Groundwater Protection

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What is groundwater?

Groundwater is water that exists beneath the Earth's surface. Most groundwater exists and flows within the small openings (pores) between soil and rock particles. Some groundwater may also exist in caverns or fractures within the rock. Either way, groundwater slowly accumulates and generally flows from high to low areas ultimately seeping into rivers, lakes, or the ocean. Groundwater and surface water are inextricably linked by the hydrologic cycle.

Groundwater is found everywhere beneath the ground surface and is especially abundant where soils and sediments occur up to tens, hundreds, or thousands of feet thick. Such areas are called groundwater basins. The permeable and porous soil, sediment, or rock where groundwater accumulates and flows is called an aquifer. Groundwater is tapped through wells placed into an aquifer.

In the San Francisco Bay Region, the most heavily tapped aquifers are found within the groundwater basins of the Santa Clara Valley, the Napa-Sonoma Valleys, the Livermore-Amador Valley, and the Petaluma Valley. Other aquifers are found within the Fairfield-Suisun Valley, the Pittsburg Plain, the East Bay Plain, the San Mateo Plain, the Westside Basin, and the myriad small coastal plains and inter-mountain valleys throughout the Region. In general, groundwater quality throughout the Region is suitable for most urban, domestic, and agricultural uses with only local impairments (DWR Bulletin 118, 2003 update).

The Hydrologic Cycle
The Hydrologic Cycle (DWR Bulletin 118, 2003 Update)

How does groundwater benefit people and the environment?

Groundwater is one of California's greatest natural resources, but because it is not highly visible, it is often taken for granted. Groundwater comprises a major source of California's drinking water supply as well as irrigation water for crops and agriculture.  Groundwater is also used in industry and manufacturing for cooling and rinsing. Consider these facts taken from the California Department of Water Resources bulletin California's Groundwater (Bulletin 118, updated 2003):

In the San Francisco Bay Region, groundwater accounts for about 20 percent of the drinking water supply and 40 percent in the South Bay (California Department of Water Resources California's Groundwater Bulletin 118, updated 2003). Lesser known but equally important is the role groundwater plays in replenishing streams, rivers, and wetlands that support wildlife including threatened and endangered species.  Because groundwater is released slowly, it replenishes streams and creeks and moderates stream temperatures and flows critical for fish spawning and other wildlife habitat.

Why protect groundwater?

Increased reliance on groundwater for drinking and other beneficial uses will be necessary to meet California's future water supply needs. Global warming and the threat of prolonged droughts forecast the need for additional groundwater storage to capture precipitation runoff. At the same time, saltwater intrusion, land subsidence, and groundwater pollution have impacted or impaired portions of some groundwater basins, making their use for drinking water or for additional storage and supply a significant challenge. Such pressures on groundwater resources require that the intimate ties between land use, human activity, water quality and water supplies be acknowledged and managed in order to promote wise, balanced, and sustainable use of groundwater resources.

How does the Water Board protect groundwater?

The California Legislature established the State Water Resources Control Board (State Water Board) and the nine Regional Water Quality Control Boards (Regional Water Boards) in 1949. Operating under the provisions of the California Water Code, their unique relationship couples state-level coordination and regional familiarity with local needs and conditions. Their joint actions constitute a comprehensive program for managing water quality in California, as well as for effective state administration of federal water pollution control laws.

The State Water Board administers water rights, water pollution control, and water quality functions for the state as part of the California Environmental Protection Agency (Cal/EPA). It provides policy guidance and budgetary authority to the Regional Water Boards, which conduct planning, permitting, and enforcement activities. The State Water Board shares authority for implementation of the federal Clean Water Act and the state Porter-Cologne Act with the Regional Water Boards.

The San Francisco Bay Water Board (Water Board) regulates surface water and groundwater quality in the Region. The area under the Water Board's jurisdiction comprises all of the San Francisco Bay segments extending to the mouth of the Sacramento-San Joaquin Delta.

The San Francisco Bay Water Board protects groundwater through implementation of its regulatory and planning programs. The key elements of this approach include:

  • Identify and update beneficial uses and water quality objectives for each groundwater basin
  • Regulate activities that can impact the beneficial uses of groundwater
  • Prevent future groundwater impacts through local and regional planning, management, education, and monitoring

Identify and update beneficial uses and water quality objectives

The Water Board adopts and implements numerical and narrative standards called water quality objectives (WQOs) to protect beneficial uses of groundwater.  For example, if the groundwater is considered adequate for drinking water, then the protection standard (WQO) for any pollutant in the groundwater would be equivalent to or lower than the State's drinking water standard, or maximum contaminant level (MCL) for protection of human health.

If, for example, the groundwater is considered adequate for crop irrigation, industrial processes, or stream replenishment, then the protection standard would be based on pollution limits protective of those uses.  In order to implement appropriate protection standards for groundwater, the Water Board has an ongoing program to identify the actual and likely future groundwater uses and the applicable protection standards for each groundwater basin with our region. This information is then used to update the groundwater beneficial uses and water quality objectives in our Basin Plan.

Regulate activities that can impact the beneficial uses of groundwater

The Water Board implements several programs that regulate the discharge of pollutants to the ground and cleanup pollution within the ground. These programs are aimed at preventing the release of hazardous substances from a variety of facilities such as landfills, waste disposal sites, service stations, refineries, and other industrial facilities. These programs are also aimed at cleaning up spills and leaks that may occur.

These regulatory programs for groundwater protection are distributed within two divisions at the San Francisco Bay Water Board.

Groundwater Programs by Division

Prevent future groundwater impacts through local and regional planning, management, education, and monitoring

In addition to its regulatory programs, the Water Board plays an important role in facilitating and promoting development of groundwater management strategies and implementation of groundwater protection concepts at the local level.  The Water Board accomplishes this through its groundwater committee, triennial basin plan review, stakeholder meetings, and other education and outreach efforts.

Focused ambient groundwater monitoring is also an important part of preventing future impacts because it provides a baseline evaluation of regional groundwater quality. The Groundwater Ambient Monitoring and Assessment (GAMA) program involves sampling community and domestic water supply wells for a variety of historic and emerging pollutants using ultra-low detection limits.  The Water Board uses these data to help prioritize our cleanup work and permitting decisions to ensure that high quality groundwater is protected.

Who else protects drinking water and groundwater resources?

State Water Board: The State Water Board administers water rights, water pollution control, and water quality functions for the state as part of the California Environmental Protection Agency (Cal/EPA). It provides policy guidance and budgetary authority to the Regional Water Boards, which conduct planning, permitting, and enforcement activities. The State Water Board shares authority for implementation of the federal Clean Water Act and the state Porter-Cologne Act with the Regional Water Boards.

California Department of Public Health (DPH): Through their Drinking Water Program, DPH regulates portions of the federal Safe Drinking Water Act to ensure that the drinking water at the well head and the faucet is protective of human health. DPH also implements the California Drinking Water Source Assessment and Protection (DWSAP) Program to provide information to communities that wish to develop local programs to protect their sources of drinking water.

California Department of Water Resources (DWR): DWR manages the large, complex State water distribution infrastructure (dams, aqueducts, canals).

Local Agencies:  Some cities and counties, water districts and water conservation districts have the authority to regulate groundwater. Find these agencies on the web for further information. Some links to our region's local agencies are provided below.