CA Gov't Code Section 54984.2

Any local agency which is authorized by law to provide water, sewer, or water and sewer service, and which is providing either or both of those services within its jurisdiction, may fix, before either (a) August 10 of any given year with respect to local agencies the taxes or assessments of which are collected for the local agency by the county or (b) the start of the fiscal year with respect to local agencies the taxes or assessments of which are collected by the local agency, a water or sewer standby charge, or both, on land within the jurisdiction of the local agency to which water, sewer, or water and sewer services are made available for any purpose by the agency, whether the water or sewer services are actually used or not. The governing body of the agency which fixes the charge may establish schedules varying the charge according to land uses, benefit derived or to be derived from the use or availability of facilities to provide water, sewer, or water and sewer service, or the degree of availability or quantity of the use of the water, sewer, or water and sewer services to the affected lands, and may restrict the assessment to one or more improvement districts or zones of benefit established within the jurisdiction of the agency. The charge may be imposed on an area, frontage, or parcel basis, or a combination thereof.