The Bay Area water system is a byzantine patchwork of agencies -- more than 50 in all -- that provides water to customers. Some are the ones you see on your water bill. Others are middlemen that provide water to local agencies at the the wholesale level.

And some of that water makes a long journey. Southern California has the reputation for tapping far-flung sources for its water needs, but the Bay Area is in the same boat.

More than two-thirds of the Bay Area's water supply comes from outside the region, which means in extreme drought years like this one, local water districts are competing with many others around the state for limited supplies.



Bay Area Water Districts by Major Source of Supply







Hetch Hetchy Water System

The system originates more than 100 miles from its primary customers, in Yosemite National Park. O’Shaughnessy Dam was built on the Tuolumne River in 1923 to create Hetch Hetchy Reservoir. The water travels through a series of pipelines before it reaches the Bay Area and blends with five local reservoirs. The Tuolumne River joins the San Joaquin River and flows into the Delta.