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Department of Ecology
Committees, Boards, and Workgroups

Water Resource Management Public Interest Project

Ecology's Water Resources Program is the state's managing entity for its water resources. We issue water rights, ensure compliance with authorized water use, and plan and fund projects that improve water availability and streamflows.

Like many other states in the western United States, Washington manages its water resources based on principles of the prior appropriation doctrine. Water is a public resource held for all to use, and private individuals establish the right to water use through an appropriation to apply that water to a beneficial use. These water rights are usufructuary, meaning that water right holders must continue to use their appropriation to maintain the rights to its use; if use diminishes or ceases for a certain amount of time, that unused appropriation is relinquished to the state. Priority between existing uses is based on seniority, so when conflicts over limited water uses arise, senior uses are satisfied in full before junior uses receive any amount.

Parties seeking to use water are free to appropriate water for a new use, provided that:

  • water is physically and legally available for appropriation;
  • other existing water uses will not be impaired by the new use;
  • the new use qualifies as a beneficial use; and
  • the new use will not impair the public interest.

In practice, however, there is very little water still available for appropriation in many of Washington's watersheds. In these areas, parties seeking new supplies must generally seek to adapt existing appropriations to meet their needs, either through the direct transfer of an existing right to a new location and/or use or else by providing mitigation through Ecology's Trust Water Rights Program. Considerations of the public interest for these transfers depends on the transfer mechanism and the watershed context.

Background Reading


Info Session Slides

Case Law and Decisions

Previous Evans School Projects

Reference Materials


Title 90 Water Rights - Environment

  • RCW 90.03 - Water Code
    • 90.03.290 - New appropriations must be nondetrimental to the public welfare
  • RCW 90.42 - Trust Water Rights
    • 90.42.040(2)(a) - Exercise of a trust water right may not impair the public interest
  • RCW 90.44 - Groundwater rights
    • 90.44.100(2) - Groundwater right change applications also subject to 90.03.290 requirement ("findings as prescribed in the case of an original application)
  • RCW 90.54 - Water Resources Act of 1971
    • 90.54.020 - General declaration of fundamentals of water use; includes considerations of public interest
  • RCW 90.82 - Watershed Planning
    • 90.82.130(4) - Watershed plans created under 90.82 process are a "primary consideration in determining the public interest"

Oregon and Idaho public interest statutes related to water resources



 File NameFile SizeDescriptionCategoryDate Added
ContactList-Washington.docx 22.6 KB
Interview 02/15/23 01:27 PM
Western States WR_contact list.docx 18 KB
None 02/10/23 04:27 PM
OR&ID PI Statutes.docx 14.2 KB
None 01/20/23 11:13 AM
WaterRightsPrimer_2023.pptx 1.9 MB
None 01/20/23 11:09 AM
Public Interest Slides.pptx 63.3 KB
None 01/20/23 11:09 AM
2013-10-13 Swinomish v Ecology.pdf 243.3 KB
None 12/21/22 12:18 PM
Restoring the Public Interest in Western Water Law.pdf 663.9 KB
None 12/21/22 11:55 AM
public-interest-wa-water-law-the-water-report-2018-excerpted.pdf 545 KB
None 12/21/22 11:54 AM
Draft Darrington US Golden Eagle Decision.pdf 932.6 KB
None 12/21/22 11:53 AM
Evans School Report Final Draft.pdf 3.7 MB
None 12/21/22 11:51 AM
Final_Report_reformatted.pdf 276 KB
None 02/11/21 03:17 PM
WaterRightsPrimer_2021.pptx 1.9 MB
None 01/19/21 04:10 PM
Landowner's Guide to WA Water Rights.pdf 9.8 MB
None 01/19/21 09:25 AM
Washington State Water Law - A Primer.pdf 143.5 KB
None 01/19/21 09:16 AM

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