Municipal Water Law

The regulation of municipal water is an important element of water management in Washington State. In 2003, the Washington State Legislature significantly amended Washington water law to provide certainty and flexibility for municipal water suppliers. The amendments, called the Municipal Water Law (MWL), give clarity to the nature of water rights issued for municipal supply purposes by defining the terms “municipal water supplier” and “municipal water supply purposes”. The law also provides flexibility to municipal water suppliers in exercising their water rights by defining when the “place of use” can be the same as a municipal water supplier’s service area and establishing that municipal water rights are not limited to the stated number of connections but to the number of connections approved in a water system plan. Lastly, the law requires municipal suppliers to use water efficiently and to comply with conservation practices and planning.

The Washington Departments of Health and Ecology share responsibilities under the Municipal Water Law and have developed agreements to coordinate planning, engineering, and public health and safety matters relating to water systems and water resources. The Department of Health is responsible for ensuring safe and reliable drinking water, and reviews and approves planning and engineering documents for water systems. We administer Washington State’s Water Resource Program, including water rights administration and watershed planning.

Municipal Water Law Interpretive and Policy Statement

We developed an Interpretive and Policy Statement (IPS) for carrying out the 2003 Municipal Water Law under the authority of the Administrative Procedure Act - RCW 34.05.230. This policy statement clarifies our management approach for carrying out the MWL for the primary audience of those interested in, and affected by, management of water rights for municipal supply purposes. This policy statement also provides a common interpretation for our staff and enables consistent application of the law.

Memorandum of Understanding

The Department of Health, Office of Drinking Water and Ecology's Water Resources Program developed a Memorandum of Understanding (MOU) and Joint Review Procedures to outline the agencies’ roles and responsibilities on aspects of MWL. The most recent update to the MOU includes new coordination procedures were required in the 2003 Municipal Water Law.

Additional Information

Washington State Supreme Court Cases


General Information

Information Sources


For region-specific information about Municipal Water
Northwest Region - Bellevue
Counties:  Island, King, Kitsap, San Juan, Skagit, Snohomish and Whatcom

Doug Wood
Office: 425-649-7077

  Southwest Region - Lacey
Counties:  Clallam, Clark, Cowlitz, Grays Harbor, Jefferson, Mason, Lewis, Pacific, Pierce, Skamania, Thurston and Wahkiakum

Mike Gallagher
Office: 360-407-6058

Central Region - Union Gap
Counties:  Benton, Chelan, Douglas, Kittitas, Klickitat, Okanogan and Yakima

Scott Turner
Office: 509-457-7106

  Eastern Region - Spokane
Counties: Adams, Asotin, Columbia, Ferry, Franklin, Garfield, Grant, Lincoln, Pend Oreille, Spokane, Stevens, Walla Walla and Whitman

Dan Tolleson
Office: 509-329-3526