Drying up the food supply

This is certainly reassuring, isn’t it? We have all the water in the world, and we can feed people indefinitely!

These days the Colorado River — which starts in the Rocky Mountains and cuts through much of the Southwest — isn’t what it once was. The water of the river has been dammed and divvied up, with more than 40 million people in the region now depending on it for irrigation and municipal supplies. But persistent drought along with the growth in the West has reduced the river’s flow, to the point that these days it usually dries up before it reaches what had been its mouth on the Pacific coast of Mexico. We’re draining the river dry.

And this year is likely to be worse than most. The Southwest is still recovering from a historic drought that lasted much of the previous year, setting off wildfires and severely damaging agricultural output. Snowpack across the Colorado River Basin — important because melting snow in the spring helps feed the river — was less than half normal levels, which made for a terribly dry spring. Water levels at Lake Mead — the man-made reservoir created by the Hoover Dam near Las Vegas — was barely half full at the end of April, and is expected to drop another 14 ft. this summer. By mid-April 61% of the lower 48 states were listed by the U.S. Drought Monitor as being in abnormally dry or drought conditions. Already wildfires are sweeping across New Mexico. The West is set to burn this summer, once again.

But what’s really scary is what long-term changes in water availability and water use could mean for our ability to feed ourselves. That’s the subject of a new paper in the journal Proceedings of the National Academy of Sciences, in which researchers from the University of Texas and the U.S. Geological Survey looked at the level of groundwater depletion in the Central Valley and in the High Plains of the Midwest, home to the country’s breadbasket. They found that during a recent intense drought between 2007 and 2009, farmers in the southern half of California’s Central Valley depleted enough groundwater to fill all of Lake Mead — a rate of depletion that is utterly unsustainable.