The Secretary of the Interior is authorized, in his discretion, to designate and appoint, under such rules and regulations as he may prescribe, the legally organized water-users' association or irrigation district, under any reclamation project, as the fiscal agent of the United States to collect the annual payments on the construction charge of the project and the annual charges for operation and maintenance and all penalties: Provided, That no water-right applicant or entryman shall be entitled to credit for any payment thus made until the same shall have been paid over to an officer designated by the Secretary of the Interior to receive the same.