Revenues collected after August 7, 1946, from power operations on each Indian irrigation project and deposited into the Treasury for credit to miscellaneous receipts pursuant to section 4 of the Permanent Appropriation Repeal Act, 1934 (48 Stat. 1227), or pursuant to other provisions of law, are authorized to be appropriated annually, in specific or in indefinite amounts, equal to the collections so credited, for the following purposes in connection with the respective projects from which such revenues are derived: (1) Payment of the expenses of operating and maintaining the power system; (2) creation and maintenance of reserve funds to be available for making repairs and replacements to, defraying emergency expenses for, and insuring continuous operation of the power system, the fund for each project to be maintained at such level, within limits set by the Director of the Office of Management and Budget, as may from time to time be prescribed by the Secretary of the Interior; (3) amortization, in accordance with the repayment provisions of the applicable statutes or contracts, of construction costs allocated to be returned from power revenues; and (4) payment of other expenses and obligations chargeable to power revenues to the extent required or permitted by law.