Foster decision

The 2015 Foster v. Ecology, City of Yelm, and Washington Pollution Control Hearings Board decision reaffirms and reinforces that instream flows adopted in a rule must be protected from impairment. The decision affects our work on water right change applications, mitigation packages, and water banking.

Streamflow restoration

Washington state has a new streamflow restoration law in response to the Hi​rst decision. The law includes a focus on the Foster decision and established five pilot projects. These projects will inform a legislative task force. We are evaluating how best to provide procedural guidance for the five identified projects.

"Foster decision" background

In the ruling, the court overturned our approval of a water right permit for the City of Yelm that would have provided water for future growth. We had conditioned Yelm’s permit on an extensive mitigation package, which included offsetting the total quantity of new water use through water-for-water mitigation (“in-kind”) and mitigating small impairment during the spring and fall with habitat improvements (“out-of-kind mitigation”). We also applied “overriding considerations of public interest” (OCPI) to approve the application because we found the public benefits would far outweigh any impacts on stream flows.

The court’s decision overturned the permit. Despite the mitigation package, the court said the permit would impair minimum instream flows in the Deschutes and Nisqually basins and therefore violates water law.

Key points

The state Supreme Court made three key rulings in the case:

  1. OCPI cannot be used to justify permanent allocations of water.
  2. No level of impairment to instream flows is allowed, regardless of magnitude or ecological impact.
  3. Out-of-kind mitigation strategies, such as habitat improvements, cannot be used to address impairment of instream flows.


The decision removes several tools we have used for allocating and reallocating water, and makes it more challenging to balance the competing needs of water users across the state.

Many rivers in Washington are regulated under instream flow rules, which essentially function as water rights for rivers. Previous state Supreme Court decisions established that we can't approve a water right permit or change application that would have any negative impact to instream flows, no matter how small. In the Foster decision, the court emphasized that this restriction applies even if a small impact happens for just part of the year.

The decision has implications for specific areas of our work:


This decision eliminates the use of “overriding considerations of public interest” (OCPI) as a tool to approve permanent uses of water. Since 2000, we used OCPI to justify small impacts to a protected stream or river when the public benefits were high. We can no longer use OCPI for this purpose.

Change applications

This decision limits our ability to approve the following types of applications in basins with closures or adopted instream flows that are not met:

  • Change in point of diversion or withdrawal — These changes can result in delayed or dispersed impacts to stream flows. For example, changing from a surface water use to a groundwater use could result in less overall impact to a protected river, but cause delayed effects that appear during different times of the year, potentially impairing instream flows.
  • Season of use — Expanding the period of use beyond the original time of impact to instream flows is not allowed under the Foster decision - even if the new impairment is mitigated with habitat restoration. For example, changing a seasonal irrigation water right to a year-round domestic right could result in impairment during fall and spring; we would have to reject that change application.


By emphasizing that mitigation must be strictly in-kind, in-time, and in-place, the court decision limits our ability to approve mitigation plans that do not perfectly match the season and place of use in basins with closures or adopted instream flows that are not met.

  • We can no longer use out-of-kind mitigation, such as habitat restoration, to offset impairment to protected rivers and streams.
  • There are few areas in the state where in-kind, in-time, and in-place mitigation water will be available.

Water banking

As communities increasingly look to water banks as a solution to water shortages, the inflexible impairment standard set forth in the Foster decision makes finding water banking solutions significantly more difficult in basins with closures or adopted instream flows that are not met. Overall, this ruling may limit water banking potential in much of the state.