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Introduction

The water resources of the United States will be subjected to more intense and broader arrays of pressure in the twenty-first century than they were in the twentieth century. Projected population growth, economic growth, and the increasing recognition of the need to preserve and enhance aquatic ecosystems will combine to make managing water resources more challenging than ever before (Postel et al., 1996). Even as these pressures mount, important transitions are occurring in water management. Dams are being decommissioned and removed. Recent models hint at potential changes in the hydrologic cycle and in hydrologic variability in the future. Although observational data do not yet confirm the presence of such changes, water resource planning in the future will need to encompass the possibilities of such change (Lins and Slack, 1999). Increases in hydrologic uncertainty, the need for more water to support aquatically based ecosystems, and general disaffection with the efficacy of dams all suggest the demise of dams as the primary means of responding to increased water demands.

On the surface these changes seem to compound the problem of addressing the new realities of water management. Yet, the transition presents many new opportunities in the form of new technological breakthroughs that may allow us to manage water in new and innovative ways. Thus, for example, there is substantial potential for increasing our understanding of hydrologic and limnologic processes and for monitoring our water resources in ways that will permit the development of extremely sophisticated management systems. The fragmented policies that guided water resources research in the twentieth century will probably be inadequate to foster the development of needed water-based technologies and understandings in such an environment. While the research policies of mid-century fostered much important research, the erosion of these policies by the century's end frequently resulted in programs that focused on short-term, narrowly defined problems, lacked coordination, and sometimes failed to anticipate the emer-



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Page 5 1 Introduction The water resources of the United States will be subjected to more intense and broader arrays of pressure in the twenty-first century than they were in the twentieth century. Projected population growth, economic growth, and the increasing recognition of the need to preserve and enhance aquatic ecosystems will combine to make managing water resources more challenging than ever before (Postel et al., 1996). Even as these pressures mount, important transitions are occurring in water management. Dams are being decommissioned and removed. Recent models hint at potential changes in the hydrologic cycle and in hydrologic variability in the future. Although observational data do not yet confirm the presence of such changes, water resource planning in the future will need to encompass the possibilities of such change (Lins and Slack, 1999). Increases in hydrologic uncertainty, the need for more water to support aquatically based ecosystems, and general disaffection with the efficacy of dams all suggest the demise of dams as the primary means of responding to increased water demands. On the surface these changes seem to compound the problem of addressing the new realities of water management. Yet, the transition presents many new opportunities in the form of new technological breakthroughs that may allow us to manage water in new and innovative ways. Thus, for example, there is substantial potential for increasing our understanding of hydrologic and limnologic processes and for monitoring our water resources in ways that will permit the development of extremely sophisticated management systems. The fragmented policies that guided water resources research in the twentieth century will probably be inadequate to foster the development of needed water-based technologies and understandings in such an environment. While the research policies of mid-century fostered much important research, the erosion of these policies by the century's end frequently resulted in programs that focused on short-term, narrowly defined problems, lacked coordination, and sometimes failed to anticipate the emer-

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Page 6 gence of critical problems. New policies to guide water resources research and new investment in that research will be needed if the nation is to respond effectively to the water problems of the twenty-first century. The United States entered the new century and millennium with over 270 million inhabitants, an increase of about 9 percent during the 1990s and an increase of 120 million (80 percent) since 1950. According to the U.S. Census Bureau's middle estimate, another 120 million people could be added by 2050, yielding a population of approximately 390 million. The implications of this forecast, even if not fully realized, are manifold and complex: the nation will essentially have to replicate all the housing and infrastructure built since World War II, in addition to repairing or replacing what already exists. In particular, the nation's water resources, which are already stressed in many regions, will have to be stretched and conserved to meet the water needs of a much larger U.S. population. 1 American agriculture, which is increasingly dependent upon irrigation, will be asked to meet new demands for food and fiber both domestically and abroad. At the same time, water will need to be managed to protect and restore aquatic habitats and serve instream functions such as navigation, hydropower, and recreation. The water resource implications of twenty-first century population growth are even more dire when the regional distribution of that growth is considered. As indicates, the Northeast and Middle West, which have relatively ample water supplies (in nondrought years at least), grew by only about 5 percent in population over the past three decades. Meanwhile, the South and West, which include the nation's most water-deficient areas, each grew by about 70 percent, more than double the national rate. Most new development has occurred in quasi-urban communities dependent upon centralized providers of water and sewerage treatment. Moreover, much of that growth occurred in truly arid regions of the Southwest (e.g., Tucson, Phoenix, Las Vegas, and southern California), where new water supplies are only available through groundwater mining or imports from other regions which are increasingly unwilling to allow their own water resources to be diverted elsewhere. Perversely, water use per capita is greater in the nation's driest regions than in the more humid areas. 1 Few data are available on the geographic, economic, demographic, and health impacts of future water resource problems. In fact, some of the most important research areas identified by the WSTB would address these gaps in knowledge (see bulleted list in the executive summary).

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Page 7 TABLE 1-1 Regional Distribution of U.S. Population, 1970–2000 (thousands) Population (1,000s) Region 1970 2000 Change in population, % Northeast 49,041 51,800 5.6 Midwest 56,572 59,600 5.3 South 62,795 96,900 71.5 West 34,804 59,400 70.6 U.S. total 203,302 267,700 31.8 SOURCE: Adapted from U.S. Census (1999). The prospect of significant increases in the demand for water contrasts with the circumstances that govern water availability. The supply of fresh water available for human consumption is limited. Only 0.3 percent of fresh water is found in rivers and lakes, the most accessible supplies for human use. Surface water renewal for rivers and small lakes is generally quite responsive to recent rainfall/runoff and can vary from a few days to several months. However, renewal for lakes that are large relative to their drainage basins (e.g., Lake Tahoe) can be as long as several hundred years. Groundwater accounts for roughly twice as much water as lakes and rivers in storing sustainable freshwater supplies (Gleick, 1993; Postel et al., 1996), suggesting that groundwater will be an increasingly important component of water supplies in the future. Renewable groundwater recharge, which is an important factor for coordinated management of groundwater systems, varies from tens to hundreds of years, depending upon climate, geology, and other factors (Freeze and Cherry, 1979; Wetzel, 2000). Fossil groundwater, which represents a resource that is not renewable by natural mechanisms during our lifetimes, may have been recharged several thousand years ago. If these sources are to be utilized effectively, it will be critical for water resource managers to better understand the distribution and variability of both surface water and groundwater supplies. Because stationarity (the assumption that past variability can be used to predict future variability) is likely to be abandoned as a foundation for estimating design events, new methodologies (e.g, ones based on long-term climate simulations or ones in which nonstationarity is incorporated in existing methodologies) need to be developed. Also, for short-term management and operation of water resources in the twenty-first century, more extensive real-time data to reduce the uncertainties associated with unusual events (e.g., regional or local extremes resulting from large-scale phenomena such as El Niño) will be needed.

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Page 8 Existing and potential threats to water quality will require careful attention. Although the United States has achieved admirable success in controlling and remediating water pollution in the last third of the twentieth century, there is little likelihood that further reductions in discharges from wastewater treatment plants and industrial sources (point sources) can achieve significant improvements. Thus, further improvements in water quality will have to be realized through the development of better technologies and techniques for controlling pollution in runoff and other diffuse (nonpoint) sources. Both the legacy of chemicals already in the ground—as exemplified by the inexorable salinization of many lands, rivers, and aquifers in the West—and future pollution of water resources must be addressed. A host of new water-quality problems may arise as synthetic chemicals are developed and advancements are made in monitoring for these compounds. The recent contamination of the nation's groundwater by the fuel additive methyltertbutylether (MTBE) is but one example of how promising technological advances can bring inadvertent environmental problems (National Science and Technology Council, 1996). The failure of modern pollution control policies to recognize that water, land, and air are intimately related as contaminant sinks is a major problem that can be addressed through more holistic approaches. The intermittent monitoring of water-quality parameters and the piecemeal regulation of individual contaminants independent of larger-scale biogeochemical and ecosystem processes, both of which characterized the twentieth century, will be inadequate. Because the availability, fate, and transport of many critical contaminants is controlled by interactions with natural organic material in soils and sediments and in solution, a holistic and predictive understanding of water, carbon, and nutrient cycles will be required to address and manage water quality problems during this century. For example, the current regional-scale enrichment of the land surface and surface waters with nitrogen directly affects water quality (via toxicity to humans and fish) and indirectly causes ecological and biogeochemical responses (such as eutrophication) that influence the mobility of other contaminants. The institutions devised for managing water resources in the twentieth century are not well suited to addressing the challenges of managing water resources in the twenty-first century. U.S. water rights were developed in times when water was plentiful and existing supplies were not fully allocated. Today, many eastern rivers are fully allocated and western resources require more flexible allocations to respond to changing demands. Existing institutions are inadequate for managing water as a common pool resource or in cases where water has the characteristics of a public good. In short, the

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Page 9 ~ enlarge ~ Much of the U.S. population growth has occurred in arid areas of the Southwest, such as New Mexico. The scarcity of water in this region is evident in the sparse vegetation found within the Sevilleta National Wildlife Refuge, 60 miles south of Albuquerque. fragmented and piecemeal institutional arrangements for managing the supplies and quality of water are unlikely to be sufficient to meet the water challenges of the future. Yet, knowledge about how such institutions might be modified and improved is scarce, and research on institutions occupies only a very small portion of the current water research agenda. The structure of the water “industry” does not lend itself to the development of a systematic, integrated, and strategic water research agenda because it comprises many different types of organizations and institutions and consequently is not cohesive. There are thousands of public and private water and wastewater treatment purveyors. Municipal and state governments also play an important role in managing the nation's water resources, acting as purveyors, regulators, and planners. There are more than a dozen federal agencies with varying responsibilities for the nation's water resources. Of these parties, the federal government is responsible for most of the sustained water research.

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Page 10 Investment in basic science has been the foundation on which scientific advancements in the management of water resources and the attendant economic growth are built. Unfortunately, federal water research efforts are fragmented, generally reflecting the missions of each agency rather than a cohesive national perspective on water resources. Indeed, virtually every cabinet department contains one or more agencies with responsibility for some aspect of water resources management. Federal agency research agendas are largely planned and conducted independently of each other and sometimes independently of the research efforts conducted at the nation's universities. Moreover, the research agendas of operating water agencies focus almost exclusively on short-term operational problems. It is clear that the level of investment in fundamental research, which will form the basis for applied research and development a decade or so hence, is inadequate. It is not at all clear whether the fundamental research that is undertaken, largely at the nation's universities, is balanced in terms of its support of the various disciplines that are needed for water research, or how the research is used. Future research of this sort will almost certainly need to be interdisciplinary in nature, and there is scant evidence of any current effort to support effective interdisciplinary research aimed at the nation's water problems. The Water Science and Technology Board (WSTB) perceives a need for a cohesive national water resources research vision for the twenty-first century, including agenda-setting, research coordination, and appropriate levels of public investment in water research. The research agenda presented in this report represents the consensus judgment of the Board about what research is likely to be most important in the early part of the twenty-first century. Research topics have been cast broadly in recognition that the specific focus and emphasis of the studies ought to reflect the circumstances and available knowledge at the time the work is undertaken. The discussion that follows has been divided into three categories: water availability, water use, and water institutions. These categories are interrelated in that water availability deals with matters that affect water supply, including water quality, while water use includes factors that affect the wants and demands for water. Water institutions are treated in a separate section to highlight the importance of research in this area and to recognize that institutional questions fall within the purview of a different set of disciplines (e.g., political science, law, geography, economics) than do water availability and water use.