This page last updated on 4/1/2020. Groundwater in California has received a lot of attention lately, and for good reason:  We use a lot of it.  So much so, California’s groundwater is use is the largest in the United States, with approximately 16% of the nation’s groundwater supplies being extracted from the state’s aquifers. Groundwater is often described as a ‘hidden resource’; because it cannot be directly seen, it is likely most Californians do not give much thought to the … Continue reading California’s groundwater