54 U.S.C. § 101901

To facilitate the administration of the System, the Secretary, under such terms and conditions as the Secretary considers advisable, may furnish, on a reimbursement of appropriation basis, all types of utility services to concessioners, contractors, permittees, or other users of the services, within the System. The reimbursements for cost of the services may be credited to the appropriation current at the time reimbursements are received.