The Tuolumne River of California begins in the Sierra Nevada Mountains where rain and snow are more abundant. Small creeks and forks join and the river grows larger as it flows downhill. It enters the San Joaquin River in the Central Valley (photo below).
Why It Matters
- The Lyell and Dana Forks converge to create the Tuolumne River in Tuolumne Meadows in Yosemite National Park.
- The river has eroded a V-shaped valley, the Grand Canyon of the Tuolumne.
- Downstream is the U-shaped Hetch Hetchy Valley. Reported to have been as spectacular as Yosemite Valley, the river was dammed and the valley flooded in 1923. The reservoir provides water to San Francisco and surrounding cities.
- The Don Pedro Dam blocks the river further downstream in the Sierra Foothills. Reservoir water is used for irrigation, municipal water supplies, and hydroelectric generation.
With the link below, learn more about the Tuolumne River. Then answer the following questions.
- Yosemite National Park, Yosemite Nature Notes – 7 - Tuolumne River: http://www.youtube.com/watch?v=80CulKuksHc
- When the Lyell Glacier has all melted away, what will happen to flow in the Lyell Fork of the Tuolumne River in late summer? What will happen to the Tuolumne River? Why?
- What are the different erosional histories of the V-shaped Grand Canyon of the Tuolumne and the U-shaped Hetch Hetchy Valley?
- If the O’Shaughnessy Dam had not been built, what would Hetch Hetchy Valley have been like today?
- How does the Tuolumne River benefit people?