Human activities have changed rivers throughout our nation. Few rivers are pristine; most large ones have been dammed. Disturbances in natural flow regimes have led to problems, including enhanced sediment erosion and transport, loss of ecological diversity, declines in commercial fisheries, non-native species introductions, and reduced water quality. The beneficial use of river goods and services and river and riparian ecosystem health is a concern at local, regional, and national scales. Rivers cross state and international boundaries, and actions taken in one state have impacts elsewhere.
NATIONAL RIVER-RELATED NEEDS, CHALLENGES, AND DRIVERS
Current national river-related policy and management drivers and challenges include ecological restoration (including dam removal), relicensing of hydropower facilities, invasive species, water allocation, climatic variability, urbanization and other land-use changes, and water quality. There have been notable federal initiatives designed to address some of these issues. However, there remains a national need for science to support policy and management decision making that addresses conflicts over use of river resources and the best ways to ensure river ecosystems remain viable both now and in the future.
RIVER SCIENCE DEFINED
River science is the study of processes affecting river systems. The primary goal of river science is to develop a predictive framework among linkages be-
tween fluvial and ecological processes and patterns at multiple scales—an interdisciplinary scientific enterprise. Unlike other emerging sciences, the spatial and temporal boundaries of river science problems are defined by the characteristic spatial and temporal scales of the problem, from local and short-term, to national and long-term. Because of the complexity of rivers, an interdisciplinary, process-based, multiscale approach to studying rivers is needed to support policy-relevant decision making for the nation.
WHAT THE USGS BRINGS TO RIVER SCIENCE
Among federal agencies, the USGS is well poised to be a leader in river science. It historically has provided impartial policy-relevant data to the nation, leading all federal agencies in collecting hydraulic data on rivers, monitoring river conditions, and mapping the nation’s mineral and water resources. It has an established data distribution infrastructure to provide quality data to the nation, multiple disciplines, and an organizational structure that engages in research at local to national scales. The USGS has a clearly well-defined responsibility to assist society in addressing science issues associated with rivers, and provide policy-relevant and policy-neutral information and understanding. Finally, river science spans traditional core scientific disciplines of the USGS—hydrology and hydraulics, sediment transport, biology and ecology, aquatic chemistry, geology, and resource mapping. As such, the USGS is uniquely positioned among federal agencies to draw from the disciplinary expertise throughout its organization to provide needed integration and synthesis.
Thus, the overall design principle for a USGS river science initiative should be to deliver objective policy-relevant science information in critical areas where the nation’s gaps in understanding intersect with the USGS’s strengths and missions. Other recommendations in this report may be viewed respectively as scientific, monitoring, data management, and institutional design principles.
Recommendation: USGS river science activities should be driven by the compelling national need for an integrative multidisciplinary science, structured and conducted to develop a process-based predictive understanding of the functions of the nation’s river systems and their responses to natural variability and the growing, pervasive, and cumulative effects of human activities.
Recommendation: The USGS should establish a river science initiative to bring together disparate elements of the USGS to focus its efforts to deal with growing river science challenges. The initiative should build upon the USGS’s history, mandate, and capabilities. It should take advantage of key attributes of the institution, such as its
mission as provider of unbiased science information,
data collection and monitoring expertise,
experience in science synthesis at many scales, and
organizational structure that combines national research programs with state-, watershed-, and university-based cooperative programs. In carrying out the initiative, the USGS should closely coordinate with other federal agencies involved in river science and related activities.
SCIENCE PRIORITY AREAS FOR USGS RIVER SCIENCE
Society has a clear need for river science, and the USGS has a variety of strengths and capacities that can be brought to bear on these needs. The intersection of society’s needs and the USGS’s strengths suggest a number of priorities for USGS river science. These suggested science priorities are grouped into crosscutting activities and topical focus areas where recommendations for USGS research are offered.
Crosscutting Science Priority Areas
The following two recommendations relate to disciplinarily crosscutting activities that would strengthen the holistic river science approach. Although they are posed individually, there is great potential for activities in these priority areas to enhance each other. These activities would underpin the USGS’s science contribution to a broad national effort in river science.
Surveying and Synthesizing
River networks are intimately connected to the landscape and are integrators of climatic, geologic, and land-use processes within their watersheds. Throughout the nation, there are large regional gradients in climate, geology, topography, land cover, and human impacts. This extensive variation makes meaningful generalizations about how streams and rivers function challenging, and complicates how information collected in one river can be transferred to another, geographically distant river. Therefore, generating a national baseline survey that characterizes the spatial variation in key landscape features and processes would provide insights into the controls of instream river processes and allow for more cross-site comparisons.
A multidisciplinary survey and mapping of rivers and streams should provide a preliminary structure of multiple information layers at a reach scale. This stratification of information would be based upon readily available data, including climate, topography, soils, and geology. It should also include land-use and
human alteration information, such as upstream diversions and impoundments that alter the flow regime. Many other elements necessary for this collection of data layers are now available in the National Hydrography Dataset products that are under development in partnership with the Environmental Protection Agency (EPA). Ultimately, this mapping effort would provide a nationally useful resource for risk-based analyses of floods, invasive species spread, and many other issues.
Recommendation: The USGS should survey and map the nation’s stream and river systems according to the key physical and landscape features that act as determinants of hydrologic, geomorphic, and ecological processes in streams and rivers. This synthesis will provide a scientific baseline that can be used to support many regional-scale river science questions and afford geographic information of use to state and federal agencies, academia, and the public.
Modeling River Processes
Quantitative models that integrate physical, chemical, and biological processes provide detailed information on pathways and interactions that are difficult to measure directly in the field or whose characteristics change over time. Models complement point measurements and surveys by interpolating across the data and providing a mechanism to predict future changes. The USGS has a 40-year history of developing mathematical models of natural systems, including estuarine ocean circulation, surface-water runoff and river hydraulics, groundwater flow and solute transport, sediment transport, biological processes in streams, and groundwater and surface-water interaction. The USGS is unique among federal agencies for its breadth of modeling applications.
Potential applications of predictive integrated models are many. The construction of ecohydrologic models that focus on the structure of streamflows coupled to models linking flow to watershed and meteorological variables could be used to test the physical and ecological response of river systems to changes in flow regime with changing climate or anthropogenic drivers. These models, if properly multidisciplinary and robust, could be invaluable in river restoration, planning, and multiple water resources issues. Models can also be used to address how flow might be decreased by groundwater pumping or enriched in excess nutrients from agricultural fields.
Recommendation: The USGS should add capacity in developing predictive models, especially models that simulate interactions between physical and biological processes, including transport and transformation of chemical constituents, pollutants, and sediment.
These tools provide the underpinning for predicting ecological change.
Topical Science Priority Areas
The following recommendations are designed to address gaps in specific research areas for which improved scientific knowledge is needed. Each of these science activities will include enhanced monitoring and modeling, and will be key components of the overall river science framework.
Environmental Flows and River Restoration
The `nation is spending billions on riverine restoration and rehabilitation projects, yet the science underlying these projects is not currently well understood and thus the approaches and their effectiveness vary widely. Therefore, a fundamental challenge is to quantitatively understand how rivers respond physically and biologically to human alterations from dredging to damming, and to specifically address: What are the required environmental flows (i.e., flow levels, timing, and variability) necessary to maintain a healthy river ecosystem? And which biota and ecological processes are most important and/or sensitive to changes in river systems?
For future restoration projects to meet their goals, they should be adaptively managed. This requires long-term monitoring of quantitative measures of flow regime, groundwater activity, and ecosystem responses such as primary productivity and habitat diversity along targeted reaches. Quantitative models relating ecological function to flow regimes are also needed to allow natural resource managers and citizens to forecast the impacts of proposed water management decisions. These efforts need to go beyond just stating the potential impacts of policy and management decisions to actually assessing the outcomes these activities have on rivers. Improving and synthesizing the scientific information on environmental flows before, during, and after river restoration will likely lead to an improved ability to predict outcomes and thus more effective, cost-efficient habitat restoration.
Recommendation: The USGS should develop the means to characterize environmental flows in rivers by developing quantitative models that link changes in the ecological structure and function of river ecosystems (aquatic and riparian) to management-scale changes in river flow regimes.
Recommendation: The USGS should, in cooperation with and support of other federal agencies involved in restoration, serve as a leader to evaluate the scientific effectiveness of river restoration
approaches to achieve its goals, synthesizing results from past restoration efforts, and designing standard protocols for the monitoring and assessment of river restoration projects.
Sediment Transport and Geomorphology
Erosion, transport, and deposition of sediments in fluvial systems control the very life cycle of rivers and are vulnerable to changes in climate and human landscape alterations. Yet, compared to water-quality and -quantity information, there is relatively little available information on sediment behavior in river systems, particularly large-order reaches, to understand the evolution of such landscapes in response to the erosion and deposition of sediment. Basic research is needed on sediment transport processes, and there is a paucity of accurate flux measurements of bedload, suspended load, and washload accompanied by flow velocity and water temperature.
To assess sediment fluxes, sediment transport technology needs to be advanced by the USGS in partnership with other research entities. These advances could be applied to problems such as determining the risk of contaminated sediment resuspension, designing and maintaining flood-control channels, predicting channel behavior, understanding sedimentation and hydraulic roughness in mountain channels, restoring and re-meandering previously channelized streams, assessing the impact of dam removal on river sedimentation and habitat, estimating flows needed for removing sand and silt from gravel-bed streams, and improving sedimentation management in lakes and reservoirs. Knowing the science of these sediment-related processes is critical to the multibillion-dollar efforts to restore wetlands, reestablish flow regimes, and maintain river reaches for transport.
Recommendation: The USGS should increase its efforts to improve the understanding of sediment transport and river geomorphology in the nation’s rivers. Activities should include advancing basic research on sediment-transport processes, developing new technologies for measuring fluxes of bedload, suspended load, and wash load, and monitoring flow velocity and water temperature associated with such sediment transport conditions. Through these activities, the USGS can provide key information and tools to predict channel morphodynamics, develop methods to mitigate future problems arising from sediment movement, and play a guiding role in multiagency efforts to deal with the increasingly important national sediment challenges.
Groundwater and Surface-Water Interactions
River flows throughout the nation are affected when groundwater that normally discharges to rivers is captured for agriculture or other uses. Yet few of the USGS’s 7400 active stream gages or hundreds of monitoring wells incorporate data on groundwater and surface-water exchange. Limited investigations have been done on the end members of potential hyporheic interactions—large-scale effects of water supply developments adjacent to large rivers and detailed hyporheic interactions on first-order streams—but the full continuum of how groundwater and river water interact is relatively unknown.
The USGS has the tools, datasets, and existing networks that make it a logical place to focus resources to investigate stream-groundwater exchange processes at a national scale. The USGS has been a leader in developing many hydrologic methods and tools used to characterize groundwater and surface-water interactions. This, combined with the USGS’s extensive streamgaging network and synoptic survey datasets, provides an important foundation. The Lake and Reservoir Studies Program of the USGS, with some modification, provides a template for the development of an aggressive data mining effort and provides approaches to new field instrumentation of exchange rates.
Recommendation: The USGS should expand its current river monitoring and river study programs so they fully integrate the floodplain, channel, and groundwater, and the exchange of water between these systems (hyporheic exchange). The exchange of water between groundwater and rivers needs examination and quantification at multiple scales in a range of different hydrologic and geologic settings, as this process is a key component influencing river discharge and water quality, geomorphic evolution, riparian zone character and composition, and ecosystem foundation, maintenance, and restoration.
INTEGRATED DATA COLLECTION AND RIVER MONITORING
Monitoring our nation’s rivers is the foundation of USGS’s contribution to river science. Historically, the USGS has been a leader in river monitoring, distinguished for its scientific rigor, quality control, interpretative products, and innovative monitoring techniques and instrumentation. Therefore, the USGS is well positioned to fulfill the growing need to concurrently monitor hydrologic, geomorphic, chemical, and ecological river conditions.
Currently, streamflow data are available for many higher-order river systems, but data on water quality, sediment transport, biology, and ecology are often lacking. To make gage data more useful for river science initiatives, the USGS should investigate cost-effective ways to collect more integrative bio-
physical data. Among these efforts, the USGS should consider the incorporation of index biological reaches, where coupled measurements of river flows, groundwater levels and fluxes, and water quality are combined with riparian cover mapping. The USGS should prioritize based on those variables with broad science and management applications, and seek opportunities to collaborate with other programs that monitor rivers so efforts build on each other and do not duplicate one another.
By building on its existing capabilities and leading an effort to enhance river monitoring to fill the science data gaps in critical or neglected areas, the USGS will be able to better support all its priority research areas in river science.
Recommendation: The USGS should expand its monitoring activities on rivers to better incorporate river physical, chemical, and biological conditions within its existing river and streamflow monitoring programs. Its goals should include development of a 21st-century river monitoring system for data collection, transmission, and dissemination.
Enhancements in Biological Monitoring
Recommendation: Expanding the collection of biological and ecological data at streamgaging sites is needed to develop integrated biophysical datasets for river science. However, fundamental questions remain on how to implement a monitoring program to support national and regional synthesis. The USGS should continue its efforts to define relevant monitoring activities for national implementation, while expanding biological and ecological monitoring in a targeted fashion to address clearly defined regional data needs.
Enhancements in Sediment Monitoring
Recommendation: Leveraging the infrastructure of the streamgaging network, the USGS should greatly expand sediment monitoring of the nation’s rivers. To meet the growing needs for sediment data, the USGS should take the lead in developing a comprehensive national sediment monitoring program.
Reach Monitoring Approach
Recommendation: An index reach monitoring approach would help address many data needs for USGS river science priorities. The USGS should begin efforts to design and implement sampling plans on reach scales to integrate monitoring of physical, chemical, and biological condition for river science investigations.
River System Monitoring—Sampling Design
Recommendation: For the design and implementation of a coordinated river monitoring system, the USGS should develop specific monitoring goals and objectives for building on its existing infrastructure. The USGS should prioritize these activities based on those variables with broad science and management applications.
River System Monitoring—Partnering in Monitoring Efforts
Recommendation: The implementation of a USGS river monitoring system should be informed by the data and science information gaps limiting effective policy and management decision making of other mission-oriented government agencies at federal, state, and local levels, as well as nongovernmental organizations and academic research institutions. Partnering with these groups to design and implement scientific data monitoring in support of site-specific management and research objectives must be a component of USGS river monitoring.
River System Monitoring—Measurement Technologies
Recommendation: The USGS must remain at the forefront of river monitoring technologies. The development of new cost-effective instrumentation and measurement techniques for monitoring physical and biological variables is an essential component of a river monitoring system.
DATA ARCHIVING, DISSEMINATION, AND MANAGEMENT
Integrative river science is supported by diverse measurements and observations. In contrast to streamflow data and point measurements of nutrient concentrations, observations to support river science include two-dimensional data and observations describing stream channel geometry, time-varying data on bed forms, channel sediments, and the land uses and vegetative cover of riparian corridors and upstream drainage areas. Three-dimensional data describing flow velocity fields are now available from innovative acoustic Doppler technologies that have been enhanced by the USGS, and even four-dimensional measurements (i.e., time-varying, three-dimensional fields) are both technologically and economically practical data forms with great potential value for river science. The USGS maintains and stores considerable information in databases from the National Water Information System (NWIS), National Water-Quality Assess-
ment (NAWQA) Program, National Biological Information Infrastructure (NBII), Earth Resource Observation Systems-Earth Data Center, and The National Map.
It is in the national interest for river science data holdings to be standardized and archived in a consistent way with sufficient ancillary information (metadata) that allows it to provide traceable heritage from raw measurements to useable information and allows the data to be unambiguously interpreted and used. Coordination and cooperation among the federal resource management agencies and their nonfederal partners will be critically important as the scope, scale, and intensity of data needs to support river science evolves. No single federal agency can collect, quality assure, manage, and disseminate all data and observations relevant for river science. Yet all federal agencies, nonfederal partners, and stakeholders with an interest in river science data will benefit from access and availability of accurate, reliable, and well-documented data. A common data model would provide an intellectual framework under which river science data holdings are catalogued and accessible. To develop such a model, a strategic plan put together by informatics experts from the USGS and other agencies and academics needs to be developed.
Recommendation: The USGS should include in its river science initiative an informatics component that includes developing a common data model for river science information that can be used to archive diverse river science metadata and data. This data model should be developed in coordination with and capable of supporting other federal agency river science data needs. The data model should accommodate data from multiple sources, including nonfederal sources. Such a program would facilitate the integration and synthesis of river science data to address the diverse range of river science questions discussed in this report.
ORGANIZING AND MANAGING RIVER SCIENCE AT THE USGS
River science at the USGS and elsewhere covers a wide variety of basic and applied research and usually incorporates a broad range of partners. Because the USGS has strengths in many of the subdisciplines of multidisciplinary river science, there may be no single best institutional place for a river science within the current structure of the USGS.
Future river science coordination mechanisms within the USGS should incorporate certain key strengths within existing USGS programs. These include place-based experience and long-term datasets of some of the Biological Resources Discipline (BRD) Science Centers and Priority Ecosystems Science sites, the two-way flow of information between the Water Resources Discipline (WRD) personnel doing research and those doing applied science, the close links with universities of the BRD Cooperative Research Units and many of the WRD
Science Centers, and the close ties between the BRD Science Centers and other federal agencies and between the WRD Science Centers and state and local agencies. These coordination efforts should work closely with programs within the USGS’s Geography Discipline to build on the wealth of existing mapping capabilities. They should also build on the consistent data collection standards, mapping, and national synthesis strengths of the USGS.
Overall, the current fragmented nature of the USGS’s approach to river science needs organization and focus. Any managerial approach that addresses river science must be born of an institutional culture that fosters integrative cooperative research. An initiative that contributes fully to regional and national needs will require interdisciplinary research teams that, if not housed together, are regularly brought together to plan, direct, and execute USGS river science activities.
Recommendation: The USGS should employ innovative managerial approaches to combine the best elements of existing Water and Biological Resources river programs and other USGS programs, and refocus a portion of existing research and field team efforts on examining and answering nationally important river science questions.
Overall, society’s linkages to rivers run deep and these linkages—from agriculture to transportation and from water supply to recreation—drive a broad need for advances in river science. The USGS, by virtue of its unique strengths among the many actors in river science, has an important part to play in meeting this need. By showing leadership in monitoring, modeling, surveying, synthesizing, and data management—concerning topics such as environmental flows, behavior of sediment, and groundwater and surface-water interactions—the USGS can contribute a great deal toward answering some of the most difficult and interdisciplinary questions involving rivers. Wise application of the knowledge gained will lead to better, more informed policy and management decisions throughout the nation.