Central Valley is a broad, elongated, flat valley that dominates the interior of California. It is 40–60 mi  wide and runs approximately 450 mi  from north-northwest to south-southeast, inland from and parallel to the Pacific coast of the state. It covers approximately 18,000 sq mi,, about 11% of California’s land area. The valley is bounded by the Coast Ranges to the west and the Sierra Nevada to the east.

It is California’s most productive agricultural region and one of the most productive in the world, providing more than half of the fruits, vegetables, and nuts grown in the United States.[3] More than 7,000,000 acres  of the valley are irrigated via reservoirs and canals. The valley hosts many cities, including the state capital Sacramento; as well as Redding, Chico, Stockton, Modesto, Merced, Fresno, Visalia, and Bakersfield.

The Central Valley watershed comprises 60,000 square miles , or over a third of California. It consists of three main drainage systems: the Sacramento Valley in the north, which receives over 20 inches  of rain annually; the drier San Joaquin Valley in the south; and the Tulare Basin and its semi-arid desert climate at the southernmost end. The Sacramento and San Joaquin river systems drain their respective valleys and meet to form the Sacramento–San Joaquin River Delta, a large expanse of interconnected canals, stream beds, sloughs, marshes and peat islands. The delta empties into the San Francisco Bay, and ultimately into the Pacific. The waters of the Tulare Basin essentially never reach the ocean (with the exception of Kings River waters diverted northward for irrigation), though they are connected by man-made canals to the San Joaquin.