Cal. Water Code § 33145

All money required for repair, operation, and maintenance of improvements constructed by the storm water district and the cost of which was borne by the owners of particular land in the storm water district may be charged and collected by tax against that land, or notwithstanding anything in the Storm Water District Act of 1909 to the contrary, the board of directors of the surviving district may by ordinance determine that the money shall be raised by tax on the entire storm water unit, in which case the money shall thereafter be so raised.