Wash. Rev. Code § 84.34.200
The legislature finds that the haphazard growth and spread of urban development is encroaching upon, or eliminating, numerous open areas and spaces of varied size and character, including many devoted to agriculture, the cultivation of timber, and other productive activities, and many others having significant recreational, social, scenic, or esthetic values. Such areas and spaces, if preserved and maintained in their present open state, would constitute important assets to existing and impending urban and metropolitan development, at the same time that they would continue to contribute to the welfare and well-being of the citizens of the state as a whole. The acquisition of interests or rights in real property for the preservation of such open spaces and areas constitutes a public purpose for which public funds may properly be expended or advanced.
RCW 84.34.200