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"  When a well pumps water from an aquifer, it lowers the water table in a &amp;quot;depression cone.&amp;quot; In severe cases this can deplete streams on the surface. Monitoring wells can track the depression cone as it expands. (Illustration by Flying-Chilli.com) Two simple facts about Las Vegas: Its population has doubled since 1990, to 570,000; and 90 percent of its water comes from the Colorado River, which is in the throes of the worst drought in recorded history. To meet the looming water crunch, the city, along with the Southern Nevada Water Authority (SNWA), proposes to build a 285-mile pipeline to haul groundwater from six valleys in eastern Nevada. The $2 billion project would mean sinking up to 195 production wells as deep as 1700 ft. below the surface to bring more than 50 billion gal. of water per year to the parched desert metropolis.  But there&amp;#039;s no such thing as a free drink. When pumping outpaces an area&amp;#039;s ability to replenish its water reserves, entire ecological systems slowly wither. Starting in 1913, Los Angeles siphoned water away from Owens Valley, eventually turning a 100-square-mile lake into a dust bowl, and kicking up clouds of cadmium and iron. And in 1998 the United States Geological Survey found that groundwater pumping had lowered the water table in parts of Kansas, New Mexico, Oklahoma and Texas by more than 100 ft. The water Sin City is eyeing starts as snowmelt from mountains, and seeps into the ground, filling an aquifer -- an underground reservoir filled with rocks and gravel. The SNWA says the pumped water would be replenished by runoff. Hydrologist John Bredehoeft, a critic of the project who was hired by the Western Environmental Law Center, agrees -- but says the aquifer won&amp;#039;t refill quickly enough. Ironically, the basis for Bredehoeft&amp;#039;s argument is a study drawn up by the SNWA, showing the rate at which one part of the aquifer refills. Looking at the study, he worries that the plan will amount to a water &amp;quot;mining operation,&amp;quot; which could lead to dry wells and sinking land. The SNWA won&amp;#039;t draw conclusions based on its own study, saying that it&amp;#039;s impossible to accurately predict how the water table will react until pumping starts. &amp;quot;That&amp;#039;s why we&amp;#039;re looking at having so many wells,&amp;quot; says J.C. Davis of the SNWA, &amp;quot;to diffuse the effects of pumping.&amp;quot; Safeguards such as monitoring wells, which detect falling water levels (see illustration), could alert hydrologists before serious damage is done. &amp;quot;If a well is causing problems, it can be pumped more gently,&amp;quot; Davis continues, &amp;quot;or rotated out of service.&amp;quot; As cities across the Southwest boom, such wrangling over water projects seems destined to accelerate. Meanwhile, the Las Vegas plan is moving forward. The SNWA hopes to complete the approval process in 2009, and turn on the faucets by 2014. "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.popularmechanics.com/science/environment/a1220/4210244/>