Whenever any drain shall have been declared vacated and abandoned, as provided in section 391, it shall be the duty of the commissioner to serve notice thereof forthwith upon the county treasurer of the county or counties in which the drainage district, or any portion thereof, is situated. If there be any money credited to or belonging to the fund of such vacated and abandoned drain, it shall be the duty of the county treasurer or treasurers to transfer and pay over the same to the treasurer or treasurers of the township or townships in which the drain was located or in which assessments for benefits to be received from such drain have been assessed and collected: Provided, That in all cases where the amount of such money belonging to the drain fund of such drain, in the hands of the county treasurer, shall be insufficient to permit the refunding and paying over to such township treasurers all of the moneys assessed and collected in such townships, the county treasurer shall prorate the amounts so paid, and each township treasurer shall be entitled to receive such proportion of the moneys remaining in the fund of the vacated or abandoned drain as the total amount of the assessments levied and collected in his township and becoming a part of such drain fund shall bear to all of the moneys assessed and collected and making up such fund. In case it is necessary to prorate in the manner provided, the county treasurer shall furnish to each township treasurer a statement showing the amount of money in the fund at the time such drain was declared vacated and abandoned, and the various amounts assessed and collected for such fund from the different townships entitled to share in the disbursement thereof.