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Introduction
In August 1999, the U.S. Global Change Research Program (USGCRP) commissioned a panel of experts (referred to in this report as the Water Cycle Study Group, WCSG) to advise the USGCRP agencies on “formulating a research strategy and scientific plan for investigating the global water cycle, its role in climate, and the fundamental processes that govern the availability and the biogeochemistry of water resources” (USGCRP, 2001). The charge to the WCSG listed six issues that the resulting research strategy and scientific plan should address:
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quantitative understanding of atmospheric, terrestrial, and oceanic interactions that govern water and energy cycles on intraseasonal to centennial time scales and on regional and global scales, including, inter alia, the roles of water vapor, clouds, and precipitation processes; biogeochemical processes; terrestrial and aquatic ecosystem influences; and the roles of surface and subsurface waters within the overall hydrologic cycle,
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an improved representation of these processes in climate and other models, across the relevant space and time scales, that will allow simulation of the hydrologic cycle and its interactions with the rest of the earth system,
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an understanding of the response of the water cycle to environmental change and accompanying impact on water resources,
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a capability to model and, where appropriate, predict variations in global and regional hydrologic processes and water resources on seasonal to interannual time scales and longer time scales,
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the requirements for comprehensive, systematic space-based, ground-based, and in situ observations in support of the water cycle sci-
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ence objectives, with consideration of the compatibility of measurements across scales and processes, and
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guidance on the linkages, areas of cooperation, and potential integration with other relevant national and international programs to make the initiative a success.
The WCSG provided its draft report to USGCRP in August 2000; a final report was issued by the USGCRP the following spring. In October 2001 (USGCRP, 2001), the cochairs of the Interagency Working Group for the USGCRP water cycle initiative requested that the National Research Council (NRC) review the water cycle science plan (see Appendix A for a copy of the letter request). This report provides that requested review.
The review focuses on (1) the responsiveness of the water cycle science plan to its charge, especially as it addresses the six areas identified in the August 1999 letter establishing the study group, (2) an evaluation of whether the water cycle science plan provides sufficient guidance to the USGCRP agencies for them to establish agency implementation plans, (3) an assessment of the feasibility of the water cycle science plan’s recommended research strategy and scientific plans, and (4) recommendations concerning priorities for the USGCRP program and agency implementation activities.