ONE TOWN SQUARE: at the intersection of peak oil, climate change, and land use

The new edition of the National Geographic has an article about impending water crisis in the west. The 20th century was the wettest of the past millennium, and the century when Americans built an incredible civilization in the desert. Now, it’s over. Global warming could make things even uglier.

“For most people in the region, the news hasn’t quite sunk in. Between 2000 and 2006 the seven states of the Colorado basin added five million people, a 10 percent population increase. Subdivisions continue to sprout in the desert, farther and farther from the cities whose own water supply is uncertain.”

Using tree rings, scientists have identified two distinct “megadroughts.” The first had begun sometime before 900 and lasted over two centuries. There followed several extremely wet decades, not unlike those of the early 20th century. Then the next epic drought kicked in for 150 years, ending around 1350. Scientists estimate that the runoff into Sierran lakes during the droughts must have been less than 60 percent of the modern average, and it may have been as low as 25 percent, for decades at a time. According to researcher Scott Stine,

“What we have come to consider normal is profoundly wet. We’re kidding ourselves if we think that’s going to continue, with or without global warming.”

There are two reasons why global warming seems almost certain to make the drylands drier. Both have to do with an atmospheric circulation pattern called Hadley cells. At the Equator, warm, moist air rises, cools, sheds its moisture in tropical downpours, then spreads toward both Poles. In the subtropics, at latitudes of about 30 degrees, the dry air descends to the surface, where it sucks up moisture, creating the world’s deserts – the Sahara, the deserts of Australia, and the arid lands of the Southwest. Surface winds export the moisture out of the dry subtropics to temperate and tropical latitudes. Global warming will intensify the whole process. The upshot is, the dry regions will get drier, and the wet regions will get wetter.

The Rio Grande and its underground aquifers are being sucked dry on both sides of the frontier, and the region is slowly heading toward a water crisis.

The Rio Grande is over-appropriated – that is, there are more users for the water than there is water in the river. It is so overused in the U.S. that it can virtually disappear in El Paso. In the summer of 2001 a 100m wide sandbar formed at the mouth of the river, marking the first time in recorded history that the Rio Grande failed to empty into the Gulf of Mexico. Since 2002 then the sandbar has remained and now forms a usable land bridge between the US and Mexico. Lack of water for irrigation is forcing Mexican farmers off the land. Says a farmer in the desert lands of Mexico’s Tamaulipas state on the Gulf of Mexico:

“They have taken our water and these lands are dying. Our children are emigrating to the United States, some illegally.”

While the Rio Grande is already one of the most stressed river basins in the world, Mexican cities on the border with Texas are projected to double their population over the next 20 years.

The US and Mexico share the waters of this river under a series of agreements administered by the joint US-Mexico Boundary and Water Commission. The most notable of these were signed in 1906 and 1944. Under the 1944 treaty, Mexico is required to transfer water to the United States every five years from the two dams the countries share on the Texas border. Mexico’s Supreme Court has been asked to rule on whether this year’s water transfer was lawful.

Jon Gertner at the New York Times recently wrote an article about climate change and the American Southwest, with the apocalyptic title The Future Is Drying Up.

Tom Englehardt in a post at TomDispatch surveys ongoing droughts around the world, then brings it home by talking about the unprecedented droughts in the American Southeast, Southwest, and Midwest.

“Let’s face it, with water, you’re down to the basics. And if, as some say, we’ve passed the point not of “peak oil,” but of “peak water” (and cheap water) on significant parts of the planet… well, what then?”

Well, what might the consequences of drought be? Englehardt repeats a quote by Roger Pulwarty, a climatologist at the National Oceanic and Atmospheric Administration, talking about the Southwest:

“The worst outcome . . . would be mass migrations out of the region, along with bitter interstate court battles over the dwindling water supplies. But well before that, if too much water is siphoned from agriculture, farm towns and ranch towns will wither. Meanwhile, Colorado’s largest industry, tourism, might collapse if river flows became a trickle during summertime.”

Mass migrations? Now where do you suppose these folks might migrate too, this time? Read the rest of this entry »