The Phoenix metropolitan area, with an annual precipitation of approximately 7.7 inches per year, is designated as a desert region. Nonetheless, grass lawns are a surprisingly common occurrence in the Valley of the Sun, and in those lawns, sprinkler systems are nearly omnipresent. At the same time that Phoenicians are watering their lush, green lawns and gardens, the Southwest is progressing ever closer to what is known as Peak Water, or the point at which the demand for water extends beyond physical, economic, and environmental limits on meeting that demand. Scripps Institution of Oceanography at the University of California in San Diego has assessed the Peak Water situation and predicts that Lake Mead, which is the primary reservoir in the Colorado River system, the major source of water for most of the Southwest, and the largest reservoir in the United States, may run dry by 2021. Already, the water levels in the Colorado River are so low that the river no longer reaches its natural delta.
With major supplies of water reaching these dire conditions, the Southwest can no longer sustain its current water consumption.
Large industries and utilities like Intel’s manufacturing plants in Chandler, the Palo Verde Nuclear Plant outside of Phoenix, and agricultural projects on the outskirts of the metropolitan area share a large portion of the total water usage, but average citizens, particularly homeowners, also consume considerable amounts of water per year. With the Phoenix metropolitan area’s rapid population growth, homeowners increasingly share a role in the Peak Water situation. According to an article on Peak Water in Wired magazine, the population of the greater valley “is expected to nearly [sic] double in the next 20 years.”
With the understanding that water is reaching such a startling scarcity and the demand is consistently rising, time has come to rethink the ways in which water is used in the Arizona. Arizona is simply not equipped with the resources to sustain any frivolous applications of its water supply, and maintaining a lawn is, unfortunately, one of the many water allocations with which Arizonians could do without.
Although Arizona’s climate and its water resources cannot sustain most landscaping practices indefinitely, some possibilities for creative, sustainable landscaping projects still do exist. The natural biodiversity of a desert region is surprisingly high. Xerophytes (literally “dry-plants”) have the water conservation mechanisms and heat tolerance necessary to survive in a desert climate, and Arizona has a plethora of indigenous xerophytes. Brittlebush, mesquite, desert hollies, hackberries, poppies, sotols, ephedras, ocotillos, cacti, prickly pears, paloverdes, junipers, yuccas, Joshua trees, and desert pines are all xerophytes indigenous to Arizona.
The best way to limit water usage when landscaping is to conform to the limitations and demands created by the local ecosystem and climate, and try to cultivate as many indigenous species as possible. In addition to the ecological sustainability of indigenous-only planting, there are also a manifold of other benefits behind indigenous-only planting. Indigenous plants are cheaper and easier to obtain, transport, and transplant. Indigenous plants require drastically less maintenance than non-indigenous plants. Aesthetically, non-indigenous plants, such as palms, may appear exotic or paradisiacal, but indigenous plants create a more unique and authentic appearance of natural beauty and continuity with the surrounding landscape. Many Arizonian species, such as saguaros, have distinctive, sometimes bizarre colors and shapes, which, through Western films, National Geographic spreads, and postcards, have become icons and symbols of Arizona and are embedded in the popular conception of the Southwest. Perhaps the greatest reward for focusing on indigenous planting is the profound connection with the land that is engendered by studying the climate, soil, flora, and fauna of Arizona and learning how to cultivate plants under the challenging conditions Arizona presents.