Cadillac Desert_ The American West and Its Disappearing Water - Marc Reisner [308]
As a matter of principle, any place where vegetation is relatively sparse, where soils are erodable, but where six inches of rain in a day or twenty inches in a month are not unknown is a less than ideal place to situate a dam. Those conditions, however, apply to a large part of the intermountain West—and, since the arrival of intensive agriculture, to a great portion of the Middle West as well. The Eel River in California is the most rapidly eroding watershed in North America—partly because the topography is ridden with erodable sediments, partly because of rampant clear-cutting earlier in the century from which the forests may never recover, partly because of stubble grazing by cattle and sheep that is still going on. There is no major dam on any branch of the Eel—at least not yet—but talk of building one there says a lot about what people are willing to ignore. Meanwhile, erosive forces are hard at work in the watersheds of the Missouri River, the Colorado, the Rio Grande, the Platte, the Arkansas, the Brazos, the Colorado of Texas, the Sevier, the Republican, the Pecos, the Willamette, the Gila—rivers on which there are dozens of dams.
Earlier in the century, it was thought by some that irrigation in those watersheds might actually slow the rate of erosion by creating more groundcover to hold the soil in place. In the 1920s, however, no one foresaw interest rates so high that farmers, pushed to the brink, would almost be forced to abandon careful husbandry of the soil for maximum profit. No one foresaw cheap fertilizers that allow land to be plowed year after year, never going fallow. No one foresaw six-ton tractors that tear up the soil and make it more apt to be carried off. No one foresaw a demand for U.S. agricultural exports that makes it profitable to farm Class VI land. As a result of all this—and because it was inevitable anyway—the dams are silting up.
Black Butte Reservoir, Stony Creek, California. Capacity in 1963: 160,009 acre-feet. Capacity in 1973: 147,754 feet.
Conchas Reservoir, Canadian River, New Mexico. Capacity in 1939: 601,112 acre-feet. Capacity in 1970: 528,951 acre-feet.
Alamagordo Reservoir, Pecos River, New Mexico. Capacity in 1936: 156,750 acre-feet. Capacity in 1964: 110,655 acre-feet.
Lake Waco, Brazos River, Texas. Capacity in 1930: 39,378 acre-feet. Capacity in 1964: 15,427 acre-feet.
Elephant Butte Reservoir, Rio Grande River, New Mexico. Capacity in 1915: 2,634,800 acre-feet. Capacity in 1969: 2,137,219 acre-feet.
Hoover Dam, Colorado River, Arizona-Nevada. Capacity in 1936: 32,471,000 acre-feet. Capacity in 1970: 30,755,000 acre-feet.
San Carlos Reservoir, Gila River, Arizona. Capacity in 1928: 1,266,837 acre-feet. Capacity in 1966: 1,170,000 acre-feet.
Howard Brothers Stock Dam, Driftwood Creek, McDonald, Kansas. Capacity in 1959: 26.58 acre-feet. Capacity in 1972: 14.18 acre-feet.
Ocoee Dam Number 3, Ocoee River, North Carolina. Capacity in 1942: 14,304 acre-feet. Capacity in 1972: 3,879 acre-feet.
Guernsey Reservoir, North Platte River, Wyoming. Capacity in 1929: 73,810 acre-feet. Capacity in 1957: 44,800 acre-feet.
Wilson Dam, Tennessee River, Tennessee. Capacity in 1928: 687,000 acre-feet. Capacity in 1961: 641,000 acre-feet.
Clouse Lake, Center Branch of Rush Creek, Ohio. Capacity in 1948: 234 acre-feet. Capacity in 1970: 142 acre-feet.
In thirty-five years, Lake Mead was filled with more acre-feet of silt than 98 percent of the reservoirs in the United States are filling with acre-feet of water. The rate has slowed considerably since 1963, because the silt is now building up behind Flaming Gorge, Blue Mesa, and Glen Canyon dams.
The Bureau of Reclamation has an Office of Sedimentation, which was being run in 1984 by a cheerful fellow named Bob Strand. One wonders whether his good cheer stems from the fact that sedimentation is the one problem the Bureau hasn’t really been forced to deal with yet. “All of our bigger reservoirs were built