This morning, on my way from Arizona to Death Valley, I stopped for a few moments at an overlook above Hoover Dam. I walked out onto the dam and looked east, past the huge intakes for the dam’s turbines, over the waters of Lake Mead and the huge swath of bleached rock surrounding the reservoir. The bleached rock told an eloquent story about how the recent drought in the Colorado Basin has affected the river’s flow, and suggests how continued drought will impact water supplies available to Las Vegas. Las Vegas currently gets 90% of its water from Lake Mead, but the surface elevation of Lake Mead dropped about 100 feet between the late 1990s and 2009. The elevation of the falling reservoir is approaching 1050 feet, the level of water intake 1; intake 2 would become inoperative at 1,000 feet. Although the Southern Nevada Water Authority (SNWA) maintains that there is only “a 1 percent probability that Lake Mead will reach an elevation of 1,075 feet by 2011 and 1,025 feet by 2014,” models suggest that conditions slightly better than those experienced between 2000 and 2008 could cause Lake Mead to decline to 1,000 feet by 2015. This would lead to severe water shortages, because sufficient water could not be drawn from Lake Mead through existing intakes. In anticipation of this problem, the SNWA is constructing a third intake at 860 feet elevation – but because the intake will use the pumping station for intake #2, the effective intake level would still be 1,000 feet.
As I see it, the declining levels of Lake Mead and Lake Powell (combined storage currently about 52% of capacity), prospects for continuing drought, and the almost inevitable growth of Las Vegas, will push exploitation of groundwater stored in the deep aquifers of northern and central Nevada. Impacts on water-dependent ecosystems will follow.
I thought of these things as I drove through the tangled sprawl of Las Vegas and pushed north into the basin and range country, toward Death Valley and the pupfish of Salt Creek and the Amargosa River.
Lake Mead from Hoover Dam