|Counties||Alameda County & Santa Clara County|
|Cities||Pleasanton & Livermore|
|⁃ location||18 mi (30 km) east of Milpitas|
|⁃ elevation||3,160 ft (960 m)|
|Mouth||Confluence with South San Ramon Creek to form Arroyo de la Laguna|
|315 ft (96 m)|
Arroyo Mocho is a 34.7-mile-long (55.8 km) stream which originates in the far northeastern corner of Santa Clara County and flows northwesterly into eastern Alameda County, California. 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 and thence to San Francisco Bay.
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, 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.:431
Watershed and course
Arroyo Mocho originates on the western slope of 3,684 feet (1,123 m) Mount Mocho in the northeast corner of Santa Clara County and flows west to Mines Road which it follows northwest into Alameda County. 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 50 feet (15 m) across the Tesla Fault and south of the Arroyo Mocho channel across the Livermore Fault.
- U.S. Geological Survey Geographic Names Information System: Arroyo Mocho
- "Mount Mocho". Geographic Names Information System. United States Geological Survey.
- U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data. The National Map Archived 2012-04-05 at WebCite, accessed March 15, 2011
- On Line Map of Arroyo Mocho Watershed
- Erwin G. Gudde; William Bright (2004). California Place Names: The Origin and Etymology of Current Geographical Names. Berkeley, California: University of California Press. p. 241. ISBN 9780520242173.
- U.S. Geological Survey Geographic Names Information System: Mud Springs
- U.S. Geological Survey Geographic Names Information System: Blackbird Valley
- U.S. Geological Survey Geographic Names Information System: Mount Mocho
- Frank F. Latta, JOAQUIN MURRIETA AND HIS HORSE GANGS, Bear State Books, Santa Cruz, California. 1980.
- Page Mosier & Dan Mosier (1986). Alameda County Place Names. Fremont, California: Mines Road Books. p. 86. Retrieved 2013-01-25.
- Environmental Site Screening Analysis, 2127 Railroad Avenue, Livermore, California, Earth Metrics rpt no. 7785, San Mateo, Ca., Feb., 1989
- Andrew J. Gunther; Jeffrey Hagar; Paul Salop (2000-02-07). An Assessment of the Potential for Restoring a Viable Steelhead Trout Population in the Alameda Creek Watershed (PDF) (Report). Alameda Creek Fisheries Restoration Workgroup. p. 90. Retrieved 2013-01-25.