The city council shall control and order the expenditure of the funds of the district for the purposes of maintenance and operation as provided in the final resolution. If at the expiration of any year there is an unexpended balance in the district fund, the balance shall, to that extent, reduce the fund to be raised from the district for the next year. Any balance remaining in the fund at the end of the term for which the district is formed shall be used to help furnish electric current for the systems maintained and operated from the funds raised in whole or in part from the district.