Monitoring the Pulse of Our 

Nation’s Rivers and Streams:

The U.S. Geological Survey 

Streamgaging Network

In the late 1800s, John Wesley Powell, second Director 

of the U.S. Geological Survey (USGS), proposed gaging 

the flow of rivers and streams in the Western United 

States to evaluate the potential for irrigation. Around 

the same time, several cities in the Eastern United 

States established primitive streamgages to help design 

water-supply systems. Streamgaging technology has 

greatly advanced since the 1800s, and USGS hydrographers have made at least one streamflow measurement 

at more than 37,000 sites throughout the years. Today, 

the USGS Groundwater and Streamflow Information 

Program supports the collection and (or) delivery of 

both streamflow and water-level information for more 

than 8,500 sites (continuous or partial record) and 

water-level information alone for more than 1,700

additional sites. The data are served online—most in 

near realtime—to meet many diverse needs; more than 

640 million requests for streamflow information were 

fulfilled during the 2017 water year (October 1, 2016‒

September 30, 2017).

Unique Partnership

The streamgages are primarily operated and maintained by 

the USGS, but most are funded in partnership with one or more of 

about 1,400 Federal, State, local, and Tribal agencies or organizations. This unique cooperation results in nationally consistent and 

impartial data that also aids local decision making. The shared 

costs result in the operation of far more streamgages than would be 

possible if financed solely by USGS appropriations, which provide 

less than one-third of the needed funding. These partnerships also 

enable fixed costs (such as costs associated with data storage and 

delivery infrastructure) to be broadly distributed, resulting in more 

economical streamgaging information for all.

A Network of Networks

The USGS streamgaging network is a multipurpose network 

that comprises more than 10,000 streamgages. It encompasses 

several smaller networks that produce specific information or 

support specific needs.

National Streamflow Network (NSN)

The National Streamflow Network (NSN) consists of all 

streamgages that continuously monitor streamflow year-round 

and from which daily mean streamflows are computed and made 

available online. The data collected at NSN streamgages serve 

several functions (including flood warning, water allocation, and 

recreation) and can be used by anyone regardless of whether or not 

they help fund the network. The use of consistent methods enables 

data from the many gages to be combined, expanding the use and 

value of the data from every gage. At present (2018), more than 

8,200 gages are in the NSN.

Federal Priority Streamgages (FPS) Network

The Federal Priority Streamgages (FPS) Network (previously 

known as the National Streamflow Information Program) was conceived in 1999 to be a core, federally funded network. The original 

network design included 4,300 then active, previously discontinued, 

or proposed new gages that were strategically positioned across 

the country to address long-term Federal information needs (such 

as supporting National Weather Service flood forecasts, or interstate and international compacts and decrees). At present (2018), 

more than 4,700 locations meet the criteria for inclusion in the FPS 

network, but only about 3,600 FPS are active because of funding 

limitations. These active FPS are supported through a combination 

of Federal and partner funding—less than one-quarter are fully 

funded by the USGS.

“The independent, science-based streamflow information that we obtain from USGS gages is paramount to assuring 

compliance under our various interstate compacts with our neighboring states.”

~Julie Cunningham, Oklahoma Water Resources Board

U.S. Geological Survey streamgage, Indian Fork at Dellroy, Ohio. Credit: Stephanie Kula (U.S. Geo ol g ci al Survey).

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2018–3081

February 2019
Information Delivery and Application

The USGS operates one of the largest streamgaging enterprises 

in the world. Water levels are measured by more than 10,000 gages; 

the data are typically transmitted to USGS computers within 1 hour of 

measurement. At most gages, continuously measured water levels are 

used to compute hourly (or more frequent) time series of streamflows 

from gage-specific rating curves that were developed using onsite 

streamflow measurements made by USGS hydrographers—more 

than 80,000 onsite measurements are made each year. The data are 

quality assured and made available online. Data users include emergency responders, water managers, environmental and transportation 

agencies, universities, utilities, recreational enthusiasts, and consulting 

firms. Specific uses of the data include the following:

• planning, forecasting, and warning about floods and droughts;

• managing water rights and transboundary water issues;

• operating waterways for power production and navigation;

• monitoring environmental conditions to protect aquatic habitats;

• describing impacts to streamflow from changing land and water 

uses;

• assessing water quality and regulating pollutant discharges;

• determining if streams are safe for recreational activities; and

• designing reservoirs, roads, bridges, drinking water and wastewater 

facilities.

By Sandra M. Eberts, Michael D. Woodside, Mark N. Landers, and 

Chad R. Wagner

“Many thanks...we sincerely appreciate your [USGS] 

support. Your data make our forecasts possible.”

Kevin Low, National Weather Service, 

Missouri River Basin Forecast Center Hydrologist, 

May 25, 2018

By the Numbers (2017 Water Year)

Streamflow and Water-Level Gages

(operated year-round or seasonally)

10,330 gages

8,580 monitored streamflow and water level

1,750 monitored water level

80,000 measurements made by hydrographers

Key Networks

National Streamflow Network (NSN)

(monitored streamflow year-round and met a variety of 

local, State, and Federal needs)

8,230 gages

5,030 had more than 30 years of record

330 had more than 100 years of record

Federal Priority Streamgages (FPS) Network

(met Federal priority information needs)

3,640 gages

3,200 monitored streamflow year-round

(included in the National Streamflow Network)

440 monitored water level or operated seasonally

1,120 eligible locations lacked funding

Funding

$188 million

$55 million from Federal appropriation

$133 million from 1,410 partners

Water Data Delivery

640 million requests made for streamflow info

98 percent fulfilled through web services

U.S. Geological Survey Water Mission Area

Groundwater and Streamflow Information Program

https://www.usgs.gov/gwsip

WaterWatch: https://waterwatch.usgs.gov/

WaterAlert: https://maps.waterdata.usgs.gov/mapper/wateralert/

WaterNow: https://water.usgs.gov/waternow/

National Water Information System: https://waterdata.usgs.gov/nwis

Techniques and Methods 3–A8—

Discharge Measurements at Gaging Stations: 

https://pubs.usgs.gov/tm/tm3-a8/

For more information

ISSN 2327-6916 (print)

ISSN 2327-6932 (online)

https://doi.org/10.3133/fs20183081 ert S ma wolf e m sa r u me ent C, hat ot oga Nat oi na Wl ild and Scen ci R vi er, Georgia. Credit: Alan Cressler (U.S. Geological Survey).