Metropolitan Water District of Southern California

The Metropolitan Water District of Southern California is a regional wholesaler and the largest supplier of treated water in the United States. The name is usually shortened to "Met," "Metropolitan," or "MWD." It is a cooperative of fourteen cities, eleven municipal water districts, and one county water authority, that provides water to 19 million people in a 5,200-square-mile (13,000 km2) service area.

Source: Wikipedia — Metropolitan Water District of Southern California (CC BY-SA 4.0)