Environmental Engineering Reference
In-Depth Information
Idaho
Wyoming
Nevada
Upper basin
Utah
Colorado
California
Lower basin
Arizona
New Mexico
Chihuahua
Sonora
FIGURE 15.1
Map of Western water projects. (From Central Arizona Project. With permission.) (Courtesy of The Pacific Institute.)
Water supply planning has in the past been the exclusive domain of water agencies,
districts, and suppliers. The job of the water purveyors and suppliers has been to ensure
sufficient supplies for existing and future populations. Many communities across the
Southwest are looking to a water future characterized by significant unknowns. Concerns
abound regarding long-term overdrafting of aquifers, or pumping in excess of the
supply, and overallocated river systems where total allocations exceed average flows (see
ChapterĀ 4). For example, studies suggest that the Colorado River's annual flow historically
varied widely around the average of 14.3 million acre feet/year, despite the fact that the
allocations total 16.5 million acre feet/year (Table 15.1).*
As we learn more about the history of droughts and the implications of climate
change, concerns exist regarding overly optimistic projections for surface water flows
and their inherent variability. The public may recognize the importance of good water
* See Gelt 1 and Colorado River Compact 1922 for a discussion of Colorado River allocations and Wong et al. 2 For
a discussion of Rio Grande allocations see Woodhouse et al. 3 for the most recent information about annual
flows in the Colorado River.
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