Sunday, May 24, 2009

Crop Circles

Flying to San Francisco my eye was drawn to crop circles. I don’t mean the kind of crop circles that were supposedly created by aliens and made such a stir a few years ago in England, I mean the kind created by pivot irrigation as in the photograph here. When I first came to the southwest from Michigan, (where water is never in short supply), I had no idea what I was seeing. Nothing in nature makes a perfect circle, and I did not understand why any farmer would irrigate in a fashion that left some of his land too dry to cultivate.

In the Midwest where water is plentiful and the land rich, farmers more and more cultivate every square inch that they own. It is a perpetual effort to persuade landowners to leave some small portion of land uncultivated so animals and game and song birds have a place live.

After a little time I finally understood why farmers acted differently here in the southwest. It is water that is valuable, not land. Land is relatively cheap. The problem is that there is not enough water to irrigate it all, or even any large portion of it.

In much of west Texas and north along the high plains, the primary source of water for irrigation is the Ogallala Aquifer. The origin of the Ogallala Aquifer dates back between two and six million years ago. Since the Ogallala started to be used for irrigation in the 1950s, its water level has dropped almost 9%. More efficient means of water use—including pivot irrigation—have slowed the decline in recent years. As you can see from the map of the Ogallala, some regions of the aquifer have actually begun to see rises in its level, while others have continued to decline.

At least in Texas it’s clear that we have to do even more work on water conservation or some day the level of the Ogallala will drop so far that irrigation will become impractical, and I won’t see any more crop circles flying to San Francisco. If that should come, and global warming threatens to bring that day about more quickly, it will mean that thousands of acres of now productive land will have been lost, and a way of life on Texas ranches and farms will come closer to disappearing.

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