Upon the execution of any contract between the United States and any irrigation district pursuant to sections 511 and 512 of this title the public lands included within such irrigation district, when subject to entry, and entered lands within such irrigation district, for which no final certificates shall have been issued and which may be designated by the Secretary of the Interior in said contract, shall be subject to all the provisions of chapter 13 of this title: Provided, That no map or plan as required by section 623 of this title need be filed by the irrigation district for approval by the Secretary of the Interior.