Aquifers - Water Education Foundation

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What are aquifers?

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Aquifers are unseen but critical resources in California’s water supply system, acting as natural basins below the surface.

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What percentage of California’s land area has aquifers?

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Aquifers are found underneath 40% of California’s land area.

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What are alluvial aquifers?

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Alluvial aquifers are formed in the space between porous materials like sand, gravel, silt, or clay, and are also known as unconfined aquifers.

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What are confined aquifers?

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Confined aquifers are located beneath a rock layer that does not allow water to permeate in measurable amounts.

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What are artesian aquifers?

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Artesian aquifers are confined aquifers under pressure that can push water to the surface, forming artesian wells when drilled.

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How deep can aquifers be?

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Aquifers can range from several feet deep to several thousand feet deep.

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What is groundwater banking?

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Groundwater banking is the process of storing water in depleted aquifers for future use.

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What percentage of California’s water needs are met by groundwater during normal years?

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About 40% of California’s water needs are met by groundwater during normal years.

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What percentage of California’s water needs are met by groundwater during droughts?

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As much as 60% of California’s water needs are met by groundwater during droughts.

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What is the Sustainable Groundwater Management Act?

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Enacted in 2014, the act requires governments and water agencies to halt overdraft and balance groundwater pumping and recharge.