Cal. Pub. Util. Code § 10153

There is granted to every municipal corporation of the State the right to take, in the manner provided by law, any waters belonging to the State, not otherwise disposed of, flowing or existing in any stream or lake intersected, crossed, or tapped by its water works, so far as is necessary to give such municipality and its inhabitants an ample supply of water for all municipal, domestic, irrigation, and manufacturing purposes.