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| Fig. 1: Lakes Mead and Powell in relation to one another and the state of Arizona. (Source: Wikimedia Commons) |
Climate patterns in the United States are changing, and different regions have been affected in different ways. For example, between 2000-2009, many areas of eastern North America experienced precipitation more than 0.15 standard deviations above the 1895-2000 mean. By contrast, regions all across the western United States experienced decreased rainfall, contributing to persistent aridity and the potential for prolonged periods of drought in the near future. [1] As shown in Fig. 1, two large man-made lakes, Lake Mead and Lake Powell, are located along the Colorado River as well as the northern edges of the state of Arizona. Since the outflow of these lakes travels to multiple states including Arizona, California, and Nevada, they play a very important role with regard to water usage in the Southwest.
Unfortunately, over the past few decades, water levels have continued to decline to the point where some studies even estimate that the two lakes may become inoperable within the decade. [2] Water levels in these bodies of water fluctuates due to snowmelt runoff, changes to weather patterns, and high levels of evaporation. Other Arizona lakes, such as Lake Havasu, must maintain their levels in order for larger projects such as the Central Arizona Project to remain functional and available to provide water to Arizonans. [3]
Currently, there does not seem to be a consensus among the populous on subsequent steps to combat changing weather patterns. For example, in a state-wide survey noting public perceptions of water reuse, two-thirds of respondents had concerns regarding recycled water, though 76% supported using consumer incentives for using recycled water. [4] To adapt to changing weather conditions, it is imperative to understand the current infrastructure and water potential in order to better prepare and anticipate future stresses related to water.
Arizona, quite literally named as a portmanteau of the words arid and zone for its lack of rainfall, provides a unique opportunity to observe how human-made innovations have adapted to provide water for millions in a place where there is so little. In fact, if there is a feasible way for millions in large urban islands to have access to clean drinking water, there may be a chance to model for more energy and cost-efficient infrastructure all across the United States, especially if the frequency of droughts across the American West continues to increase.
Phoenix, Arizona epitomizes a city that could face water challenges due to its climate, booming population growth, and large suburban development.
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| Fig. 2: Map of Central Arizona Project. [12] (Courtesy of CAP) |
In simulations that project what water usage and utilization may look like in the year 2030, scientists have found that, with or without climate change, drastic changes, such as limiting population growth by 50% or curtailing landscaping and pool use, may be needed in order to prevent a sustainability crisis. [5] Currently, there are countless dams, aqueducts, and canals that have been built and are continuing to be built in the Western United States.
To really understand their roles in the grand scheme of water usage in the 21st Century, it would be best to analyze the potential of one project structure that was constructed with the intention of providing water in a place where there was originally none. As such, analysis of the Central Arizona Project, the largest and most expensive water transfer project ever constructed in the United States, should illuminate the potential for water delivery throughout the Southwestern United States. [6]
The Colorado River Basin Project Act of 1968 authorized the construction of the Central Arizona Project (CAP), and it was officially completed in 1973. Since then, CAPs diversion canal, pumps, and tunnels have provided most of the water supply for central and southern Arizona. [7] In fact, water from CAP is delivered to counties that constitute more than 5 million people, or 80% of the population in the driest state in the United States. [8]
It is difficult to understate the tremendous role that the Central Arizona Project plays on Central and southern Arizona. Fig. 2 shows the wide expanse covered by the Central Arizona Project across the state of Arizona as it travels through some of Arizona's largest cities, including Phoenix and Tucson. CAP has the capacity to pump 3000 cubic feet of water per second from Lake Havasu through the Hayden-Rhodes Aqueduct, the primary path of water into the greater Phoenix area. [9] This corresponds to
| 3000 ft3 sec-1 0.134 ft3 gal-1 |
× 3600 sec h |
= | 1.93 × 109 gal day-1 |
and thus a number of customers served with water
| 1.93 × 109 gal
day-1 120 gal day-1 person-1 |
= | 1.61 × 107 people |
This number is merely a theoretical yield, however, and large amounts of water are lost along the path of the Central Arizona Project (mostly due to surface water evaporation). It is also theoretical as more than half of the water that is delivered by CAP is used for agriculture or put underground for further use. CAP would also not like to pump great amounts of water when rather supply or demand are low due to the electrical costs required to move the water; thus, the calculations are based upon peak demand and maximum daily potential yield of the Project. This analysis does not consider the economic burden, nor the environmental costs associated with the CAP; rather, it simply looks at the potential for access to water for millions of Arizonans given the current infrastructure and utilization rates in the state, though the apportionment for the water may change depending on local, state, and interstate policies.
Politics related to CAP have been contentious for decades; in fact, due to the fact that the Colorado River is shared by four other states, the reality is that CAP, as well as the state of Arizona, does not have the legal right to take the river's water with reckless abandon. In the past, CAP and the other Lower Basin states have been criticized for their usage policies for the river, and it is likely that such accusations will continue in the upcoming years. [10]
What does have the potential to change is the science behind new technological and mathematical advances related to the canals. For instance, recently, scientists have found a new method by which to control water levels on the CAP in which real-time feedback of water levels between canal gates can be used to regulate canal volume within hours. Such methods have been shown to have the potential to be generalized to all large canals across the country and indicate that the calculated numbers may increase as newer technologies develop. [11]
In the United States, and specifically in Southwestern Arizona, water utilization continues to gain importance as urbanization continues to increase. It is important to note that water issues are not specific just to the southwestern United States. As global temperatures continue to increase, regions all around the world may soon lose access to clean drinking water due to changes in climate and weather patterns. As economics, environment, and land utilization often clash in issues related to water projects, the field of water conservation and utilization has become highly politicized. The reality is that with increasing temperatures and prolonged drought periods, the future will require more energy effective and environmentally conscious solutions to these modern problems; whether or not projects such as the Central Arizona Project are the best policies for each state will require further investigation into the financial costs and benefits of such large undertakings.
Nevertheless, the analysis has shown that these structures do have the ability to supply water to even the largest metropolitan areas in the United States. If the United States fails to concentrate attention on issues related to the future of American sustainability, millions of people may suffer greatly as accesses to water, electricity, and other resources significantly diminish. The future may not require the prolongation of larger Western water projects, but the data demonstrate that scientists, policymakers, and engineers must plan for more sustainable methods throughout the American Southwest.
© Alexander Bhatt. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] G. M. MacDonald, "Water, Climate Change, and Sustainability in the Southwest," Proc. Natl. Acad. Sci. (USA) 107, 21256 (2010).
[2] T. P. Barnett and D. W. Pierce, "When Will Lake Mead Go Dry?" Water Resour. Res. 44, W03201 (2008).
[3] K. Baird, "On the Level: Lake Remains Normal Despite Release into Mexico," Havasu News-Herald, 4 Apr 14.
[4] C. Rock, F. I. Solop, and D. Gerrity, "Survey of Statewide Public Perceptions Regarding Water Reuse in Arizona," Aqua 61, 506 (2012).
[5] P. Grober and C. W. Kirkwood, "Vulnerability Assessment of Climate-Induced Water Shortage in Phoenix," Proc. Natl. Acad. Sci. (USA) 107, 21295 (2010).
[6] M. Hanemann, "The Central Arizona Project," University of California at Berkeley, October 2002.
[7] C. V. Modeer, "Confronting the Intersection of Water, Energy, and Air Quality at the Central Arizona Project," J. Am. Water Works Assoc. 102, 46 (2010).
[8] C. Scott, J.-P. Venot, and F. Molle, "Water, Land, and Development: Comparative Arizona-Israeli-Palestinian Perspective," in Shared Borders, Shared Waters, ed. by S. B. Megdal, R. G. Varady, and S. Eden (CRC Press, 2012).
[9] R. S. Gooch and A. L. Graves, "Central Arizona Project Supervisory Control System," J. Water Res. Plan. Man. 112, 382 (1986).
[10] T. Davis, "Four States That Also Get Colorado River Water Say CAP Keeps Too Much For Arizona," Arizona Daily Star, 16 Apr 18.
[11] G. Guan et al., "Applying Water-Level Difference Control to Central Arizona Project," J. Irrig. Drain. Eng. 137, 1943 (2011).
[12] "2018|2019 Biennial Budget," Central Arizona Project, 2018.
