Hetch Hetchy

The Hetch Hetchy Valley is the valley of the upper reaches of the Tuolumne River on the western flank of the Sierra Nevada in California. It is located in the northwestern part of Yosemite National Park, about 320 kilometers east of San Francisco. The valley was like the south adjacent and more famous Yosemite valley of the Merced River in the Ice Age glaciers formed as a U-shaped valley of aging and has been inhabited for thousands of years by indigenous people ( Native Americans ) before the first Europeans reached the region in the 1850s. In the late 19th century the valley was often compared because of its natural beauty with the Yosemite Valley - but also for the development of water supply interesting.

Hetch Hetchy Project

After the great earthquake in San Francisco in 1906, in consequence of devastating fires had devastated the city, the lack of adequate water supply became clear. The city appealed to the Ministry of the Interior of the United States to get the water rights at Hetch Hetchy. 1908 approved by the then Minister of the Interior James R. Garfield the rights to use the Tuolumne River. The Hetch Hetchy Project envisaged to build on the narrowest part of the valley, a dam that was to dam the river. This triggered a seven-year dispute with the environmental movement, Sierra Club, whose most prominent representative was John Muir.

As the valley is within the Yosemite National Park, the Congress of the United States had to agree to the project. He did so with the proviso that the water and the use of water power should only be accessible to the public. President Woodrow Wilson signed the law ( Raker Act ) in 1913. With the planning and preparations ( among others, the construction of a 109 km long railway line to supply ) was started in 1914.

Michael O'Shaughnessy, an Irish -born civil engineer planned and executed by the construction (1919-1923) was later named after him dam O'Shaughnessy Dam. In May 1923, the reservoir was flooded for the first time. At this time, the arch-gravity dam was 69 feet high. His current height of 95 meters got the dam until 1938. Twenty years after the start of the planning, so in 1934, 20,000 inhabitants came together in San Francisco to celebrate the arrival of the first water from Hetch Hetchy. The aqueduct, which directs the water to the west coast is about 270 kilometers long and can carry about 10.4 m3 / s of water.

With the water from the Hetch Hetchy Valley about 80 percent of the population of San Francisco and the Bay Area ( 2.6 million people ) are supplied. The water is one of the cleanest drinking water in the USA. San Francisco is one of only six cities in the United States that are not required by law to their water filtering. However, the water is disinfected with ozone and irradiated with UV light since 2011.

Conservationists see the project as one of the great environmental damage to the 20th century and are aiming for a restoration, which is to restore the once famous for its beauty valley.