Arroyo Mocho is a U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data
The National Map
, accessed March 15, 2011 stream which originates in the far northeastern corner of

Santa Clara County Santa Clara County, officially the County of Santa Clara, is the sixth-most populous county in the U.S. state of California, with a population of 1,936,259 as of the 2020 census. Santa Clara County and neighboring San Benito County form the ...

and flows northwesterly into eastern

Alameda County, California Alameda County ( ) is a List of counties in California, county located in the U.S. state of California. As of the 2020 United States census, 2020 census, the population was 1,682,353, making it the 7th-most populous county in the state and List ...

. After traversing the cities of Livermore and Pleasanton it joins South San Ramon Creek to become Arroyo de la Laguna, which in turn flows to

Alameda Creek Alameda Creek () is a large perennial stream in the San Francisco Bay Area. The creek runs for from a lake northeast of Packard Ridge to the eastern shore of San Francisco Bay by way of Niles Canyon and a flood control channel. Along its course, ...

and thence to

San Francisco Bay San Francisco Bay (Chochenyo language, Chochenyo: 'ommu) is a large tidal estuary in the United States, U.S. state of California, and gives its name to the San Francisco Bay Area. It is dominated by the cities of San Francisco, California, San ...

History

Arroyo Mocho means "cutoff creek". Erwin G. Gudde's ''California Place Names'' says it got the name because it historically had no outlet but dissipated into the ground after spreading out into many smaller streams between Livermore and Pleasanton. As early as 1852 it was also called Mocho Creek. Frank Latta, in his book on

Joaquin Murrieta Joaquin Murrieta Carrillo (sometimes misspelled Murieta or Murietta) (c. 1829 – July 25, 1853), also called the Robin Hood of the West or the Robin Hood of El Dorado, was a Mexicans, Mexican figure of disputed historicity. The novel ''The Lif ...

, says it got its name from the nickname of the man who ran the Murrietta gang's water stations and holding corrals in this area along La Vereda del Monte, the route of their drives of captured mustangs and stolen horses to the south. These stations were on the arroyo near Mud Springs and at Valle de Mocho, what is now known as Blackbird Valley, near the source of the arroyo, just south of Mount Mocho, which was also named for this man, known as "Mocho" (meaning lopped off or short) for his diminutive stature.Frank F. Latta, JOAQUIN MURRIETA AND HIS HORSE GANGS, Bear State Books, Santa Cruz, California. 1980.

Watershed and course

The Arroyo Mocho watershed drains . Arroyo Mocho originates on the western slope of Mount Mocho in the far northeast corner of

and flows west to Mines Road which it follows northwest into

Alameda County Alameda County ( ) is a county located in the U.S. state of California. As of the 2020 census, the population was 1,682,353, making it the 7th-most populous county in the state and 21st most populous nationally. The county seat is Oakland. A ...

. It passes rural woodland and grassland along Mines Road. It passes Sweet Springs, a magnesia spring known for its sweet taste. Although historically it sank into the area between Livermore and Pleasanton now the site of multiple gravel pits, there is an engineered channel connecting it to Arroyo de la Laguna. The underlying aquifer is the Mocho Subbasin, whose eastern boundary is the Tesla Fault. Some groundwater flow occurs across this fault boundary, but flows are discontinuous below a depth of across the Tesla Fault and south of the Arroyo Mocho channel across the Livermore Fault. Major watercourses feeding the Arroyo Mocho include the Alamo, Tassajara, Cayetano, Altamont, Arroyo Seco, and Las Positas Creeks.

Ecology and geology

Arroyo Mocho has a self-sustaining

rainbow trout The rainbow trout (''Oncorhynchus mykiss'') is a species of trout native to cold-water tributary, tributaries of the Pacific Ocean in North America and Asia. The steelhead (sometimes called steelhead trout) is an Fish migration#Classification, ...

(''Oncorhynchus mykiss'') population, and trout can migrate to the lower watershed from Alameda Creek. Channels in the Arroyo Mocho watershed are mostly in the forms of arroyos and gullies: characterized as cuts into a broad valley floor, with steep eroding banks. Elevations in the Arroyo Mocho basin are between 60 and 1200 meters; mean annual precipitation is 428 mm on average.

Gallery

File:Arroyo Mocho flooding.jpg, Arroyo Mocho flooding during the 2022–2023 California floods. File:Arroyo Mocho with Pleasanton Ridge and Hangar One Blimp.jpg, Arroyo Mocho at dusk flowing under the El Charro Rd. bridge. Pleasanton Ridge in the background. File:Arroyo-Mocho-watershed-showing-the-six-major-basins-mainstem-channels-and-flood-control.png, Arroyo Mocho watershed; Livermore is near the right of the green area

References

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External links