A few hundred farms in the southern tip of California, along the Mexican border, may hold the key to saving the drought-plagued Colorado River from collapse.

These farmers, in Imperial County, currently draw more water from the Colorado River than all of Arizona and Nevada combined. They inherited the legal right to use that water, but they're now under pressure to give up some of it.

The Imperial Valley is a place of jarring contrasts. Half is in its natural state, a bone-dry desert. The other half is mile after mile of green fields lined by irrigation canals. A few of the fields are shrouded by showers of water delivered from long lines of sprinklers.

Steve Benson, managing partner of Benson Farms, points out a neighbor's field where a crew is planting lettuce.

"It's very early planting," he says. "There's been a bad crop in northern California. So it's been a high market. They're trying to jump on the market early and have the first lettuce to be harvested."