Wash. Rev. Code § 90.40.040
Whenever said secretary of the interior or other duly authorized officer of the United States shall cause to be let a contract for the construction of any irrigation works or any works for the storage of water for use in irrigation, or any portion or section thereof, for which the withdrawal has been effected as provided in RCW 90.40.030, any authorized officer of the United States, either in the name of the United States or in such name as may be determined by the secretary of the interior, may appropriate, in behalf of the United States, so much of the unappropriated waters of the state as may be required for the project, or projects, for which water has been withdrawn or reserved under RCW 90.40.030, including any and all divisions thereof, theretofore constructed, in whole or in part, by the United States or proposed to be thereafter constructed by the United States, such appropriation to be made, maintained and perfected in the same manner and to the same extent as though such appropriation had been made by a private person, corporation or association, except that the date of priority as to all rights under such appropriation in behalf of the United States shall relate back to the date of the first withdrawal or reservation of the waters so appropriated, and in case of filings on water previously withdrawn under RCW 90.40.030, no payment of fees will be required. Such appropriation by or on behalf of the United States shall inure to the United States, and its successors in interest, in the same manner and to the same extent as though said appropriation had been made by a private person, corporation or association. The title to the beds and shores of any navigable lake or stream utilized by the construction of any reservoir or other irrigation works created or constructed as a part of such appropriation hereinbefore in this section provided for, shall vest in the United States to the extent necessary for the maintenance, operation and control of such reservoir or other irrigation works.
RCW 90.40.040