where do most cities get their water supply
Drinking water supply and sanitation in the United States The centralized drinking water supply infrastructure in the United States consists of dams and reservoirs, well fields, pumping stations, aqueducts for the transport of large quantities of water over long distances, water treatment plants, reservoirs in the distribution system (including water towers), and 1.8 million miles of distribution lines.[5]:14 Depending on the location and quality of the water source, all or some of these elements may be present in a particular water supply system. In addition to this infrastructure for centralized network distribution, 14.5% of Americans rely on their own water sources, usually wells.[11][12]
Water in California Water use in California is divided into approximately 51% for environmental uses, 39% agricultural use and 11% urban uses, though that varies considerably between regions and between wet and dry years.[20] Solely relying on these statewide volumes is controversial because they don't consider the fact that most of the volume of water used for environmental purposes includes flows down Wild and Scenic Rivers in the North Coast where there is no practical way to recover it for either agricultural or urban use because it lacks many connections to the statewide water supply system.[21] It also doesn't factor in the amount of water required to keep salty water from the Pacific Ocean from intruding into the Delta beyond a certain small concentration.[21] Otherwise, "reduced water quality resulting from large amounts of salt water drawn into the Delta could shut down the export pumps that supply fresh water to agriculture and cities."[22][23]