Cal. Gov't Code § 65352.5
(c) Upon receiving, pursuant to Section 65352, notification of a city’s or a county’s proposed action to adopt or substantially amend a general plan, a public water system, as defined in Section 116275 of the Health and Safety Code, with 3,000 or more service connections, shall provide the planning agency with the following information, as is appropriate and relevant:
(7) A description of the total number of customers currently served by the water supplier, as identified by the following categories and by the amount of water served to each category:
(d) Upon receiving, pursuant to Section 65352, notification of a city’s or a county’s proposed action to adopt or substantially amend a general plan, a groundwater sustainability agency, as defined in Section 10721 of the Water Code, or an entity that submits an alternative under Section 10733.6 of the Water Code shall provide the planning agency with the following information, as is appropriate and relevant: