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Instream Flow photo identifier

Instream Flow

Skagit River Photo



Ria Berns

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Skagit River Basin - Water Management Rule Overview

WAC 173-503 Instream Resources Protection Program - Lower and Upper Skagit Water Resources Inventory Area (WRIA 3 And 4)

In 2001, Ecology established instream flow levels in state rule (WAC 173-503) to help protect the ecosystem of the Skagit River.  The rule supports adequate water in the river for healthy salmon runs, good water quality and recreational activities, as required by state law.  It also protects existing water rights.

Instream flows are like a water right for the river.  Under Washington water law, new water uses of water (in this case, those started after the effective date of the rule) cannot impact existing water rights, no matter how small that impact may be.  This includes any impacts to stream flows.  Therefore, there are limits on new water uses of any size, and including permit-exempt wells, in the Skagit River Basin.  See what options are available to you now.

Ecology is actively pursuing a number of projects to find water supplies and solutions for property owners in the Skagit Basin.

Water availability zone

We notified Skagit County in January 2017 about a new water availability zone in the Bayview area. This 56-square-mile zone appears to not require mitigation for new water use because the groundwater there flows to saltwater and would not impact the protected Skagit River.

See the map and read more on the Skagit River basin developing solutions page.


The Skagit River Basin Instream Resources Protection Program Rule (WAC 173-503) went into effect on April 14, 2001.  It was the culmination of an open, public process which began in 1994 with research on the Cultus Mountain tributaries of the Skagit River.  These early efforts to evaluate estimated future out-of-stream water uses and their impacts on fish were led by the Skagit PUD.  Over the years since then, research and planning for Skagit River Basin water has been a multi-organization effort, which includes:

  • City of Anacortes
  • General public and interested stakeholders
  • Skagit County
  • Skagit PUD
  • Swinomish Indian Tribal Community and the Sauk-Suiattle Indian Tribe (known collectively as the Skagit System Cooperative)
  • Upper Skagit Indian Tribe
  • Washington Department of Ecology (Ecology)
  • Washington Department of Fish and Wildlife (WDFW)

In 2006, the rule was amended in response to Skagit County’s lawsuit claiming that the rule did not provide adequate guarantees of future water for Skagit property owners. Text about reservations The amendment established reservations of surface and groundwater not subject to the instream flows, for future out-of-stream uses.  The sizes of the reservations were limited to amounts that Ecology and Washington Dept. of Fish & Wildlife fish biologists determined would not substantially harm long-term fish survival.  The reservations provided uninterruptible (year-round) water supplies for new agricultural, residential, commercial/industrial and livestock uses, distributed among 25 subbasins.  They were effective as of the original date of the rule, April 14, 2001.  The Swinomish Tribe challenged the reservations on the grounds that they compromised adequate protection for fish.

Supreme Court decision and its impact on water use in the Skagit Basin

On October 3, 2013, the Washington State Supreme Court ruled in Swinomish Indian Tribal Community v. Department of Ecology that Ecology exceeded its authority in establishing the water reservations.  The rule reverted to its original text, from 2001.  Without reservations, year-round water uses that began after the rule took effect in 2001 can be interrupted when stream flows are below the regulatory instream flow levels.

For a more detailed look at the history of the rule, from 1994 through to the present day, see the Timeline.

Water use options available now

Text about reservations

The Supreme Court decision means that all new consumptive uses of water cannot impact instream flows. And because groundwater and surface water are interconnected, this includes the use of domestic permit-exempt wells. Since the river water levels fall below the instream flows at various times of year -- most often in the summer and early fall – water uses needing a reliable year-round supply would not be possible.

As Ecology works towards more water supply solutions, there are still options available for new legal water use in the Skagit Basin.  These include:

  • Connect to a public water supply.
  • Collect rainwater; store water in a cistern.
  • Drill a well in a location that has no impact on the river.
  • Mitigate: drill a well and offset the impact on stream flows.

For more information about these water supply options, and possible long-term options:

Note: The Swinomish ruling does not affect water uses established before April 14, 2001, or customers of public water systems.

Ecology and Swinomish Tribe agree 2001-2013 Skagit groundwater uses secure while water supply solutions are developed

The Swinomish ruling created legal uncertainty for the water use by approximately 480 homes and businesses that have relied on the water reservations since adoption of the 2001 rule.  Since the court decision, Ecology has been looking for water supply solutions for those homes and businesses affected by the ruling.  The Swinomish Tribe agrees existing water uses should not be curtailed while mitigation is being developed:

Overview of the basin


Skagit County Interactive Map - to find out whether the rule applies to your property:

Go to Skagit County’s interactive map:

  1. Open the map
  2. Under Map Categories on the left, click on Planning and Development
  3. Click on Skagit Instream Flow Rule Area 4.
  4. Go to “Search” at the lower left and enter your information.

Skagit River Facts

  • Size: The Skagit River is more than 160 miles long and the third largest river on the West Coast of the contiguous United States, after the Columbia and Sacramento rivers.  It provides about 20 percent of the fresh water flowing into Puget Sound, or nearly 10 billion gallons a day.
  • Location: The river originates in Canada then flows south and west through the North Cascade Range.  With some 2,900 tributaries, it drains 3,130 square miles of watershed in 2,730 square miles in Washington and 400 in British Columbia.
  • Animal Species: 5 species of salmon, globally rare Salish sucker, neotropical migrant birds, bald eagles, fishers, grizzly bear, wolves, trumpeter swan, gray-bellied brant, and many raptors and waterfowl.  The Skagit is the only river system in Washington which supports all five species of salmon. It contains some of the largest and healthiest wild Chinook salmon runs in Puget Sound and the largest pink salmon stock in Washington.

Watershed Planning information:

Additional WRIA information: