Groundwater is an important source of water stored in the earth beneath our feet, in spaces between sand, soils, and fractured rock known as an aquifer. Layers of aquifers make up a groundwater basin. California’s 515 alluvial groundwater subbasins contribute approximately 40% of the State’s total water in wet years and up to 60% during dry years. Groundwater serves as a critical buffer against the impacts of drought and climate change. Many municipal, agricultural, and disadvantaged communities rely on groundwater for up to 100 percent of their water supply needs. 

We mostly access groundwater through wells and pumps, and it is a crucial buffer against drought when surface water levels, like that inlakes and reservoirs, are running low. When groundwater is extracted in excess of what nature or manmade recharge efforts can replenish, groundwater elevations drop.

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