The Municipal Water Law

Growing communities, agriculture, industry, and the importance of conserving water for fish have placed an increasing demand 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 will:

  • Provide more certainty and flexibility for water rights held by water systems.
  • More closely tie water system planning and engineering approvals by the Department of Health to water rights administered by the state Department of Ecology.
  • Improve the ability to plan for future growth.
  • Offer greater flexibility to solve public health problems with water right changes and transfers.
  • Advance water use efficiency.
  • Assure greater reliability of safe drinking water for communities.

The Department of Health is implementing 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 will help municipal water suppliers understand the benefits of MWL and comply with the additional requirements for their planning documents. Here are the additional requirements:


Fact Sheets

Municipal Water Law Contacts

Water Use Efficiency

Rule Implementation Mike Means, 360-236-3178

Planning and Engineering Requirements

Brian Sayrs Sayrs, 509-329-2137

Regional Office Contacts


Jennifer Kropack, Technical and Planning, 253-395-6769

Richard Rodriguez, Planning, 253-395-6771


Jamie Gardipe, Planning, 509-329-2137

Brenda Smits, Planning, 509-329-2122


Vacant, Planning, 360-236-3030

Vacant, Planning, 360-236-3030