Tuolumne County Museum

The Tuolumne River flows for 149 miles through Central California, from the high Sierra Nevada to join the San Joaquin River in the Central Valley. Originating at over 8,000 feet above sea level in Yosemite National Park, the Tuolumne drains a rugged watershed of 1,958 square miles , carving a series of canyons through the western slope of the Sierra. While the upper Tuolumne is a fast-flowing mountain stream, the lower river crosses a broad, fertile and extensively cultivated alluvial plain. Like most other central California rivers, the Tuolumne is dammed multiple times for irrigation and the generation of hydroelectricity. Humans have inhabited the Tuolumne River area for up to 10,000 years. Prior to the arrival of Europeans, the river canyon provided an important summer hunting ground and a trade route between Native Americans in the Central Valley to the west and the Great Basin to the east. First named in 1806 by a Spanish explorer after a nearby indigenous village, the Tuolumne was heavily prospected during the California Gold Rush in the 1850s, and the lower valley was cultivated by American settlers over the next few decades. The city of Modesto grew up on the Tuolumne as a railroad hub, absorbing most of the population of the Tuolumne valley around the turn of the century. As agricultural production rose, farmers along the Tuolumne formed California's first two irrigation districts to better control and develop the river. From the 1900s to the 1930s, the river was dammed at Don Pedro and Hetch Hetchy to provide water for Central Valley farmers and the city of San Francisco, respectively. The Hetch Hetchy project, located inside Yosemite National Park, incited national controversy, and is widely regarded as the origin of the modern environmental movement. As the mid-20th century progressed, demands on the Tuolumne continued to increase, culminating in the completion of New Don Pedro Dam in the early 1970s. These projects halved the amount of water flowing from the Tuolumne into the San Joaquin, greatly reducing the once-abundant runs of salmon and steelhead in both rivers.
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