Arroyo Mocho

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Arroyo Mocho
Country United States
State California
Regions Alameda County, Santa Clara County
Cities Pleasanton, Livermore
Source Mount Mocho[1]
 - location 18 mi (30 km) east of Milpitas
 - elevation 3,160 ft (963 m)
 - coordinates 37°27′13″N 121°31′22″W / 37.45361°N 121.52278°W / 37.45361; -121.52278 [2]
Mouth Confluence with South San Ramon Creek to form Arroyo de la Laguna
 - location Pleasanton, California
 - elevation 315 ft (96 m) [2]
 - coordinates 37°40′37″N 121°54′44″W / 37.67694°N 121.91222°W / 37.67694; -121.91222Coordinates: 37°40′37″N 121°54′44″W / 37.67694°N 121.91222°W / 37.67694; -121.91222 [2]

Arroyo Mocho is a 34.7-mile-long (55.8 km)[3] 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.[4]


Arroyo Mocho means "cutoff creek" 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.[5]

Watershed and Course[edit]

Arroyo Mocho originates on the western slope of 3,684 feet (1,123 m) Mount Mocho[1][5] 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.[6] 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.[4]

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.[7]


Arroyo Mocho has a self-sustaining Rainbow trout (Oncorhynchus mykiss) population, and trout can migrate to the lower watershed from Alameda Creek.[8]

See also[edit]


  1. ^ a b "Mount Mocho". Geographic Names Information System. United States Geological Survey. 
  2. ^ a b c U.S. Geological Survey Geographic Names Information System: Arroyo Mocho
  3. ^ U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data. The National Map, accessed March 15, 2011
  4. ^ a b On Line Map of Arroyo Mocho Watershed
  5. ^ a b 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. 
  6. ^ Page Mosier and Dan Mosier (1986). Alameda County Place Names. Fremont, California: Mines Road Books. p. 86. Retrieved 201-01-23.  Check date values in: |accessdate= (help)
  7. ^ Environmental Site Screening Analysis, 2127 Railroad Avenue, Livermore, California, Earth Metrics rpt no. 7785, San Mateo, Ca., Feb., 1989
  8. ^ 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 201-01-23.  Check date values in: |accessdate= (help)

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