This has been the largest and longest water rights adjudication in the state’s history. It has long been known that water rights are over-appropriated in the Yakima Basin, so it was important to establish who has water rights and the relative priority dates and quantities legally available to water users. Most of the water rights reviewed during the adjudication date back to before 1917 when Washington’s first surface-water law was adopted. The adjudication provides clarity and certainty for the relative priorities of all surface water rights in the basin, which is essential for water resources use, protection, and planning, and for water right transfers.
Over the last 42 years, more than 4,000 claims to water were thoroughly reviewed by Ecology, the court, and other parties. Claims ranged from smaller individual uses to several major claims for irrigation districts and cities, and for federally-based water rights such as Indian tribes and the U.S. Forest Service. The geographic scale of the adjudication stretches across the Yakima Basin’s 31 tributary watersheds comprising 6,150 square miles, spanning large portions of Kittitas, Yakima, and Benton counties,and the lands of the Yakama Nation.