The Merced River (), in the central part of the U.S. state of California, is a 145-mile (233 km)-long tributary of the San Joaquin River flowing from the Sierra Nevada into the San Joaquin Valley. It is most well known for its swift and steep course through the southern part of Yosemite National Park, where it is the primary watercourse flowing through Yosemite Valley. The river's character changes dramatically once it reaches the plains of the agricultural San Joaquin Valley, where it becomes a slow-moving meandering stream.
The river first formed as the Sierra Nevada rose about 10 million years ago, and sediment eroded from its canyon helped form the flat floor of the San Joaquin Valley. Glaciation during the ice ages carved the high elevation parts of the watershed, including Yosemite Valley, into their present shape. Historically, there was an extensive riparian zone which provided habitat for millions of migrating birds, and the river had one of the so...Read more
The Merced River (), in the central part of the U.S. state of California, is a 145-mile (233 km)-long tributary of the San Joaquin River flowing from the Sierra Nevada into the San Joaquin Valley. It is most well known for its swift and steep course through the southern part of Yosemite National Park, where it is the primary watercourse flowing through Yosemite Valley. The river's character changes dramatically once it reaches the plains of the agricultural San Joaquin Valley, where it becomes a slow-moving meandering stream.
The river first formed as the Sierra Nevada rose about 10 million years ago, and sediment eroded from its canyon helped form the flat floor of the San Joaquin Valley. Glaciation during the ice ages carved the high elevation parts of the watershed, including Yosemite Valley, into their present shape. Historically, there was an extensive riparian zone which provided habitat for millions of migrating birds, and the river had one of the southernmost runs of chinook salmon in North America.
Miwok and Paiute people lived along the river for thousands of years before Spanish and Mexican military expeditions passed through in the early 19th century. The California Gold Rush brought many people into California and some settled in towns along the lower Merced River. A railroad was built along the Merced canyon, enabling mining and logging in the upper watershed, and later carrying tourists to Yosemite National Park. Conflicts between settlers and Native Americans resulted in wars, including the expulsion of the Ahwahnechee from Yosemite.
Large-scale irrigation was introduced to the San Joaquin Valley in the late 19th century, and led to the construction of numerous state, federal and privately owned dams, which blocked migrating salmon and caused a large decline in riparian habitat. Diversion of water for irrigation often reduces the river to a small stream by the time it reaches its mouth. Efforts to mitigate environmental damage include habitat conservation work, re-establishment of historic streamflow patterns, and the construction of a salmon hatchery.
Tenaya Lake was named for Chief Tenaya, leader of the Ahwahneechee tribe that originally lived in Yosemite Valley
Of the many Native American tribes that have lived on the Merced River the most prominent were the Miwok (consisting of Plains Miwok and Sierra Miwok), Paiute, and Ahwahnechee. Many Plains Miwok settled in the lowlands along the lower Merced River. The Sierra (or Mountain) Miwok lived in the upper Merced Canyon and in Yosemite Valley, and at the time the first white explorers came to the area, there were about 450 Sierra Miwok split among ten permanent villages.[1][2] Paiute, of origin from the eastern Sierra near the Mono Lake area, also lived in the upper watershed of the Merced River. The Sierra Miwok and Mono Lake Paiute eventually, through cultural interaction over time, formed a new culture, the Ahwahnechee, derived from Ahwahnee, meaning "the valley shaped like a big mouth" (referring to U-shaped Yosemite Valley).[3]
In the early 19th century, several military expeditions sent by Spanish colonists from coastal California traveled into the Central Valley. One of these trips, headed by lieutenant Gabriel Moraga, arrived on the south bank of the Merced River on September 29, 1806. They named the river Rio de Nuestra Señora de la Merced (River of Our Lady of Mercy), who is the patron saint of the diocese of Barcelona and is celebrated on September 24. Another expedition to the Central Valley in 1805 also named the Kings River upon reaching it on January 6, 1805, which is the feast of the Magi or Epiphany.[4] Moraga's expedition was part of a series of exploratory ventures, funded by the Spanish government, to find suitable sites for missions in the Central Valley and the Sierra Nevada foothills. In 1808 and 1810, Moraga led further expeditions along the lower Merced River below Merced Canyon, each time coming to nothing. Eventually, plans to establish a mission chain in the Valley were abandoned. In 1855, Merced County was created, named after the Merced River.[5]
Following the establishment of Merced County and the independence of California from Mexico, many settlers came to the Merced River area and established small towns on the Merced River. One of the first was Dover, established in 1844 at the confluence of the Merced River with the San Joaquin River. Dover functioned as an "inland seaport" where boats delivered supplies from the San Francisco Bay area to settlers in the San Joaquin Valley.[6] Some towns that followed were Hopeton, Snelling and Merced Falls, the latter named for a set of rapids on the Merced River near the present-day site of McSwain Dam. In the late 1880s a flour mill, woolen mill and a few lumber mills were constructed at Merced Falls. The Sugar Pine Lumber Company and Yosemite Lumber Company operated lumber mills at Merced Falls for over thirty years, relying on narrow-gauge railroads to ship lumber from the Sierra Nevada along the Merced River.[7] Following the construction of the Central Pacific and Southern Pacific Railroads, many of the river towns on the Merced River were deserted. Several cities that did achieve prominence, however, include Merced and Turlock, both located on the railroad.[8]
The Merced River, Yosemite, California, by George Henry BurgessThe California Gold Rush in the 1850s saw gradually increasing mining in Merced Canyon and Yosemite Valley. Many Native Americans in the area revolted, leading to conflicts between miners and the Ahwahnechee. In 1851 the Mariposa Battalion was formed to drive the remaining Ahwahnechee out of the valley into reservations. The Battalion fought an Ahwahnechee group led by Chief Tenaya over the South Fork of the Merced River.[9] Eventually, they succeeded in driving most of the Indians out of the Yosemite Valley, first into a reservation near Fresno. Following the gold rush, the Ahwahnechee were allowed back into Yosemite Valley, but further incidents prompted a second battalion to drive them out, this time to the Mono Lake area.[10] Many place names in the valley have their origin from the Mariposa Battalion.
Even before the establishment of Yosemite National Park, tourists began to travel into the Merced Canyon and Yosemite Valley as early as 1855. The first roads were constructed into Yosemite Valley in the 1870s. The first was Coulterville Road, followed by Big Oak Flat Road, a trading route from Stockton to Merced Canyon. Environmental movements led by John Muir and Robert Underwood Johnson convinced the U.S. Congress to establish Yosemite National Park in 1890.[11] With the creation of the national park tourism to the Valley and the Merced River increased significantly, leading to many other roads being built throughout the upper Merced River watershed. Other national forests protecting more of the Merced River upper basin followed, including Sierra National Forest and Stanislaus National Forest.
The Yosemite Valley Railroad, originally established with the discovery of mineral deposits in Yosemite Valley and Merced Canyon, continued functioning through the early 20th century carrying tourists to Yosemite Valley along the Merced River. El Portal Road, constructed through Merced Canyon in 1926, put an end to passenger service on the railway, but operations continued until the mid-1940s, when major flooding occurred, destroying sections of the railroad.[12] In the early 20th century, when the upper Merced River basin lay mostly protected, the lower river was the subject of dam-building and irrigation diversions by the Merced Irrigation District. The District proposed the Exchequer Dam, completed in the mid-1920s and raised in the 1960s, as a water storage facility on the Merced River.[13]
Irrigation with water from the Merced River continued to grow substantially until most of the arable land around the river, some 120,000 acres (490 km2), was under cultivation. By the late 1950s and early 1960s, irrigation in the San Joaquin Valley was to such an extent that many of the rivers ran dry in sections. Upriver of the Merced River confluence with the San Joaquin, the latter river was usually dry, only regaining flow where the Merced River enters. In the mid-20th century, the flow in the Merced River diminished to such a degree that very few salmon returned to spawn in the lower section of the Merced River. In 1991, a fish hatchery, the Merced River Hatchery, was built beside the Merced River just downstream of the Crocker-Huffman Diversion Dam, the lowermost Merced River dam. Fall chinook salmon travel up a fish ladder into the hatchery's pools, which are supplied with water diverted from the Merced River.[14][15]
Yosemite Valley saw significant amounts of damage when the river flooded the valley in 1997.
In 2024 the New York Times reported that farmers and growers had drained significant volumes of water during the 2022 drought leaving part of the Merced dry without authorities being aware.[16]
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