Hetch Hetchy Reservoir & O'Shaughnessy Dam

Most visitors to Yosemite never see the Hetch Hetchy Reservoir. Many, including John Muir, argued with the 1913 Congressional Act to build it. It will probably be the last dam to be built in the park. It is not well publicized, and the road leading to it is narrow, winding and dangerous. However, the hike thrrough a mountain tunnel and on around the reservoir to a waterfall makes the trip worthwhile. This reservoir provides 85 percent of the water for the San Francisco Bay Area. The water is probably the purest in the nation in that it comes from the melting snow on the mountains in Yosemite. After being drawn from the reservoir, it is transferred 161 miles to the San Francisco urban area through huge pipes constructed to use gravity to facilitate the transfer. To control the water level, seven vents in the O'Shaughnessy Dam allow the surplus water to thrust through into the beautiful Tuolumne River.

As we were returning to camp from the Hetch Hetchy on scenic
Rt. 49, we passed through the quaint town of Mocassin. Note the little bridge to nowhere. If you click on it, you will see the pipelines mentioned above.