Biology Reference
In-Depth Information
to inland waterways. In the three decades between 1920 and 1950, humans
made the largest physical alterations to the estuary in its history.
At first, these alterations just involved dams. By 1920, myriad small
dams blocked creeks and rivers flowing into the estuary, as local landown-
ers worked to store water or fill irrigation hoses and kitchen faucets. Not
long afterward, much bigger dams were in the works, among them Hetch
Hetchy and Shasta.
Hetch Hetchy's O'Shaugnessy Dam submerged a glacial canyon as dra-
matic in its topography as neighboring Yosemite under 360,000 acre feet
of Tuolumne River water. The battle over whether to flood this beautiful
canyon galvanized the nation's young conservation movement, including
one of its early visionaries, John Muir. Dam advocates in the early 1900s
argued, “the 400,000 people of San Francisco are suffering from bad water
and ask Mr. Muir to cease his aesthetic quibbling.” The people prevailed,
and the City of San Francisco completed the Hetch Hetchy Dam in 1923,
as well as the water connections to the city miles away a decade later. The
inundation of the valley devastated Muir, and ignited a battle to remove
the dam that continues today.
Shasta Dam, completed in 1945, dwarfed anything built before or since
in the estuary watershed. Its reservoir covers 29,500 acres and stores up to
4.5 million acre feet of water. The dam itself backs up the mighty Sacra-
mento River into the Sierra foothills just above Redding, stopping a huge
river from spilling down into the Central Valley plains.
Shasta Dam under construction in 1942. (Lee Russell, Library of Congress)
