The county treasurers shall carry as a separate account upon the books of their office a revolving fund and all accounts and items pertaining thereto. A record shall be kept of the amount of money paid from the revolving fund for the use and benefit of any particular drainage district and upon payment to the county treasurer of the taxes assessed in the particular drainage district, the county treasurer, out of the moneys received, shall transfer to the revolving fund pro rata according to the number of installments of taxes the sum expended.