“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 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.
Related Content
Is there a way to get alerts about streamflow conditions?
Yes! The U.S. Geological Survey WaterAlert service provides notifications to your email or phone for changes in water conditions based on thresholds you choose.
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, environmental agencies, universities, consulting firms...
Why does the USGS use the spelling "gage" instead of "gauge"?
The spelling of “gage” is part of our very rich USGS history. We have used that spelling for over a hundred years. In 1888, USGS Director John Wesley Powell met a very forward-thinking graduate student named Frederick Haynes 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...
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, springs, atmospheric) and select to show inactive sites...
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...
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. This NOAA website has a map showing the location of the forecast centers, their areas of responsibility, and by clicking into a region the location of the gages they use. The also provide a section for long-range river flood risk. The vast majority...
Streamflow—Water year 2020
Reach-scale monitoring and modeling of rivers--Expanding hydraulic data collection beyond the cross section
StreamStats, version 4
Compilation of streamflow statistics calculated from daily mean streamflow data collected during water years 1901–2015 for selected U.S. Geological Survey streamgages
Discharge measurements at gaging stations
From the River to You: USGS Real-Time Streamflow Information...from the National Streamflow Information Program
StreamStats: A U.S. Geological Survey Web Application for Stream Information
The stream-gaging program of the U.S. Geological Survey
Related Content
- FAQ
Is there a way to get alerts about streamflow conditions?
Yes! The U.S. Geological Survey WaterAlert service provides notifications to your email or phone for changes in water conditions based on thresholds you choose.
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, environmental agencies, universities, consulting firms...
Why does the USGS use the spelling "gage" instead of "gauge"?
The spelling of “gage” is part of our very rich USGS history. We have used that spelling for over a hundred years. In 1888, USGS Director John Wesley Powell met a very forward-thinking graduate student named Frederick Haynes 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...
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, springs, atmospheric) and select to show inactive sites...
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...
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. This NOAA website has a map showing the location of the forecast centers, their areas of responsibility, and by clicking into a region the location of the gages they use. The also provide a section for long-range river flood risk. The vast majority...
- Multimedia
- Publications
Streamflow—Water year 2020
The maps and graphs in this summary describe national streamflow conditions for water year 2020 (October 1, 2019, to September 30, 2020) in the context of streamflow ranks relative to the 91-year period of water years 1930–2020. Annual runoff in the Nation’s rivers and streams during water year 2020 (11.10 inches) was higher than the long-term (1930–2020) mean annual runoff of 9.40 inches for theAuthorsXiaodong Jian, David M. Wolock, Harry F. Lins, Ronald J. Henderson, Steven J. BradyReach-scale monitoring and modeling of rivers--Expanding hydraulic data collection beyond the cross section
For over 125 years, the U.S. Geological Survey streamgage network has provided important hydrologic information about rivers and streams throughout the Nation. Traditional streamgage methods provide reliable stage and streamflow data but typically only monitor stage at a single location in a river and require frequent calibration streamflow measurements. Direct measurements are not always feasibleAuthorsBrandon T. Forbes, Claire E. Bunch, Geoffrey DeBenedetto, Corey J. Shaw, Bruce GungleStreamStats, version 4
IntroductionStreamStats version 4, available at https://streamstats.usgs.gov, is a map-based web application that provides an assortment of analytical tools that are useful for water-resources planning and management, and engineering purposes. Developed by the U.S. Geological Survey (USGS), the primary purpose of StreamStats is to provide estimates of streamflow statistics for user-selected ungageAuthorsKernell G. Ries, Jeremy K. Newson, Martyn J. Smith, John D. Guthrie, Peter A. Steeves, Tana Haluska, Katharine R. Kolb, Ryan F. Thompson, Richard D. Santoro, Hans W. VragaCompilation of streamflow statistics calculated from daily mean streamflow data collected during water years 1901–2015 for selected U.S. Geological Survey streamgages
Streamflow statistics are needed by decision makers for many planning, management, and design activities. The U.S. Geological Survey (USGS) StreamStats Web application provides convenient access to streamflow statistics for many streamgages by accessing the underlying StreamStatsDB database. In 2016, non-interpretive streamflow statistics were compiled for streamgages located throughout the NationAuthorsGregory E. Granato, Kernell G. Ries, Peter A. SteevesDischarge measurements at gaging stations
The techniques and standards for making discharge measurements at streamflow gaging stations are described in this publication. The vertical axis rotating-element current meter, principally the Price current meter, has been traditionally used for most measurements of discharge; however, advancements in acoustic technology have led to important developments in the use of acoustic Doppler current prAuthorsD. Phil Turnipseed, Vernon B. SauerFrom the River to You: USGS Real-Time Streamflow Information...from the National Streamflow Information Program
This Fact Sheet is one in a series that highlights information or recent research findings from the USGS National Streamflow Information Program (NSIP). The investigations and scientific results reported in this series require a nationally consistent streamgaging network with stable long-term monitoring sites and a rigorous program of data, quality assurance, management, archiving, and synthesis.AuthorsJoseph P. Nielsen, J. Michael NorrisStreamStats: A U.S. Geological Survey Web Application for Stream Information
No abstract available.AuthorsKernell G. Ries, Peter A. Steeves, Jacqueline D. Coles, Alan H. Rea, David W. StewartThe stream-gaging program of the U.S. Geological Survey
The U.S. Geological Survey stream-gaging program provides streamflow data for a variety of purposes. The uses of streamflow data are described, and the growth of the stream-gaging program is related to legislation and the need to manage the Nation's water resources more effectively. A brief description is provided of the data-collection processes, computation of streamflow records, dissemination oAuthorsKenneth L. Wahl, Wilbert O. Thomas, Robert M. Hirsch - News