— Interactive by Zach Wise

Las Vegas was first settled for its springs, springs that made it an oasis in the desert. Although those springs have decades since run dry, water is still the most import resource to Las Vegas and the dry Southwest.

And by all indications the region is only going to get dryer. Scientists predict devastating effects from global warming, conservationists are calling for a halt to growth in Southern Nevada as a way to preserve supplies and water managers are looking to ever more creative ways to reduce reliance on the overburdened Colorado River. A Colorado River reservoir at Lake Mead is the source of 90 percent of the valley's water supply. Water levels there have fallen steadily for nearly a decade.

Now Southern Nevada water managers say they can no longer rely on the river so heavily, and must construct a massive pipeline to draw water stored underground for centuries in rural Nevada to Las Vegas. They say no amount of conservation can replace the need for this backup source of drinking water.

Opponents say the effects of the pumping would be devastating and that the plan would sacrifice a rural, ranching way of life in Eastern Nevada for casinos and tract home in the south.

But it's not only the lack of water that worries environmentalists and water managers alike. It's also water quality, the endangered species that life in Southern Nevada's rivers and streams and the recreation opportunities that make the region's national parks so popular.

Water is one of the most politically charged issues in Nevada today, and it's certainly one of the most important.

— Phoebe Sweet