Does the Colorado River supply most of Southern California’s water?

The Colorado River accounts for approximately one-third of Southern California’s water supply, while the rest comes from Northern California and local sources. 

Most of what California draws from the Colorado River goes to crop irrigation. Drinking water is managed by the Metropolitan Water District of Southern California, which brings water from the Colorado River through the Colorado River Aqueduct. The district serves about 18 million people, including Los Angeles and San Diego counties. 

The Colorado River Compact, a 1922 agreement that allocated the river’s water, lets California draw up to 4.4 million acre-feet per year. Colorado was allocated up to 3.85 million acre-feet. In all, the U.S. can draw up to 15 million acre-feet, and Mexico up to 1.5 million acre-feet. 

However, these allocations exceed the current annual water supply partly due to years of drought in the West. That means parties to the agreement receive less than their full allocation.