The Mokelumne River ( or ; Mokelumne, Miwok for "People of the Fish Net") is a river in northern California in the United States. The river flows west from a rugged portion of the central Sierra Nevada into the Central Valley and ultimately the Sacramento–San Joaquin River Delta, where it empties into the San Joaquin River-Stockton Deepwater Shipping Channel. Together with its main tributary, the Cosumnes River, the Mokelumne drains in parts of five California counties. Measured to its farthest source at the head of the North Fork, the river stretches for .
The river is colloquially divided into the Upper Mokelumne River, which stretches from the headwaters to Pardee Reservoir in the Sierra foothills, and the Lower Mokelumne River, which refers to the portion of the river below Camanche Dam. In its lower course, the Mokelumne is used heavily for irrigation and also provides water for the east San Francisco Bay Area through the Mokelumne Aqueduct. Several major tributaries of the river have been developed for the generation of hydroelectric power.
The name is Plains Miwok and is constructed from moke, meaning fishnet, and -umne, a suffix meaning "people of".Bright, William (1998). 1500 California Place Names: their origin and meaning. University of California Press; Berkeley, California, 1998. . The town of Mokelumne Hill was named for the river in about 1850.
Course
The Mokelumne is formed by the confluence of several forks that rise in the central Sierra Nevada in the Stanislaus National Forest. The North Fork is the largest, originating at Lower Highland Lake at an elevation of . From its source it flows north then west for to Salt Springs Reservoir. Below Salt Springs it receives the Bear River from the north and then passes through the smaller Tiger Creek Reservoir before joining with the Middle Fork southeast of Pine Grove. The lower portion of the North Fork defines the border between Amador and Calaveras Counties.
The Middle Fork rises at on the west side of Bailey Ridge, near Ganns. It flows generally west, past Wilseyville and West Point, to its confluence with the North Fork. The South Fork begins at an elevation of very near the head of the Middle Fork, and flows west , roughly parallel and south of the Middle Fork, to join the Middle Fork about above the confluence of the North and Middle Forks.
The confluence of the North and Middle Forks forms the Mokelumne River proper. The main stem flows west-southwest past Mokelumne Hill into Pardee Reservoir, formed by the Pardee Dam. Below Pardee the river flows directly into Camanche Reservoir, formed by Camanche Dam. The entire stretch of the Mokelumne between the forks and a point just above Camanche Dam defines the Amador—Calaveras county line; below here, it flows westwards into San Joaquin County.
The Camanche Dam is the first non-passable barrier for anadromous fish. Below Camanche Dam the Mokelumne meanders to its confluence with the San Joaquin River, first continuing southwest out of the Sierra foothills past Lockeford and then turning northwest at Lodi, where the small Woodbridge Dam impounds the river, forming Lodi Lake. The river receives Dry Creek from the east near Thornton and shortly afterwards receives its major tributary, the Cosumnes River, from the northeast. At this point, the river has reached its northernmost point about south of Sacramento.
The river continues west then south into the Sacramento–San Joaquin River Delta where it becomes tidal and splits into a pair of distributaries, the North and South Mokelumne River (not to be confused with the North and South Forks in the Mokelumne headwaters) which together encircle the of Staten Island. About downstream the branches rejoin, and two miles (3.2 km) below this point the Mokelumne flows into the San Joaquin River.
Watershed
The Mokelumne River watershed drains in parts of Alpine, Amador, Calaveras, San Joaquin, and Sacramento Counties. Elevations range from sea level at the confluence with the San Joaquin River to at the crest of the Sierra Nevada in the headwaters of the North Fork.
The Mokelumne watershed divide borders the basins of the American River on the north, the Calaveras and Stanislaus rivers to the south, and the Carson River to the east. The American, Calaveras and Stanislaus rivers, like the Mokelumne, drain westwards into the Central Valley, while the Carson flows eastwards into the Great Basin. Drainage within the Mokelumne watershed generally occurs from east to west with all of the perennial streams originating in the Sierra Nevada.
The Mokelumne River and its headwater forks above Lodi drain the southernmost part of the basin. The part of the basin above Pardee Dam is referred to as the Upper Mokelumne River Basin and drains about , or 25.7% of the total watershed. The Cosumnes River and its own North, Middle and South forks drain about in the northern part of the basin, or about 33.8% of the total watershed. Dry Creek, which itself is formed by four Sierra streams – Jackson, Sutter, Amador and Rancheria Creeks – drains most of the area between the upper Mokelumne and Cosumnes basins, or about .<ref></ref</ref>
The upper watershed is situated principally in Alpine, Amador and Calaveras Counties and consists mostly of wilderness managed under various federal designations. Most of the Mokelumne and Cosumnes River headwaters lie within the Stanislaus and Eldorado National Forests. Much of the upper watershed is also protected under the Mokelumne Wilderness. The Salt Springs State Game Refuge is located along the Mokelumne River near Salt Springs Reservoir. There are also significant private holdings in the upper basin including commercial timber land and protected watershed areas administered by the East Bay Municipal Utility District, which diverts urban and industrial water from Pardee Reservoir.
The lower watershed, mainly within San Joaquin and Sacramento Counties, is part of the rich agricultural region of the Central Valley. Grapes are the major crop grown in the Mokelumne River watershed; as of 2001, vineyards comprised 51% of the basin's farmland. Of the remaining land, 31% is used for livestock, 9% for orchards, and 8% for annual crops. About in the lower basin are part of the Mokelumne River AVA.
In May 2021, it was reported that a trove of 5- to 10-million-year-old fossils was unearthed in June 2020 in the Mokelumne River watershed near Valley Springs, California, including a two-tusked mastodon, a four-tusked gomphothere, rhinoceros, camel, horse, tortoise, tapir, bird, fish, and other specimens.
History
The Mokelumne River basin was originally inhabited by Yokuts, Miwok, and Wintun Native American people. The lower (western) basin was the most densely populated, with numerous villages between the fringe of the Sierra foothills and the eastern edge of the Sacramento–San Joaquin Delta. This area is believed to have been predominantly Plains Miwok; various subgroups that lived in the Mokelumne River basin included the Mokellos, Lalas, and Machacos. The Miwoks called the river Wakalumitch, possibly meaning "big river".
The first European parties to explore the river were likely Spanish military expeditions in Alta California in the late 18th or early 19th century. The name Mokelumne was first recorded by Spanish missionary Narciso Durán as Muquelumnes in 1817. However it was not until 1830 when the first permanent European settlement was established on the Mokelumne River, at Happy Valley near present-day Mokelumne Hill, as an outpost for French fur trappers. John C. Frémont is credited with establishing the modern spelling of the name Mokelumne circa 1844.
During the California Gold Rush, the Mokelumne was a major gold-producing stream. The first person to discover gold in the Mokelumne was likely Charles Weber in 1848. Weber did not stay in the area for long; he moved on to the Coloma diggings on the South Fork American River before establishing a supply center at present-day Stockton, several miles south of the Mokelumne River. Most of the Gold Rush profits and trade on the Mokelumne River would end up passing through Stockton. Also in 1848, Samuel W. Pearsall found gold at Mokelumne Hill, which by 1850 grew into a boomtown of 15,000 people.
Recreational uses
The Mokelumne River is home to five notable whitewater kayaking runs: Fantasy Falls, Devil's Nose, Tiger Creek Dam, Ponderosa and Electra-Middle Bar. Fantasy Falls, a Class V+, 26-mile wilderness reach, runs from below Highway 4 in Alpine County to the backwaters of Salt Springs Reservoir. Devil's Nose, Class IV-V, runs 17 miles from Salt Springs Dams to Tiger Creek Powerhouse. Below Tiger Creek Dam is the Tiger Creek Dam Whitewater run, a scenic, 3 mile Class IV run. The Ponderosa run goes from Ponderosa Way to Electra Powerhouse. The westernmost run is Electra-Middle Bar, a 5+-mile Class II-III run. It begins just below the Electra Powerhouse, passes under Highway 49 south of Jackson, CA and ends at the Middle Bar Bridge.
The Mokelumne is also a popular site for fishing, camping, water play, birding, picnics, gold panning, spring wildflower watching, and other activities. Electra Road, just east of Highway 49, is a popular place to run, walk, and enjoy the river. The large granite domes, Calaveras Dome and Hammer Dome, near Salt Springs Reservoir, are popular for technical rock climbing. Three campgrounds are also located near Salt Springs: Mokelumne River, White Azalea, and Moore Creek.
Downstream, the river is also a popular recreational destination, particularly the day-use area at the base of the Camanche Dam, which includes the Mokelumne River Fish Hatchery, and Lodi Lake, a city park in the small town of Lodi.
The California Office of Environmental Health Hazard Assessment (OEHHA) has developed a safe eating advisory for Lower Mokelumne River based on levels of mercury or PCBs found in fish caught from this water body.
River modifications The first diversions of the Mokelumne were made during the California Gold Rush in the mid-1850s to provide water for placer and hydraulic mining. The first irrigation scheme was organized by a local collective, the Mokelumne Ditch and Irrigation Company, in 1875, but their dam was demolished by a flood and never rebuilt. The Woodbridge Canal and Irrigation Company was founded in 1891, and was somewhat more successful at tapping Mokelumne River water, but they were still hampered by damaging spring floods and lack of water in the dry season.
In 1929 the East Bay Municipal Utilities District (EBMUD) built the large Pardee Dam several miles upstream from Lodi and the irrigation diversion points on the Mokelumne River. Pardee is the primary storage facility and diversion point for the Mokelumne Aqueduct, which provides water to 35 municipalities in the eastern San Francisco Bay Area in Alameda and Contra Costa Counties. The first water deliveries to the Bay Area were made on June 23, 1929. The dam can store about which is slightly over one quarter of the Mokelumne's annual flow. Through an agreement between EBMUD and local farmers, Pardee also stabilized the dry season water level in the lower Mokelumne, allowing much greater use of the river for agriculture.
As early as 1897, the Mokelumne was utilized for the generation of hydroelectric power at the Blue Lakes powerhouse, near Jackson, to provide power for local communities. Pacific Gas and Electric (PG&E) began to develop the river for hydroelectricity in the late 1800s. In 1925, the Mokelumne hydroelectric project was licensed, and its major dam, Salt Springs, was completed on the North Fork of the Mokelumne in 1931. The project also includes two dams on the Bear River, the Tiger Creek Dam, and several smaller reservoirs in the Mokelumne headwaters. The project can provide a maximum output of 206 megawatts of electricity from four powerhouses.