Foster v. Ecology: Court Decision and Implications

Updated 01/04/2017

A 2015 Washington State Supreme Court 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.

In October 2015, 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 violate water law.

Key court rulings

The Washington State Supreme Court made three key rulings in the case:

  1. We cannot use OCPI (“public interest”) to justify permanent allocations of water.
  2. No level of impairment to instream flows is permissible, regardless of magnitude or ecological impact.
  3. We cannot use “out-of-kind” mitigation strategies, such as habitat improvements, to address impairment of instream flows.

What this means for Ecology

The decision removes several of our tools for allocating and reallocating water and makes it more challenging for us 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 Washington State Supreme Court decisions established that we cannot 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 our 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:


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.

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, Foster may limit water banking potential in much of the state.


Carrie Sessions
Policy and Legislative Coordinator
Water Resources Program
(360) 407-6094