Managing Water Resources in the West Under Conditions of Climate Uncertainty A Proceedings (1991) / Chapter Skim
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19. Managing Water Supply Variability: The Salt River Project
19. Managing Water Supply Variability: The Salt River Project
Pages 303-323
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From page 303... ...
The slightly cooler and wetter conditions of the highlands are responsible for much of Arizona's forest land, streamflow, and riparian habitat and provide a place to escape the summer heat of the desert below. BACKGROUND The Salt and Verde watersheds have very dry spring and fall periods, separated by a winter season (lasting from December through mid-March)
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From page 304... ...
MILES i, \J: FLAGSTAFF FRESCO' ~ RIO W LOW PHOENIX GLOBE SALT RIVER PROJECT GILA BEND 372 SO. M I LES _ FIGURE 19.1 The watersheds of the Salt and Verde rivers stretch in a dividing band across Arizona.
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From page 305... ...
These characteristics attracted Native American agriculturalists for hundreds of years before Anglo settlement (Figure 19.3) , but the Native Americans abandoned the land along the Salt River long before Anglo settlers arrived (although they were still occupying land along the nearby Gila River)
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From page 307... ...
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From page 309... ...
(Most of this demand is now urban rather than agricultural.) SUPPLY VARIABILITY The extraordinary variability of Salt River flows bedeviled Native American societies and drove farmers to seek federally-funded storage projects.
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From page 312... ...
Since most of the water in the Salt and Verde rivers originates from winter and spring precipitation, the variability of the winter season is the key to describing water supply variability in Arizona. One influence on Arizona water supply variability is a change in the pattern of Pacific storms that typically begins in late November or early December and continues until mid-March.
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From page 313... ...
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From page 315... ...
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From page 316... ...
RESPONSES TO SUPPLY VARIABILITY The Salt River Project, like most other water providers in the western United States, must meet a relatively constant water demand with a widely fluctuating water supply. Clearly, the SRP must plan for these water supply fluctuations and make changes to its operations.
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From page 317... ...
As water supplies and reservoir levels drop, pumping is increased. The customer simply pays a little more and otherwise notices little difference in the available water supply during surface water shortages.
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From page 318... ...
Water quality concerns and pumping costs aside, there is the longer-term problem of relying upon what in some ways is a finite ground water supply. Natural recharge in the Phoenix area is very small, especially because surface water flows are now captured behind the dams above the valley.
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From page 319... ...
Are there other sources that the Salt River Project could turn to for backup supplies when surface water supplies are low? , SEARCHING FOR BACKUP SUPPLIES Population growth long ago outstripped renewable water supplies in central Arizona, although the Central Arizona Project (CAP)
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From page 320... ...
It is difficult to expect governing boards and state legislatures to pay for weather modification programs when the benefit is uncertain and unmeasurable. Then too, the public may be skeptical of any attempt to "meddle with Mother Nature." As with watershed management, there may be opportunities here and there for small increases to river flows, but these will not be large enough or regular enough to be any kind of real solution to water supply variability problems.
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From page 321... ...
First, the use of this water would have subjected SRP agricultural water users to the Reclamation Reform Act, and no one undertakes that sort of burden lightly. Second, other water users in the state had no access to local surface water supplies like those of the Salt and Verde rivers.
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From page 322... ...
This is clearly not, however, a simple solution to the Salt River Project's supply variability problem. CONCLUSIONS Though future climate change patterns are anything but certain, some of the most likely scenarios now being painted suggest that the already extreme surface water supply variability in the Salt and Verde river watersheds may increase in the future.
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From page 323... ...
Supply variability will be met by varying ground water pumping, by increasing conservation and effluent reuse, and by some water transfers. The time will come in the next century when these various sources of water will no longer be sufficient to sustain Sun Belt growth rates.
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