U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2009–3020

March 2009

National Streamflow Information Program

Introduction

The U.S. Geological Survey (USGS) operates and maintains a nationwide network of about 

7,500 streamgages designed to provide and interpret long-term, accurate, and unbiased streamflow 

information to meet the multiple needs of many diverse national, regional, state, and local 

users. The National Streamflow Information Program (NSIP) was initiated in 2003 in response 

to Congressional and stakeholder concerns about (1) the decrease in the number of operating 

streamgages, including a disproportionate loss of streamgages with a long period of record; 

(2) the inability of the USGS to continue operating high-priority streamgages in an environment of 

reduced funding through partnerships; and (3) the increasing demand for streamflow information 

due to emerging resource-management issues and new data-delivery capabilities. The NSIP’s 

mission is to provide the streamflow information and understanding required to meet national, 

regional, state, and local needs.

Most of the existing streamgages are funded through partnerships with more than 850 other 

Federal, state, tribal, and local agencies. Currently, about 90 percent of the streamgages send data 

to the World Wide Web in near-real time (some information is transmitted within 15 minutes, 

whereas some lags by about 4 hours). The streamflow information collected at USGS streamgages 

is used for many purposes:

• In water-resource appraisals and allocations—to determine how much water is available 

and how it is being allocated;

• To provide streamflow information required by interstate agreements, compacts, and court 

decrees;

• For engineering design of reservoirs, bridges, roads, culverts, and treatment plants;

• For the operation of reservoirs, the operation of locks and dams for navigation purposes, 

and power production;

• To identify changes in streamflow resulting from changes in land use, water use, and 

climate;

• For streamflow forecasting, flood planning, and flood forecasting;

• To support water-quality programs by allowing determination of constituent loads and 

fluxes; and

• For characterizing and evaluating instream conditions for habitat assessments, 

instream-flow requirements, and recreation.

Implementation Status Report

... 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 collection, quality assurance, management, archiving, and synthesis. NSIP 

produces multipurpose, unbiased surface-water information that is readily accessible to all.
Streamgage-Network Instability

The number of streamgages 

operated by the USGS over the past 40 

years (fig. 1) has varied from a high of 

about 8,300 in 1970 to a low of about 

6,800 in 1998. Over this 40-year period, 

the number of streamgages has decreased 

by more than 660 even though the need 

for streamflow information has increased 

due to increasing population, required 

habitat assessments, new water-quality 

requirements such as total maximum 

daily loads, and the need to understand 

the effects of climate change. The 

instability of the streamgage network 

over the past 40 years can also be 

illustrated by the loss of streamgages 

that had at least 30 years of information 

when they were discontinued (fig. 2). 

Data from long-record streamgages 

are critical for identifying changes in 

the amount and timing of streamflow 

caused by changes in land use, water use, 

and climate. 

Much of the streamgage-network 

instability is directly attributable to 

variations in funding. For example, 

funding sources for the USGS 

streamgage network in fiscal year 2008 

are shown in figure 3. The USGS has 

direct control of only about 15 percent 

of the funds required to operate and 

maintain the network (the NSIP funds). 

The USGS contributes another 18 percent 

of the streamgage-network funding 

through the USGS Cooperative Water 

Program (CWP), which requires at least 

a 50-percent match from the cooperating 

partner for the USGS to invest the CWP 

funds for streamgaging. Funds from 

state and local agencies for streamgaging 

are not being matched dollar for dollar 

by the USGS CWP; those agencies are 

currently providing about $2.6 for every 

$1 provided by the CWP. Consequently, 

when partner funding is reduced, the 

water community often loses streamgages 

because it does not have adequate 

funding to maintain them. As a result, 

the network’s ability to meet long-term 

Federal needs for streamflow information 

is uncertain. 

To respond to this issue, the USGS 

developed a plan for the National 

Streamflow Information Program (U.S. 

Geological Survey, 1999). This fact sheet 

briefly describes the current status of the 

NSIP and the progress that has been made 

in implementing the five goals outlined 

in the NSIP plan. Because the needs 

for and uses of streamflow information 

are ever-changing and technology is 

constantly advancing, the NSIP plan 

must be modified over time to ensure its 

continued usefulness and relevance. 

The five goals of the program, the 

objectives associated with each goal, 

and the implementation status of each 

objective are described below.

Goal 1: Stable Streamgage 

Network

The NSIP’s primary goal is to 

establish a stable “backbone” streamgage 

network to fulfill the five Federal needs 

for streamflow information described 

in the box on the next page. A total of 

4,744 streamgage locations strategically 

distributed across the country have 

been identified to meet these needs; 

more than 900 of these streamgages 

will meet more than one of the Federal 

needs. The NSIP’s plan is for the total 

operation and maintenance costs of this 

core set of permanent, continuously 

operated streamgages to be provided by 

the USGS. This stable Federal funding 

will ensure that real-time delivery 

of critical streamflow information is 

uncompromised by fluctuating funding. 

The plan is also for all streamgages to be 

modernized and hardened to withstand 

both floods and extreme weather so the 

data are reliably available when they are 

most needed.

Objective 1

Add new (or reactivate discontinued) 

streamgages at specific identified critical 

locations to establish the complete 

federally funded “backbone” network 

of 4,744 streamgages. As of 2001, 484 

new streamgages and 864 reactivated 

streamgages were needed to complete the 

network as designed.

Status. Currently, 2,940 (62 

percent) of the 4,744 NSIP “backbone” 

streamgages are operated year round by 

the USGS. An additional 250 (5 percent) 

are operated by the USGS for less than 

a full year (partial record), and 172 (4 

percent) are operated by a non-USGS 

agency. Currently (2009), 421 new and 

944 reactivated streamgages are needed 

to complete the network as designed, 

indicating that 80 additional streamgages 

have been lost from the NSIP network 

since 2001. The priority to date for 

the limited funds available has been to 

8,500

8,000

7,500

7,000

6,500

1970197219741976197819801982198419861988199019921994199619982000200220042006

Figure 1. Number of active U.S. Geological Survey streamgages, 

1970–2007.

0

20

40

60

80

100

120

140

160

1970197219741976197819801982198419861988199019921994199619982000200220042006

NUMBER OF DISCONTINUED

STREAMGAGES WITH 30 OR MORE

YEARS OF RECORD

Figure 2. Number of discontinued U.S. Geological Survey streamgages 

with 30 or more years of record, 1970-2007.
OFA $28.5M

(21%)

USGS-NSIP

$20.1M

(15%)

USGS-CWP

$24.2M

(18%)

State/local

$63.8M

(46%)

Figure 3. Funding sources for the U.S. 

Geological Survey streamgaging network, 

2008. (Values are in millions of dollars; total 

funding $136.6 million; OFA, other Federal 

agencies; NSIP, National Streamflow 

Information Program; CWP, Cooperative 

Water Program)

sustain the operation and maintenance 

of existing streamgages threatened with 

discontinuation rather than to fund new 

or reactivated streamgages.

Objective 2

Upgrade equipment at existing 

streamgages that do not currently have 

the capability to transmit data in real 

time, and upgrade to high data rate 

(HDR) transmitters at all streamgages. 

The expected outcomes are that 

additional streamgages will deliver 

real-time information to the World 

Wide Web at shorter time intervals, and 

that compliance with the directive that 

all transmitters to the Geostationary 

Operational Environmental Satellite 

(GOES) be equipped with HDR 

transmitters by 2013 will be achieved.

Status. The USGS streamgage 

network currently (2009) is at about 

90-percent real-time capability; about 

50 percent of those streamgages are 

equipped with the new HDR transmitters.

Objective 3

Implement the NSIP network 

of federally funded streamgages as 

authorized in Public Law 111.11, for 

the operation and maintenance of a 

stable network of 4,744 streamgages. 

The NSIP network of federally funded 

streamgages to meet national needs 

would be supplemented with partnerfunded streamgages to meet additional 

state and local needs. The expected 

outcome is that NSIP funding for critical 

streamgages currently operated under 

the CWP or with other Federal agency 

funds would be secure and would ensure 

the uninterrupted delivery of critical 

streamflow information to meet Federal 

needs. Moreover, CWP and associated 

state and local funds released as a result 

of the NSIP funding of streamgages 

would be available to support additional 

streamgages to meet local needs and 

to supplement the core set of federally 

funded streamgages.

Status. Currently, 2,940 (62 

percent) of the 4,744 NSIP “backbone” 

streamgages are operated year round by 

the USGS. NSIP currently fully funds 

A typical U.S. Geological Survey streamgage on the Little Walker River near 

Bridgeport, Nevada.

Critical Federal Needs for 

Streamflow Information

Five critical Federal needs for 

streamflow information that would be 

met by the core set of 4,744 USGSfunded streamgages in NSIP have 

been identified:

•	 Interstate and International

Waters—Interstate 

compacts, court decrees, 

and international treaties 

mandate long-term, accurate, 

and unbiased streamgaging 

by the USGS at State-line 

crossings, compact points, and 

international boundaries.

•	 Streamflow Forecasts—

Real-time stage and discharge 

data are required to support flood 

and other streamflow forecasting 

by the National Weather Service 

and other Federal agencies across 

the country.

•	 River Basin Outflows—

Resource managers need to 

account for the contribution of 

water from each of the Nation’s 

350 major river basins to the 

next downstream basin or other 

receiving water body (estuary, 

Great Lake, or ocean).

•	 Sentinel Watersheds— 

A network of streamgages is 

needed to document and evaluate 

streamflow characteristics in 800 

watersheds across the country 

that are relatively unaffected by 

flow regulation or diversion and 

typify major ecoregions and river 

basins to determine effects of 

changes in land use, water use, 

and climate.

•	 Water Quality—Streamgaging 

stations are needed to provide 

the stream-discharge information 

in support of the three 

USGS national water-quality 

networks. Through these three 

networks, the USGS monitors 

and documents water quality 

in the Nation’s streams, from 

the largest river basins to the 

smallest watersheds.
only about 520 (11 percent) of these 

streamgages; NSIP shares costs with 

partners for another 530 streamgages (11 

percent). The remaining 1,890 existing 

NSIP streamgages are completely funded 

by other Federal, State, tribal, and local 

agencies and the CWP. Nearly 1,400 

additional streamgages, which will also 

require Federal NSIP funds to operate 

and maintain, remain to be added to 

complete the planned network.

Objective 4

Flood-harden streamgages at 

National Weather Service forecast 

locations to the 200-year-flood level 

to ensure that they continue to provide 

critical data during floods. The 

expected outcome is that approximately 

3,600 streamgages used for forecasts 

would be flood hardened under full 

NSIP implementation.

Status. NSIP resources have not 

been sufficient to meet this objective 

to date, as all available resources have 

been invested in higher priority NSIP 

objectives. However, approximately 140 

NSIP streamgages were flood-hardened 

with supplemental funding obtained as a 

result of Hurricanes Katrina and Rita.

Objective 5

Federally fund infrastructure costs of 

the entire national streamgage network. 

Supporting additional streamgages 

to meet state and local needs, funded 

through the CWP, adds little to overall 

infrastructure costs. These incremental 

added costs include those for activities 

such as national database development 

and maintenance, local database 

administration and project oversight 

costs, and the USGS Office of Surface 

Water, which provides technical guidance 

and oversight for all USGS surface-water 

activities at the national level.

Status. USGS Water Science 

Centers (WSCs) have been allowed to 

apply their NSIP funding allocation 

to this objective for several years, but 

the overwhelming percentage of WSC 

funding allocations are used to fund 

the operation and maintenance of NSIP 

Federal-goal streamgages. It is estimated 

that less than 10 percent of the allocated 

NSIP funds are used to help meet 

this objective.

Goal 2: Improved Delivery of 

Streamflow Data to Users 

Developing new, state-of-the-art 

methods to transmit, store, and distribute 

streamflow information is an essential 

component of the NSIP. Improving the 

delivery of streamflow data includes a 

wide spectrum of activities, such as the 

automatic transmission of data from the 

streamgage on the river bank into the 

database, analysis of the rating curve, 

and reporting of and access to the data 

on the World Wide Web. Also included 

is ensuring the information is available 

when needed by establishing backup 

data-delivery systems and providing 

enhanced data-storage, -retrieval, and 

-analysis capabilities.

Objective 1

Implement a system to help ensure 

uninterrupted delivery of streamflow 

information under all conditions. 

Status. The USGS made this 

objective a high priority and was able to 

achieve it by implementing a national 

system of backup servers. All existing 

streamflow information, both real-time 

and historical, is available for the entire 

Nation 24 hours a day, 365 days a year, 

regardless of conditions. The USGS 

also worked with other Federal agencies 

to establish a back-up receiver site for 

satellite data transmissions through the 

GOES system. 

Objective 2

Develop enhanced systems and 

processes for quality assurance of 

streamflow information to provide highquality data in a timely and efficient 

manner. This objective includes the 

development of a process for the realtime quality assurance of streamflow 

information, as well as computer 

programs and techniques to more rapidly 

and cost effectively compute streamflow. 

Status. The USGS has developed 

and implemented a system that 

automatically detects when a streamgage 

may be transmitting erroneous data and 

sends an e-mail notice to the responsible 

office for evaluation. A method to 

automatically correct erroneous data 

is planned. The USGS has developed 

numerous computer applications to 

assist hydrographers in processing raw 

streamflow information in order to 

reduce the time required to finalize the 

streamflow record.

Objective 3

Maximize the usefulness and 

accessibility of streamflow information to 

users of the information. This objective 

includes providing confidence intervals 

for the data, increasing the availability of 

instantaneous-value data, and developing 

new products to present the information. 

Status. The USGS developed a 

database (Instantaneous Data Archive, 

or IDA), available through the World 

Wide Web, that currently (January 

2009) contains more than 2.3 billion 

Recreating on a river. Streamflow information is used by many recreationists 

to help ensure a safe and enjoyable experience.
instantaneous values of streamflow 

information from 39 states. The 

USGS has also developed a powerful 

streamflow-information synthesis tool on 

the World Wide Web called WaterWatch. 

WaterWatch allows the user to compare 

real-time streamflow information with 

historic streamflow information to obtain 

a current assessment of hydrologic 

conditions. The ability to apply 

confidence intervals to the streamflow 

data has not yet been achieved.

Goal 3: Regional Assessments of 

Streamflow Characteristics

Although the USGS National Water 

Information System (NWIS) database 

contains billions of pieces of streamflow 

information, there has been no systematic 

process to evaluate and analyze those 

data. In cases where data have been 

analyzed, the effects of changes in land 

use, water use, and climate are commonly 

observed. Although the USGS currently 

operates about 7,500 streamgages, there 

are many more river reaches that are 

not measured; being able to estimate the 

streamflow at these ungaged locations 

is critical. In addition, for many uses 

of the data, trends in streamflow need 

to be identified. The NSIP’s goal of 

regional assessments includes providing 

a means to estimate flow at ungaged 

locations, a mechanism for identifying 

trends in streamflow, and information 

required to assess the adequacy of the 

streamgage network.

Objective 1

Evaluate appropriate methods for 

utilizing streamflow information to 

perform regional streamflow assessments. 

These evaluations will be designed to (1) 

estimate streamflow at ungaged locations, 

(2) identify any trends in streamflow, and 

(3) attempt to determine the cause of any 

trends detected.

Status. Because other goals and 

objectives had a higher priority for the 

funding available, efforts toward this 

objective have been minimal.

Objective 2

Utilize the streamflow information 

available in the NWIS database 

to determine regional streamflow 

characteristics based on the methodology 

developed in Objective 1. These analyses 

will produce, at a minimum, streamflow 

statistics (mean and median streamflows, 

streamflow per unit area, low flows, peak 

flows, and trends), as well as explanatory 

causes and effects, if possible. This 

objective also includes an assessment 

of the adequacy of the streamgage 

network in the region to provide both 

the data to conduct these types of 

assessments and predictive equations 

for estimating streamflow at ungaged 

sites. When these regional assessments 

have been completed nationwide, they 

will be compiled, a national synthesis 

will be produced, and the process will 

begin again. 

Status. The USGS has been 

developing a “point-and-click” tool 

that, as equations become available, 

will provide the ability to select any 

location on any river in the country 

and obtain estimates of the streamflow 

characteristics at that location. This 

tool, called StreamStats, has been or is 

currently being implemented in 30 states. 

Much additional work is needed to update 

regression equations for estimating flow 

at ungaged locations and to implement 

StreamStats nationwide. Because other 

goals and objectives had a higher priority 

for the funding available, efforts toward 

this objective beyond implementing 

StreamStats have been minimal.

Goal 4: Expanded Data Collection 

During Floods and Droughts

Maximizing data collection prior 

to, during, and following both floods 

and droughts is critical to improving 

our understanding of and predictive 

capability with regard to hydrologic 

extremes. The spatial and temporal 

scales at which streamflow information 

is collected during extreme events 

need to be expanded. In addition, new 

and creative analysis techniques must 

be utilized. The new techniques will 

improve our understanding of floods 

and droughts and the risks they pose to 

life and property. The ultimate goal is to 

improve the prediction of extreme events 

with improved accuracy and increased 

lead time. 

Objective

Increase the intensity of data 

collection, improve data analysis, and 

produce interpretive reports to improve 

the understanding of, and response to, 

floods and droughts.

Status. Although few NSIP 

funds have been available to invest in 

enhanced data collection during floods 

and droughts, the NSIP has been able to 

provide funds for analyses of existing 

flood data. These efforts have provided 

increased understanding of floods and 

their occurrence through reports such as 

O’Connor and Costa (2003), O’Connor 

and Costa (2004), Perry (2005), and 

Costa and Jarrett (2008).

In addition, the USGS has been 

a leader in applying hydroacoustics 

technology for use in measuring 

streamflow. Although hydroacoustics 

can be used to measure much more than 

flood flows, this technology allows flood 

measurements to be made much more 

quickly and safely, thereby allowing 

additional measurements to be made. 

This also results in more accurate 

flood-flow estimates because flows at 

fewer locations need to be estimated by 

non-measurement techniques.

Severe drought. Data from the streamgage network are used to help 

predict droughts, define their extent, and provide information on recovery.
Goal 5: Research and 

Development

In many cases, the collection of 

streamflow data today is much the same 

as it was in 1889, when the first USGS 

streamgage began operation. Recent 

technological advances have provided 

new tools that allow the USGS to do 

a more efficient, more effective job of 

obtaining the streamflow information 

required for the safety and well-being 

of the Nation. Continued research and 

development of new tools, technologies, 

and methodologies will minimize cost 

increases while improving data quantity 

and quality.

Objective

Perform basic and applied research 

to develop new tools and technologies 

that (1) improve the way surface-water 

information is obtained and analyzed 

and (2) improve the understanding of 

surface-water flow. It is expected that this 

research will be conducted by scientists 

within and outside the USGS.

Status. Although only minimal 

NSIP resources have been applied 

to this objective to date, the USGS 

has made significant progress in 

the application of hydroacoustic 

instruments for the measurement of 

streamflow. The USGS has worked 

closely with hydroacoustic instrument 

vendors to further the development 

of hydroacoustic instruments to meet 

the USGS’s operational needs for 

streamflow measurements in a variety of 

physical settings. The USGS is viewed 

as the world leader in the application 

of hydroacoustic technology to the 

measurement of streamflow. In addition, 

the USGS used radars in a series of 

“proof-of-concept” experiments to 

measure stream discharge directly and 

with no physical contact with the water. 

The experiments showed that it was 

possible to measure streamflow in this 

manner, but that technological advances 

would be required to utilize the technique 

in many locations.

Future Priorities

Currently (2009), the NSIP is 

funded at about $22.4M (fig. 4). The 

complete program is estimated to 

require about $114 million per year. 

The majority of any new funds received 

will be targeted toward stabilizing and 

furthering the implementation of the 

streamgage network in support of the five 

critical Federal streamflow-information 

needs. The USGS will give a high 

priority to maintaining an awareness 

of, and attentiveness to, the needs 

and expectations of partner agencies, 

advancing technologies, and additional 

uses to which the streamflow information 

can be applied.

For additional information, please visit:

http://water.usgs.gov/nsip/

Or contact:

Mike Norris, Coordinator

National Streamflow Information 

Program

mnorris@usgs.gov

References Cited

Costa, J.E., and Jarrett, R.D., 2008, An 

evaluation of selected extraordinary 

floods in the United States reported 

by the U.S. Geological Survey and 

implications for future advancement of 

flood science: U.S. Geological Survey 

Scientific Investigations Report 2008-

5164, 232 p., available at http://pubs.

usgs.gov/sir/2008/5164/.

O’Connor, J.E., and Costa, J.E., 2003, 

Large floods in the United States: 

Where they happen and why: U.S. 

Geological Survey Circular 1245, 19 

p., available at http://pubs.usgs.gov/

circ/2003/circ1245/.

O’Connor, J.E., and Costa, J.E., 2004, 

The world’s largest floods, past and 

present: Their causes and magnitudes: 

U.S. Geological Survey Circular 1254, 

13 p., available at http://pubs.usgs.gov/

circ/2004/circ1254/.

Perry, C.A., 2005, Summary of significant floods in the United States and 

Puerto Rico, 1994 through 1998 water 

years: U.S. Geological Survey Scientific Investigations Report 2005-5194, 

327 p., available at http://pubs.usgs.

gov/sir/2005/5194/.

U.S. Geological Survey, 1999, Streamflow information for the next century: 

A plan for the National Streamflow 

Information Program of the U.S. 

Geological Survey: U.S. Geological 

Survey Open-File Report 99-456, 13 

p., available at http://pubs.usgs.gov/

of/1999/ofr99456/

by J. Michael Norris

Figure 4. Annual National Streamflow Information Program funding, 1999-2009. 

Full funding for the program would require $114 million per year. MILLION DOLLARS PER YEAR

Full funding

0

20

40

60

80

100

120

1999 2001 2003 2005 2007 2009