proposed research agenda and to identify appropriate roles for governmental and nongovernmental entities. This report builds on a 2004 National Research Council report that provided a scientific assessment of the Bureau of Reclamation’s and Sandia National Laboratories’ Desalination and Water Purification Technology Roadmap, or Roadmap, which was intended to serve as a strategic pathway for future desalination and water purification research (USBR and Sandia National Laboratories, 2003).

WATER FOR THE FUTURE: THE ROLE OF DESALINATION

When considering future water supplies, it is important to recognize that past patterns of water use will not always be a reliable indicator of future demand. In particular, the assumption that water demands will inevitably parallel population and economic growth no longer appears to be correct. Nevertheless, water scarcity in some regions of the United States will certainly intensify over the coming decades, and no one option or set of options is likely to be sufficient to manage this intensifying scarcity. Desalination, using both brackish and seawater sources, is likely to have a niche in the future water management portfolio of the United States.

The committee was specifically asked to address the potential for seawater and brackish water desalination to help meet anticipated water supply needs in the United States. The committee concluded that the potential for desalination cannot be definitively determined because it depends on a host of complicated and locally variable economic, social, environmental, and political factors. In the complete absence of these factors, the theoretical potential for desalination is effectively unlimited. Large quantities of inland brackish groundwater appear to be available for development; in coastal areas, ocean resources are essentially infinite in comparison to human demands. But, as with most resource questions, the theoretical potential and the practical potential are far different. All water management and planning takes place in the context of economic, social, environmental, and political factors, and these factors are far more important than technological desalination process constraints in limiting the potential for desalination to help meet anticipated water supply needs. As a result, this report addresses key technological issues that may lend themselves to focused research and development efforts, but the report also addresses nontechnical questions that may ultimately prove to be more limiting.

The costs of producing desalinated water—the cost of removing salts to create freshwater—is no longer the primary barrier to implementing



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