The Mocho Subbasin is the largest of the
groundwater subbasins in the
Livermore Valley watershed
Watershed is a hydrological term, which has been adopted in other fields in a more or less figurative sense. It may refer to:
Hydrology
* Drainage divide, the line that separates neighbouring drainage basins
* Drainage basin, called a "watershe ...
in
Northern California
Northern California (colloquially known as NorCal) is a geographic and cultural region that generally comprises the northern portion of the U.S. state of California. Spanning the state's northernmost 48 counties, its main population centers incl ...
. 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. Surface
watercourses in this unit include
Arroyo Valle and
Arroyo Seco.
Aquifer details
To the north, the Tiago Macheira Subbasin contacts the
Tassajara Formation
The Tassajara Formation is a geologic unit within the Livermore Valley of Northern California, United States. The formation surfaces only in the northern upland parts of the Livermore Valley and underlie the central part of the valley floor at a ...
, 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 of the surface, while deeper confined water has levels that occur at various depths from to below the surface.
Groundwater quality
Water quality in the subbasin is generally fair with regard to
sodium bicarbonate
Sodium bicarbonate (IUPAC name: sodium hydrogencarbonate), commonly known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cation ( Na+) and a bicarbonate anion ( HCO3−) ...
and
magnesium bicarbonate, However, the trend in adverse water quality due to
total dissolved solids indicates un
potable conditions may exist as early as 2020 due to
overpopulation of the Livermore-Amador Valley by humans and associated discharge of salts to the groundwater.
Geology
This subbasin is in the vicinity of the seismically active
Greenville Fault The Clayton-Marsh Creek-Greenville Fault is a fault located in the eastern San Francisco Bay Area of California, in Alameda County and Contra Costa County. It is part of the somewhat parallel system of faults that are secondary to the San Andreas ...
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.
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
Hacienda Business Park is a 900-acre (364 hectare) mixed-use job center and housing development in Pleasanton, California.
History
Approved in 1982 and ratified by Pleasanton voters in 1983, the business park covers approximately 20 square blocks ...
*
Niles Cone - groundwater basin in Alameda County.
*
Bernal Subbasin - aquifer in the Livermore Valley.
External links
Groundwater bulletinCalifornia Dept. of Water Resources website
References
Aquifers in California
Bodies of water of Alameda County, California
Livermore, California
Livermore Valley
Geology of Alameda County, California
{{AlamedaCountyCA-geo-stub