California Code, Water Code - WAT § 10753

(a) Any local agency, whose service area includes a groundwater basin, or a portion of a groundwater basin, that is not subject to groundwater management pursuant to other provisions of law or a court order, judgment, or decree, may, by ordinance, or by resolution if the local agency is not authorized to act by ordinance, adopt and implement a groundwater management plan pursuant to this part within all or a portion of its service area.

(b) Notwithstanding subdivision (a), a local public agency, other than an agency defined in subdivision (g) of Section 10752, that provides flood control, groundwater management, or groundwater replenishment, or a local agency formed pursuant to this code for the principal purpose of providing water service that has not yet provided that service, may exercise the authority of this part within a groundwater basin that is located within its boundaries within areas that are either of the following:

(c) Except as provided in subdivision (b), this chapter does not authorize a local agency to manage groundwater planning within the service area of another local agency.

(d) Except as otherwise provided in this part, the process for developing and adopting a revised groundwater management plan shall be the same as the process for developing and adopting a new groundwater management plan.