HOW DID LAS VEGAS GET ITS NAME? Kelsi Nelson For centuries, life was sustained in the Las Vegas valley by groundwater that bubbled to the surface creating a desert oasis. Under artesian pressure, groundwater was forced up through sediments onto the valley floor, supporting grassy meadows. Any water remaining after consumption and evapotranspiration recharged into the aquifer system. This abundant artesian spring had been a source of water for Native Americans of the Mojave and Paiute tribes for more than 13,000 years. In the early 1700's, Spanish traders were making their way to Los Angeles via the Spanish Trail. A scout by the name of Rafael Rivera was the first European to discover this desert oasis. He named the valley "Las Vegas," which translates roughly into "The Meadows," to acknowledge the wild grasses which grew in the nutrient rich desert soil with ample supply of water. Development of the Las Vegas valley began in 1907 with the installation of the first flowing groundwater well. Prior to that time, the aquifer system's natural discharge and recharge was in equilibrium, with an estimated flow of 7,500 acre-feet per year. As development progressed, nature's balance was disturbed as water flowed freely onto the desert floor from uncapped artesian wells, resulting in a drop in the groundwater table and the drying of the springs. In 1912, groundwater discharge from these free flowing artesian wells was almost 15,000 acre-feet per year. Due to this excessive drain on the aquifer system, the groundwater levels decreased by an average rate of one foot per year from 1912 to 1944. The groundwater table dropped more than 90 feet in some areas between 1944 and 1963. By 1955, groundwater pumped from the Las Vegas aquifer approached 40,000 acre-feet per year. The springs stopped flowing by 1962, resulting in the lush grassy meadows to fade away. The name "Las Vegas" is the only remaining evidence of the desert oasis that once existed in the now parched landscape. Groundwater pumpage continued to increase, peaking at 90,000 acre-feet per year in the 1970s. By 1990, the groundwater table had dropped more than 300 feet in some areas of the valley. The stress on the aquifer system forced a change on the sole reliance on groundwater. To meet consumption demands, Las Vegas began importing water from the Colorado River. Currently, Las Vegas imports 90 percent of its water from the Colorado River via Lake Mead. Groundwater pumped from the local aquifer provides the valley with only 10 percent of the demand. Despite the Las Vegas valley obtaining the majority of its water demand from Lake Mead, more water has been pumped from the basin than nature can sustain. The decline in the groundwater table even threatens the stability of the ground in the Las Vegas Valley. Due to the absence of water supporting the subsurface sediments, compaction of the fill and faults is occurring, resulting in subsidence throughout the valley. Groundwater levels must be increased above the current levels to hinder the subsidence. Since 1988, groundwater recharge programs have attempted to store surplus water during winter months to be used during the high demand summer months and replenish the principal aquifers to prevent further subsidence. The local agencies are trying to achieve these goals by injecting treated surface water from Lake Mead into groundwater wells. In spite of these efforts, the cumulative groundwater consumption for the valley exceeds natural recharge and injection from Lake Mead. In order to prevent further subsidence and protect the groundwater resource for future use, conservation of water usage needs to be implemented in addition to increasing the amount of surface water being injected into the aquifer. REFERENCES Pavelko, M. T., D. B. Wood, and R. J. Laczniak, 2008. "Las Vegas, Nevada: Gambling with Water in the Desert." U.S. Geological Survey Circular 1182, 17 September.

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