How to create more water during a drought
September 18, 2007
The U.S. Department of the Interior has discovered a way to produce more water from the overworked Colorado River.(I learned of this not from my own dogged journalistic investigations, but from Phil Doe of Littleton, who chairs a group of troublemakers known as the Citizens Progressive Alliance.)At issue last summer was a pipeline from the San Juan River to serve Gallup, N.M., and portions of the Navajo nation. Before it can be built, the Interior Department has to issue a “Hydrologic Determination” that there will likely be enough water available to make the project worth building. After all, there’s no point in constructing 267 miles of pipeline if there’s no water to put into the pipes.On June 8, Interior Secretary Dirk Kempthorne sent a letter to New Mexico Gov. Bill Richardson. “The finding in the Determination is that there is likely to be sufficient water to support the proposed contract,” Kempthorne wrote, which “removes any Department of Interior concern about potential limitations of water supply.”The San Juan River is a major tributary of the Colorado River, which is governed by the Colorado River Compact. The compact was drawn up in 1922, and it was based on the best data available then, which indicated an average annual flow in the Colorado of about 17 million acre-feet.The problem is that those statistics were compiled during years that, in the grand sweep of things, were unusually wet. More recent studies put the average closer to 13.5 million acre-feet per year.So we have a river that was allocated on the basis of 17 million annual acre-feet, but rarely carries that much water. In our state’s water jargon, the river is “over-appropriated,” meaning there are more legitimate claims on the river than it has water to supply.And that was before this pipeline was approved by Interior. So how did Interior determine “that there is likely to be sufficient water”?Take two logical statements, combine them into illogic, and you can make water – at least if you’re the Interior Department.Logical Statement 1: The lower the evaporation from the surface of reservoirs in the Colorado River basin, the more liquid water in the system. No argument there.Logical Statement 2: The lower the levels of the reservoirs in the Colorado River basin, the less surface area there is to suffer from evaporation.So, the reservoirs are smaller and thus they lose less water, and therefore, there is more water available. Believe it or not, that’s how our Interior Department determined that there was water available for this New Mexico pipeline.No one seems to have asked, “Why are the reservoirs smaller?” The answer to that question would be something like, “Years of drought,” and that would imply that there isn’t enough water to go around with current uses, let alone adding another diversion from the river.Consider Lake Mead behind Hoover Dam near Las Vegas. That’s hot, dry country, and so the reservoir drops 6.4 feet a year on account of evaporation, which works out to 791,000 acre-feet a year – enough water for more than 3 million people.Move up the Colorado River to Powell Reservoir (also in a hot desert), and there’s an estimated 884,000 acre-feet a year lost to evaporation and seepage into the surrounding sandstone. Let’s figure only half the loss is evaporation, and that’s 442,000 acre-feet – enough for at least 1.7 million people.In other words, the combined evaporative loss from just these two reservoirs is enough water for all 4.7 million of us Coloradans. So if we were to remove the dams, the reservoirs would shrink away and evaporation losses would diminish. Thus there’s more water for everybody in our arid West.If it works this way, as Interior now argues, why did it build dams in the first place? Ed Quillen is a writer in Salida, Colo., where he produces regular op-ed columns for The Denver Post and publishes Colorado Central, a small regional monthly magazine.