Cadillac Desert_ The American West and Its Disappearing Water - Marc Reisner [323]
The storm series lasted, almost without interruption, for ten days, lending credibility to Noah’s flood. Central and northern California, where most of the big reservoirs are, were the hardest hit. I had always had a mordant wish to watch a dam collapse, and this seemed like the best opportunity I might get in my life. I arrived at Oroville Dam just as the storm was beginning to break up. (It took me hours longer than usual to get there, because shallow lakes had formed across Interstate 680, creating instant new refuges for mallards and pintails.) In the previous week and a half, the Feather River watershed at five thousand feet had unofficially recorded fifty-five inches of precipitation, most of it as rain, which melted several feet of snow lying on the ground. Tampa gets that much rain in an average year. The spillway at Oroville is a big concrete channel that loops around the right abutment of the immense earthen dam. It was dumping a hundred and fifty thousand cubic feet of water per second, a couple of rivers the size of the Tennessee. That much water in that confined a space—the spillway is about as wide as a basketball court—is in a hurry-up mood. My guess is that it was moving thirty or forty miles per hour. Small trees and shrubs lining the spillway fence were bent double under the force of vortex winds created by so much mass in a rush. A crow, sailing arrogantly a few feet overhead, suddenly executed some frantic maneuvers to avoid being sucked in himself; he too had never seen anything like this before. Where the spillway poured the river back into the river below the dam—it didn’t so much pour in as fly in—a dense plume of mist mushroomed eighty stories high, split by three arching rainbows.
A dam did actually burst during the flood, though I didn’t see it happen. It was a temporary cofferdam built at the prospective site of Auburn Dam, whose construction had been mired in lawsuits and debate for years. The cofferdam held back about a hundred thousand acre-feet of water—thirty-two billion gallons—that merged, almost instantaneously, with a river already swollen to ten times its normal size. The flood-on-a-flood headed into Folsom Lake, which sits twenty miles above Sacramento and has a capacity of about a million acre-feet. Folsom Dam would have to spill the whole reservoir, 320 billion gallons of water, in three or four days in order to absorb the mythic flood pouring in. If it did not, the dam itself would be jeopardized, and if Folsom ended up like Teton Dam then a lot of Sacramento would float under the Golden Gate Bridge. When I arrived, a whole crowd of disaster buffs was already there, held at bay by dozens of highway patrol. I managed to sneak briefly onto the dam crest anyway; it trembled as a bank might tremble during a hurricane. The spillway at Folsom, a concrete and rock dam, was built into its center; it’s really a man-made, two-hundred-foot waterfall. At the time, it was dumping much more water than Niagara Falls. You couldn’t have heard a jet taking off five hundred feet away; that’s the kind of noise a million pounds of water makes—a million pounds a second—as it tumbles a couple of hundred feet and crashes into a canyon riverbed. (If Folsom was going to be destroyed, it would probably be a consequence of the falling river chewing out the bedrock on which the dam was built.) The waterfall reversed direction about eighty yards downriver and rose up in a towering, backfalling hydraulic wave that raced back and