National Academies Press: OpenBook

Watershed Research in the U.S. Geological Survey (1997)

Chapter: SCIENTIFIC OPPORTUNITIES FOR USGS

« Previous: SCIENTIFIC RATIONALE FOR WATERSHED RESEARCH
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

4
Scientific Opportunities for USGS

FOCUS AREAS AND ISSUES IN WATERSHED RESEARCH

Historically, the term "watershed research," as carried out by the U.S. Geological Survey (USGS), has referred to detailed studies of physical, chemical, and biological systems and processes occurring in watersheds ranging in area from 1 or 2 hectares to a few square kilometers. Scientific studies in such watersheds have focused on basic physical processes such as sediment yield and transport, streamflow generation, and rainfall-runoff relationships. As discussed in Chapter 3, investigators also have used such watersheds as natural environmental laboratories to study processes related to atmospheric deposition, acid rain, and the transport of trace constituents through the environment as well as for biological surveys and vegetation studies. The results of such work have formed the basis for much of our current understanding of hydrologic processes.

The relatively small scales of these historic research watersheds have made detailed data collection and process studies possible but sometimes have limited the transferability of the research to larger-scale problems. For example, understanding the transport and fate of pesticides in the environment is of great interest to state and federal agencies charged with monitoring and regulating pesticide use, but these agencies are commonly responsible for regions encompassing thousands of square kilometers and containing multiple watersheds. Scientific studies of pesticide transport and fate, in contrast, usually have been either site specific or confined to small watersheds.

The committee believes the USGS will need to focus its efforts on resolving important problems, even more strongly in the future than it has in the past. Thus, future watershed research programs at the USGS must focus on scientific topics having direct relevance to current and future water policy

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

issues. This study identified six general focus areas that provide a context for potential future watershed research at the USGS (Table 4.1). The topics range in scope from local to regional to national and even global and will require research at a variety of spatial scales. Some topics are purely scientific, in the context of traditional watershed studies (hydrology, hydrogeology, geochemistry, soil science, engineering, biology). Many others cross disciplinary lines and may involve such areas as economics, risk assessment, toxicology, and environmental policy.

Several aspects of the focus areas and issues identified in Table 4.1 deserve mention. First, there are obvious interrelationships among focus areas, and no single focus area can be addressed in the absence of other issues. For example, most or all water quality issues have implications for water quantity and land use. Second, the range of disciplines involved is very broad, ranging from classical hydrology and hydrogeology to more general economic and public policy considerations. Third, there is a vast array of spatial scales, from site-specific studies to global issues of climatic change and carbon cycling. Finally, all the issues are relevant to the pursuit of sustainable development. The following discussion highlights some of these issues in the context of watershed research needs.

Water Quality

Water quality can have a direct impact on human health and on the health of ecosystems. Thus, protection and improvement of the quality of ground water and surface water in the United States, particularly the protection of drinking water supplies, continue to be high priorities. Protection of surface water quality has long been a concern of most federal and state regulatory agencies and involves all components of the surface water budget. Programs in the Black Earth Creek priority watershed in Wisconsin (GAO, 1995) are good examples of attempts to maintain and improve surface water quality through coordinated efforts of local landowners; concerned citizens; and local, state, and federal regulatory agencies. Most such watershed management projects have focused on agricultural areas and have a duration of several years. The projects include an assessment phase, in which the current water quality is characterized; an implementation phase, in which specific water quality improvement steps, usually in the form of best management practices, are carried out; and a postaudit phase, in which improvements in water quality are documented. Best management practices (BMPs) are activities designed to maintain or improve overall watershed quality. Typical best management practices implemented in

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

TABLE 4.1 Focus Areas and Example Issues in Watershed Science

Focus Area

Issues

Water quality

- Protection of ground water and surface water quality

- Material transport and fate

- Process scaling

- Urban storm water

- Sediment transport

- Ground water flow in karst areas and fractured rocks

- Model development and improvement

Water availability and conservation

- Water availability

- Multiobjective water management

- Optimization management

- Ground water recharge

- Ground water/surface water relationships

- Consistent ground water supplies during periods of inconsistent precipitation

Land use and land use change

- Basin-wide water management

- Effects of agricultural and industrial best management practices

- Effects of urbanization

- Effects on sediment and trace constituents

- Contaminated sites and urban brownfields

- Habitat protection

- Susceptibility mapping

Natural hazards

- Flood hazards (erosion, deposition, structural damage, water quality impacts)

- Flood forecasting

- Drought

- Slope stability

Climatic variability and change

- Hydrologic responses as indicators of climatic change

- Hydrologic feedback to climatic change

- Global carbon cycling

Aquatic habitat alteration and restoration

- Aquatic habitats in streams

- Natural flow regimes

- Wetlands function and restoration

- Structural versus restorative approaches

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

agricultural watersheds include streambank erosion controls, improved storage and disposal of animal wastes, improved agricultural tillage practices, and water control structures; local landowners and regulatory agencies share the expenses of implementing these practices.

A major problem with many such watershed management programs is that the water quality benefits resulting from the management practice changes are often difficult to predict or assess using current models and field techniques. Some parameters, such as sediment loading in small upland watersheds, respond rapidly to upstream management practices, producing measurable downstream sedimentation changes in only a few months or years and within relatively short distances. However, other parameters, such as nitrates, pesticides, and trace metals, often have much longer residence times in the hydrologic system, and downstream changes in these parameters resulting from BMP implementation may not become apparent for years or decades. Further, those changes may occur far downstream. A case in point is the Big Spring Basin in Iowa (Hallberg et al., 1983), where significant reductions in the amount of nitrogen fertilizer applied to agricultural fields have so far failed to have any statistically significant impact toward reducing nitrate concentrations in ground water in aquifers below the fields or in downstream surface waters. Investigators in other watersheds have made similar observations. To quote from a recent General Accounting Office report to Congress (GAO, 1995, p. 13), "... even given rigorous monitoring, demonstrating a link between changes in land use and diminished chemical pollution is difficult, if not impossible, especially within a short time frame." Obviously, there is a need for longer-term (10- or 20-year) surveillance and research on the effects of changing land use on watersheds. The USGS has the scientific staff, data management facilities, and long-term funding mechanisms necessary to undertake just such long-term studies. Therefore, long-term evaluation of the effects of land use changes and management practices on watersheds presents significant scientific opportunities for the USGS.

Critical issues also exist for ground water quality at watershed scales. The 1996 reauthorization of the Safe Drinking Water Act included an earlier mandate that U.S. Environmental Protection Agency (EPA) provide guidelines for the establishment of wellhead protection areas (WHPAs) around public drinking water supply wells. A WHPA is the area of the land surface that corresponds generally to the hydrogeologic capture zone from which the well collects water. Local governments can, in theory, control land use within the WHPA to eliminate or reduce contamination sources, thereby protecting the quality of water produced by the well. Unfortunately, the delineation of well capture zones can be technically difficult, particularly in complex hydrogeo-

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

logic settings, and local municipalities rarely have the financial resources to conduct detailed hydrogeologic studies around each well to be protected. Many municipalities are therefore basing WHPAs on the results of simplified semianalytic or analytic element computer codes, such as those developed by Blandford and Huyakom (1990) and Haitjema et al. (1994), which account for only limited hydrogeologic complexity. The resulting capture zone estimates are therefore uncertain. Furthermore, the actual capture zone can be almost impossible to verify in the field. Clearly, more work is needed, both on field methods for assessing hydrogeologic conditions near water supply wells and on computer techniques for developing capture zone estimates.

While techniques for measuring and estimating contaminant loads and runoff from small watersheds are plentiful, tracking the fate of nutrients, heavy metals, sediments, and other contaminants in water bodies subject to large variability remains an elusive task. The physical processes affecting these substances—deposition, resuspension, and various transport mechanisms—often take place in aquatic environments where streamflow, temperature, velocity, wind, and other forces acting on those environments are subject to large fluctuations over short periods of time. Typically, it is unclear whether the fate of material in a system is being controlled by reaction or transport processes. In general, then, an integrated understanding of the biogeochemistry of sediments and subsurface environments is lacking. Without this knowledge the responses of a system to changes in inputs cannot be predicted.

The atrazine story demonstrates these challenges. Farmers have used the herbicide atrazine effectively for over 30 years in many parts of the Midwest to control invasive grassy weeds in corn and other crops. Unfortunately, atrazine has become a ground water contaminant and was shown recently to be present at trace (part per billion) quantities in over 50 percent of the drinking water wells in some parts of Wisconsin (LeMasters and Doyle, 1989). Detection of the pesticide at such low levels was not possible just a few years earlier because sufficiently sensitive analytical techniques were not yet available. The fate of this pesticide in ground water and surface water is a complex process), involving advective-dispersive transport, sorption-desorption to soil particles and degradation, as the parent atrazine compound is transformed into atleast three known metabolic products. Even though atrazine use in many parts of the Midwest currently is being banned or sharply reduced, it is likely that atrazine and its metabolites could persist at low concentrations in watersheds for many years. As a result, contaminant levels in ground water and surface water might increase as atrazine leaches downward from the soil zone. Presently there are no

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

BOX 4.1 ILWAS—The Small Watershed Approach

The Integrated Lake-Watershed Acidification Study (ILWAS) illustrates the value of simplifying an environmental problem using the small watershed approach. ILWAS, conducted in the early 1980s by a consortium of academic, federal, and private researchers, asked a well-posed question: ''In lake-watershed systems receiving similar amounts of acidic deposition, why are some lakes acidified and others neutral?'' By studying small watersheds, this problem became tractable; the processes controlling water acidification and neutralization could be isolated and identified.

ILWAS was conducted in the Adirondack Mountains of northern New York, an area that receives high levels of acidic deposition and is sensitive to acidification because of its crystalline bedrock. The study focused on two small (~2 square kilometers) lake-watershed systems 30 kilometers apart. Both watersheds were pristine, forested, and had similar compositions of bedrock and glacial till. Both watersheds also received nearly identical acidic deposition (mean annual pH of 4.2). Yet Panther Lake was neutral (typical pH near 7.0), whereas Woods Lake was acidic (pH 4.5 to 5.0). Woods Lake was too acidic to support fish.

Many components of the two lake-watershed systems, including vegetation, soils, surficial geology, till and bedrock mineralogy, and in-lake features, were evaluated for four years. The chemical composition of water was monitored along its flowpath in each watershed from when it entered as precipitation until it left as lake outflow. Samples were collected of incident rain and snow, throughfall (canopy drip), soil water percolate from the organic and mineral horizons, ground water in the glacial till, inlet stream water, and lake water outflow. Changes in chemistry along a flowpath were related to the physical environment through which the water was moving (canopy, soil, till, etc.), providing the clues needed to understand the acid neutralization process.

The key to the contrasting chemical response of the two systems is differences in the catchment hydrology. Peak flow at Panther Lake outlet is more attenuated, and base flow is more sustained, relative to Woods Lake. These differences, in turn, stem from differences in surficial geology, as revealed by geophysical surveys. At Woods Lake,

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

the till cover is relatively thin, and water infiltrates only a short distance before moving laterally downslope. At Panther Lake, till is much thicker and water follows longer flowpaths. Despite similar mineralogical compositions of the surficial material and bedrock in the two watersheds, the longer water residence time within the much deeper tills of the Panther Lake system is sufficient to allow weathering reactions to buffer atmospheric acidity.

A lasting contribution of ILWAS is the recognition that hydrology, as controlled by surficial geology, is often an important factor in determining the sensitivity of a lake or watershed to acid deposition.

verified integrated process models to predict the long-term transport, transformation, and fate of atrazine and related pesticides in ground water/surface water systems.

The tracking of contaminants from one scale to another presents many research challenges. Problems associated with extrapolating laboratory results and models to small watersheds and small watershed results to large watersheds are well documented (NRC, 1991). Models that are appropriate at one scale are not necessarily useful or practical at larger or smaller scales. Inaccurate estimates of kinetic parameters relative to transport rates particularly handicap modeling efforts. Overall, very, few models have been formulated, calibrated, and verified at larger scales. Much fundamental process-oriented watershed research is tractable only at the scale of a small experimental watershed, yet actual environmental problems usually occur at larger scales. Investigative and analytical techniques to transfer knowledge gained at small scales to watershed management and problem solving at larger scales, both spatial and temporal, are clearly lacking.

Many scientific opportunities exist for water quality monitoring and research in urban and suburban watersheds. Urban settings can deliver a broad mix of potential contaminants to surface water and ground water, and hydraulic residence times are commonly short, offering little opportunity for degradation or sorption of contaminants prior to downstream discharge. Two principal sources of rainfall-related water quality problems in urban and suburban watersheds are point sources, including both combined sewer overflows (CSOs) and sanitary sewer overflows (SSOs), and storm-water discharges (SWDs), including nonpoint sources of pollution. Both CSOs and SSOs violate water quality standards, while SWDs also contribute suspended solids, create bed loads, and exacerbate problems associated with accumula-

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

tion and transport of contaminated sediments. In either case, transient events can create serious adverse impacts on receiving waters that have tended to defy resolution. Very little is known about the ecotoxicological impact of these periodic urban discharges to downstream regions. Best management practices for urban watersheds are still evolving. Predictions of urban storm water quality based on models developed in rural or undeveloped areas are prone to failure.

Because of its established record of achievement in data collection and assessing major point and nonpoint sources of nutrient flux in U.S. watersheds, the USGS is well suited to broaden its current activities to include complementary scientific evaluations of large urban and suburban watersheds affected by hydrometeorological events. Such an expanded focus would help identify and record the indicator parameters descriptive of the spatial and temporal impacts of discharges from the urban/suburban complex into contiguous water resources and contribute to development of policy and management strategies protective of human health and the environment.

Sedimentation studies represent additional research opportunities. There is a long history of study of sediment erosion, transport, and deposition by the U.S. Department of Agriculture's (USDA) Agricultural Research Service and Natural Resources Conservation Service and by universities, but major scientific, issues related to sedimentation remain. Perhaps the most pressing of these is in the area of contaminant transport, fate, and impact, as sediments play an important and poorly understood role in the behavior of chemicals in both surface water and ground water (NRC, 1991). Because most hydrophobic pollutants are associated with particulate material, many have accumulated to high levels in sediments and evolved into "in place" pollutants (i.e., polychlorinated biphenyl (PCBs); see, for example, Harris et al., 1988; Larsson et al., 1992). Contaminated sediments may pose a continuous threat to a system due to resuspension events or remobilization caused by biological activity (e.g., bioaccumulation, biomagnification; Harris et al., 1990; Smith et al., 1988). Once again, major difficulties encountered in scaling up research findings at individual sites to large heterogeneous watersheds persist.

Karst features and fractured rocks occur over large areas of the United States, yet methods for measuring and modeling ground water flow and ground water surface water interactions in such terrains are currently poor. Most hydrogeologic models are based on the physics of porous media flow, yet severe ground water and surface water problems occur in areas where ground water moves through underground cavities and solution channels (karst) or through interconnected fractures. Some fracture-flow models make the simplifying assumption that the fracture distribution is essentially two-

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

dimensional (Rouleau, 1988; Smith et al., 1989). Recently, several fracture-network models capable of characterizing three-dimensional fracture geometries have been developed (Dershowitz et al., 1994). These models require statistical characterization of the geometric and hydraulic properties of field-measured fracture sets. The models then simulate flow and transport through stochastically generated fracture networks. Few sets of field data exist with which to test and validate such models. Furthermore, integration of fractured rock investigations with larger-scale watershed studies has been attempted only rarely.

The variety of hydrologic processes operating in watershed systems can best be studied using integrated models, such as the Modular Modeling System described by Leavesley et al. (1996). Such modeling systems link specific process models, such as precipitation models or rainfall runoff models, to environmental data sets through a geographic information system. Such models are powerful tools that can be used to study many watershed processes in a unified fashion and are particularly useful in identifying data gaps.

Water Availability and Conservation

Water supply and conservation continue to be critical issues over broad areas of the United States. As the nation's population continues to grow, demands for additional water for potable and industrial uses will also increase, and there will be increasing pressure to find and develop new sources of ground water and surface water while maintaining water quality and quantity. On a global basis, it is estimated that society's ability to appropriate runoff will increase by 10 percent in the next 30 years, while the population will increase by 45 percent in the same time period (Postel et al., 1996). With anticipated diversions from streams, together with the potential adverse effects of global change, aquatic species may become endangered by reduced instream flows over the coming decades. Thus, there is a continuing need for reliable, up-to-date water resource information to help water managers and regulatory officials make the best possible decisions about water supply alternatives. Such decisions are impossible without considering all the competing uses and costs involved in water supply. For example, even in humid areas of the United States, increasing ground water withdrawals in a particular area may have unwanted side effects, such as diminished base flow to streams and wetlands or land subsidence. Planning decisions cannot be made without a clear understanding of the physical interrelationships between ground water and surface water systems.

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

Meeting current and future demands for water supply while simultaneously minimizing the financial and environmental costs of water use and treatment is an example of multiobjective water management. Recently developed mathematical models and computer codes can link various water management options to the policy constraints of each option. For example, ground water policy evaluation and allocation models can be used to study the influence of regional institutional polices, such as taxes and quotas, on regional ground water use (Wagner and Gorelick, 1987). Hydraulic management models can help determine optimal locations of pumping wells and optimal pumping rates based on a variety of restrictions on local drawdown, hydraulic gradients, water quality, and production targets. Such optimization models can be powerful management tools, but the physical hydrologic and hydrogeologic data necessary for their use often are lacking.

Future watershed management will require a better understanding of natural ground water recharge processes and of artificial recharge techniques (NRC, 1994a). Natural ground water recharge is the process by which water moves downward from the land surface to reach the saturated zone and becomes ground water. Natural recharge varies temporally and spatially and is notoriously difficult to measure (Mercer et al., 1982), yet accurate estimates of recharge rates and delineations of recharge areas are essential for most commonly used ground water models, such as MODFLOW. Field and modeling studies of recharge frequently involve several disciplines, including climatology, surface water hydrology, soil physics, geochemistry, and vaclose zone hydrology. Although several investigators (e.g., Stephens and Knowlton, 1986; Stoertz and Bradbury, 1989) have conducted detailed studies of recharge at specific sites, there have been few, if any, rigorous studies of the rates and spatial variations of ground water recharge at watershed scales.

Artificial recharge projects have become common in areas of the United States experiencing ground water shortages and usually involve the construction of permanent or temporary surface impoundments with permeable beds (NRC, 1994a). Surface water held in such impoundments is allowed to seep slowly downward to recharge underlying aquifers. More research is needed to evaluate the long-term effectiveness of such projects in sustaining local and regional ground water withdrawals and their short-- and long-term effects on water quality, both locally and throughout watersheds. It is also important to evaluate water quality issues associated with artificial recharge practices. For instance, in parts of the arid southwest, low-quality surface waters are sometimes used to recharge ground water. The risks to future users of the ground water are largely unknown.

Exchanges between ground water and surface water are key components of every watershed system, yet many past studies have focused on only the

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

surface water or ground water aspects of particular watersheds. Over the past 20 years USGS scientists and others have conducted significant studies of the interactions between lakes and ground water systems. The early work of Winter (1978) established a framework for describing the dynamics of ground water flow into and out of lakes and demonstrated how modern computer techniques can be used to guide the collection of appropriate field data through numerical simulation of lake systems. More recent studies (e.g., Krabbenhoft, 1992; Krabbenhoft et al., 1990) have added chemical and isotopic components to understanding of ground water/lake interactions, and such studies have implications for managing lakes to avoid or mitigate such problems as lake acidification due to acid rain, eutrophication due to nutrient-rich runoff, and accumulation of toxic substances such as mercury in lake sediments and biota.

While contamination of ground water from landfills, hazardous waste sites, and underground storage tanks has come under special scrutiny during the past 15 years, much less attention has been given to the transport and fate of agricultural chemicals and nutrients in animal waste after they are applied to land surfaces. Important fractions of materials so applied infiltrate to ground water and move through shallow aquifers to nearby streams. Leakage from subsurface disposal systems also can follow similar pathways to streams. Knowledge of the fate of substances as they move through subsurface environments to surface waters is important not only in understanding the nature of contamination but also in designing management programs.

Interactions between surface and ground waters are particularly important to understanding depletion and replenishment of aquifers during drought events. The science of these processes is poorly developed, and existing capabilities to predict aquifer responses to droughts and recharging surface water events are limited.

Land Use and Land Use Change

Watersheds at various scales respond as an integrated whole to the hydrologic changes imposed on them. Most local, national, and global environmental issues involve some aspect of land use or land use change. Such land use issues range from local agricultural practice to regional timber-harvesting methods to large-scale deforestation, and most of these issues can become emotionally and politically charged during public debate. In the interest of providing clear scientific guidance to decisionmakers, it is critical that we define the scientific questions involved in each issue and then collect

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

The Loch Vale watershed in Rocky Mountain National Park, Colorado. The Loch is just visible in the upper center of the photograph, beyond Andrews Tarn and Glacier, which appear in the foreground. Source: U.S. Geological Survey.

appropriate data to answer the questions. Watershed research provides one obvious framework in which to collect such data.

Basin-wide water management requires information about current land use. Land use/land cover inventories constructed from satellite imagery are becoming commonplace for the analysis of large watersheds. Use of this information represents a substantial advancement in watershed analysis, but its utility also can be limited by level of resolution, errors in classification, and limited precision within categories. For instance, a preferred management practice in many watersheds is the use of riparian buffers, often requiring widths of less than 10 meters to be effective. Assessment of the extent of such practices at that scale within a watershed is pushing the limits of resolution of satellite data. Information at that scale is also insufficient for identification of wildlife habitat and other ecological analysis. Higher

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

resolution may be necessary for ecological analysis, but use of those data is currently very labor intensive. There is a need to expand coverage of computerized information at small scales.

Knowledge of land uses alone is not sufficient to adequately describe watershed processes. How lands are managed can dramatically affect these processes. For example, while cropland area in the United States changed only modestly during the past several decades, the use of fertilizer on those lands changed dramatically. From 1960 to 1980, nitrogen applied to crops in commercial fertilizers more than tripled (see Figure 4.1). It has remained essentially constant since 1980. From 1964 to 1982, agricultural uses of herbicides in the United States increased by over 700 percent (see Figure 4.2). Herbicide usage has declined slightly since 1982. Animal operations also can have dramatic impacts on nutrient fluxes in watersheds. Significant proportions of median annual loadings of phosphorus and nitrogen to agricultural and forest lands are derived from animal manure (Puckett, 1995). In some locations, loadings of phosphorus and nitrogen from animal manure can exceed the rates at which those materials can be taken up by crops (Barker and Zublena, 1995). Loadings of nutrients from this source vary by over an order of magnitude from one manure management practice to another.

The effect of urbanization on the hydrologic environment is a critical land use issue in many parts of the United States. In most population centers in the country there is an ongoing trend of suburban growth in which rural and agricultural land at the perimeter of urban centers is subdivided for housing developments and light industry. In 1982 developed areas in the United States, excluding Alaska, accounted for 4.8 percent of lands owned by entities other than the federal government. Data reported by the Bureau of the Census indicate that within a decade, from 1982 to 1992, that amount increased by 25 percent. These shifts are of much greater significance in several states. As indicated in Figure 4.3, eight states experienced more than a 40 percent increase in developed land from 1982 to 1992, and another 10 had increases in the range of 30 to 40 percent.

In many areas of land use change, wetlands have been drained or their watersheds have been significantly altered. The result of wetlands drainage often is a complete change in almost all hydrologic properties of the landscape, including such parameters as drainage patterns, slope, vegetation, surface roughness, impermeable area, and soil compaction. The watershed response to such alterations can include increased flood peaks and flood frequency, increased bank erosion, degradation of surface water quality, and reduced ground water recharge. In addition, many new subdivisions rely on individual private septic systems for waste treatment and disposal, and there

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

FIGURE 4.1 Commercial fertilizer applied to cropland in the United States, 1960–1992. Source: Lin et al. (1995).

FIGURE 4.2 Pesticides applied to cropland in the United States, 1964–1992. Source: Lin et al. (1995).

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

FIGURE 4.3 Percentage increase in developed land, 1982–1992.

Source: Bureau of the Census,  Statistical Abstracts of the United States, 1990 and 1995 editions.

is evidence that individual conventional septic systems contribute to ground water contamination (Robertson et al., 1991). What is the long-term effect of suburban development on the quantity and quality of ground water and surface water? Watershed studies in urbanizing areas are needed to help address these and related questions.

The fate of "brownfields," or contaminated industrial and commercial sites, is of particular concern in urban settings. These sites exist in nearly every urban center in the United States and contain some level of contamination in soil, ground water, or both. Returning these sites to "uncontaminated" status usually is not feasible technically or financially; yet if nothing is done, such sites can become abandoned urban wastelands. To resolve this dilemma, regulatory agencies have proposed relaxing some environmental standards in brownfields areas to make the cleanup process feasible and to encourage sale and redevelopment of the sites. What are the long-term implications of such policies for urban watersheds?

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

To help guide land use decisions, planners often turn to contamination susceptibility models to predict which parts of a landscape are most vulnerable to ground water or surface water contamination. The best known of such models for ground water is probably DRASTIC (Aller et al., 1987), which rates relative landscape vulnerability according to a few basic attributes such as depth to groundwater and soil type. Other similar models have been constructed with mixed results (NRC, 1993). A recurrent problem with all such models is assessing their accuracy. Because these models are designed to predict the probability of a future event (ground water contamination) that may or may not occur, there is little or no possibility of calibrating or verifying the models in most areas, yet such vulnerability assessments are attractive as a planning tool. Watershed studies, in conjunction with more detailed chemical transport models that integrate hydrologic events over various areas and scales, should be useful in improving the ability to design and test susceptibility models.

Natural Hazards

Geologic hazards, broadly defined for the hydrologic sciences, include such catastrophic events as floods, droughts, slope failures, and sinkhole development. Floods are the most frequently occurring natural hazard, and improved flood forecasting and real-time modeling in support of flood mitigation efforts are clearly important objectives of ongoing watershed studies. After the devastating 1993 floods in the upper Midwestern United States, the National Oceanic and Atmospheric Administration (NOAA, 1994) identified a need for longer-range flood-stage forecasts, better soil moisture information, and better precipitation models. Were the 1993 floods the result of a series of random low-probability hydrologic events? Or do the floods signal a significant change in hydrologic response related either to climatic change or long-term anthropogenic changes in watersheds throughout the upper Midwest? Watershed studies at various scales can help address these questions.

Significant progress has occurred in recent years in the capability for real-time flood forecasting. The National Weather Service is in the midst of modernizing its system for forecasting floods, including flash flood occurrences on small streams and peak stage levels and their timing on major river channels. Improved models for rainfall-runoff prediction over short and intermediate time scales are a key component of this forecasting capability. Ongoing stream gauge monitoring also is needed to calibrate and verify the predictions of flood forecast models.

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

Beyond the impacts on lives and property, there remain many indirect consequences of floods that are often obscure or subtle, whether occasioned by accidental releases of contaminants into the environment or by malicious or opportunistic dumping. The implications of such scenarios in the usually congested arena of the urban-suburban setting are far-reaching and often overlooked in the confusion associated with flood events. The challenges of safeguarding populations from hazardous materials swept away by flooding, monitoring pollutants from both recognized (e.g., combined sewer overflows) and unidentified or nonpoint sources, and restoring the integrity and dependability of public services, constitute only a few issues on an agenda for action that involves both short-term and long-term policy and technological decisions.

The floods of 1993 also raised significant concerns related to the fate of toxic contaminants in water and sediment. For example, Goolsby et al. (1993, p 19) report that ''... the heavy rainfall and severe flooding from mid-June to early August flushed extraordinarily large amounts of agricultural chemicals into the Mississippi River, many of its tributaries, and ultimately the Gulf of Mexico.... The total load of atrazine discharged to the Gulf of Mexico from April through August 1993 (539,000 kg) was about 80 percent larger than the same period in 1991 and 235 percent larger than this same period in 1992.'' Toxic materials were contained in some sediments deposited by the flood waters. The flooding also caused ground water contamination in areas where flood waters overtopped well casings or ground water recharge areas. There was also significant destruction of wildlife habitat in the flooded areas, some of which were inundated for weeks. Can the impacts of future floods of equal magnitude be reduced? How long will it take the environment to recover from the effects of the 1993 floods?

Drought, at the opposite end of the hydrologic spectrum, is a more nebulous occurrence than flooding. In part, this is because a drought is more poorly defined in space and time than is a flood and, therefore, is more difficult to characterize generically. Indeed, drought can be defined differently according to one's interest or purpose (e.g., meteorological drought, hydrologic drought, agricultural drought, or economic drought). The most widely used measure of drought, the Palmer Drought Severity Index, is widely viewed as inadequate for many operational purposes, especially in hydrology. Specifying when a drought biggins and ends is particularly difficult. Research on the flux of moisture over, through, and from the land, at watershed scales, may provide the basis for deriving a better "dynamic" definition and model of hydrologic drought. One particular question that watershed research may provide an answer to is to what extent, and how, does the terrestrial hydrologic system set up, reinforce, or maintain a

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

hydrologic drought through feedback processes? The answer to this and related questions could have significant implications for adapting more efficient strategies for managing water resources during drought periods.

Sinkholes constitute another common but poorly understood natural hazard. Sinkholes are natural features that occur in terrains underlain by carbonate rocks such as limestone and dolomite. Such terrains cover about 15 percent of the United States. Catastrophic large collapses at the land surface sometimes occur during sinkhole formation, and these sinkholes have opened beneath highways, railroads, bridge structures, building foundations, and rivers or surface water impoundments. The financial and environmental costs of sinkhole development can be significant. Sinkhole development also can contribute significantly to ground water contamination, the sinkholes acting as conduits for surface waters to enter ground water systems with little or no attenuation of contaminant loads.

Many human activities can induce or accelerate sinkhole formation. The most common cause is probably declining ground water levels due to ground water withdrawals or drainage projects. Other causes include induced recharge, construction of large surface impoundments, and vibration. A better scientific understanding of the effects of sinkholes on water quantity and quality, causes of sinkhole formation, and improved means to predict their occurrence are issues that can be addressed through watershed studies in karst and related terrains.

Slope stability and slope failure concerns compose a third major area of geologic hazards related to watershed science. Slope failures often are tied to hydrologic phenomena, such as excess soil moisture, excess precipitation, poor internal drainage, or slope undermining by erosion. For example, rising water levels in the Great Lakes during the late 1970s resulted in significant shoreline erosion and slope failures (Sterrett and Edil, 1982). Such changes in water levels are the result of interacting hydrologic and climatic processes in the watershed. The Corps of Engineers estimated that in the United States there are 925,000 kilometers of stream bank with erosion problems, about 25 percent of which are classified as severe. Average annual economic losses resulting from this erosion were placed at $295 million. The heaviest losses were estimated for California, the Arkansas-White-Red River systems, and the Lower Mississippi River Basin (Federal Interagency Floodplain Management Task Force, 1992).

Climatic Variability and Change

Watershed studies related to the general focus area of climatic change

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

encompass a variety of issues. First among these may be the evaluation of watershed responses as indicators of climatic change. Watersheds integrate hydrologic and geologic processes over a range of overlapping spatial and temporal scales and preserve a record of the past in many different ways. The geomorphology and channel morphometry of a watershed are physical records of past water levels, flow regimes, and flood events (e.g., Knox, 1988). The stratigraphy and composition of sediments and soils in a watershed provide evidence of past erosion and deposition. Materials contained in the sediment column, such as fossils, pollen, and archeological relics, give clues to past biological communities. Ground water systems frequently contain geochemical or isotopic signatures that, once interpreted and understood, can help in the understanding of hydrogeologic processes operating in the past. Such paleohydrologic data are extremely relevant to understanding and documentation of climatic change on local, regional, and global scales.

Several critical issues associated with understanding how climate and hydrologic systems interact are dependent upon process-level information acquired at watershed scales. Most important is the determination of how hydrologic, geochemical, and geomorphological processes respond to shorter-term variations and longer-term changes in climatic conditions. High-resolution, event-based sampling within watersheds provides the basis for improved modeling of flowpaths and streamflow generation, weathering, chemical transport, and water quality genesis processes (Lins, 1994).

Over longer time scales the hydrologic and geologic conditions recorded within watersheds represent a spatial and temporal integration of the prevailing local- to regional- to hemispheric-scale climate. Discharge records, for example, provide a basis for determining interannual to decadal trends, as well as regional and seasonal shifts, in hydroclimatic conditions (Lins et al., 1990).

A second issue is associated with the feedback effect that the terrestrial hydrologic system has on the atmosphere. Although many of the unanswered questions relate to the atmospheric pathways of evaporated moisture and to the sensitivities of atmospheric dynamics to the exchanges of heat and moisture between land and atmosphere, realistic modeling of land surface processes at the watershed scale is essential to the successful simulation of climate at regional to global scales (NRC, 1991). Spatial heterogeneities in surface hydrologic processes exert significant effects on local to regional atmospheric dynamics. For example, several investigations have indicated that soil moisture anomalies were at least secondary contributors to the persistence of the 1988 drought over North America (Trenberth and Branstator, 1992). Identifying those effects, their controls, magnitudes, and

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

appropriate parameterizations can only be attained through ongoing and systematic observations and analysis of watershed processes.

A third significant unresolved issue associated with long-term climatic change is that the global CO2 budget of known sources and sinks cannot be balanced over any time scale. Several lines of evidence based on interhemispheric gradients in atmospheric CO2 concentration, intraannual atmospheric CO2 variation, models of ocean-atmosphere CO2 exchange, and patterns of forest growth together suggest that the northern hemisphere terrestrial biosphere may be the sink for this "missing carbon." However, current estimates of CO2 exchange, based on carbon inventories of ecosystems and patterns of land use change, suggest that the terrestrial biosphere should be a net carbon source.

The National Research Council (1994b) stated recently that "until the current global carbon budget can be balanced, there is little hope of predicting the future changes in atmospheric CO2 concentration and, therefore, the radiative properties of the atmosphere that will determine future climatic changes." The NRC report outlined a number of activities for deriving a more complete accounting of the global carbon budget. These included determining (1) how changes in temperature and hydrology affect methane and carbon dioxide fluxes from tundra and boreal wetlands to the atmosphere; (2) how changes in soil temperature, moisture, and nitrogen input affect methane uptake and nitrous oxide production by temperate and boreal forests, grasslands, and agriculture ecosystems; and (3) how clearing of tropical forests for crop and pasture, and subsequent management and abandonment of crop and pasture land, affect the fluxes of CO2, CO, CH4, N2O, and NO between soils and the atmosphere.

The USGS's WEBB (Water, Energy, and Biogeochemical Budgets) watersheds are well designed for studying these high-priority carbon budget processes. The USGS should be a critical contributor to the solution of the missing carbon problem. It has already provided some important insights on the flux of carbon in an aggrading forest ecosystem at its Panola Mountain WEBB site (see Box 4.2). There, an analysis of carbon pools indicated that aggrading forests (in this case recovering from intensive cultivation from the early, a 1800s to the early 1900s) in the southeastern United States are an important regional carbon sink (Huntington, 1995). The cultivation resulted in extensive erosion that depleted soil carbon pools. Over the 70-year period that forest regeneration has been taking place at the Panola Mountain watershed, the rate of soil carbon sequestration is estimated to be between 0.34 and 0.79 mg of C per hectare per year. The USGS work is important documentation in support of the thesis that carbon sequestration in temperate forest ecosystems may be partially mitigating the effects of increased

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

BOX 4.2 Atmospheric Acidic Deposition and Carbon Cycling in Small Forested Watershed in the Georgia Piedmont

At the Panola Mountain Research Watershed, near Atlanta, Georgia, the USGS has been investigating biogeochemical processes related to the influences of the atmospheric deposition of sulfur, a nonpoint source pollutant, on terrestrial ecosystems and aquatic resources. The forest and soils at Panola Mountain are representative of the southeastern Piedmont Province. Watersheds comprise discrete hydrochemical environments allowing quantification of element budgets. Monitoring stream water chemistry, basic climate, soil, and biotic variables provides a means to integrate complex biogeochemical processes and evaluate trends in water quality.

Despite the high sulfate retention capacity of soils at Panola, episodic stream water alkalinity depression is sufficient to result in net negative alkalinity during many storms because of the routing of runoff through acidified surface soil horizons and dilution of more alkaline waters associated with deeper flowpaths. The model of acidification of ground water in catchments (MAGIC) predicts that chronic sulfur loading at current rates will result in substantially more pronounced alkalinity depression during storms in as little as 20 years. Modeling also suggests that future changes in rainfall amounts or seasonal distributions that result in decreases in runoff will result in greater watershed acidification than if rainfall patterns remain the same for fixed sulfur loading.

Work at Panola Mountain Research Watershed also has investigated carbon cycling processes as they may be related to issues of global climate change. The forested watershed at Panola is representative of a broad area of southeastern Piedmont forest soils. Results of study at Panola have indicated that soils have been accumulating carbon at a rate of between 0.34 and 0.79 mg of C per hectare per year during an approximately 70-year period. When applied to much larger areas of comparable recovering forests lands in the northern temperate regions, such soil carbon accumulation represents a potentially significant flux in relation to the apparent unexplained "missing carbon sink" in the global carbon cycle.

Results suggest that there is a large potential for continued carbon accumulation at Panola. However, the rate of carbon accumulation is

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

likely to substantially decrease over the next 50 to 100 years as forest soils begin to approach predisturbance levels. The fact that this sink is likely to decline is significant because it suggests that the role of recovering forests as partial mitigation of atmospheric loading of carbon dioxide will diminish, resulting in more rapid increases in atmospheric carbon dioxide concentrations.

atmospheric loading of CO2.

Improving forecasts of climate change and climate variation is a topic of much current interest and one that demands additional work. Knowing that climate is an inherently dynamic feature of the planet over all time and space scales does not simplify the problem of predicting what atmospheric conditions will prevail at a certain time and place in the future. Statistical models, although useful for providing a perspective on large-scale oceanic, atmospheric, and hydrologic connections, do not incorporate the necessary dynamics for ensuring physically consistent interactions among the various components of the climate system. The most promising approach to improved prediction of climatic variability and change requires improvement of the characterization of water, energy, and biogeochemical exchanges between the terrestrial surface and the atmosphere. Long-term monitoring, analysis, and modeling of watershed processes are vital to this characterization, resulting in the attainment of improved predictions.

Aquatic Habitat Alteration and Restoration

One of the most significant contributions of watershed planning in the 1990s is the prominent role given to relationships among land use, water resources, ecological systems, and sustainable development. While cases of watershed planning in the 1990s cited by the EPA tended to highlight the flux of either sediments, nutrients, pesticides, or heavy metals from land-disturbing activities, they also point out the linkage between water quality and aquatic organisms and ecosystems. In several cases water quality was shown to be linked to the health status of wildlife and farm animals; several cases address problems of degradation of terrestrial ecosystems (U.S. EPA, 1991a, 1991b, 1992).

Aquatic habitat can be defined to include a range of areas that support aquatic organisms, from the microscale level (instream or in-lake conditions),

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

to adjacent riparian areas, to the large scale (tributary watershed areas). Aquatic habitat alteration and destruction together are perhaps the most significant ecological problem in watersheds today, often acting as the limiting factor, controlling biological integrity (Parkhurst et al., in press; Karr, 1996; Rankin, 1996; U.S. EPA, 1996; Ohio Environmental Protection Agency, 1992).

Five factors affect overall water resource integrity—energy source, water quality, habitat quality, flow regime, and biotic interactions (Rankin, 1996; Karr, 1996). Both habitat structure and flow regime can be affected by alterations of natural habitat conditions. Habitat structure includes such factors as width/depth ratios, bank stability, channel morphology, sinuosity, pools, riffles, substrate, gradient, current, siltation, instream cover, canopy, and riparian vegetation (Barbour and Stribling, 1991). Factors that define flow regime include extreme high-and low-flow conditions, variability of flows, velocity, and storm event runoff conditions.

Disturbance of the natural flow regime of rivers, resulting in changes in the timing and quantity of flows, can have a large effect on aquatic habitats. One of the major causes of such disturbance is the construction of dams on rivers. Although dams have provided benefits for mankind, this construction on most of the large rivers in this country has transformed many free-flowing rivers into series of standing-water lakes, providing obstacles to natural migratory movement and altering the natural variability of flows. The Columbia River, which is controlled by several dams, provides an example, with the natural salmon fishery reduced to a primarily stocked fishery and with the need for fish ladders and barge transport to assist the fish in reaching spawning grounds. The placement of dams to control flooding also has moderated the pulsing action of flood flows and has reduced the natural movement of sediment and nutrients throughout aquatic ecosystems. On the Colorado River, the reduction of this pulsing flow action has led to concerns about impacts on threatened and endangered fish species that rely on fresh sediment for spawning habitat and about impacts on cottonwood trees that rely on periodic formation of sand bars to support regeneration.

Urbanization and the associated increase in impervious area also have disrupted natural hydrologic patterns, by increasing peak flow volumes and reducing the time of flow concentration, which results in very short-lived, high-flow conditions associated with storm events (Schueler, 1987). At the other extreme, many of the nation's water resources, particularly in the Southwest, have been depleted due to an overappropriation of water rights for irrigation and other uses. In many states there has been a move to allocate minimum instream flows, purchasing or exchanging water rights specifically for instream use. Transbasin movement of water from rural areas

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

to meet the demands of water users in concentrated urbanized areas also has modified natural flow regimes.

Habitat structure can be disrupted by many of the same alterations that affect flow regime, as well as a few others. For example, channelization of waters for flood control and construction of levees disrupts the natural interaction of river and stream channels with riparian zones, floodplains, and backwater areas. The loss of this natural interaction upsets the balance of sediment, nutrients, riparian vegetation, and water (NRC, 1992a). Channelization and "hard-engineering" bank stabilization projects also result in the direct destruction of riparian and instream habitat, greatly degrading the habitat structure and ability to support biological communities. Drainage of riparian and wetlands areas for agricultural land development and filling or modification for urban development also has resulted in significant losses of aquatic habitat.

The extent of problems caused by habitat alteration has not been quantified in a comprehensive way across the country, but the NRC (1992a) estimates that approximately 1.7 million hectares of lakes is degraded, primarily due to siltation, anywhere from 5 to 70 percent of the approximately 5.1 million river kilometers in this country have been channelized, and approximately 50 percent of the nation's wetlands have been lost over the last 200 years.

Most states have not yet fully recognized the importance of habitat alterations when assessing water quality improvements. A 1992 EPA assessment of the condition of the nation's waters indicated that, of 47 states that responded in 305(b) reports (i.e., summaries of the condition of state waters), 25 did not indicate any limitations by habitat conditions (U.S. EPA, 1992). However, many other states are making progress toward including habitat measurements within their regulatory programs through integration into biocriteria and narrative water quality standards (U.S. EPA, 1996). An example is the state of Washington, which has recognized that habitat can be a limiting factor and has developed methods to incorporate habitat within its Total Maximum Daily Load program, the cornerstone of the Washington state regulatory water quality program (Washington Department of Ecology, 1996).

Restoration, defined as "returning an ecosystem to a close approximation of its condition prior to disturbance" (NRC, 1992a), can help reverse the degradation caused by habitat alterations. A wide variety of techniques can be applied to restore altered habitat areas from instream or in-lake, to riparian, to upland watershed. Restoration techniques may range from administrative solutions, like preserving floodplains as regulatory floodways or allocating water for minimum instream flows, to physical improvements

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

like removal of dams and levees or restoration of natural meandering stream morphology (U.S. EPA, 1995; NRC, 1992a). Surveillance of both structural and functional attributes, before and after restoration, is key to determining the environmental benefits of such activities.

Restoration of contaminated or damaged hydrologic regimes and associated ecosystems to more natural conditions has become an important public policy goal in many parts of the United States. For example, restoration of wetlands environments that were previously drained or filled is now seen as important for habitat protection, biodiversity, flood control, water quality maintenance, and a host of other objectives. Recently, the concept of "wetlands mitigation banking" and "mitigation credits" has been put in place in many areas of the United States. Under such policies, wetlands destruction for some economic purpose, such as highway construction, can be allowed as long as equal or greater areas of wetlands are restored or constructed elsewhere. What is the long-term effect of such policies on watersheds? Successful restoration of hydrologic and biological systems requires an understanding of the complex hydrologic and biogeochemical processes operating in the area to be restored, knowledge of the environmental criteria (plant and animal species, water levels, chemical concentrations) desired for a successful restoration, and the steps to be accomplished for the restoration to succeed. For example, a wetlands restoration carried out by simply impounding surface water might not be successful if complex ground water/surface water exchanges are ignored (e.g., Hunt et al., 1996).

POTENTIAL FOR WATERSHED RESEARCH TO ADDRESS NEEDS

The needs for research in watershed science are very diverse (see Table 4.1). Information of the kind discussed in this report has come and will continue to come from a variety of sources. The USGS is not the only source of this information, but it is a particularly important one. The USGS is of special importance because it is a nonregulatory agency that systematically collects hydrologic data on a large number of watersheds and conducts long-term research on selected watersheds. To make the best use of its resources, the USGS must focus research on areas that can provide key information on problems of significance to the nation. This study identifies four interrelated areas for research that could form the base for USGS activities over the next decade. Information needed for management of large watersheds is lacking. Much research has been conducted on small watersheds in relatively undisturbed areas, but methods for transferring knowledge about processes

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

to infer responses of large watersheds are not available. Urbanization creates severe hydrologic changes, but relatively little work has been done to synthesize quantitative information relative to processes that affect water quantity and quality in urbanizing areas. The restoration of damaged watersheds has become a topic of considerable national interest. The scientific bases for selecting among restoration alternatives and for measuring the effects of actions are lacking. New problems involving erosion from watersheds, especially the transport and fate of sediment-bound hazardous materials, indicate that a renewed emphasis on research on sediment transport is required. In each of the four areas mentioned above—large watersheds, urban watersheds, watershed restoration, erosion, and sedimentation—the USGS could play a pivotal role in the development of a knowledge base for effective watershed management.

The ingredients of an effective watershed research program to address the interrelated areas identified in this study include (1) a measurement and monitoring program for a hierarchy of basins of various sizes; (2) several intensively studied, small experimental watersheds that are run expressly to support the information needs of the overall efforts in the research areas; and (3) a modeling research program to interpret the measurements made at the large scale in terms of processes understood to be important from the small watershed experiments. The USGS already has many elements that are needed for such a research program. What appears to be lacking is the organization to forge links among the elements.

A Knowledge Base for Large Watersheds

The use of small watersheds to study hydrologic and hydrochemical processes is a staple in the research arena of watershed science. Well-known examples include studies of the effects of forestry practices (e.g., Hornbeck et al., 1987; Swank et al., 1988), effects of agricultural practices, vegetation changes, and meteorological variations (e.g., Abrahams et al., 1995; Owens et al., 1983), and of the effects of "acid rain" on streams draining small watersheds (e.g., Bricker and Rice, 1989; Williams et al., 1993). There continues to be a basic research need to work with small watersheds because questions about processes most often are addressed best at scales where variability can either be accounted for or minimized. There are nevertheless management issues of significant consequence to society that relate to watersheds of a size beyond that of most research watersheds. Furthermore, some important processes may be observable only in large watersheds (e.g., floodplain storage of sediments for tens to thousands of years). The USGS

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

should organize its research efforts in watershed processes to address the need to understand hydrologic effects at the scale of watersheds hundreds to thousands of square kilometers in area.

The first of the three general requirements for an effective research program in this area—an extensive measurement and monitoring network for basins of various sizes, including major rivers—is satisfied to a large extent by the National Water Quality Assessment (NAWQA) program. NAWQA is an ambitious program that seeks to evaluate the status of the nation's water quality (NRC, 1990). The program already has achieved many successes and the effort to synthesize results from around the country (the ''national synthesis'') is quite active (NRC, 1994c). By design, the NAWQA program has only a modest research component. The key to making the most out of the NAWQA results will be linkages to research efforts of other programs within the Water Resources Division (for example, see Box 4.3).

To incorporate the second component of the "large-watershed research program—an integration of process studies on experimental watersheds—will require cooperation and collaboration between the USGS and other agencies. For example, the USGS can rely on the Agricultural Research Service (ARS) for research on processes related to agricultural practices and on the Forest Service for research on processes related to forestry practices. The USGS has much experience in monitoring and studying natural processes within relatively undeveloped watersheds. For the most part, manipulation experiments are not possible in these watersheds. The USGS should consider where gaps in watershed experimentation exist and keep its own watershed research program active by concentrating on these areas. For example, it might be determined that experimentation on hydrologic effects of urbanization is lacking. In this case the USGS could shift its efforts to implementation of such a program that would be designed to interface with information coming from the NAWQA program.

The final component needed for the success of the "large-watershed' program is an active modeling effort. The USGS historically has had great success in developing models that have bridged the gap between detailed research and more regional studies. Examples include the ground water code MODFLOW and the geochemical code WATEQ. With the exception of the relatively recent work on the Modular Modeling System by George Leavesley and his colleagues, the USGS has not had similar successes in modeling for watershed science. The success of the USGS effort in watershed research demands that this aspect of the work be recognized as an ingredient of equal importance to the measurement and experimentation portions. The overall effort will entail the use of statistical analyses and mechanistic process modeling.

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

BOX 4.3 Sleepers River WEBB, NAWQA, and the Role of Small Watershed Research in Large Basin Studies

Sleepers River in northeastern Vermont is the only WEBB site in an NAWQA basin. The Sleepers River WEBB study uses both a nested basin and a paired basin design to investigate hydrologic and biogeochemical processes in different land uses and at different basin scales. The outlet of the largest basin, the entire 111-square kilometers drainage of Sleepers River, was chosen as an indicator site by the Connecticut River NAWQA study. It is at this scale—approximately 100 square kilometers—that WEBB and NAWQA interface.

WEBB and NAWQA have fundamentally different scientific missions. WEBB studies are process-oriented research projects, geographically restricted to one or two land uses in a single ecosystem. Sites are generally small undeveloped watersheds where processes are more effectively isolated. The goal of NAWQA is assessment of water quality status in large river basins, which encompass a broad range of land uses and often more than one ecosystem. Both programs have in common the goal of trend detection through long-term monitoring.

The operational approaches of the two programs are likewise quite different. WEBB implements a spatially and temporally intensive sampling design to infer processes by linking closely spaced observations.

Sampling in NAWQA, by contrast, is of necessity spatially and temporally sparse, limited to that deemed necessary to assess current water quality. NAWQA indicator sites each are characterized by one dominant land use and are an attempt to isolate water quality influences of that land use. Integrator sites reveal the combined influences on larger rivers.

Process understanding gained by WEBB investigations is valuable to NAWQA. The frequent sampling in WEBB studies has shown that nutrient and contaminant fluxes are quite dynamic—information that can be used to guide the frequency of NAWQA sampling. For example, this approach was applied at an indicator site in the Hudson River NAWQA, where frequent sampling showed that pesticide transport occurs primarily during significant storms shortly after application. If streams are sampled only monthly, much of the annual export can go undetected. Sampling during snowmelt at Sleepers River

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

likewise revealed dynamic fluctuations in nitrate concentrations that were not captured by the NAWQA sampling at the same site.

WEBB sites also serve as test sites for modeling efforts. For example, the NAWQA National Synthesis Team used TOPMODEL to map the susceptibility of pesticide runoff for the contiguous 48 U.S. states. TOPMODEL was applied to predict the percentage of overland flow in total flow, and the predictions were combined with pesticide application records to assess the risk of pesticide runoff to streams. The assumptions and generalizations needed to apply TOPMODEL at a national scale were tested directly in WEBB and other small watersheds. Issues such as appropriate digital elevation model (DEM) scale, topographic index calculation algorithm, and grid size for the final map were resolved in these research watersheds where model results could be evaluated in light of existing process understanding.

Information from NAWQA studies also can point to areas where WEBB-like studies are needed. For example, within the Connecticut NAWQA, nutrient concentrations at indicator sites varied considerably. While some sites were similar to Sleepers River, other agricultural sites had much higher concentrations, and certain urban sites had the highest of all. Nutrient export from urban and intensive agricultural basins clearly dominates the loading to the main stem and the coastal zone. Process-level understanding of controls on nutrients would be of benefit to understanding current water quality and predicting its future trend. For example, isotopic analysis to identify point and nonpoint sources of nitrate would help to indicate where water quality improvement efforts should be targeted.

As mentioned above, pieces of the ingredients for a program on "large-watershed" research already exist within the USGS. There are indications that integration of these ingredients is taking place on a selected basis. A few cases about which this committee is aware include the work of Leavesley and co-workers on the Gunnison Basin in Colorado (Battaglin et al., 1993); the work of Wolock on modeling nested basins (Wolock, 1995), which is being extended within the NAWQA umbrella and the research basin efforts at Sleeper's River (see Box 4.3); the work of Bencala and coworkers to interpret in-stream tracer studies throughout the Willamette NAWQA study on the basis of processes identified to be important in a series of small-basin experiments; and the work of Helsel (1994) to "break the scale barrier." If

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

a way can be found to organize and coordinate these efforts, the USGS may fill an important research niche in "large watersheds."

A Knowledge Base for the Restoration of Watersheds

Hydrologic alterations made to watersheds stem from stream channelization, impoundments, wetlands drainage, deforestation, and urbanization. Although many social and economic benefits have been realized from these human activities, some areas have experienced the unintentional consequences of exaggerated flood and drought, water quality degradation, reduced ground water recharge, and habitat impairment. In response, watershed restoration—a move to recreate some of the predisturbance hydrologic processes and landscape features—has been advocated as the best means to address problems of concern. One of the challenges to future water management is knowing the effectiveness and costs to restore the hydrologic regimes and ecological functions of watersheds, where such restoration is desired by society.

Central to the success of watershed restoration is an understanding of, and ability to predict, how changes on the landscape and in water management affect hydrologic processes and ecological outcomes at different watershed scales. Some efforts to monitor and then judge the results of restoration efforts for particular landscape features, such as wetlands (Mitsch and Wilson, 1996), have been made. However, at present almost all assessment efforts are geared toward particular landscape features (e.g., wetlands or riparian zones) or to remediation of some contaminant as a target site. In evaluating the USGS program on hazardous materials science and technology, this committee concluded that the USGS should take an active role in helping to evaluate the effectiveness of remediation efforts for particular ground water areas (NRC, 1996). A similar recommendation to the USGS here with regard to restoration of whole watersheds is appropriate.

The USGS has taken an active role in providing technical assessments of alternatives in some areas where whole watershed restoration efforts are under way (see Box 4.4). As this role expands, the USGS should commit to improving the science base supporting assessment protocols for watershed scale restoration. The strength of the USGS has been in areas of geoscience: in collecting data that allow assessment of the quality of water, in gaining a fundamental understanding of what natural processes are important in the flow of water and the transport of materials (including biogeochemical reactions), and in producing models that are useful in analyzing flow and transport in natural systems. The opportunity to derive ecological implica-

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

BOX 4.4 Redwood River Water Management Project

The upper Mississippi River and its backwaters, wetlands, and floodplain forests are crucial habitat for many fish and wildlife species. The river is a major flyway for migratory birds, including up to 40 percent of North America's ducks, geese, swans, and wading birds. Many of these species breed in the prairie pothole country in the great river's watershed, including the Redwood River basin, which drains roughly 180,000 hectares of southwestern Minnesota into the Minnesota River.

Flooding in the Redwood River basin has resulted in agricultural, urban, and residential damages, particularly at the town of Marshall, Minnesota. Wetlands drainage could be a major contributing factor to increased flood peaks and flood damages in the basin. Prior to agricultural drainage, roughly 43 percent of the basin was wetlands. Roughly 19 percent of these former wetlands areas are depressional and have potential value for stormwater storage. Over 82 percent of the watershed is in agricultural use, indicating extensive wetlands drainage for agriculture. Prior to drainage for agriculture, many of the wetlands in the Redwood River watershed were closed basins that stored water during rainfall events and did not contribute directly to flows in the Redwood River.

Two flood control projects that were planned for the basin have not yet been constructed because of public opposition and anticipated adverse environmental impacts. One would divert water from the Redwood River to an adjacent river basin during periods of heavy flows. The residents of the other basin do not want to accept the water. The other project is a dam that would back water up on farm land and cause fluctuating water levels in a state-owned wildlife area.

The Redwood and Minnesota rivers are also heavily polluted by suspended sediments, fertilizers, and pesticides that largely run off of agricultural land. The state of Minnesota has initiated a "Clean Water Action Partnership" to involve communities in the cleanup of the Minnesota River basin.

Wetlands restoration and the installation of soil and water conservation practices could generate substantial benefits in the Redwood basin. Wetlands and soil and water conservation practices can significantly reduce nonpoint source pollution. The Redwood watershed is

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

also in the prairie pothole region of the upper Midwest, one of the most important waterfowl breeding areas in the United States, which makes it a high priority for wetlands restoration. Other potential benefits of a restoration approach to flood damage reduction include reduced soil erosion and increased groundwater recharge and water supply.

A county-level joint powers board, the Redwood-Cottonwood Rivers Control Area, is taking the lead in developing a water management plan for the Redwood River watershed that would use wetlands restoration and soil and water conservation practices to reduce flooding, improve water quality, increase wildlife habitat, and provide other benefits. The board is made up of local farmers. A wide range of federal, state, and local agencies, as well as private-sector representatives are assisting with this initiative. The USGS has been involved in a hydrology work group to assess watershed models for use in predicting outcomes of various management scenarios.

tions from this knowledge has been enhanced with the recent formation of the Biological Resources Division. Building on past strengths and this new opportunity, the USGS should advance the science of whole-watershed restoration in four critical areas (1) improvements in the ability to understand relationships among watershed hydrology, water quality, and habitat; (2) helping better understand conditions prior to disturbance; (3) relating the consequences of restoring damaged sites to watershed-scale outcomes; and (4) translating knowledge gained from data collection and experimental watershed studies into models that can be used to evaluate restoration actions.

Developing the appropriate knowledge base for making informed decisions about watershed restoration will require a long-term commitment to research. Changes in water quantity and quality stemming from restoration efforts may occur over periods of years to decades. That is, interacting physical, chemical, and biological processes may take long times to equilibrate following alterations. Given the background variability in climate and weather, building the knowledge base for watershed restoration will require long-term monitoring and, possibly, long-term experiments on selected systems. Once again, the development of appropriate modeling tools to interpret and to generalize results must be recognized as being of equal importance to fieldwork.

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

Water chemistry sampling system in the Icacos watershed, Luquillo Forest WEBB site, Puerto Rico. Source: U.S. Geological Survey.

A Knowledge Base for Urban-Suburban Hydrology

The impacts of changes in land use on hydrology and, more recently, the combined impacts of climate change and land use, have been a focus for hydrologic research. Due to the efforts of a variety of individuals and organizations (including the ARS and the Forest Service), some quality information related to agricultural and forestry effects on watershed hydrology is available. Work on urban hydrology has been somewhat more scattered, perhaps because there is no agency responsible for determining the effects of urban and suburban land use changes. Because of this fragmentation, a concerted effort by the USGS to develop more systematic information related to hydrologic changes in response to suburban and urban development should be considered.

Research needs in the area of urban hydrology are many and varied (e.g., Heaney, 1986). The USGS cannot hope to do all of the research that is needed. Rather, the consideration should be the organization of a research

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

thrust that would utilize existing strengths of the agency. The key is to integrate the efforts of researchers in the National Research Program with those of scientists working in the districts, either on NAWQA or other projects within the cooperative program. That is, there are efforts within NAWQA to investigate urban effects on water quality (e.g., Bruce and McMahon, 1994); there are efforts to understand recharge in urban areas (e.g., Michel et al., 1994); and there are efforts to apply simulation models to estimate the effects of urbanization on floods (e.g., Dinicola, 1994). What appears to be lacking is a coordinated program to accumulate extensive data for urban watersheds with the aim of adding to fundamental scientific understanding of processes in these watersheds and of extending and improving the ability to assess quantitatively the effects of land use changes in an urbanizing area. As with the previously discussed areas that this study has identified as possibilities for USGS emphases, the integration of monitoring, observations on small research watersheds, and modeling is critical for an effective program.

A Knowledge Base for Erosion, Sediment Transport, and Sediment Deposition

The USGS historically has been heavily involved in research on sediment transport in rivers. Over the past decade or so, there has been a decreasing emphasis within the agency on such research. The recognition that toxic chemicals often are transported in association with sediments has prompted renewed interest in work to understand sediment budgets and the processes by which sediments are removed from watersheds. The sediment budgets for large watersheds have large uncertainties (Parker, 1988). In conjunction with a concerted program on the hydrology of "large" watersheds (see above), the USGS should develop an integrated effort on sediment transport. This effort should include a measurement program for a hierarchy of basins around the United States nested so as to address issues of scaling from small watersheds to large watersheds and to record sediment inventories and processes that occur only on larger watersheds. The measurement program should be supplemented with a modeling effort to interpret the measurements and provide the framework for scaling process understanding from small to large watersheds. Special consideration should be given to urban watersheds where improved knowledge of sediment budgets may be of critical importance in understanding the effects of development on water quality and channel stability. An excellent example of what can be done is the USGS work in Puerto Rico (see Box 4.5), where basic research results in

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

BOX 4.5 Water, Energy, and Biogeochemical Budgets in and Adjacent to the Luquillo Experimental Forest of Eastern Puerto Rico

The Water, Energy, and Biogeochemical Budgets (WEBB) program began funding research in eastern Puerto Rico during 1990. Sites are in and adjacent to the Luquillo Experimental Forest (LEF). Core funds come from the USGS Global Change Research Program. The Caribbean District Office of Water Resources Division (WRD) manages the program, with guidance from investigators of the National Research Program of WRD.

Multiple-paired watersheds are used to compare geologically matched, natural and agriculturally developed environments. The USGS endeavors to characterize the processes that control the distribution and transport of carbon, major, important minor, and nutrient elements through soils, downslope, and out of watersheds. The core of this program is long-term, event-based chemical sampling and physical monitoring. A feature that distinguishes this WEBB site is a strong emphasis on geomorphic processes. Additional efforts include gas exchange studies and innovation of new biogeochemical approaches such as the development of equilibrium erosion theory and the design of techniques based on in situ-produced cosmogenic beryllium-10. Geographic information systems are used to extrapolate from site-specific studies to regional scales.

Since its inception, work in the LEF has involved cooperation with the Long Term Ecological Research Program, with the International Institute for Tropical Forestry of the Forest Service, and with universities, Outside the LEF, most research has involved internal coordination with cooperator-based research programs developed by the USGS district office. The cooperators are agencies of the Puerto Rico's government concerned with hazards, such as floods and landslides, or with capacity loss in the Carraizo Reservoir, the principal water supply for San Juan.

Puerto Rico is an excellent metaphor for future development in the tropics, having problems associated with deforestation and urbanization. The linkage between the research needs of cooperators and some of the basic scientific questions established a synergy. For example, researchers asked "do landslides ultimately control much of

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

the chemistry of tropical rivers in mountainous regions?", while cooperators asked "how can we assess landslide hazards?" Researchers asked "by what mechanisms does agricultural development accelerate erosion?''; cooperators asked "why is so much sediment being delivered to the Carraizo reservoir, so much so, that a 10-year drought provokes water rationing?" By melding the basic research envisioned in the WEBB program with cooperator-funded research, scientists came up with new and sometimes surprising answers. It was shown that denudation in the forested watersheds was at a near-steady state, whereas physical denudation in the agricultural watersheds was out of equilibrium and proceeding at an order-of-magnitude greater rate. Upland erosion in the agricultural watershed, driven by landslides, is resulting in vast deposits of colluvium and alluvium, which may indicate years of vexation for water providers.

conjunction with monitoring efforts are providing the knowledge base that will be critical for informed decisions on watershed management practices (e.g., see Guzmán-Ríos, 1989; Larsen and Torres-Sánchez, 1996; Stallard, 1995).

The basic data required for analyzing sediment transported from watersheds must be collected by using bedload samplers and flow-weighted suspended sediment sampling. The measurements are costly in terms of maintaining the gauging station and in terms of personnel. The number of sediment-sampling stations, like the number of stream-gauging stations, operated by the USGS has declined in recent years. The backbone of any scientific program on watershed erosion and related sediment transport and deposition is the collection of basic data. As with stream gauging (NRC, 1992b), careful attention should be given to supporting at least a minimal set of measurement stations for sediment transport studies.

In the area of watershed management, effective utilization of research results associated with sediment transport requires that the USGS pursue coordination with agencies charged with managing water resources. Clearly, the USGS is aware of this need, as recently demonstrated in the controlled flood on the Colorado River below Glen Canyon Dam. USGS investigators had shown that the natural annual sediment scour and fill process maintained large sand bars along the river banks, kept sand bars clear of vegetation, and kept debris fans from constricting the river. Construction of the Glen Canyon Dam retarded the large annual spring floods and led to a reduction in the

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×

size of sand bars, allowed vegetation to encroach on the channel and debris fans to build up, and caused filling of backwater areas used by native fish. As a solution to these problems, the USGS proposed to the Bureau of Reclamation a controlled flood from the Glen Canyon Dam as a way of reestablishing more natural river conditions, a proposal that was implemented successfully by the bureau in the spring of 1996.

The USGS should exploit similar collaborative opportunities where practical. For example, the ARS is leading an effort to improve models for erosion prediction (Lane et al., 1988). Through minor extensions to its existing efforts in sediment transport mechanics and modeling, the potential exists for the USGS to enhance significantly the ARS program as well as other USDA programs.

Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 33
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 34
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 35
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 36
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 37
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 38
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 39
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 40
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 41
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 42
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 43
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 44
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 45
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 46
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 47
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 48
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 49
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 50
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 51
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 52
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 53
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 54
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 55
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 56
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 57
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 58
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 59
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 60
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 61
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 62
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 63
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 64
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 65
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 66
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 67
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 68
Suggested Citation:"SCIENTIFIC OPPORTUNITIES FOR USGS." National Research Council. 1997. Watershed Research in the U.S. Geological Survey. Washington, DC: The National Academies Press. doi: 10.17226/5589.
×
Page 69
Next: CONCLUSIONS AND RECOMMENDATIONS »
Watershed Research in the U.S. Geological Survey Get This Book
×
Buy Paperback | $49.00 Buy Ebook | $39.99
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

Watershed research is conducted by the U.S. Geological Survey (USGS) to expand our understanding of basic hydrologic mechanisms and their responses at the watershed scale and to provide information that serves as the basis for water and environmental management activities carried out largely by other governmental and private entities. The work of the USGS in this area is carried out by its Water Resources Division and occurs in three general program areas: basic research, regional and site assessments, and data collection. These activities are becoming increasingly important, especially in the context of water and environmental management, where contemporary problems are being approached more than ever on an integrated ecosystems or watershed basis and where the underlying physical, chemical, and biological science is complex.

Although the value of this type of hydrologic research is well recognized within the USGS, available financial resources to support it remain modest. Thus, this study seeks to help maximize the effectiveness of the agency's work. The study took two years, during which time the committee visited field sites, received briefings, reviewed descriptive materials, deliberated toward conclusions, and wrote this report. Recommendations are intended to assist the USGS in improving its overall strategy for work in this area; descriptions of a number of scientific opportunities are included, and appropriate circumstances for collaboration with and support for others are identified.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    Switch between the Original Pages, where you can read the report as it appeared in print, and Text Pages for the web version, where you can highlight and search the text.

    « Back Next »
  6. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  7. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  8. ×

    View our suggested citation for this chapter.

    « Back Next »
  9. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!