Konikow, L.F., 2013, Groundwater depletion in the United States (1900−2008): U.S. Geological Survey Scientific Investigations Report 2013−5079, 63 pages.
California grows a third of America’s food, so what happens here affects everyone.
California lost nearly 145 cubic kilometers of groundwater since 1880, with a fifth of that water disappearing in just 9 years from 2000 to 2008 (31.4 km3).
In parts of the San Joaquin Valley and Tulare Basin, water levels had declined nearly 400 feet, depleting groundwater from storage and lowering water levels to as much as 100 feet below sea level. Long-term water-level records in some wells indicate that water levels were already declining at substantial rates when water levels were first observed as early as the 1930s. The extensive groundwater pumping caused changes to the groundwater flow system, changes in water levels, changes in aquifer storage, and widespread land subsidence in the San Joaquin Valley, which began in the 1920s.
The thickness of sediments comprising the freshwater parts of the aquifer averages about 3000 feet in the San Joaquin Valley and 1500 feet in the Sacramento Valley. The shallow part of the aquifer system is unconfined, whereas the deeper part is semi-confined or confined.