Water Resources in the Twenty-First Century: A Study of the Implications of Climate Uncertainty [open pdf - 4MB]
"The interactions of the water resources on and within the surface of the Earth with the atmosphere that surrounds it are exceedingly complex. Increased uncertainty can be attached to the availability of water of usable quality in the 21st century, therefore, because of potential anthropogenic changes in the global climate system. For the U.S. Geological Survey to continue to fulfill its mission with respect to assessing the Nation's water resources, an expanded program to study the hydrologic implications of climate uncertainty will be required. The goal for this program is to develop knowledge and information concerning the potential waterresources implications for the United States of uncertainties in climate that may result from both anthropogenic and natural changes of the Earth's atmosphere."
U.S. Geological Survey Circular 1030
Government Publishing Office: http://www.gpo.gov/