If a contract with the state, the department, any other district, or the United States requires the payment by the district of capital charges in periodic installments, the total amount of such charges may be levied in the same manner as an original assessment pursuant to Chapter 2 (commencing with Section 46150) of Part 9 of this division, or the respective amounts of such installments may be levied from time to time in the same manner as periodic service charges, as provided in Section 44030, but an assessment or assessments shall in any event be levied in such a manner as to provide for the payment of all such charges, for which funds are not otherwise available, as they become due under the contract.