In the cities herein designated, owning an electric-light plant and municipal water plant, where the utility or utilities are free and clear of general obligation bonded indebtedness, or where deposits in their appropriate sinking funds have been made as provided in Kan. Stat. Ann. § 13-1270, and amendments thereto, the governing bodies of the cities or the board of public utilities at the direction of the city shall, on the first business day of each fiscal year, transfer to the funds to be used for governmental functions of such cities, not less than four percent nor more than fifteen percent of the gross operating revenue of their public utilities hereinbefore designated, for the year immediately prior to the preceding fiscal year.