Nature Noir, Jordan Smith [early reader chapter books .txt] 📗

town lots for sale, and those who bought the lots set up stores, restaurants, hotels, and livery stables. It was a disastrous choice.

By the time the two meet in the utter flatness of the Central Valley, the Sacramento River, flowing south out of the mountains of Northern California, and the American, flowing southwest out of the Sierra Nevada, are no longer the swift mountain streams they began as. From Sacramento, the Sacramento River must go another sixty miles to reach salt water at San Francisco Bay, and in that distance it loses only two feet of elevation at low, summer flows, and only about thirty feet when the water stacks up on itself trying to get out of the valley during floods. To make matters worse, every other river on the west side of the Sierra Nevada and the east side of the Coast Ranges must, like the American, join the Sacramento to pass through the only breach in the mountains around the four-hundred-mile-long bathtub of the Central Valley—an aggregate, before human modifications, of over half of the state's annual rain and snowmelt.

The nature of Sacramento's site was revealed to its citizens in the first winter of the city's existence, when the American and Sacramento Rivers transgressed on the city a mile back from their banks. There were floods again that spring of 1850, in March of 1851, a few days before Christmas in 1852, on New Year's Eve of 1853, and again that March. After a string of deceptively reassuring years in the late 1850s, during which there was much building, in December 1861 and January 1862 the whole middle of the Central Valley became an inland sea sixty miles wide and a hundred long. Scores of people and thousands of cattle drowned, hundreds of homes and businesses were destroyed, property losses equaled a quarter of the assessed valuation of improvements in California at the time, and on Inauguration Day in 1862, the state's new governor, Leland Stanford, made his way to the festivities in a rowboat. Although attenuated by flood control structures, that sort of thing has continued in Sacramento every decade or two until the present day.

And yet the problem with the climate of California was worse than just floods.

During the Gold Rush, with supplies coming expensively by sea around Cape Horn, a market for locally produced food was created and some immigrants took up farming. The new farmers had come from the East, from Europe, and from other places where it rained in the summertime, but in California they had to make it through five or six rainless months every year. Some winters and springs the rains failed to come; fresh on the heels of the catastrophic floods of 1861–62 came the drought of 1864, and the Central Valley was littered with dead and dying cattle and abandoned crops and homesteads. So farmers were soon attracted to irrigation.

By 1854 the first diversion dams were constructed on the American, one of them at the later site of the Auburn Dam. The North Fork Dam was made out of tree trunks stacked in cribs, log-cabin style, and filled with stones. It served ditches and aqueducts that eventually reached some sixty miles in length, and by the late nineteenth century it supplied a growing number of irrigation farms. Never higher than 25 feet, the dam didn't store water, just diverted some of it, and therefore it had no impact on flooding downstream. But by the end of the nineteenth century, with the technologies of concrete and earth-moving machinery, came a solution to both floods and drought: the storage of flood waters behind huge dams for use in the summertime. The advent of electric light and power in the 1890s made the damming of rivers in the mountains triply attractive, and between 1910 and the late 1920s demand for electricity grew at the rate of 10 or 11 percent a year in California. By the mid-twenties surveyors ranged all over the hills, looking for dam sites. One they found was a bowl-like valley around the confluence of the American's North and South Forks near Folsom; another was upstream, in the eight-hundred-foot gorge of the North Fork below Auburn, where the little North Fork Dam already stood.

It took over twenty years for either site to be used. Folsom was the first, and at the time a 340-foot concrete dam was rising from the riverbed there in the early 1950s, its builders believed it would protect Sacramento from floods of a size seen only once in two hundred years, or longer. But before it was even finished, a huge storm over Christmas 1955 filled Folsom's million-acre-foot reservoir in a single week. (An acre-foot is just what it sounds like, the amount of water it would take to cover an acre of land with a foot of water if nothing soaked in, or just over 326,000 gallons. This is roughly the amount an American family uses in a year.) By the following year bills were introduced in Congress to authorize a larger dam upstream at Auburn. It took a while to get Congress's approval, but after Northern California suffered catastrophic flooding again in 1964, by September 1965, Auburn Dam was law.

To construct Auburn's foundations, the Bureau of Reclamation had to dry out the riverbed. So the engineers built a tunnel big to enough to drive a train through, which created a shortcut at a bend in the river through over two thousand feet of canyon wall. When the diversion tunnel was finished, they constructed a temporary earthen dam over two hundred feet high at its entrance to steer the river into it.

Basing their conclusions on only a half-century of data (river gauges had not been installed on the forks of the American until 1911), the Bureau's engineers calculated that the temporary dam—called a "cofferdam"—could safely contain a storm that came only once every thirty-five years on the average, and the main dam could be finished in far less time