View source for Mocho Subbasin

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The '''Mocho Subbasin''' is the largest of the [[groundwater]] subbasins in the [[Drainage basin|watershed]] of the [[Livermore Valley]] in [[Northern California]].  This subbasin is bounded to the west by the [[Livermore Fault]] Zone and to the east by the [[Tesla Fault]].  Some groundwater flow occurs across these fault boundaries, but flows are discontinuous below a depth of fifty feet across the Tesla Fault and south of the [[Arroyo Mocho]] channel across the Livermore Fault.<ref>''Environmental Screening Analysis, 2127 Railroad Avenue, Livermore, California'', Earth Metrics rpt no. 7785, San Mateo, Ca., Feb., 1989</ref>  Surface [[watercourse]]s in this unit include [[Arroyo Valle]] and [[Arroyo Seco (Alameda County)|Arroyo Seco]].

==Aquifer details==
To the north, the Tiago Macheira Subbasin contacts the [[Tassajara Formation]], with which no groundwater exchange occurs.  Groundwater flow in the subbasin is generally from southeast toward the northwest or north, corresponding to the slope of the regional terrain and [[water table]] surface.  Uncontained shallow groundwater occurs within {{convert|25|ft|m|0}} of the surface, while deeper confined water has levels that occur at various depths from {{convert|75|ft|m|-1}} to {{convert|150|ft|m|-1}} below the surface.

==Groundwater quality==
[[Water quality]] in the subbasin is generally fair with regard to [[sodium bicarbonate]] and [[magnesium bicarbonate]],<ref>State of California Department of Water Resources, 1974</ref> However, the trend in adverse water quality due to [[total dissolved solids]] indicates un[[drinking water|potable]] conditions may exist as early as 2020 due to [[Human overpopulation|overpopulation]] of the Livermore-Amador Valley by humans and associated discharge of salts to the groundwater.<ref>[https://web.archive.org/web/20040617161532/http://bonniebros.com/lhs/english/RO-word.pdf] Thomas L. Bonnie, ‘'What are the projected impacts of injecting reclaimed, [[reverse osmosis]] water into the Livermore-Amador Groundwater Basin?'‘ (2000)</ref>

==Geology==
This subbasin is in the vicinity of the seismically active [[Greenville Fault]] associated with the [[Diablo Range]].  In fact the name of the second segment of the Greenville Fault (starting from north to south) is the '''Arroyo Mocho Segment'''.<ref>{{Cite web |url=http://gldims.cr.usgs.gov/webapps/cfusion/Sites/qfault/qf_web_disp.cfm?disp_cd=P&qfault_or=1303&ims_cf_cd=cf |title=W.A.Bryant: Description of the Greenville Fault |access-date=2007-02-11 |archive-url=https://web.archive.org/web/20110721070305/http://gldims.cr.usgs.gov/webapps/cfusion/Sites/qfault/qf_web_disp.cfm?disp_cd=P&qfault_or=1303&ims_cf_cd=cf |archive-date=2011-07-21 |url-status=dead }}</ref>  The Arroyo Mocho Segment is  generally considered to be more well developed and not as youthful as traces delineating the Marsh Creek-Greenville Segment, for example.

==See also==
*[[Bishop Subbasin]]
*[[Hacienda Business Park]]
*[[Niles Cone]] - groundwater basin in Alameda County.
*[[Bernal Subbasin]] - aquifer in the Livermore Valley.

==External links==
* [http://www.water.ca.gov/pubs/groundwater/bulletin_118/basindescriptions/2-10.pdf Groundwater bulletin]
* [http://www.water.ca.gov/ California Dept. of Water Resources website]

== References==
{{reflist}}

{{Livermore, California}}
{{Alameda County, California topics}}

[[Category:Aquifers in California]]
[[Category:Bodies of water of Alameda County, California]]
[[Category:Livermore, California]]
[[Category:Livermore Valley]]
[[Category:Geology of Alameda County, California]]


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