California Code, Water Code - WAT § 71640

A district may restrict the use of district water during any emergency caused by drought, or other threatened or existing water shortage, and may prohibit the wastage of district water or the use of district water during such periods for any purpose other than household uses or such other restricted uses as the district determines to be necessary. A district may also prohibit use of district water during such periods for specific uses which it finds to be nonessential.