Wash. Rev. Code § 54.16.050
A district may take, condemn and purchase, purchase and acquire any public and private property, franchises and property rights, including state, county, and school lands, and property and littoral and water rights, for any of the purposes aforesaid, and for railroads, tunnels, pipe lines, aqueducts, transmission lines, and all other facilities necessary or convenient, and, in connection with the construction, maintenance, or operation of any such utilities, may acquire by purchase or condemnation and purchase the right to divert, take, retain, and impound and use water from or in any lake or watercourse, public or private, navigable or nonnavigable, or held, owned, or used by the state, or any subdivision thereof, or by any person for any public or private use, or any underflowing water within the state; and the district may erect, within or without its limits, dams or other works across any river or watercourse, or across or at the outlet of any lake, up to and above high water mark; and, for the purpose of constructing or laying aqueducts or pipelines, dams, or waterworks or other necessary structures in storing, retaining, and distributing water, or for any other purpose authorized hereunder, the district may occupy and use the beds and shores up to the high water mark of any such lake, river, or watercourse, and acquire by purchase or by condemnation and purchase, or otherwise, any water, water rights, easements, or privileges named herein or necessary for any of such purposes, and a district may acquire by purchase, or condemnation and purchase, or otherwise, any lands, property, or privileges necessary to protect the water supply of the district from pollution: PROVIDED, That should private property be necessary for any of its purposes, or for storing water above high water mark, the district may condemn and purchase, or purchase and acquire such private property.
RCW 54.16.050
Water rights: Title 90 RCW.