THREE
The Great Droughts of the Twentieth Century
The rains disappeared—not just for a season but for years on end. With no sod to hold the earth in place, the soil calcified and started to blow. Dust clouds boiled up, ten thousand feet or more in the sky, and rolled like moving mountains—a force of their own.
TIMOTHY EGAN, The Worst Hard Time
THE GREAT DUST BOWL DROUGHT was considered the worst climate tragedy of the twentieth century in the United States and the worst prolonged environmental disaster in its recorded history. The years between 1928 and 1939 were among the driest of the twentieth century in the American West and Midwest, with heart-breaking impacts stretching into the Midwest and Colorado, New Mexico, Oklahoma, Texas, and Kansas. At its peak in 1934, this drought affected three-quarters of the nation—stretching from the Great Plains north into the Canadian Prairie, and along the West Coast.
WHAT WENT WRONG?
On the Great Plains, unsustainable agricultural practices compounded the impacts of the drought on the land. For centuries, if not millennia, prairie grasses had stabilized the topsoil by retaining moisture beneath the surface through freezing winters and dry summers. Even in times of drought, the grasses provided food and shelter for snakes, jackrabbits, prairie chickens, and other wildlife.
During the 1920s, however, farmers on the Great Plains began removing the native grasses down to their roots. Initially, the effects were not apparent. But as millions of acres of prairie were converted to wheat production with dry farming on a colossal scale, the damage was done. The farmers knew that the loose soils they were creating had nothing to stabilize them should drought return to the region, but they assumed the abundant rainfall of the early twentieth century would continue. Over a few short years, the prairie lands were ploughed so deeply and grazed so heavily that almost all the native grasses were gone and the land left vulnerable.
FIGURE 11. Dust storm approaching a midwestern town during the Dust Bowl in 1932. (Photo from the Natural Resources Conservation Service, U.S. Department of Agriculture.)
The West began its decline into drought in 1930. Many of the farmers held on, hoping the rains would return as they always did. But the drought continued unabated for eight years. In the early 1930s, strong winds began roaring over the prairies, creating a new and more visible catastrophe. The winds swept up topsoil from the Great Plains, forming thick clouds of dust, silt, and sand and darkening the skies—covering the earth like a blanket of dirty snow. The dust seemed to find its way everywhere: seeping under doors and through window cracks into the houses and into food stores, clothes drawers, beds, eyes, noses, and scalps.
The dust storms, or “black blizzards,” blew across hundreds of miles, even reaching as far as Washington, D.C., New York, and New England. Some reports described the dust falling on ships sailing across the Atlantic Ocean, and, when lofted high enough to be entrained by the jet stream, the dust reached as far away as Europe.
At the peak of the Dust Bowl, dust settled over nearly three-quarters of the United States. An estimated 100 million acres were destroyed or debilitated to varying degrees. The residents of the Great Plains could tell where the dust originated by its color: red dust came from eastern Oklahoma, yellow-orange dust from Texas, and black dust from Kansas (see figure 11).
BLACK SUNDAY
April 14, 1935, is remembered as Black Sunday, when a particularly bad dust storm blew in from the north. In Kansas, the day started out sunny, clear, and windless—a brief hiatus from the dusty clouds that had blown through the region regularly the previous four years. Lulled by this seemingly quiescent day, the Kansas residents began removing the sheets that covered their windows—opening them up to let in the rare fresh air. They walked outside without their usual protective aids: goggles, homemade sponge-masks over their mouths, petroleum jelly in their nostrils. This spring day seemed to be a turning point—a new start. As the day wore on, however, people spotted enormous black clouds moving in from the north, and some momentarily thought a rainstorm was headed their way. But they soon learned that these were not ordinary storm clouds, dark with water: these clouds were blackened by silt and sand.
A towering wall of earth, 2,000 feet high and 200 miles wide, soon plunged them into darkness. So thick and dense was the dust that people could not see their own hands in front of them, or their house just a few feet away. Many were blinded and suffocated as the wind blew dust into their eyes and lungs. The cold, turbulent winds moved south at 80 miles per hour, entraining soil and dirt and throwing it aloft as it traveled across South Dakota and into Nebraska, Kansas, Colorado, Oklahoma, and the Texas panhandle.
After years of breathing dust, residents of the Great Plains suffered respiratory ailments such as sinusitis, laryngitis, bronchitis, and even pneumonia and tuberculosis. Children and the elderly suffered severe chronic coughing and chest pain, shortness of breath, and nausea. Although the Red Cross opened emergency hospitals to help deal with this medical crisis, impassable roads covered with dust drifts made it impossible for many people to reach them.
As the Great Plains became increasingly uninhabitable throughout the 1930s, many residents were forced to leave. Banks foreclosed the homes and farms of millions of people, driving hundreds of thousands of the homeless and desperate farther west to places like Arizona, Oregon, and California.
THE DUST BOWL DROUGHT: THE WEST COAST
California and other neighboring states were facing hard times of their own. This region was suffering the longest and most severe drought on record, as measured by rapid drops in lake levels, lower precipitation, and reduced river flows across the West. Samuel Harding, a University of California scientist, compiled these data in a 1965 report, and he noted that many western states—including California, Arizona, Nevada, and Oregon—had enjoyed two very wet decades in the early twentieth century. But the climate took a dry turn after 1925, when rainfall and runoff began to steadily decline until the late 1930s.
In California, the flows of major rivers like the Sacramento, Feather, and Kern dropped below average levels from 1927 to 1935. At the same time, Lake Tahoe—the largest alpine lake in North America—fell fourteen feet below its sill depth to a historic low. The lake’s only outlet, the Truckee River, experienced its lowest flow rates on record during this period, finally ceasing to flow altogether. Downstream, low river flows led to significant saltwater intrusion into the Sacramento–San Joaquin Delta between 1931 and 1939, causing record high salinity levels in both the delta and San Francisco Bay as well as declines in aquatic ecosystems.
To the north, at the border of California and Oregon, the level of Goose Lake steadily dropped between 1926 and 1931 before the lake finally desiccated in 1936. Similar declines were seen in closed-basin lakes from eastern Oregon to central British Columbia. Farther east, the Great Salt Lake in Utah also dropped to its lowest level on record during 1934 and 1935, and, in the Southwest, Colorado River flow measured at Lees Ferry, Arizona, fell below its long-term average between 1930 and 1940. Looking at all the evidence, Harding concluded in his report that the period from 1927 to 1935 was the driest of the previous 200 years.
The Dust Bowl drought years were cause for grave concern to water planners and residents in Southern California as well, where lower than average river flows were measured on the Santa Ana and San Gabriel rivers. The newly constructed Los Angeles Aqueduct from the Owens Valley to Southern California allowed the population of Los Angeles to grow from 500,000 to 1.2 million between 1920 and 1930. The lingering drought caused water planners to doubt whether the new aqueduct would be sufficient to supply the growing city into the future. In a vicious cycle, the aqueduct allowed the region’s population to grow, but the larger population required still more water.
As the Dust Bowl drought continued unabated, Los Angeles voters felt they had no choice but to approve a bond measure to extend the Los Angeles Aqueduct farther north, into the Mono Basin. In the 1930s, the city of Los Angeles built diversion dams on four of the five tributary rivers that fed Mono Lake. As this water was diverted south to the growing metropolis over the next four decades, Mono Lake shrank steadily.
TAPPING ANCIENT GROUNDWATER
Meanwhile, a third of a million Dust Bowl refugees made their way to California, settling in the southern two-thirds of California’s Central Valley—a region known as the San Joaquin Valley. At the time, the drought was threatening to curtail California’s developing agricultural industry. However, powerful electric pumps, which became available to farmers for a reasonable price in the 1930s, allowed farmers to tap an extensive source of water that had been accumulating beneath the ground for thousands of years. These ancient aquifers had already been used to irrigate approximately one and a half million acres in the San Joaquin Valley by 1930, transforming that region into the “bread basket of the world”—or, more precisely, the “fruit and nut basket of the world.”
During the Dust Bowl drought, Central Valley farmers relied on this vast reservoir of groundwater for their crops—water that used to bubble to the surface as natural springs. Groundwater was pumped so extensively that the water table dropped dramatically, in some places by up to three hundred feet, killing deep-rooted oak trees that were several hundred years old. At the rate it was being pumped, this vast underground water reservoir would be depleted in only thirty to forty years.
Agriculture was becoming California’s top industry, and, in the face of the Dust Bowl drought and rapidly depleting groundwater, an immense water project was planned. The goal of this project was to capture rain and snowmelt draining from the Sierra Nevada mountain range behind dams and then to transport the water in reservoirs via pipes and aqueducts from the moist northern half of the state to the much drier southern half, including the burgeoning San Joaquin Valley agricultural lands and growing cities in Southern California. A massive water conveyance canal, called the California Aqueduct, was completed during a relatively wet period in the state that followed the Dust Bowl drought, in the 1940s and 1950s.
THE DROUGHT OF 1987–1992
The Dust Bowl drought was one of only two droughts that have lasted more than four consecutive years in California since 1850, when the state began keeping records. A later drought of similar magnitude and duration began in 1987, and it makes for an interesting comparison. California’s population had expanded from seven million in the 1930s to thirty-one million in the 1980s, and agriculture had grown to an industry worth $30 billion a year, heavily dependent on the extensive water infrastructure that had been built during the intervening years.
During the multiyear drought that began in 1987, annual precipitation over much of California was down to only 50 percent of the twentieth-century average. This drought affected the entire state, and, though no single year was as severe as the 1976–77 drought described in chapter 1, the cumulative effects were ultimately more devastating.
The 1987–92 drought crept up on the state. Reservoirs had enough water stored to buffer the first three to four years, but, after the fourth year, reservoir storage statewide was down 60 percent. Severe restrictions, with reductions of 75 percent, were imposed on water delivery for agricultural uses, and reduced river flows caused a decline in hydroelectric power generation.
In Southern California, the two reservoirs for the city of Santa Barbara dried up almost entirely, forcing the city to build a pipe connecting to the California Aqueduct through the Santa Ynez Mountains at a cost of hundreds of millions of dollars. Many more millions were spent by the city on one of the world’s largest seawater desalination plants, built as an insurance policy for the vulnerable city.
The impacts on the environment were also mounting. Bark beetle infestations caused widespread mortality in the forests of the Sierra Nevada, where extensive stands of pine trees, already weakened from the drought, succumbed to disease. Reduced stream flow led to major declines in fish populations, including the chinook salmon and striped bass, decimating commercial and recreational fisheries.
People sought new sources of water as, year after year, the drought continued. The use of groundwater became especially popular: private well owners deepened existing wells or drilled new ones, and thirsty consumers in the San Joaquin Valley extracted eleven million acre-feet more groundwater than could be replenished naturally, further lowering the water table. Cloud-seeding operations were expanded in the Sierra Nevada in the hopes of increasing precipitation, even if only by a fraction of a percent.
Overall, the 1987–92 drought resulted in financial losses of $3 billion to the state of California. This was an even greater financial disaster than the drought of the 1930s had been. The state’s population had expanded by over four times what it had been earlier in the century, and a burgeoning agricultural industry relied more heavily on water from reservoirs.
California has not experienced as severe a multiyear drought since 1992, but the population of the state continues to grow and is predicted to double by the year 2050. Moreover, California faces an uncertain climatic future: global warming is predicted to change the state’s hydrology, with less snowpack and overall warming and drying, more frequent flooding as more winter precipitation falls as rain rather than snow, and an increase in major storms. California, like the rest of the American West, also faces the recurrence of more severe climate events. This will be discussed in the coming chapters.
CLIMATE: THE LONG VIEW
The extreme climate events of the past century and a half that have been presented in this chapter were indeed severe. However, paleoclimate evidence suggests that they were by no means the worst we can expect from nature. In fact, compared to what records indicate of the long-term climate patterns for this region, the climate of the North American West over the past 150 years has been nearly ideal for human settlement.
We are now learning that the floods and droughts of this period are an incomplete sampling of the extreme events that have been a “normal” part of the West’s hydrology for thousands of years. The clues from past climates depict extremely dry periods—in some cases lasting decades or even centuries—often punctuated by torrential rains and floods. We now realize that vastly larger floods and more severe and protracted droughts, though rare, are as inevitable as the earthquakes and volcanic eruptions that Pacific Coast residents know will occur.
But most westerners are unaware of these prehistoric extreme climate events that complete the story of the region’s long-term climate pattern. The evidence has been growing, but only recently have the clues been pieced together to form a more accurate picture. This book presents an outline of what we know about the past 20,000 years, from the peak of the last ice age to the present. During those millennia, climate has often varied by extremes in the American West. Close examination of the evidence suggests that the benign conditions of the past century and a half have not prepared us adequately for what could come in the region’s climatic future.
The droughts of the 1930s and 1987–92 are believed to have originated in the Pacific Ocean. During these periods, sea surface temperatures in the tropical Pacific were unusually cold, which is characteristic of the ocean-atmosphere phenomenon known as La Niña. The next chapter explores the connections between the Pacific Ocean and the American West and how extremes of wet and dry are products of the interactions between this enormous body of water and the atmosphere above it.