Wash. Rev. Code § 90.03.010
The power of the state to regulate and control the waters within the state shall be exercised as hereinafter in this chapter provided. Subject to existing rights all waters within the state belong to the public, and any right thereto, or to the use thereof, shall be hereafter acquired only by appropriation for a beneficial use and in the manner provided and not otherwise; and, as between appropriations, the first in time shall be the first in right. Nothing contained in this chapter shall be construed to lessen, enlarge, or modify the existing rights of any riparian owner, or any existing right acquired by appropriation, or otherwise. They shall, however, be subject to condemnation as provided in RCW 90.03.040, and the amount and priority thereof may be determined by the procedure set out in RCW 90.03.110 through 90.03.240.
RCW 90.03.010