(a) There is hereby authorized to be appropriated for construction of the Central Arizona Project, including prepayment for power generation and transmission facilities but exclusive of distribution and drainage facilities for non-Indian lands, $832,180,000 plus or minus such amounts, if any, as may be justified by reason of ordinary fluctuations in construction costs as indicated by engineering cost indices applicable to the types of construction involved therein and, in addition thereto, such sums as may be required for operation and maintenance of the project.

(b) There is also authorized to be appropriated $100,000,000 for construction of distribution and drainage facilities for non-Indian lands plus or minus such amounts, if any, as may be justified by reason of ordinary fluctuations in construction costs as indicated by engineering and cost indices applicable to the types of construction involved therein from September 30, 1968: Provided, That the Secretary shall enter into agreements with non-Federal interests to provide not less than 20 per centum of the total cost of such facilities during the construction of such facilities. Notwithstanding the provisions of section 1543 of this title, neither appropriations made pursuant to the authorization contained in this subsection nor revenues collected in connection with the operation of such facilities shall be credited to the Lower Colorado River Basin Development Fund and payments shall not be made from that fund to the general fund of the Treasury to return any part of the costs of construction, operation, and maintenance of such facilities.