to this account as offsetting collections, to remain available until expended for the sole purpose of making purchase power and wheeling expenditures: Provided further , That for purposes of this appropriation, annual expenses means expenditures that are generally recovered in the same year that they are incurred (excluding purchase power and wheeling expenses). Falcon and amistad operating and maintenance fund For operation, maintenance, and emergency costs for the hydroelectric facilities at the Falcon and Amistad Dams, $4,176,000, to remain available until expended, and to be derived from the Falcon and Amistad Operating and Maintenance Fund of the Western Area Power Administration, as provided in section 2 of the Act of June 18, 1954 (68 Stat. 255): Provided , That notwithstanding the provisions of that Act and of 31 U.S.C. 3302 , up to $3,948,000 collected by the Western Area Power Administration from the sale of power and related services from the Falcon and Amistad Dams shall be credited to this account as discretionary offsetting collections, to remain available until expended for the sole purpose of funding the annual expenses of the hydroelectric facilities of these Dams and associated Western Area Power Administration activities: Provided further , That the sum herein appropriated for annual expenses shall be reduced as collections are received during the fiscal year so as to result in a final fiscal year 2018 appropriation estimated at not more than $228,000: Provided further , That for purposes of this appropriation, annual expenses means expenditures that are generally recovered in the same year that they are incurred: Provided further , That for fiscal year 2018, the Administrator of the Western Area Power Administration may accept up to $872,000 in funds contributed by United States power customers of the Falcon and Amistad Dams for deposit into the Falcon and Amistad Operating and Maintenance Fund, and such funds shall be available for the purpose for which contributed in like manner as if said