City of Los Angeles v. City of Glendale

Between bedrock and the surface soil and sand, on the floor of the San Fernando Valley, there is a layer of gravel and rocks into which most of the water reaching the floor of the valley sinks. As a result, the subsurface of the valley holds a large mass of water that fills the interstices between the rocks and flows toward the lower end of the valley, eventually rising to become part of the surface flow of the Los Angeles River. This water has four sources: (1) the waters normally present in the valley; (2) the flood waters of Pacoima Creek and Tujunga Creek, which formerly flowed violently…