USGCRP
Program Elements

Atmospheric Composition

Ecosystems

Global Carbon Cycle

Decision-Support Resources Development and Related Research on Human Contributions and Responses

Climate Variability and Change

The Global
Water Cycle

Observing and Monitoring the Climate System

Communications

International Research and Cooperation

In FY 1999, the USGCRP established a Water Cycle Study Panel and charged it with redefining the USGCRP approach to the study of the water cycle. This group, which includes government and academic scientists, is developing a new set of comprehensive research and applications strategies that will take advantage of existing and planned observing systems to address major issues concerning the global water cycle and global and national water resources. A combination of observations, modeling, and analysis at a range of spatial and temporal scales will provide the foundation for understanding the water cycle. The ultimate goal of the water cycle research program is to address three fundamental scientific questions:

• What are the underlying causes of variations in the water cycle on global and regional scales, and to what extent is this variation induced by human activity?
• To what extent are variations in the global and regional water cycle predictable?
• How will variability and changes in the cycling of water through terrestrial and freshwater ecosystems be linked to variability and changes in the cycling of carbon, nitrogen, and other nutrients at regional and global scales?