Yosemite Valley is a glacial valley in the Sierra Nevada, part of the Yosemite National Park, drawing close to 3.7 million visitors annually. The Hetch Hetchy Valley is virtually an identical twin to Yosemite Valley, but you will never see its stunning rock formations and dramatic waterfalls. With steep valley walls, a narrow outlet and 3,812 feet in elevation, it was the perfect site for a reservoir.
Hetch Hetchy Before Dam
At 5:12am on Wednesday, April 18, 1906 an earthquake of between 7.7 and 8.25 in magnitude struck San Francisco. Fires broke out and destroyed nearly 80% of the city as the already inadequate water supply failed. If San Francisco wanted to rebuild, it was apparent that a new source of water was badly needed.
Using the Hetch Hetchy’s Tuolumne River as a water source was proposed 50 years before the earthquake, but the devastation was enough to motivate government officials to authorize the development of the river. Wilderness conservation was at its early stages and to appease the arguments, permission was given to flood the valley under the condition that the power and water it provided could only be used for the public good, with no private profit derived.
The O’Shaughnessy Dam began construction in 1919 and was completed in 1923. Construction of the 137-mile pipeline that would eventually carry the Hetch Hetchy’s water to San Francisco was able to begin, as was the construction of hydroelectric power stations and the lines they would use to transmit that power to the city. Unfortunately, the city of San Francisco ran out of money to fund the project in 1925 – coincidentally as it reached Pacific Gas & Electric’s newly constructed substation, just across the San Francisco Bay.
Hetch Hetchy After Dam
PG&E announced that the company would temporarily take over the delivery of that power to the city, buying the power from it and selling it back to its citizens at a profit. Legal challenges to the situation began in 1941 and still continue today as it is believed PG&E continues to profit from Hetch Hetchy’s water and power.
This is one of the largest and most successful gravity-fed and power-generating municipal water supply systems in the world today and it was built amidst protest and the argument to remove the dam continues today. The flooding of the valley has not been an environmental disaster as protesters had thought; it provides over 2 million San Francisco residents with clean water and generates 1.6 billion kilowatt hours of electricity annually. Many argue that without the reservoir, the Hetch Hetchy would become overdeveloped and overcrowded just as the Yosemite Valley is now.