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GROUNDWATER RESOURCES

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Groundwater Issue: Groundwater Quality

California depends heavily on groundwater to meet its water supply needs, using more groundwater than any other state. During a typical year, approximately 40 percent of the state's total water supply comes from groundwater. During dry years, groundwater contributes up to 60 percent (or more) of the state's total supply, and serves as a critical buffer against the impacts of drought and climate change. Approximately 31 million Californians obtain their drinking water from a public water system that relies on groundwater for at least part of the drinking water supply. Additionally, two million Californians are served by private domestic wells or small water systems. However, because groundwater is not easily visible, it is often taken for granted, putting important drinking water and irrigation sources at risk of contamination (by both naturally-occurring and man-made contaminants).

The Water Boards protect, monitor, and restore groundwater quality through a number of programs and actions, including:

  • GROUNDWATER QUALITY MONITORING – The Groundwater Ambient Monitoring and Assessment Program (GAMA) is California's comprehensive groundwater quality monitoring program, providing public access to groundwater quality data through GeoTracker GAMA. GAMA projects include the Priority Basin ProjectDomestic Well Project, and Special Studies ProjectMore information...
  • OIL AND GAS – The Oil and Gas Monitoring Unit monitors groundwater in oil and gas production areas to protect groundwater for all beneficial uses, including drinking water. More information...
  • ANTIDEGRADATION POLICY – The State Water Board is reviewing the Antidegradation Policy to improve the policy’s application to regulating discharges that affect groundwater. More information...
  • DRINKING WATER – The Communities that Rely on a Contaminated Groundwater Source for Drinking Water Report (released in 2013) identifies communities that rely on contaminated groundwater as a primary source for their drinking water, groundwater sources for these communities, principal contaminants and concentrations, and potential solutions and funding to clean up or treat groundwater (or provide alternative water supplies). More information...
  • NITRATE POLLUTIONNitrate pollution in groundwater is a widespread water quality problem that can pose serious health risks. Nitrate contaminated groundwater can be found in many areas of California, but is a particularly significant concern in the Tulare Lake Basin and Salina Valley areas. More information...
  • DOMESTIC WELLS – Learn about private domestic well water quality and how to take care of it by following the steps in the Well Owner Guide. More information...
  • DRINKING WATER QUALITY MONITORING – The Division of Drinking Water (DDW) provides information on reporting drinking water analytical data, monitoring schedules for public water systems, and accessing the drinking water quality monitoring database. More information...
  • DRINKING WATER – DDW provides information on chemicals and contaminants pertinent to drinking water and groundwater sources. More information...

Want More Information?

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