Perhaps, the biggest sustainability problem in Tucson is potable water supply. Household water use comprises the principal consumption of the water supply, with agriculture a close second. Like golf courses, agricultural lands are turning toward reclaimed water. Mining and other industrial water uses combined accounted for about a 15 percent of water use in 1997. Massive drawing down of groundwater resources over the last 100 years has occurred, visible as ground subsidence in some residential areas.
To prevent further loss of groundwater, Tucson has been involved in water conservation and groundwater preservation efforts, shifting away from its reliance on a series of Tucson area wells in favor of conservation, consumption-based pricing for residential and commercial water use, and new wells in the more sustainable Avra Valley aquifer, northwest of the city. An allocation from the Central Arizona Project Aqueduct (CAP), which passes more than 300 mi (480 km) across the desert from the Colorado River, has been incorporated into the city's water supply, annually providing over 20 million gallons of "recharged" water which is pumped into the ground to replenish water pumped out. Since 2001, CAP water has allowed the city to remove or turn off over 80 wells.
Davis-Monthan AFB is locally leading the way with a 3.3 Megawatt (MW) ground-mounted solar photovoltaic (PV) array and a 2.7 MW rooftop-mounted PV array, both of which are located in the Base Housing area. The base will soon have the largest solar-generating capacity in the Defense Department after awarding a contract on September 10, 2010, to SunEdison to construct a 14.5 MW PV field on the northwestern side of the base.
Global Solar Energy, which is located at the University of Arizona's science and technology park, is one of the planet's largest CIGS solar fields at 750 kilowatts.
WaterLess than 100 years ago, the Santa Cruz River flowed nearly year-round through Tucson. This supply of water has slowly disappeared, causing Tucson to seek alternative sources.
In 1881, water was pumped from a well on the banks of the Santa Cruz River and flowed by gravity through pipes into the distribution system.
Tucson currently draws water from two main sources: Central Arizona Project (CAP) water and groundwater. In 1992, Tucson Water delivered CAP water to some customers that was referred to as being unacceptable due to discoloration, bad odor and flavor, as well as problems it caused some customers' plumbing and appliances. Tucson's city water currently consists of CAP water mixed with groundwater.
In an effort to conserve water, Tucson is recharging groundwater supplies by running part of its share of CAP water into various open portions of local rivers to seep into their aquifer. Additional study is scheduled to determine the amount of water that is lost through evaporation from the open areas, especially during the summer. The City of Tucson already provides to its inhabitants, but it is only used for "applications such as irrigation, dust control, and industrial uses." These resources have been in place for more than 27 years, and deliver to over 900 locations.
Light PollutionTucson and Pima County first adopted ordinances to control light pollution in support of the region's astronomical observatories in 1972. Last amended in 2012, the City of Tucson/Pima County Outdoor Lighting Code establishes maximum illumination levels, shielding requirements, and limits on signage in "continuing support of astronomical activity and minimizing wasted energy, while not compromising the safety, security, and well being of persons engaged in outdoor nighttime activities."
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