Tucson, ArizonaIn response to a decades-long decline in Tucson’s traditional groundwater supplies caused by overpumping, Tucson and the surrounding municipalities have turned to the Colorado River as an alternate water source. The river water, delivered via the Central Arizona Project, is recharged into local aquifers at a variety of state and locally operated facilities. The largest of these, Tucson’s Clearwater Renewable Resource Facility, is the only project that provides recovery and delivery of a drinking water supply. This facility, which opened in 2001, provides approximately one-half of the drinking water currently used in Tucson.Although the shift to Colorado River water has helped reduce groundwater overdraft in the area, it has also expanded the potential for climate change impacts from a largely local phenomenon to a regional issue that encompasses the Colorado River watershed. Tucson’s Drought Preparation and Response Plan recognizes that climate conditions along the river will have a greater impact on Tucson as the community becomes more reliant on the Colorado River. The University of Arizona, located in Tucson, has reported on studies indicating that global warming may reduce Colorado River runoff by between 8 and 11 percent by the end of the century, which would further strain water supplies in Tucson and throughout the Southwest. Increasing reliance on the Colorado River is also leading to a rise in drinking water mineral content (Total Dissolved Solids or TDS). Should climate change increase the TDS in the Colorado River water, Tucsonans may expect that the mineral level of their drinking water, and the wastewater effluent that results, also will rise. This may result in increasing use of water softeners or lead to a community decision to reduce mineral levels through membrane treatment. A comprehensive ‘environmental footprint’ analysis of a potential membrane treatment facility is already underway. Tucson has been successfully advocating water conservation and efficiency for more than 30 years, and per capita water usage continues to drop, despite on-going drought conditions. Tucson Water sponsors a wide-ranging Conservation Program, which includes general public education, age-appropriate grade school programs, free landscaping workshops, in-home conservation assistance, professional training for landscape managers and nurseries, numerous water-use ordinances, and a steeply inclining water rate structure that encourages customers to reduce their use and eliminate water waste. The utility is currently evaluating a number of additional conservation and efficiency strategies, including ULF toilet, irrigation system upgrade and greywater system rebates, in part to better enable the community to respond to continued drought and other potential climate change issues. 
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