Geoscience Reference
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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.
h is region was suf ering the longest and most severe drought on record,
as measured by rapid drops in lake levels, lower precipitation, and reduced
river l ows across the West. Samuel Harding, a University of California sci-
entist, 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 at er 1925, when rainfall and runof began to steadily decline until
the late 1930s.
In California, the l ows 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. h e lake's only outlet, the Truckee River,
experienced its lowest l ow rates on record during this period, i nally ceasing
to l ow altogether. Downstream, low river l ows led to signii cant 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 i nally desic-
cated 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 l ow 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.
h e Dust Bowl drought years were cause for grave concern to water plan-
ners and residents in Southern California as well, where lower than average
river l ows were measured on the Santa Ana and San Gabriel rivers. h e newly
constructed Los Angeles Aqueduct from the Owens Valley to Southern
California allowed the population of Los Angeles to grow from 500,000 to
