Linking Water and Energy Along the -Sonora Border

Christopher A. Scott, Robert G. Varady, Anne Browning-Aiken, and Terry W. Sprouse – University of Arizona

he Southwest, including the which initially led to an increase in total approach—the plant would have supplied U.S.- border region, is energy and groundwater consumption, electricity to both Arizona and Mexico— Texperiencing dramatic population likely due to lower costs and reduced the plan has not moved forward. and economic growth, which in turn is controls on irrigation at night when driving steep increases in the demand labor costs are higher. However, one Also in the works is Mexico’s plan to for both water and energy. Population year after the nighttime irrigation rate build a wastewater treatment plant in Los is increasing twice as fast on the border Alisos, about 10 miles south of Nogales, as at the national level in either country, Sonora. The plant would treat wastewater and is projected to grow by 50 percent Mexico has taken a strong in excess of the 9.9 mgd allocation at from 2005 to 2030. Much of this growth position on limiting global the NIWTP. Under the existing treaty is occurring in 14 border sister cities. warming and is among with the United States, Mexico could retain and reuse scarce water on its side Pumping Water Requires those nations calling for of the border; however, this would likely Consuming Energy mitigative strategies. prove to be a costly choice in energy In the perpetually water-short Southwest, terms, as the wastewater would have to be pumped upgradient and over a with its rugged terrain and high was introduced, total energy consumed watershed divide to reach the proposed evapotranspiration rate, most options and groundwater pumped for Mexican new plant. Additionally, Mexico would for increasing water availability require agriculture continued their decline. increased energy consumption. Depending lose the cost advantage of allowing on the type of contract and customer Similarly on the Arizona side, irrigation wastewater to flow downgradient to served, energy costs of pumping currently represents 10 percent of electrical the NIWTP and the economy-of-scale comprise a quarter to a half of the total power sales revenue for the Sulphur benefits the larger NIWTP offers. rate charged for Springs Valley Electric Cooperative, but water (CAP, 2007/2008). Utilizing electricity use by irrigation increased As the foregoing discussion has shown, Arizona’s full water 45 percent from 2002 to 2005, largely the demand for a range of water services allocation through CAP deliveries due to customers switching to electricity in the border region has been accompanied will cost tens of millions of dollars as natural gas prices increased. by increased energy use. With energy costs annually in energy. On a smaller scale, rising, its sources politically unstable, and Sonora has its own interbasin water Energy for Water Treatment its supplies uncertain, this trend places transfers, such as the Los Alisos/Rio Wastewater treatment requires significant water management at odds with the Magdalena-Nogales aqueduct, that supplies of energy. On the U.S. side of palpable need to limit energy consumption. entail significant energy for pumping. the border, the Nogales International Wastewater Treatment Plant (NIWTP) Add Climate Change to the Mix On both sides of the border, agricultural treats about 15 million gallons per day At the same time, the impacts of climate pumping represents a major energy (mgd) of wastewater originating from both variability and change are becoming more demand. In the Mexican border states Nogales, Arizona and Nogales, Sonora. widely accepted as important contributors of Sonora and , groundwater Mexico has an allocation of 9.9 mgd to the water-energy link. In Mexico, the pumping for irrigation accounts for per day at the plant, yet has regularly government and scientific establishment, 10 and 16 percent respectively of total exceeded that amount over the last several sensitized by recent impacts of El Niño state energy demand (Scott, 2007; CFE, years due to increased water supply and and La Niña, recognize the importance 2006), although total agricultural power wastewater collection infrastructure in of climate on the agricultural and urban consumption began declining in 2000 Nogales, Sonora. In 2004, the Maestros sectors. Mexico has taken a strong position in response to increasing power rates. Group outlined a plan to build a on limiting global warming and is among The Comisión Federal de Electricidad 411-megawatt electrical generation plant those nations calling for such mitigative (CFE) introduced reduced power rates in Nogales, Arizona, utilizing Mexican strategies as adoption of carbon caps and for nighttime irrigation in 2003-04, effluent for cooling. Despite its innovative reduction of greenhouse gas emissions.

26 • September/October 2007 • Southwest Hydrology CAP

3,000 ft.

Lake Havasu City Santa CAP Canal Cruz River Phoenix elevation Tucson Nogales Arizona Sonora de los Alisos 12,611 ft. 0 336 mi. Colorado Riverdistance Tucson Los Alisos/Rio 72 ft. Magdalena-Nogales aqueduct 3200 kWh to pump one acre-foot of CAP water from the Colorado River to Tucson.

Los Alisos Basin

Interbasin water transfers in Arizona and Nogales, Sonora require large amounts of energy. The profile of the Central Arizona Project through Arizona (right) shows an increase in elevation of 2900 feet from the Colorado River to its end near Tucson. The Los Alisos/Rio Magdalena-Nogales aqueduct in northern Sonora must cross over a watershed divide to reach Nogales. The United States, as is well-known, has over the past several months, the U.S. In 2005, the states of Arizona and Sonora criticized and refused to sign the Kyoto public and its politicians are beginning signed a “Declaration of Cooperation” to Accords, while the Bush administration to accept the need to address climate establish a joint binational climate change has until very recently questioned change. And in the border region, with initiative (Arizona-Sonora Declaration, scientific research on global warming its serious water and energy constraints, 2005), with follow-up activities planned and denied human causation. However, the issue has gained strong momentum. by the Arizona-Mexico Commission. see Arizona-Sonora, page 31

September/October 2007 • Southwest Hydrology • 27 Arizona-Sonora, continued from page 27 resource implications of power generation, 2007/2008 rate schedule. www.cap-az.com/ there is a concomitant need to more static/index.cfm?contentID=30. Planning Together for the Future Comisión Federal de Electricidad (CFE), 2006. fully consider the energy implications of Unpublished energy sales data. In the border region, U.S. and Mexican growing demands for water services. Ray, A.J., G.M. Garfin, L. Brito Castillo, M. Cortez scientists and social scientists are meeting Vázquez, H.F. Diaz, J. Garatuza Payán, D. regularly and developing instruments to Contact Christopher Scott at [email protected]. Gochis, R. Lobato Sánchez, R.G. Varady, and C. Watts. 2007. region climate use jointly. One such effort would yield applications: Integrating climate science with an ongoing, binational, U.S.-Mexico regional planning and policy, Bull. Amer. References Meteor. Soc., 88(6): 1-3. border climate diagnostic summary (Ray Arizona-Sonora Declaration, 2005. Declaration of Scott, C.A., 2007. Energy boom and groundwater bust: and others, 2007). This summary, to be cooperation to establish the Arizona-Sonora Mexico’s water-energy nexus with implications Regional Climate Change Initiative, www. prepared collaboratively and at regular for the U.S. border region, presented at azclimagechange.gov/initiatives/ 1st Western Forum on Energy & Water intervals, would provide forecasts and Central Arizona Project (CAP), 2007/2008. Final Sustainability, Santa Barbara, CA, March 2007. value-added information on temperature, precipitation, and drought within the region. Once in place, the tool would help managers and policymakers in the water and energy sectors make more realistic and accurate decisions. And in a region of chronic multiyear drought, the importance of addressing societal and economic impacts of climate is essential to effective use of scarce water and energy resources.

Water and energy are closely coupled resources in the rapidly growing Arizona- Sonora border region. While there is increasing recognition of the water

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