Streamgages measure water level and related streamflow at streams, rivers, lakes, and reservoirs across the country. Streamgages provide foundational information for diverse applications that affect a variety of constituents. Congress has supported a national streamgage program for 130 years. These streamgages operate in every state, the District of Columbia, and the territories of Puerto Rico and Guam; therefore, national streamgage operations garner interest from many Members of Congress. Data fro m streamgages informs real-time decisionmaking and long-term planning on issues such as hazard preparations and response, infrastructure design, water use allocations, ecosystem management, and recreation. Direct users of streamgage data include a variety of agencies from all levels of government, utility companies, consulting firms, scientific institutions, and recreationists. Streamgages are operated across the globe with national programs in North America, Europe, Australia, and Brazil, among others. In the United States, the U.S. Geological Survey (USGS), the Department of the Interior's (DOI's) lead scientific agency, manages the USGS Streamgaging Network ( Figure 1 ). The network encompasses 10,300 streamgages that record water height or streamflow for at least a portion of the year. Approximately 8,200 of these streamgages measure streamflow year-round and are part of the National Streamflow Network. This subnetwork includes 3,640 Federal Priority Streamgages (FPSs), which Congress and the USGS designated as national priorities (see section on " Federal Priority Streamgages "). Some entities, such as state governments, operate their own streamgages separate from the USGS Streamgaging Network. Congressional appropriations and agreements with approximately 1,400 nonfederal partners funded the USGS Streamgaging Network at $189.5 million in FY2018. Some streamgages are funded solely through congressional appropriations for the USGS and other federal agencies, such as the U.S. Army Corps of Engineers (USACE), Bureau of Reclamation (Reclamation), and Department of Defense (DOD). Much of the USGS Streamgaging Network is funded cooperatively. Interested parties sign funding agreements with the USGS to share the cost of streamgages and data collection. The USGS Cooperative Matching Funds Program (CMF) provides up to a 50% match with tribal, regional, state, and local partners (see section on " Cooperative Matching Funds Program "). Other federal agencies, nonfederal governments, and nongovernmental entities may provide reimbursable funding for streamgages in the USGS Streamgaging Network without contributed funds from the USGS. Evolving federal policies and user needs from diverse stakeholders have shaped the size, organization, and function of the USGS streamgage program. This report provides an overview of federal streamgages by describing the function of a streamgage, the data available from streamgage measurements, and the uses of streamgage information. The report also outlines the structure and funding of the USGS Streamgaging Network and discusses potential issues for Congress, such as funding priorities and the future structure of the nation's streamgage network. A streamgage's primary purpose is to collect data on water levels and streamflow (the amount of water flowing through a river or stream over time). Streamgages estimate streamflow based on (1) continuous measurements of stage height (the height of the water surface) and (2) periodic measurements of streamflow, or discharge, in the channel and floodplains. USGS measurements are used to create rating curves, in order to convert continuously measured stage heights into estimates of streamflow. Selected streamgages may provide additional measurements, such as measurements of water quality (see box on "Supergages"). Streamgages house instruments to measure, store, and transmit stream stage height ( Figure 2 ). Stage height is usually transmitted every hour, or more frequently at 5 to 15 minute intervals for emergency or priority streamgages. Most streamgages transmit data by satellite to USGS computers; the data then are provided online to the public. Numerous streamgages also have cameras that capture and transmit photos of streamflow conditions. Periodic streamflow measurements require USGS personnel to measure discharge at various sections across the stream. Streamflow measurements are made every six to eight weeks to capture a range of stage heights and streamflows, especially at high and low stage heights. Repeated measurements allow scientists to capture changes to the channel from vegetation growth, sedimentation, or erosion, which can affect the relationship between stage height and streamflow. The USGS National Water Information System (NWIS) receives and converts all stream height data from USGS streamgages into streamflow estimates. An example of streamgage data from NWIS is shown in Figure 3 for a site capturing peak streamflow during a hurricane event. The free and publicly accessible data are frequently accessed online or by request to users. For example, the agency responded to over 670 million requests for streamflow and water level information in 2018. The NWIS website is the main repository for current and historical streamflow data, in addition to other water information. Tools such as WaterWatch summarize the current conditions of the nation's streams and watersheds through maps, graphs, and tables by comparing real-time streamflow conditions to historic streamflow from streamgages with records of 30 years or more. The USGS Streamgaging Network provides streamflow information to assist during natural and man-made disasters, such as flooding and drought, and to inform economic and statutory water management decisions, such as the allocation of water supplies for irrigation. Individual streamgages in the network also can serve multiple uses. For example, a streamgage intentionally established for the purpose of reservoir management may provide data to inform water quality standards, habitat assessments, and recreational activities. Additionally, the value of a single streamgage is enhanced by the operation of the entire network, particularly for research, modeling, and forecasting. Streamgages were first established in the United States to inform water use and infrastructure planning—applications that benefit from continuous, long-term hydrologic records (see box on "Evolution of Streamgage Uses"). Long and continuous periods of data are used to construct baselines for water conditions and to identify deviations in the amount and timing of streamflow caused by changes in land use, water use, and climate. Some stakeholders contend that the value of streamflow records increases over time, with at least 20 years of continuous coverage needed for many applications. Technological advances allowing access to streamflow information in real time have expanded the uses of streamgages. Real-time forecasting and operational decisionmaking are used in many applications of streamflow data. Web and phone applications also have facilitated increased public use of water information. Streamgage data is used for a wide range of applications, including supporting activities of federal agencies. There are also a variety of streamgages tailored for specific purposes. The following is a noncomprehensive selection of streamgage uses to illustrate the scope of applications. W ater M anagement and Energy D evelopment . USACE, Reclamation, and various state and local water management agencies use streamgages to inform the design and operation of thousands of water management projects across the nation. Timely streamflow information helps water managers make daily operational decisions as they balance water requirements for municipal, industrial, and agricultural uses. Energy production and mineral extraction operations also rely on continuous streamflow measurements to comply with environmental, water quality, or temperature requirements. For example, the Federal Energy Regulatory Commission (FERC) requires hydropower companies to support USGS streamflow and water-level monitoring as part of their FERC licensing process. Infrastructure Design . Transportation agencies use streamflow data to develop regional flow frequency curves for the design of bridges and culverts, stream stability measures, and analysis of bridge scour—the leading cause of bridge failure. Without adequate information, some observers contend that engineers may overdesign structures, resulting in greater costs, or may not make proper allowances for floods, compromising public safety. Interstate and International Water Rights . Federal streamgages are used to collect streamflow information at U.S. borders and between states. Streamgage data informs interstate compacts, Supreme Court decrees, and international treaties (e.g., under the purview of the International Boundary and Water Commission and the International Joint Commission). Water Science Research . Many federal agencies depend on consistent, long-term data from streamgages to conduct water research and modeling (e.g., USACE, National Oceanic and Atmospheric Administration [NOAA], Environmental Protection Agency [EPA], DOI, U.S. Department of Agriculture [USDA], and National Aeronautic and Space Administration [NASA]). To monitor climate trends and ecological patterns, the USGS distinguishes a subset of streamgages that are largely unaffected by development to serve as benchmarks for natural conditions. Flood Mapping . The Federal Emergency Management Agency (FEMA) uses floodplain maps to establish flood risk zones and requires flood insurance through the National Flood Insurance Program (NFIP) for properties with a 1% annual chance of flooding. Long-term streamflow records are used to determine 1% annual chance flood flows and to develop water surface profiles to map areas at risk of flooding. The USGS often works with FEMA to produce new inundation maps after streamgages record new streamflow peaks from weather events such as hurricanes. Emergency F orecasting and Response. Streamgages inform flood forecasting and emergency response to protect lives and property. Real-time data from more than 3,600 streamgages allow NOAA's National Weather Service (NWS) river forecasters to model watershed response, project future streamflows, forecast monthly to seasonal water availability, and issue appropriate flood watches and warnings (see box on "National Water Model"). Flood warnings provide lead time for emergency response agencies, such as FEMA, to take effective action in advance of rising waters. In addition, the USDA National Resource Conservation Service (NRCS) uses streamgages to forecast flows for water supply, drought management and response, hydroelectric production, irrigation, and navigation in western states. Water Q uality . Streamflow data is important for measuring water quality and developing water quality standards for sediments, pathogens, metals, nutrients (e.g., nitrogen and phosphorus), and organic compounds (e.g., pesticides). At select streamgages, the USGS also operates instruments recording water quality data (see box on "Supergages"). Section 303(d) of the Clean Water Act requires states to develop total maximum daily load (TMDL) management plans for water bodies determined to be water quality impaired by one or more pollutants. When determining TMDL levels for specific pollutants, agencies may consider historic streamflow data, along with other factors, in their evaluations. Agencies may use current flow conditions when determining the proper release of wastewater to ensure compliance with TMDL standards and National Discharge Elimination System permitting. Ecosystem Management and Species . Some water users and resource agencies use streamflow data to meet the flow requirements needed to protect endangered or threatened fish and wildlife under the Endangered Species Act (16 U.S.C. §1531 et seq.). Natural resource agencies, such as the U.S. Fish and Wildlife Service (FWS), collect streamflow data to understand how threatened and endangered species respond to flow variations. The USGS operates streamgages to monitor ecosystem restoration progress, such as restoration of the Chesapeake Bay watershed. Recreation . Real-time streamgage data can help individuals and tourism businesses assess stream conditions for recreational outings. USGS data can be used to decide if conditions are suitable for recreational activities such as fishing, boating, and rafting. The USGS also partners with the National Park Service (NPS) to provide water science and data to help manage parks and to enhance interpretive programs. The USGS Streamgaging Network is part of the Groundwater and Streamflow Information Program under the USGS Water Resources mission area. The President's budget request for FY2020 proposes a restructuring of the mission area to create a Water Observing Systems Program that would combine the USGS Streamgaging Network and other water observation programs. The primary operators of streamgages are the regional and state USGS Water Science Centers, which maintain hydrologic data collection and conduct water research in the region. Approximately 8,200 of the 10,300 USGS streamgages measure year-round streamflow (National Streamflow Network; see Figure 4 ), with the rest only measuring stage height or measuring streamflow on a seasonal basis. USGS streamgages are also differentiated based on cooperative funding (CMF) and federal interest (FPSs). Much of the streamgaging program has been cooperative in nature as interested parties sign funding agreements to share the cost of streamgages and data collection. Through CMF, the USGS funds up to a 50% match with tribal, regional, state, and local partners. In 2018, CMF supported 5,345 streamgages (52% of the USGS Streamgaging Network). The first cooperative agreement began in 1895 with the Kansas Board of Irrigation Survey and Experiment (now known as the Division of Water Resources of the Kansas Department of Agriculture). Funds from cooperative entities steadily increased in the early 20 th century. Congress passed legislation in 1928 stipulating that the USGS can share up to 50% of the costs for water resources investigations carried out in cooperation with tribes, states, and municipalities (see Figure 5 ). In 2016, this Federal-State Cooperative Water Program was renamed the Cooperative Matching Funds Program (CMF), which provides cooperative funding for programs across the USGS Water Mission Area. To participate in the CMF, potential partners approach the USGS to discuss the need for a specific streamgage. The USGS determines its feasibility based on available funds and program priorities. If the USGS deems establishing the streamgage is feasible, the USGS and cooperator sign a joint funding agreement (JFA), which is a standard agreement that specifies how much each party will contribute to funding the streamgage and the payment schedule for the cooperator. These agreements span five years or less. During the agreement, the cost-share generally remains the same, but there is flexibility to alter the cost-share on an annual basis for multi-year agreements. Once a streamgage is operating, if a partner can no longer contribute funds, the USGS seeks to work with other partners that use the streamgage to augment funding. The USGS provides a website identifying streamgages that are in danger of being discontinued or converted to a reduced level of service due to lack of funding. The website also identifies streamgages that have been discontinued or are being supported by a new funding source. Approximately 3,700 of the 10,300 USGS streamgages (36%) are funded by nonfederal and federal partners without matching funds from the USGS (i.e., not with CMF). Nonfederal partners sign JFAs, and federal partners share interagency agreements with the USGS (except USACE which uses a military interdepartmental purchase request). These gages are part of the USGS Streamgaging Network and are operated in accordance with the quality control and public access standards created by the USGS, with the agency assuming liability responsibility for the streamgages. Public and private entities may also elect to own and operate streamgages tailored to their specific needs and not affiliated with the USGS. These independent streamgages may differ in various ways compared to streamgages in the USGS Streamgaging Network (e.g., capital and operating costs, operating periods, measurement capabilities, and data standards and platforms). The SECURE Water Act of 2009 (Title IX, Subtitle F of P.L. 111-11 ) directs the USGS to operate a reliable set of federally funded streamgages. The law requires the USGS to fund no fewer than 4,700 sites complete with flood-hardened infrastructure, water quality sensors, and modernized telemetry by FY2019. Originally titled the National Streamflow Information Program (NSIP), the USGS now designates these streamgages as FPSs. Out of the 4,760 FPS locations identified by the USGS, 3,640 sites were operational in 2018. In FY2018, the USGS share of funding was $24.7 million for FPSs. The idea of a federally sustained set of streamgages arose in the late 20 th century when audits revealed the number of streamgages declining after peaking in the 1970s (see decrease in Figure 5 ). In a 1998 report to Congress, the USGS stated that the streamgage program was in decline because of an absolute loss of streamgages, especially those with a long record, and asserted that the loss was due to partners discontinuing funding. Partners also had developed different needs for streamflow information. The USGS proposed the creation of an entirely federally funded NSIP to ensure a stable "backbone" network of streamgages to meet national needs. The USGS used five national needs to determine the number and location of these streamgage sites: 1. Meeting legal and treaty obligations on interstate and international waters. 2. Forecasting flow for NWS and NRCS. 3. Measuring river basin outflows to calculate regional water balances. 4. Monitoring benchmark watersheds for long-term trends in natural flows. 5. Measuring flow for water quality needs. The original design included 4,300 active, previously discontinued, or proposed streamgage locations. The proposed program was to be fully federally funded, conduct intense data collection during floods and droughts, provide regional and national assessments of streamflow characteristics, enhance information delivery, and conduct methods development and research. The SECURE Water Act of 2009 authorized the NSIP to conform to the USGS plan as reviewed by the National Research Council. The law required the program to fund no fewer than 4,700 sites by FY2019. The law also directed the program to determine the relationship between long-term streamflow dynamics and climate change, to incorporate principals of adaptive management to assess program objectives, and to integrate data collection activities of other federal agencies (i.e., NOAA's National Drought Information System) and appropriate state water resource agencies. In FY2018, congressional appropriations and nonfederal partners provided $189.5 million for the USGS Streamgaging Network ( Figure 6 ). The USGS share included $24.7 million for FPSs and $29.8 million for CMF. Other federal agencies provided $40.7 million ( Table 1 ). Nonfederal partners, mostly affiliated with the CMF program, provided $94.3 million. The appropriations bill for the Interior, Environment, and Related Agencies funds the USGS share of the USGS Streamgaging Network. Funding for streamgages is included in the Groundwater and Streamflow Information Program under the USGS Water Resources Mission Area. The line item includes funding for the streamgage network and groundwater monitoring activities, as well as other activities. Congress provided $74.2 million in FY2018 and $82.7 million in FY2019 for the Groundwater and Streamflow Information Program. While maintaining level funding for FPS and CMF streamgages in FY2019, Congress directed increased funding of $8.5 million for the deployment and operation of NextGen water observing equipment. The President's budget request for FY2020 proposes creating a new Water Observing Systems Program combining the Groundwater and Streamflow Information Program and elements of the National Water Quality program focused on observations of surface water and groundwater. The President's FY2020 budget requests $105.1 million for the proposed program, a decrease of $7.5 million compared to $112.5 million of FY2018 funding for a similar structure. The budget request would maintain funding for active FPS locations and provide no funding for the NextGen system. For CMF, the request proposes a decrease of $500,000 for Tribal Water, which would result in a loss of $250,000 for CMF streamgages, and a decrease of $717,000 for Urban Waters Federal Partnership, which would reduce water quality monitoring at select streamgages. Other federal agencies contribute to whole or partial funding of streamgages for agency purposes ( Table 1 ). Since FY2012, funding from other federal agencies has doubled from $19.9 million to $40.7 million in nominal dollars. This increase may be due to meeting inflation and other streamgage cost increases; to new needs for monitoring data with existing cooperators (e.g., USACE in the Savannah and Jacksonville Harbor expansion projects); and to the introduction of additional funding partners (e.g., the EPA) that are supporting new streamgages. Nonfederal partners funded approximately half the costs of the USGS Streamgaging Network from FY2012 to FY2018. Cooperative partners include tribal, regional, state, and local agencies related to natural resources, water management, environmental quality, transportation, and regional and city planning. Irrigation districts, riverkeeper partnerships, and utility agencies and companies also fund the program. Contributions by nongovernmental partners to streamgages are very limited (1% in FY2018) and are not eligible for cost-sharing through the USGS CMF program. From FY2003 to FY2019, USGS funding for FPS streamgages increased from $11.7 million to $24.7 million (in 2018 dollars; Figure 7 ). However, USGS funding has not met the SECURE Water Act of 2009 mandate for an entirely federally funded suite of not fewer than 4,700 streamgage sites. In FY2018, 35% of FPSs were funded solely by the USGS FPS program funds. The USGS must rely on other federal agencies or nonfederal partners to fund the rest of the FPSs: 27% were funded by a combination of USGS CMF and partner funds, 24% were funded by a combination of other federal agencies and nonfederal partners, and 14% were funded solely by other federal agencies (not the USGS). USGS funding for CMF has remained relatively level, ranging from $27.5 million to $30.7 million (in 2018 dollars) over 15 years, aside from a drop in FY2007 ( Figure 7 ). For the entire USGS Streamgaging Network, the nonfederal cost-share contribution has increased from near 50% in the early 1990s to an average of about 63% in FY2018. With CMF appropriations remaining level, and demand for streamgages from stakeholders rising, the USGS cost-share available has declined. Cost-share commitments for long-term streamgages are generally renewed at consistent percentages, but JFAs for newer streamgages may include less contribution from the USGS. Increasingly, the USGS may opt to only provide matching funds for installation and operation in the first year, with the agreement that the partner provides full funding in subsequent years. Congress may consider funding levels and policy priorities for the USGS Streamgaging Network. Congressional appropriations may affect the size of the network and the design of streamgages. Congress may provide direction regarding the policy priorities when considering the mandates of the SECURE Water Act of 2009 and initiating the NextGen system. Congress determines the amount of federal funding for the USGS Streamgaging Network and may direct its allocation to FPS, CMF, and other initiatives. The USGS and numerous stakeholders have raised funding considerations including user needs, priorities of partners, federal coverage, infrastructure repair, disaster response, inflation, and technological advances. Congress may consider whether to maintain, decrease, or expand the network, and whether to invest in streamgage restoration and modernization. The USGS uses appropriated funding to develop and maintain the USGS Streamgaging Network. While some stakeholders advocate for maintaining or expanding the network, others may argue that Congress should consider reducing the network in order to prioritize other activities. Congress may provide funding to maintain existing streamgages. The Administration continues to request funding for the Groundwater and Streamflow Information Program, which funds the USGS Streamgaging Network. The FY2020 budget request states that "one of the highest goals of the USGS is to maintain long-term stability of a 'Federal needs backbone network' for long-term tracking and forecasting/modeling of streamflow conditions." Some stakeholders may advocate to maintain the current network as it provides hydrologic information for diverse applications (see section on " Streamgage Uses "). The FY2020 budget requests FPS funding at FY2019 enacted levels. If inflation increases costs, level funding may not fully maintain the current operations of FPSs. In addition, 71% of the network, including some FPSs, are funded by other federal and nonfederal partners, which makes those streamgages potentially vulnerable for discontinuation. According to the Government Accountability Office, maintaining streamgages through partners can be a challenge due to both the changing priorities and financial limitations of the partners. Congress may consider reducing the network, either for FPSs, cooperative streamgages, or both. The USGS has discontinued some streamgages because of other funding priorities or because cooperators decided to no longer fund them and alternative funding was not available for the operating costs. Closures may affect individual streamgages or a collection of streamgages. The Administration requested reductions for the Groundwater and Streamflow Information Program in FY2018, FY2019, and FY2020 compared to previous congressional appropriations. For FY2018, the Administration requested a decrease of $742,000 for the Groundwater and Streamflow Information Program, which the budget justification said would diminish the USGS's ability to execute its core activities including strengthening the national streamgaging and groundwater monitoring networks. For FY2019, the proposed reduction included a decrease of $160,000 for U.S.-Canada Transboundary Streamgages. The FY2019 and FY2020 requests proposed a decrease for Tribal Water CMF, which would result in a loss of CMF funding for select streamgages. Congress did not make these cuts in FY2018 and FY2019, and is considering appropriations for FY2020. Reducing the USGS Streamgaging Network could alleviate federal spending on streamgages and allow other entities to operate streamgages tailored to their needs. On the other hand, discontinuing currently operational streamgages may result loss of data acquisition, discontinuation of long-term datasets, and decreased coverage in some basins. Some stakeholders have proposed that entities with specific needs build and operate their own streamgages separate from the USGS network. Some states, such as California and Oregon, already operate their own streamgaging networks. This approach may contain some challenges (e.g., the data may be of higher or lower quality, the data be restricted for public use, or the host may use different standards). However, if individual streamgages were operated at the same level of quality as USGS streamgages, the USGS could incorporate such data into the NWIS network. Some also argue that disparate data sets could be available on a shared platform with USGS streamgages; such a platform could include information on methods of collection, quality, and accuracy. Congress may increase funding to expand the network, which could include establishing the remaining locations for FPS, providing more funds for cooperative streamgages, or pursuing new initiatives like the NextGen system. Congress mandated completion of a national network of no less than 4,700 streamgages in the SECURE Water Act of 2009. At the close of FY2018, 3,640 of the 4,760 FPSs designated by the USGS were operational, with 52% of their funding coming from the USGS. The USGS estimates that $125 million in additional funding each year would be needed to complete the network; however, an average of only about $25 million (in 2018 dollars) was appropriated annually for FPSs between FY2014 and FY2019. While some stakeholders have advocated for Congress to provide full appropriations for FPSs to meet the mandate based on network needs, Congress may consider other funding priorities (e.g., the NextGen system). Congress may also consider if other federal agencies and nonfederal cooperative partners could provide more funding for FPSs. These entities may not be interested in financing some of the designated streamgages in the FPS network, particularly those in isolated river basins with little anthropogenic activity. Some stakeholders advocate for more federal funding to expand the cooperative part of the network, which addresses more localized needs. Some may argue against more federal funding for cooperative streamgages as it lacks a direct statutory mandate (unlike FPSs). Others have proposed increasing nontraditional funding sources for streamgages. They suggest that businesses, homeowner associations, non-for-profit organizations, academic institutions, and other nontraditional entities could provide funding for streamgaging; therefore, increasing the amount of nonfederal investment. Contributions by nongovernmental partners to streamgages are currently relatively limited (1% in FY2018) and are not eligible for federal matching funds. Congress could potentially encourage wider participation by nontraditional partners through such means as authorizing cooperative matching opportunities for public-private partnerships. Traditional stakeholders may oppose making matching funds available to entities not currently eligible, which could result in more competition for limited funds. Congress increased the Groundwater and Streamflow Information Program appropriations by $1.5 million in FY2018 and $8.5 million in FY2019. These increases were directed to streamgages for the NextGen system (see section on " NextGen System "). Congress may consider expanding the network through the NextGen system based on results from the pilot project. Increases solely directed to the NextGen system may intensify funding constraints for FPSs and CMF streamgages. Streamgages are vulnerable to hazards if not properly hardened. The SECURE Water Act directed the USGS to ensure all FPSs were flood hardened by FY2019. According to the USGS, structural restoration is usually funded because of emergencies; for example, disaster supplemental appropriations may provide funds for hardening streamgages, or funds are diverted from operational budgets to repair affected streamgages. The 2017 hurricane season resulted in damage to more than 100 streamgages. In response, Congress provided $4.6 million in the Bipartisan Budget Act of 2018 to repair, replace, and restore these streamgages and recover their data, and for hydrologists to reconstruct stream channel measurements. When the USGS does not receive disaster supplemental funding from Congress, the agency is not reimbursed for funding it redirects in order to provide around-the-clock monitoring during the events and equipment repair during and after the events. Some stakeholders have advocated for Congress to provide funds specifically for strengthening and restoring infrastructure, especially to withstand natural disasters. These stakeholders estimate that $238 million is needed to update half of the streamgages in the network to enable them to withstand major flood events and to meet new data transmitting requirements. Under budget constraints, increases in congressional appropriations are often prioritized to maintain or expand the network instead of restoration. Congress might consider investments in new technologies for the USGS Streamgaging Network. While regarded as reliable, many of the current streamgage operations are based on labor-intensive and more expensive techniques. Some stakeholders suggest that investing in modern technological and computational capabilities could provide enhanced streamflow information with reduced costs. Others raise that these approaches may not provide the quality and consistency of data expected of USGS streamgages and may reduce funds available for existing operations. The SECURE Water Act of 2009 directed the USGS to equip all FPSs with modernized telemetry systems by FY2019. According to stakeholders, the current U.S. streamgage telemetry and information infrastructure may be vulnerable to failure, and the existing data collection platforms and computer networks might eventually be inefficient for real-time and detailed data. In September 2018, an error in telemetry equipment resulted in an outage of 11% of the network. The USGS stated that redundancy in telemetry using cellular signals or camera streaming could have alleviated the problem, which affected the network for weeks. The IMAGES Act of 2018 ( H.R. 4905 ) introduced in the 115 th Congress would have directed FEMA to work with USGS to modernize hardware and increase the speed of data transmittal, but the legislation did not specify funding amounts. Some stakeholders have suggested a figure of $112 million as the amount needed to upgrade the enterprise data management systems, information technology infrastructure, and real-time data delivery capabilities. Past increases of appropriations for streamgages have prioritized continued operation and network expansion over technological improvements. To mitigate costs for such upgrades, federal science agencies are considering cloud computing that could also benefit cloud providers if other users develop applications on the cloud network using the data already hosted there. The FY2020 budget request for the USGS outlines enhancement and modernization of NWIS with a centralized platform meeting the Federal Cloud First Computing Strategy. Some argue that Congress should fund alternative data infrastructure to ensure capacity and reliability of increased data while reducing the cost, though others may argue these strategies are not ready for full implementation. The USGS suggests that modern models and computational methods to estimate streamflow in ungaged or sparsely gaged basins may provide an alternative approach to conventional streamgaging. These methods require more observational data, particularly for reference river basins, than that provided by the current streamgage network. In an effort to assess this approach, the USGS initiated a NextGen system pilot project in the Delaware River Basin with $1.5 million in FY2018 ( Figure 8 ), and the Consolidated Appropriations Act, 2019 ( P.L. 116-6 ) provided $8.5 million for the NextGen system. Reports accompanying FY2019 Interior appropriations bills by the House and Senate in the 115 th Congress addressed the NextGen system. The Senate committee report encouraged the USGS to have a cost-effective strategy for the NextGen system ( S.Rept. 115-276 ), and the House committee report directed the USGS to provide the committee with a report on the NextGen system, explaining the limitations of the current water monitoring system, the enhancements and modernization needed, and costs to implement the system over a 10-year period and operate and maintain the system ( H.Rept. 115-765 ). The USGS says the funding will allow further the NextGen system implementation in the Delaware River Basin; continued progress in modernizing USGS data infrastructure; and the selection of the next basin. Advances by the NextGen system to estimate streamflow at ungagged locations based on modeling of highly measured reference basins could also result in reduced need for streamgages, lower costs, and expansion of coverage of streamflow data. Others may suggest that modeling streamflow may not provide adequate data as physical measurements, and initiating the NextGen system may result in decreased funding available for traditional operations. Congress may also consider directing the USGS to pursue innovative observation technologies: satellite-based or airborne platforms, ultrasound sensors for river stage-height measurement, radar technology for stream velocity, and autonomous vehicles for Light Detection and Ranging (LIDAR) and other types of remote sensing. The USGS is currently evaluating combining cameras and radars with advanced imagery analysis and installing these combined technologies on drone platforms to collect streamflow in difficult or inaccessible areas. Data coverage could also potentially increase with high-density sensing and sensor networks that use miniaturization, artificial intelligence, and economy of scale. Statistical advances to estimate streamflow at locations without streamgages could also result in reduced need for streamgages. Some suggest that such technologies may eventually satisfy streamflow information needs at lower cost, while others caution that advanced technologies may not provide as robust and reliable data as traditional methods. Congress may consider outlining the future direction for the USGS Streamgaging Network through oversight or legislation. At the close of FY2018, 3,640 of the 4,760 FPS locations designated by the USGS were operational, with 52% of their funding coming from the USGS. As the USGS faces a deadline by the SECURE Water Act of 2009 to operate no less than 4,700 FPSs by FY2019, Congress directed the USGS through appropriations legislation to invest in the NextGen system. Congress may consider pursuing both the FPS mandate and the NextGen system, amending the SECURE Water Act of 2009 to facilitate completion of FPSs, or replacing the FPS mandate with the Next Gen system. Congress may consider pursuing both FPS coverage and the NextGen system. This approach could allow the USGS to meet the SECURE Water Act mandate while fully exploring new methods to obtain streamflow information. Financial constraints may limit this approach and pursuing both initiatives simultaneously may result in duplication of resources and coverage. Congress may consider revising the SECURE Water Act of 2009 to facilitate completion of FPSs (i.e., extending the deadline for FPSs, reassessing the program goals, and changing the number of FPSs). Extending the mandate may provide more time to complete the FPS network. Some suggest that the national interests have evolved and the national goals and FPS locations should be reassessed. For example, monitoring streamflow for ecological purposes was not considered in the original design but has become an increased priority. The SECURE Water Act of 2009 directed the USGS to incorporate principles of adaptive management by conducting period reviews of the FPSs to assess whether the law's objectives were being adequately addressed. An analysis of the network could reveal whether some currently funded FPS sites are no longer in the national interest and funding could be reallocated to complete other sites. Changes in the national goals may also result in the discontinuation of long-term streamgages or the need for new streamgages, and coverage may increase or decrease in various river basins. Congress may consider replacing FPSs with the NextGen system by authorizing the NextGen system as a pilot program or broader program. For example, the Weather Research and Forecasting Innovation Act of 2017 ( P.L. 115-25 ) required NOAA to conduct a pilot program for commercial weather data. The act stipulated program criteria, authorization of appropriations, reporting requirements, and future directs for NOAA based on the success of the pilot program. Congress could provide similar mandates in legislation including which basins are chosen for NextGen system improvements and whether the basins are determined by an external study, the Administration, or Congress. While some acknowledge new streamgaging approaches are forthcoming, others may suggest that modeling streamflow may not provide as adequate data compared to traditional streamgages and altering the network design may result in loss of coverage at specific sites or across basins.

Summary: Streamgages are fixed structures at streams, rivers, lakes, and reservoirs that measure water level and related streamflow—the amount of water flowing through a water body over time. The U.S. Geological Survey (USGS) in the Department of the Interior operates streamgages in every state, the District of Columbia, and the territories of Puerto Rico and Guam. The USGS Streamgaging Network encompasses 10,300 streamgages, which record water levels or streamflow for at least a portion of the year. Approximately 8,200 of these streamgages measure streamflow year round as part of the National Streamflow Network. The USGS also deploys temporary rapid deployment gages to measure water levels during storm events, and select streamgages measure water quality. Streamgages provide foundational information for diverse applications that affect a variety of constituents. The USGS disseminates streamgage data free to the public and responds to over 670 million requests annually. Direct users of streamgage data include a variety of agencies at all levels of government, private companies, scientific institutions, and recreationists. Data from streamgages inform real-time decisionmaking and long-term planning on issues such as water management and energy development, infrastructure design, water compacts, water science research, flood mapping and forecasting, water quality, ecosystem management, and recreational safety. Congress has provided the USGS with authority and appropriations to conduct surveys of streamflow since establishing the first hydrological survey in 1889. Many streamgages are operated cooperatively with nonfederal partners, who approach the USGS and sign joint-funding agreements to share the cost of streamgages and data collection. The USGS Cooperative Matching Funds (CMF) Program provides up to a 50% match with tribal, regional, state, and local partners, as authorized by 43 U.S.C. §50. The average nonfederal cost-share contribution has increased from 50% in the early 1990s to 63% in FY2018. In the early 2000s, the USGS designated federal priority streamgage (FPS) locations based on five identified national needs. The SECURE Water Act of 2009 (Title IX, Subtitle F, of P.L. 111-11) directed the USGS to operate by FY2019 no less than 4,700 federally funded streamgages. In FY2018, 3,640 of the 4,760 FPSs designated by the USGS were operational, with 52% of their funding from the USGS. Congressional appropriations and agreements with 1,400 nonfederal partners funded USGS streamgages at $189.5 million in FY2018. The USGS share included $24.7 million for FPSs and $29.8 million for cooperative streamgages through CMF. A dozen other federal agencies provided $40.7 million. Nonfederal partners, mostly affiliated with CMF, provided $94.3 million. In FY2019, Congress appropriated level funding for FPS and CMF streamgages. Congress directed an additional $8.5 million to pilot a Next Generation Integrated Water Observing System (NextGen), establishing dense networks of streamgages in representative watersheds in order to model streamflow in analogous watersheds. The President's budget request for FY2020 does not include NextGen system funding and would reduce CMF for streamgages by $250,000. The USGS uses appropriated funding to develop and maintain the USGS Streamgaging Network. The USGS and numerous stakeholders have raised funding considerations including user needs, priorities of partners, federal coverage, infrastructure repair, disaster response, inflation, and technological advances. Some stakeholders advocate for maintaining or expanding the network. Others may argue that Congress should consider reducing the network in order to prioritize other activities and that other entities operate streamgages tailored to localized needs. Congress might also consider whether to invest in streamgage restoration and new technologies. Congress may consider outlining the future direction for the USGS Streamgaging Network through oversight or legislation. As the USGS faces a deadline by the SECURE Water Act of 2009 to operate no less than 4,700 FPSs by FY2019, Congress directed the USGS through appropriations legislation to invest in the NextGen system. Congress may consider such policy options as pursuing both the FPS mandate and the NextGen system simultaneously, amending the SECURE Water Act of 2009, and the relative emphasis of the NextGen system.