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Groundwater

Groundwater comprises about 20 percent of the Bay Area Region’s water supply. Groundwater is most heavily used in the Santa Clara, Napa-Sonoma, Livermore, and Petaluma Valleys. At the same time, groundwater throughout the Region supports local water supplies.

Aquifer recharge is an important component of sustainable groundwater management. Typically, local agencies use percolation ponds, spreading basins, in-stream recharge, and injection wells to recharge aquifers.

Groundwater in the Region is generally of high quality, but faces numerous threats including, industrial spills, leaking underground storage tanks, improperly maintained septic systems, urban runoff, and inefficient agricultural operations. Degradation of groundwater quality primarily occurs from industrial chemicals and salt from seawater intrusion. Pollution from nutrients (i.e. nitrate) can be significant in localized areas particularly in areas where fertilizer and wastewater discharges predominate.

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Groundwater exists beneath the earth’s surface within the soil and rock pore spaces, fractures, and caverns. As part of the hydrologic cycle, groundwater generally flows with the topography, from high to low areas, and ultimately discharges into rivers, lakes, or the ocean. In this way, groundwater and surface water are essentially one resource. Groundwater and surface water interactions are controlled by their hydraulic communication. Groundwater basins are thick accumulations of soils and sediments that often occur in valleys or other areas between bedrock slopes or ridges. Aquifers are the more permeable soil and rock formations where groundwater yields are higher than surrounding areas. Groundwater for human use is most often tapped by wells installed within an aquifer, or by naturally-occurring springs. For more information visit the following links:

Groundwater basins are thick accumulations of soils and sediments that often occur in valleys or other areas between bedrock slopes or ridges. Aquifers are the more permeable soil and rock formations where groundwater yields are higher than surrounding areas. Groundwater for human use is most often tapped by wells installed within an aquifer, or by naturally-occurring springs. For more information visit the following links:

Existing and potential beneficial uses applicable to groundwater in the Region include municipal and domestic water supply (MUN), industrial water supply (IND), industrial process supply (PRO), agricultural supply (AGR), groundwater recharge (GWR), and freshwater replenishment to surface waters (FRSH). Groundwater also replenishes and moderates the temperatures of streams, rivers, and wetlands supporting wildlife including threatened and endangered species. Unless otherwise designated by the Water Board, all groundwater is considered suitable, or potentially suitable, for municipal or domestic water supply (MUN). In making any exceptions, the Water Board will consider the criteria referenced in State Water Board Resolution No. 88-63 and Water Board Resolution No. 89-39, “Sources of Drinking Water”.
Groundwater
Figure Above: The Hydrologic Cycle

There are 35 groundwater basins in our region as identified in our Basin Plan and DWR’s Bulletin 118, as shown in the table and figure below.

Regional Water Board staff have compiled fact sheets for groundwater basins in the San Francisco Bay Region which summarize use, quality, recharge, and management. Contact WB-RB2-SustainableGroundwater@waterboards.ca.gov for electronic copies of these fact sheets or for general inquiries about sustainable groundwater management in the Region.

For more information about groundwater basins in the San Francisco Bay Region, visit: DWR Bulletin 118 Basin Descriptions

Groundwater

We use these tools to monitor and assess groundwater related information in support of our groundwater programs:

GeoTracker
Groundwater Ambient Monitoring and Assessment (GAMA)

Groundwater

Contacts

Have a program-specific question? Ask the program. Contact information is available on the program's website (accessible through the "Regulate", “Plan and Coordinate”, and “Monitor and Assess” tabs).