Headwaters are the source of a stream or river. They are located at the furthest point from where the water body empties or merges with another. Two-thirds of California’s surface water supply originates in these mountainous and typically forested regions.

Rooted in Roman law, the public trust doctrine recognizes the public right to many natural resources including “the air, running water, the sea and its shore.”

The doctrine requires the sovereign, or state, to hold in trust designated resources for the benefit of the people. Traditionally, the public trust applied to commerce and fishing in navigable waters, but its uses were expanded in California in 1971 to include fish, wildlife, habitat and recreation.

Hetch Hetchy – a Sierra Miwok word for a type of wild grass – is a valley in Yosemite National Park whose river was dammed to create a water supply for the San Francisco Bay Area. The O’Shaughnessy Dam on the Tuolumne River forms Hetch Hetchy Reservoir.

Owned by the city of San Francisco, Hetch Hetchy Reservoir provides water to 2.7 million residents and businesses in the San Francisco Bay Area.