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Groundwater Data & Monitoring

North Central Region
Groundwater Quality Monitoring

California's future depends on protecting groundwater quality. Groundwater with poor quality may not be a useable resource.

Some groundwater basins bordering the San Francisco Bay and the Delta have experienced saline water intrusion due to over-extraction of groundwater. In a few places in the Sacramento Valley, shallow salt water makes the groundwater unusable. In other areas, elevated levels of naturally occurring boron restrict the type of crops that can be irrigated with groundwater. In some areas, nitrates and other introduced chemicals make the groundwater unfit for domestic use.

DWR's Central District monitors groundwater quality in about 400 wells in Central California to identify areas of poor quality and to track changes in overall groundwater quality. Groundwater quality analyses typically include field measurements (temperature, pH, conductivity), minerals (calcium, magnesium, chloride, etc.) nutrients (phosphorus, nitrate, etc.), minor elements (arsenic, cadmium, iron, etc.), organic compounds (pesticides, petroleum derivatives, etc.), and pathogens (bacteria). The District's groundwater quality data extends back to the early 1950's.

The DWR water quality data can be accessed from the Water Data Library (WDL).