Water right adjudications

Adjudication is a Superior Court process that legally determines whether a water right is valid, how much water can be used, and its priority during shortages. It prioritizes each individual water right according to Washington water law's “first-in-time, first-in-right” prior appropriation rule.

As the agency responsible for managing the state’s water resources, we have an important role in supporting the Superior Court’s process and decision-making in a water right adjudication.

Benefits of adjudication

Determining the validity, extent, and priority of water rights within a subbasin can be vital for:

  • Community planning.
  • Protecting the water resource.
  • Protecting legal water users.
  • Supporting the transfer of water to new uses.
  • Preventing and resolving water conflicts.

State adjudications may:

  • Be as small as two water right holders (a limited adjudication).
  • Be as large as all water rights in a large river basin (a general adjudication).
  • Address surface water use, groundwater use, or both.

Active adjudications

Currently, the Yakima River Basin Adjudication is the only active water right adjudication in Washington. There have been 82 completed adjudications in addition to a number of petitions for other areas of the state.

The Yakima River Basin surface water adjudication

The Yakima County Superior Court is currently finalizing the adjudication of surface water rights in the Yakima River Basin to resolve the rights of thousands of water users in an area with frequent water shortages. The basin includes large portions of Benton, Kittitas, and Yakima counties and a small portion of Klickitat County.

In the Yakima River Basin, the Yakama Nation holds the earliest water rights -— dating back to time immemorial. Most water rights in the basin were first established before 1905. Read more about the Ecology v Acquavella adjudication.

After an adjudication

In Washington, the oldest water rights from a water source have priority over more recent rights to the same source. The transfer of older water rights to new uses through water banking provides reliable water supplies for future development in some areas where new water rights are no longer available.