PROBLEMS FROM DEVELOPMENT 65 



to extract all the supply perennially available, and until that 

 is done some waste will continue by evapotranspiration. 



Las Vegas Valley, Nevr° Las Vegas Valley is officially a 

 tributary of the Colorado River, but the water that flows 

 from Las Vegas Wash into Lake Mead is limited to the 

 negligible quantities that run off from the lower part of the 

 valley after intense storms, and the valley to all intents and 

 purposes is a closed basin. Most of the precipitation upon 

 the drainage basin soon returns to the atmosphere by 

 evapotranspiration; the rest percolates downward to enter 

 the ground-water reservoir, and nowhere is there sufficient 

 surplus to form a perennial stream. Most of the ground 

 water comes from the high Spring Mountains west of the 

 valley and moves eastward toward the valley floor; under 

 natural conditions it came to the surface near the city of 

 Las Vegas in large springs and seeps, which watered the 

 broad meadows that caught the eye of early Spaniards and 

 suggested the name for the valley. The springs, with a com- 

 bined annual yield of about 7,000 acre-feet, furnished all 

 the water supplies for the valley's residents until 1907. 



A flowing artesian well drilled in 1907 started a boom, 

 and by 1912 there were about 75 flowing and 25 nonflowing 

 wells in the valley. The flow from springs decreased some- 

 what, but the total yield from wells and springs rose to more 

 than 20,000 acre-feet a year. In the next 30 years the number 

 of wells increased to more than 300, but the total ground- 

 water draft remained about 22,000 to 24,000 acre-feet a 

 year. During this time artesian pressures declined markedly, 

 especially in the vicinity of Las Vegas where wells were 

 closely spaced, and several wells ceased flowing. 



Since 1942, the population of Las Vegas Valley has more 

 than doubled, and water requirements have increased ac- 

 cordingly. In part, the increased demand has been met by 



20 Reference: Maxey, G. B., and C. H. Jameson, Geology and Water Resources 

 of Las Vegas, Pahrump, and Indian Spring Valleys, Nevada, 

 Nev. State Engr. Water Res. Bull. 5, 1948, 121 pp. 



