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1.2 million between 1920 and 1930. h e lingering drought caused water
planners to doubt whether the new aqueduct would be sui cient 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 i ve 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. h ese ancient aquifers had already been used to irrigate approximately
one and a half million acres in the San Joaquin Valley by 1930, transform-
ing 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. h e 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,
