The Sumner Dam and Lake Sumner on the Pecos River, New Mexico, is authorized and declared to be for the purposes of controlling floods, regulating the flow of the Pecos River, providing for storage and for delivery of stored waters, for the reclamation of lands, and other beneficial uses, and said dam and reservoir shall be used, first, for irrigation; second, for flood control and river regulation; and third, for other purposes. The Chief of Engineers and the Secretary of the Army are directed to report to the Congress the amount of the total cost of said Sumner Dam and Lake Sumner which is properly allocable to flood control. The appropriation and transfer of such amount from the general fund of the Treasury to the reclamation fund, for credit by reduction of the maximum obligation of the Carlsbad Irrigation District to repay the total cost thereof, is authorized.