From NPR:

Southern California's Imperial Valley produces about 80 percent of the nation's winter vegetables. But years of drought, and a population boom in the Southwest, now threaten the water supply in the desert region — and all those cheap winter greens.

The next time you eat a salad this winter, picture the valley Vince Brooke is driving through: A beige desert set against glittering fields of green. Brooke works for the local irrigation district, and gives tours to busloads of water wonks from various Southwest cities through this valley — down the bumpy roads, past cropland and canals.

"You know, you can tell when they just are not, how can I say this diplomatically?"

They're just not, on board, Brooke says with the way agriculture uses water down here.

Brooke says that in some eyes, "We're water wasters, we're water hogs, the Ag sponge, a waste of water."

The water they're talking about is the Colorado River — the life-blood of a billion-dollar agricultural industry in the Imperial Valley. The system works, thanks to the giant cement Imperial dam.

Fighting For Water In The Arid Imperial Valley