Tuolumne River

The Tuolumne River ( /tuːˈɒləmiː/; Yokutsan: Tawalimnu) is a California river that flows nearly 150 miles (240 km) from the central Sierra Nevada to the San Joaquin River in the Central Valley. The river flows from the Sierra Crest on the west Sierra slope, through the Sierra foothills of the Sierra Nevada, to Don Pedro Reservoir, through farmland in the Central Valley, to its mouth near Modesto.

Slightly larger than its counterpart in the south, the Merced River, the Tuolumne River's upper watershed was shaped by glaciations in the previous Ice Age, which produced Hetch Hetchy Valley and the Grand Canyon of the Tuolumne. The river has been a source of controversy for many years, especially from Hetch Hetchy Valley. Much of its water is now diverted to San Francisco from Hetch Hetchy Reservoir, which fills the valley in the Sierra Nevada once compared to famous Yosemite Valley. More water is diverted from La Grange Diversion Dam to irrigate farmland in the Central Valley, which leaves the lower course of the river with less than 60% of its historic flow. Despite these extensive water system developments, the Tuolumne is still a popular area in Yosemite National Park, although far less visited than the Merced River.