, and slope. It can also be the length of a stream or river (with varying conditions) between two streamgages, or a length of river for which the characteristics are well described by readings at a single streamgage.

In practical use, a reach is just any length of a stream or river. The term is often used by hydrologists when they’re referring to a small section of a stream or river rather than its entire length.  

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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...

Why does the USGS use the spelling "gage" instead of "gauge"?

The spelling of “gage” is part of our very rich USGS history. In 1888, USGS Director John Wesley Powell met a very forward-thinking man named Frederick H. Newell. Powell was so impressed that he made Newell the first full-time appointee to the new Irrigation Survey, which was created to investigate the potential for dams and canals in the western...

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 Web site 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...

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...

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,...

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: May 11, 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: March 22, 2016

Follow Your Stream to Learn About Water

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

Date published: February 26, 2013

Stay Current on Your Rivers with USGS WaterNow

For the first time, anyone can find out the current conditions on thousands of rivers and streams across the country, right from their phone, using USGS' latest system WaterNow.WaterNow makes the water conditions monitored by more than 16,000 streamgages and other sites across the country available via text or email. 

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July 31, 2017

Advances in Streamgaging | Reach-Scale Monitoring Experiment (1 of 2)

In this first installment of a two part series, The Arizona Water Science Center has developed new stream gaging methods that would measure flood flows remotely. However, they have to verify the accuracy of these techniques, so they designed an experiment in partnership with the USDA Southwest Watershed Research Center at the Walnut Gulch Experimental Watershed that

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May 31, 2017

Reach-Scale Monitoring | Advances in Stream Gaging

The Arizona Water Science Center demonstrates new methods in Reach-Scale Monitoring to improve accuracy and measurability of high flow events. By installing pressure transducers and using LiDAR to measure topography data, hydrologists are able to simulate flows with two dimensional models which will help better calibrate stream gages. These advances have potential to aid

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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.

trees and stream
September 19, 2006

Gaged stream reach East Brook east of Walton, NY

Gaged stream reach East Brook east of Walton, NY