After the completion of construction of the works, the board shall, in the month of July in each year, cause a tax to be levied and collected in the manner provided in Chapter 11 of this part. The amount of such tax, after deducting any available and applicable moneys on hand (exclusive of moneys in the reserve interest fund) and the estimated amount of revenues of the works for the ensuing 12 months, which estimated amount shall not exceed the actual revenues for the preceding 12 months or, if the works have not been in operation for as long as 12 months, not to exceed an amount computed on the basis of the average daily revenues for the lesser period, shall be sufficient to produce the sums required to be set aside into separate funds by Section 27300, as well as any deficit in such funds and the principal and interest of any outstanding revenue and tax anticipation notes.