The snowmelt from Mt. Lyell, the highest peak in Yosemite National Park, and Mt. Dana forms the headwaters of the Tuolumne River.

The Tuolumne River is the largest of the three tributaries of the San Joaquin River. From its headwaters at Mount Lyell the Tuolumne River runs as a somewhat wavy line from east to west. The river eventually reaches the Pacific Ocean via the San Joaquin Delta. The Dana Fork of the Tuolumne River flows from Mount Dana and meets the Lyell Fork descending from Mount Lyell in Tuolumne Meadows. The Tuolumne meanders through gorges and canyons making its way through Hetch Hetchy Valley welcoming waters from other creeks and rivers as it continues its path to its final destination. Further downstream the river flows into Don Pedro Dam and Lake Don Pedro. Downstream the Tuolumne continues its journey towards the San Joaquin River where it flows through the Delta on its way to the ocean near San Francisco.