The Bernal Subbasin is an

aquifer An aquifer is an underground layer of water-bearing, permeable rock, rock fractures, or unconsolidated materials ( gravel, sand, or silt). Groundwater from aquifers can be extracted using a water well. Aquifers vary greatly in their characteris ...

located in the southwestern corner of Livermore Valley Groundwater Basin,

Alameda County, California 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. Alam ...

, United States. All of the groundwater in

Livermore Valley The Livermore Valley, historically known as the Valle de San José (Valley of San José), is a valley in Alameda County, California, located in the East Bay region. The city of Livermore is located in the valley. Geography The valley is bound ...

moves toward the Bernal Subbasin, which is bounded on the east by Pleasanton Fault, on the north by the Park Fault, and on the west by the

Calaveras Fault The Calaveras Fault is a major branch of the San Andreas Fault System that is located in northern California in the San Francisco Bay Area. Activity on the different segments of the fault includes moderate and large earthquakes as well as aseismi ...

.(Earth Metrics, 1989) All the streams draining the Livermore Valley merge above the Bernal formation and exit this subbasin and Livermore Amador Valley via the Arroyo de la Laguna.

Groundwater Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidated ...

occurs throughout the valley floor portion of the Bernal Subbasin under conditions ranging from unconfined to confined. There is no inflow of groundwater across the Pleasanton Fault south of the City of Pleasanton, because any movement of groundwater in the southern section is essentially parallel to the fault.(Bonnie, 2000) Groundwater in the Bernal Subbasin typically occurs at an approximate depths of 12 to 30 feet (3.7 to 9.1 meters) below ground surface and flows from east to west.

Notes

* Bonnie, Thomas L.
''Projected impacts of injecting reclaimed, reverse osmosis water into the Livermore-Amador Groundwater Basin ''
(2000) * Earth Metrics Incorporated, '' Phase I Environmental Site Assessment, Hopyard Village Shopping Center, Pleasanton, California '', Report 7952W0.00, May 24, 1989
Evaluation of Groundwater Resources, Livermore and Sunol Valley, 1974

Notes

See also