Cal. Wat. Code § 31032
In case any water standby charge remains unpaid on the first day of the month before the month in which the board of supervisors of the county in which the district or any part thereof is located is required by law to levy the amount of taxes required for county purposes, a 6 percent penalty thereon shall accrue. The amount of the unpaid standby charge plus the said penalty shall be added to and become a part of the annual tax levied upon the land to which water for which the standby charge is unpaid was available and same shall constitute a lien on that land.
If a district collects taxes pursuant to Chapter 2 (commencing with Section 31700) of Part 7 of this division, the amount of tax attributable to unpaid water standby charges, and the penalty thereon, shall be stated on the tax bill separately from all other taxes.
If a district collects taxes pursuant to Chapter 3 (commencing with Section 31730) of Part 7 of this division, it shall provide each person whose property is subject to taxation for unpaid water standby charges, and the penalty thereon, with a tax bill stating the amount of such charges and penalty separately.
In such case and at least fifteen (15) days before the first day of the month in which said board of supervisors is required by law to levy the amount of taxes required for county purposes, the board of directors of the district shall furnish in writing to the board of supervisors and to the county auditor, respectively, a description of each and every parcel of land within the district upon which a standby charge remains unpaid, together with the amount of said unpaid charge plus said penalty on each said parcel of land. Whenever land in two or more counties is included in a district, the board of directors of the district shall furnish in writing to the board of supervisors and to the county auditor of each of said counties, respectively, a description of each and every parcel within said county upon which a standby charge remains unpaid, together with the amount of said unpaid standby charge plus penalty thereon.
Ca. Water Code § 31032