Its construction authorized by the Rivers and Harbors Act of 1937, the massive Central Valley Project (CVP) encompasses 20 reservoirs with a combined storage capacity of 11 million acre-feet, eight power plants, two pumping-generating plants and some 500 miles of major canals and aqueducts. In a normal year, the CVP delivers 7 million acre-feet of water to about 3 million acres of farmland in the Central Valley.
About 30 percent of California’s total annual water supply comes from groundwater in normal years, and up to 60 percent in drought years. Local communities’ usage may be different; many areas rely exclusively on groundwater while others use only surface water supplies. Contrary to popular opinion, groundwater does not exist in underground lakes. Groundwater fills pores (spaces) between sand, gravel, silt and clay in water-bearing formations known as aquifers.