Tuolumne River
About the River
The Tuolumne River, originating from the Sierra Nevada mo in California, has a rich history intertwined with both indigenous cultures and modern development. Historically, the river was a crucial resource for the Miwok and Yokuts peoples. In the 19th century, the river gained prominence during the California Gold Rush, as miners diverted its waters to sluice for gold.
The Tuolumne River stretches approximately 149 miles (240 kilometers) from its source in the Sierra Nevada mountains to its confluence with the San Joaquin River. It flows through diverse landscapes, including rugged mountain terrain, expansive meadows, and canyons.
Near the edge of Yosemite National Park, a dam on the Tuolumne River forms the Hetch Hetchy Reservoir. The Tuolumne River continues to flow below Hetch Hetchy, downhill through high mountains, beautiful valleys and forests of pine trees until it reaches a place in the foothills 40 miles east of Modesto. There it collects into Don Pedro Reservoir, which is owned and operated by MID and TID. It then continues downstream to La Grange Diversion Dam to be diverted into MID and TID systems or continue down the river.
Below La Grange Diversion Dam, the water that remains in the Tuolumne River continues to flow downhill to the San Joaquin River, Delta and ultimately the Pacific Ocean the way it has for thousands of years.
Benefits of the River
For more than half a century, the Tuolumne River and the Don Pedro Project have served some of the most productive farmland in the world. With affordable, reliable irrigation water, the Project directly supports the vibrant agricultural sector, while also providing municipal and industrial water supply, flood control, water storage, recreation, clean power, and fish and wildlife conservation benefits.
Water from Hetch Hetchy Reservoir is also vital for the San Francisco Bay Area. The Hetch Hetchy Regional Water system provides clean drinking water to 2.7 million people and thousands of businesses in four Bay Area communities.
The result is a thriving Central Valley economic engine that supports over $4 billion in output, $735 million in labor income, and nearly 19,000 jobs annually. The system also supports the Bay Area’s more than $1 trillion in economic output and serves internationally recognized research institutions, leading biotech centers, and commercial job hubs, including Silicon Valley.
The Tuolumne River is more than just a source of water – it is the cornerstone of life across the region. Hetch Hetchy and Don Pedro Reservoirs’ primary purpose is to serve as a reliable source of water and power under all conditions, including extended droughts, which is why the Tuolumne River Partners have long taken a role protecting the Tuolumne River watershed.
Interests in the River
The Tuolumne River's current makeup includes a combination of natural and engineered features. Diversions from the river are made through a system of water rights for the purpose of municipal drinking water, agricultural irrigation water and the use of water as fuel in generating hydroelectricity. Additionally, the river is vital for maintaining the ecological health of the surrounding habitats. Efforts to balance human needs with environmental protection are ongoing amongst stakeholders.
The agencies with stewardship over the river advocate for the preservation and restoration of the river’s natural flow and habitat while providing for local communities that depend on the river for water, recreation, and scenic beauty. Multiple interests underscore the need for collaborative management strategies that address both human and ecological needs.
Updates on the River
In an exciting and unexpected conservation success, 1,200 adult spring-run Chinook salmon—originally released as part of the San Joaquin River Restoration Program—made their way to the Tuolumne River, where they’ve found abundant habitat and cold, clean water in which to spend the summer prior to spawning in the fall.