Subject to regulation 17(4), the proportion of the expenses of a board which shall be raised from the proceeds of drainage rates shall be determined in accordance with the provisions of this regulation.

In respect of the financial years beginning in 1990, 1991 and 1992, the proportion shall be determined in accordance with regulation 22.

In respect of the financial year beginning in 1993 and each subsequent financial year, the proportion shall be determined by dividing the aggregate of the annual values of the annual value properties in the board’s district by the aggregate of the annual values of all the land and buildings in that district, such values to be determined in accordance with regulation 18.