The Municipal Water Law

Growing communities, agriculture, industry, and the importance of conserving water for fish place increasing demands on our state's water resources. To help meet these growing needs, the state legislature passed the Municipal Water Supply-Efficiency Requirements Act (PDF), commonly called MWL. The MWL was challenged and later upheld by the Washington State Supreme Court. Visit the MWL Legal Challenges page for more information about the lawsuit.

Municipal water suppliers are all Group A community water systems with 15 or more residential connections and Group A non-community systems that provide water for residential uses (such as bathing, cooking, and cleaning) to a non-residential population for 25 or more people for 60 or more days a year.

We believe the law:

  • Provides more certainty and flexibility for water rights held by water systems.
  • More closely ties water system planning and engineering approvals by us to water rights administered by the state Department of Ecology.
  • Improves the ability to plan for future growth.
  • Offers greater flexibility to solve public health problems with water right changes and transfers.
  • Advances water use efficiency.
  • Assures greater reliability of safe drinking water for communities.

We implement the MWL through:

The Department of Ecology developed the 2003 Municipal Water Law Interpretive and Policy Statement (PDF) that explains how they implement the MWL.

Municipal water suppliers now have more water right flexibility and certainty, but they also need to include more information in their water system plan or small water system management program.

The guidance documents and fact sheets below help municipal water suppliers understand the benefits of MWL and comply with these additional requirements for their planning documents. 


Fact Sheets

Municipal Water Law Contacts

Water Use Efficiency

Rule Implementation Mike Means, 360-236-3178

Regional Contacts

Eastern Regional Office

Anna Duron, Planning, 509-329-2132

Brenda Smits, Planning, 509-329-2122

Northwest Regional Office

Vacant, Technical and Planning, 253-395-6750

Vacant, Planning, 253-395-6750

Southwest Regional Office

Meridith Jones, Planning, 564-233-1394

Ben Majors, Planning, 564-669-0855