Dole, R. M., 2003: Predicting climate variations in the American West: What are our prospects? In Water and Climate in the Western United States, W. M. Lewis Jr. (ed.), University Press of Colorado, 9-28.


Water has always been a precious resource in the American West. Consequently, variations in climate -- which play a crucial role in both water supply and demand -- have had profound social, economic, and environmental consequences for the region. Extended periods of above-normal precipitation have provided ample water supplies to meet consumptive and agricultural growth. Conversely, periods of extended drought have exposed major vulnerabilities in both human and natural systems. With rapid population growth projected to continue for the foreseeable future, the effective management of water resources will become even more vital for the future of the West. Water managers will face increasingly difficult challenges as they attempt to address the often conflicting demands arising from consumptive needs, agriculture, energy production, recreation, environmental and species preservation, and flood protection. Advances in climate forecasts can provide information useful for projecting future water supply and demand and thereby support more effective water-management decisions in this region.

Despite their obvious potential utility, climate forecasts presently are little used in western water-management decisions. One of the principal reasons cited by water managers is the absence of forecasting skill; other important factors include their lack of familiarity with or difficulty in interpreting current forecasts and failure of forecasts to address directly the needs of users. This review first considers the problems and prospects of predicting climate variations in the West, focusing particularly on seasonal and longer timescales. A second section provides an overview of climate predictions, including a discussion of the scientific basis of climate forecasts as well as of the major factors that influence climate variations and forecasts in the western United States. Following this, several examples of climate forecasts are presented, emphasizing especially recent research aimed at developing new forecast products of particular relevance to the water-resources community. The chapter concludes with a summary of major issues that must be addressed if we are to develop new climate forecast capabilities that will better serve water management in this critically water-sensitive region.