Cadillac Desert_ The American West and Its Disappearing Water - Marc Reisner [309]
“The dams are wasting assets,” says Rafael Kazmann, a retired professor of hydrology from Louisiana State University and one of the world’s foremost authorities on water. “When they silt up, that’s it.” Can’t the mud be removed somehow? “Sure,” says Kazmann, “but where are you going to put it? It will wash right back in unless you truck it out to sea. The cost of removing it is so prohibitive anyway that I can’t imagine it being done. Do you understand how many coal trains it would take to haul away the Colorado River’s annual production of silt? How would you get it out of the canyons? You can design dams to flush out the silts nearest to the dam, but all you get rid of is a narrow profile. You create a little short canyon in a vast plateau of mud. Most of the stuff stays no matter what you do.”
The one place with some experience at desilting dams is Los Angeles, which has built a number of flood debris reservoirs around the basin whose capacity it can ill afford to lose. Between 1967 and 1977, the Metropolitan Water District and the Department of Water and Power removed 23.7 million cubic yards of mud from behind those dams. The cost was $29.1 million. At that rate, it would cost more than a billion and a half dollars, in modern money, to remove the silt that accumulated in Lake Mead over thirty years—if one could find any place to put it.
“The average politician,” says Luna Leopold, another hydrologist who seems to have some appreciation of the magnitude of the problem, “has a time horizon of around four years. The agencies are tuned to Congress, so theirs is about the same. No one has begun to think about this yet. But keep in mind that thousands of big dams were built in this country during a very brief period—between 1915 and 1975. Many are going to be silting up at the same time. There already are some small reservoirs in the East that are mud up to the gunwales. These are little manageable reservoirs—nothing like the big canyon reservoirs we’ve built in the West. But I haven’t heard of anything being done about them.”
The silt that is now accumulating behind the dams used to settle near the mouths of the rivers. The Mississippi-Atchafalaya Delta, which is bigger than New Jersey, is made up entirely of silt from the West and Middle West. About half of the sediment that used to reach it every year no longer does. Rafael Kazmann, who made a career of studying the Delta and may understand it better than anyone else alive, is convinced that a third to half of it will disappear within the next few decades; a significant percentage already has. He also believes the Mississippi will change course—probably by the year 2000—and begin pouring down the Atchafalaya Basin, wiping out many miles of interstate highway and several of the nation’s largest gas pipelines. “The river has been straitjacketed and robbed of its silt,” says Kazmann. “It’s a much more powerfully scouring river that it was. It’s just a matter of time before it eats away one of its bends and seeks out a completely new course.” Kazmann also believes that, in an economic sense, such an event could be the greatest peacetime disaster in American history. The only thing that might eclipse it is the silting up of the dams.
“The answer I have always heard from bureaucrats,” says Kazmann, “is that scientific and technological progress has accelerated at such a tremendous rate that some solution will come along. I don’t know that they think—that we’re going to have fusion energy pumping out the dams? The only answer I can see is to make the dams higher or build new ones. Right now I can think of few places where it would make economic sense to do that, even if it were