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Sustainable Society:  A society that balances the environment, other life forms, and human interactions over an indefinite time period.

 

 

 

 

 


 

The Global Water Cycle

Report to the United States Climate Change Global Research Program
Water Cycle Study Group,  2001
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USGCRP-supported research on the global water cycle focuses on:

(1) the effects of large-scale changes in land use and climate on the capacity of societies to provide adequate supplies of clean water; and

(2) how natural processes and human activities influence the distribution and quality of water within the Earth system and to what extent the resultant changes are predictable.

Specific areas include: identifying trends in the intensity of the water cycle and determining the causes of these changes (including feedback effects of clouds on the global water and energy budgets as well as the global climate system); predicting precipitation and evaporation on timescales of months to years and longer; and modeling physical/ biological processes and human use of water, to facilitate efficient water resources management.

Figure 5.1. Conceptualization of the water cycle.

 

Water vapor is a greenhouse gas that maintains temperatures in a range required by life on Earth. Many of the uncertainties in the current projections of the effects of the atmospheric buildup of carbon dioxide are related to the feedbacks between the climate and the water cycle.

On a national basis, near-crisis situations have occurred in several dry southwestern river basins, including the Colorado and Rio Grande, where over-allocation has taken place. Recent drought conditions and rapid development in these basins have exposed  the intensity of competition that exists over the available water resources. The development of a capability to predict where water management crises will emerge due to a drought or extended flood conditions is a priority for the Global Water Cycle program. The ability to provide probabilistic forecasts of rainfall and snowfall at various time and space scales is at the center of all potential applications of climate change science and climate information systems.

Human activity is an integral part of the water cycle.  A recent USGCRP-commissioned report concluded that, among other priorities, there is a pressing need to determine the causes of water cycle variations on both global and regional scales, and to what extent these variations are induced by human activities. In view of this emerging link between water science and water resource issues, the USGCRP global water cycle strategic plan addresses two major questions: (1) What are the effects of large-scale changes in land use and climate on the capacity of societies to provide adequate supplies of clean water, and (2) how do natural processes and human activities influence the distribution and quality of water within the Earth system and to what extent are resultant changes predictable?

The USGCRP Global Water Cycle program focuses on characterizing, explaining, and predicting variability and long-term changes in the global water cycle and their impacts. To address the issues arising from the intimate role of the water cycle in controlling climate variability on seasonal to multidecadal timescales, the program investigates the pathways of water movement between the biosphere and surface hydrologic systems, the atmosphere, and the oceans, as well as feedback processes between climate, weather, and biogeochemical cycles.

The Office of Science and Technology Policy, the Office of Management and Budget, and the Council on Environmental Quality provide oversight on behalf of the Executive Office of the President.
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* Excerpts from the USGCRP Program Element
Courtesy of United States Climate Change Global Research Program.
Suite 250, 1717 Pennsylvania Ave, NW, Washington, DC 20006.
Telephone: 1-202-223-6262.
The U.S. Global Change Research Program was Codified by Congress in 1990 under P.L. 101-606.
See original at < http://www.usgcrp.gov/usgcrp/ProgramElements/water.htm >.

Home ] Study on the Global Water Cycle ] Global Water Cycle Chapter 2: Causes of Water Cycle Variation ] Global Water Cycle Study Chapter 3: Predictability of Variations in Water ] Global Water Cycle Study Chapter 4: Determining Links between Water ] Global Water Cycle Study References ]
 

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