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USGS National Streamflow Information Program

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Streamflow Information for the Nation

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Since 1889, the U.S. Geological Survey (USGS) has operated a streamgaging program to collect information about the Nation's water resources. As part of this program, the USGS collects streamflow data needed by Federal, State, and local agencies for planning and operating water-resources projects and regulatory programs. For a more complete list of uses of streamflow information, see

Over time, the USGS streamgaging network grew and changed as new needs for streamflow data emerged and new technologies for data collection, analysis, and dissemination evolved. In recent years, the USGS has focused on adapting new communications technologies to serve water-resource managers better, developing more efficient data-collection technologies, and expanding partnerships with other Federal, State, and local agencies.


Real-Time Streamflow Information Delivery

One of the most profound changes in the USGS streamgaging program in recent years has been the development and widespread use of real-time streamflow data. As the expansion of water-development projects has slowed, the emphasis has shifted to developing management strategies that make optimum use of the Nation's existing water-resources infrastructure. Developing optimal management strategies, however, requires more information in greater detail and in more constrained timeframes than was needed in the past. Through its streamgaging program, the USGS provides data that are critical to the most effective management of the country's vital water resources.

Throughout the country, USGS streamgages equipped with real-time telemetry are integral components of reservoir operations and river-forecast and flood-warning systems. About 6,700 streamgages (Figure 1) or about 90 percent of all USGS streamgages are equipped with automated Data Collection Platforms (DCPs) that use satellite radio transmitters or phone lines to broadcast stream data 24 hours a day directly to the USGS and major partners, such as the National Weather Service (NWS), the U.S. Army Corps of Engineers, and the Bureau of Reclamation. These and other Federal, State, and local agencies use the river data to forecast river conditions, to issue flood warnings and river-conditions statements, and to plan reservoir releases or water withdrawals. So important are real-time data to the missions of these agencies that the number of streamgages equipped with DCPs is steadily increasing even as the overall streamgaging network is not growing or is even being reduced (fig. 1).

Graph of number of real-time streamgages
Figure 1. Streamgages with satellite Data Collection Platforms, total number, by year.

To facilitate the dissemination and use of discharge data, the USGS began to provide real-time discharge data to government agencies and the general public through the World-Wide Web (WWW) in 1995. Now hourly streamflow data for more than 6,800 streamgages are provided through the WWW.

In addition to near-real-time data, the USGS also provides historical daily streamflow data on the WWW. Daily data for nearly 20,000 streamgages are available. The on-line availability of the USGS data enables users to perform more easily hydraulic and hydrologic analyses that are essential to the planning, design, and operation of water-resources projects. At the same time, serving the data through the WWW has greatly reduced the number of data requests that the USGS previously processed manually.

Daily Streamflow Conditions

The colored dots on this map depict streamflow conditions as a percentile, which is computed from the period of record for the current day of the year. Only streamgages with at least 30 years of record are used.

The gray circles indicate other streamgages that were not ranked in percentiles either because they have fewer than 30 years of record or because they report parameters other than streamflow. Some streamgages, for example, measure stage only.

Map of Waterwatch

USGS Streamgaging Network Partners and Funding

(For additional discussions on this topic, see
Picture of Snake River, WY

The USGS streamgaging network is operated and maintained as part of a unique partnership that fulfills many functions, is funded by numerous (over 800) agencies, and is operated by one. This unique arrangement provides several important strengths and at least one weakness related to the determination of priorities for the number and location of streamgages. Among its strengths, the USGS streamgaging program provides nationally consistent and impartial data essential to water management and regulation across jurisdictional boundaries. Data are available to all potential users regardless of whether they help fund the network, which greatly expands the use of the information. Within each State, members of the water resources community play an active role in helping the USGS set priorities for streamgages, thereby enlisting financial support and fostering agreements on the functions and locations of the streamgages. Sharing the cost of streamgage operations means that over 7,500 streamgages can be operated across the country with USGS appropriated funds contributing only about 25 -30 percent of the required amount.

The major weakness of this arrangement is that the USGS cannot design the network unilaterally. Less than 12 percent of the funds that support streamgages are solely under the control of the USGS. And Federal priorities for streamgages in some areas are left unmet.

Picture of irrigated fields

The USGS streamgaging program fulfills many purposes -- water resources planning and flood mitigation, design of water storage and treatment facilities, water management and reservoir operations, water quality control, and flood forecasting. (See for more on the uses of streamflow information.) Balancing the priorities of streamgages to meet these purposes is driven by market forces as Federal, State, and local agencies, as well as USGS, contribute to the program based on their need for data for long-term planning or day-to-day operations. State agencies such as natural resource and transportation departments typically need data for planning and design. Other agencies such as water supply or pollution control departments at the State and local level need data for managing daily withdrawals and levels of treatment. Federal agencies, particularly the Corps of Engineers, traditionally have supported streamgages for both planning and design and day-to-day operations.

The market system assures a high degree of effectiveness and relevance for the USGS streamgaging program, but it has an imperfection related to an under-investment in some national benefits to the program which the USGS is primarily responsible for providing. These include streamgages that are used primarily as indices of climate and streamflow variability and those used for flood warning. The index streamgages provide long-term background information on how streamflow (floods, droughts, average flows) changes over long periods of time in response to forces such as land-use change, long-term climate variability (e.g., El Nino), and long-term climate change (e.g., due to greenhouse warming). As State and Federal budgets have become constrained, funds from the supporting agencies have been directed to support current purpose streamgages instead of index streamgages. Also, flood warning streamgages lack a constituency for a couple of reasons. The first is that hazard warning information is generally thought of as a Federal function and States and localities are not accustomed to paying for it. For example, information on severe storms (tornado or hurricane), earthquakes, volcanic eruptions are all funded by Federal money. Thus, emergency management agencies are not accustomed to budgeting for the data-collection and data-dissemination functions. Also, because of technological changes in the last couple of decades (satellite data transmission, doppler radar for precipitation estimates and improvements in flood forecast models), the USGS streamflow data are now much more valuable from a hazard warning perspective than they were in the past. However, no agency's budget (NWS, USGS, FEMA, or State or local agencies) have been enhanced to take advantage of this real-time benefit.

Picture of children

The USGS uses its appropriations to support the parts of the USGS streamgaging program that the market-driven mechanism under-invests in. However, our ability to balance the system is limited because of the distribution of funds for the program. In 2008, the funding for the USGS streamgaging program was $136.6 million; USGS appropriations were $44.3 million (32 percent); contributions of other Federal agencies were $28.5 million (20.9 percent); and contributions from State and local agencies were $63.8 million (46 percent) (fig. 2). The USGS appropriations include $20.1 million from the National Streamflow Information Program and $24.2 million from the Federal-State Cooperative Water Program. By law, the $24.2 million in Cooperative Program funds must be matched with at least an equal contribution from State and local agencies.

Streamgaging Program Funding for 2008
Figure 2. Sources of funds for the U.S. Geological Survey streamgaging program, 2008.

The Cooperative Water Program (CWP) also is an effective tool for supporting the under invested parts of the USGS National streamgaging network. The criteria for determining whether Federal Coop funds will be used to support streamgages are based on the national interest for the streamflow data. Streamgages are supported with cooperative funds if the data are used by other Federal agencies for flood and drought forecasting or operational purposes, or if the data enhances the hydrologic understanding (improved definition of streamflow characteristics) of a particular region of the Nation. If data from a streamgage is of local interest only, such as an intrastate water allocation or water-quality control permit, the streamgage will not be supported by Coop Program funds. The USGS negotiates annually with its funding partners and tries to make sure that the three critical priorities listed above are met, and that the cooperators' needs are met. Any attempt to optimize the network for any one of these priorities without regard for cooperator needs would result in a loss of support from these agencies, and the network would become less effective.

Picture of Road Damage Picture of drought conditions

The third element of the USGS National streamgaging network funding base is the funds provided by other Federal agencies and unmatched funds from State and local agencies. The streamgages supported by the $28 million contributed from other Federal agencies are also important components of the flood forecasting network. Although these streamgages provide data for a specific operational purpose, many of them are used by the NWS for flood forecasting. Some of the streamgages supported by funds from State and local agencies also support the flood forecasting network. These are streamgages that are used by State or local agency for an operational purpose, but are also used by the NWS as model control points.


USGS Circular 1123, The Stream-gaging Program of the U.S. Geological Survey (By Kenneth L. Wahl, Wilbert O. Thomas, and Robert M. Hirsch)

USGS Fact Sheet FS-209-95, Stream Gaging and Flood Forecasting, A partnership of the U.S. Geological Survey and the National Weather Service (By Robert R. Mason, Jr., USGS, and Benjamin A. Weiger, NWS)

USGS Fact Sheet FS-006-97, Streamflow Information for the Nation (By Robert R. Mason, Jr. and Thomas H. Yorke, USGS)

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