Climate Variability and Western Water: What Can We Expect? (original) (raw)

Fresh water has been called a strategic resource that structures the West's natural and cultural landscapes and is a major determinant of sub-regional economies and demographic patterns. The West is characterized by variable climates, diverse topography and ecosystems. The past and present alterations of hydrology in the western U.S. reflect complex histories of human settlement, large-scale water diversions, the development and evolution of water policy and law and, expanding frameworks of water resources management. The nine western water regions identified by the USGS (excluding Alaska and Hawaii) account for 90% of the total (surface and ground) water withdrawn for irrigation and almost half of the total freshwater withdrawals in the U.S. About 47% of all dams and 55% of the total storage in the U.S. occur in the 17 western states (Frederick, 1990). Rapid, relatively recent, population increases, economic growth (including agriculture), the rise of urban centers over the last century (and more so recently) have resulted in intense pressures being placed on western lands, water and institutions. Recent emphases on water demand management, on meeting long-standing obligations, and on environmental concerns have also altered the traditional roles of federal, state and local agencies. In the midst of all of this , the complications of major changes in the spatial and temporal distribution of precipitation, soil moisture, runoff, frequency, duration and magnitudes of droughts and floods, have not, in many cases, been explicitly included in response planning.