river in central California, U.S. It is formed by forks rising on Mount Goddard in the Sierra Nevada and flows southwest and then north-northwest past Stockton to join the Sacramento River above Suisun Bay after a course of 350 miles (560 km). It is dammed for hydroelectric power (impounded thereby are Florence, Shaver, and Huntington lakes). The river drains the northern half of the San Joaquin Valley, itself the southern part of the Central Valley and one of the most productive agricultural regions in the United States. Several national wildlife refuges are located in the river's wetlands.