(1) The director of the department of ecology, when he deems it to be an overriding public interest requirement, may reduce the minimum instantaneous and/or average weekly flows for the Columbia River established in this chapter up to twenty-five percent during low flow years, except that in no case shall the outflow from Priest Rapids be less than 36,000 cfs. The amount of the reduction (from zero to twenty-five percent) shall be: (a) Based on the March 1 forecast for April through September runoff at The Dalles, Oregon, as published by the National Weather Service in Water Supply Outlook for the Western United States, and (b) determined from Figure 1 in WAC 173-563-900.

(2) Prior to implementing the critical flow adjustment to minimum flows in a low water year, the department of ecology shall conduct a public hearing to announce its intentions and to solicit public and agency comment on the proposed action.

(3) The department has determined that some damage to instream values may be incurred at flow values equivalent to eighty-eight million acre-feet or less. Therefore, the reduced flows shall be referred to as critical flows and shall be authorized by the director of the department of ecology under the critical flow adjustment only when the March 1 forecast of April through September flow at The Dalles is below eighty-eight million acre-feet (MAF). The critical flows shall, in no case, provide less than 39.4 MAF (seventy-five percent of 52.5 MAF for the April through September period).

(4) The director of the department of ecology may waive the state's minimum flow requirements delineated in this chapter for a defined period of time for the purpose of studying the impacts of various flow levels on the river system and its operation when such studies are to be conducted in consultation with the Washington departments of fisheries and/or wildlife and when said exemption is requested by the departments of fisheries and/or wildlife. Such a request shall be made by letter to the director of the department of ecology. This waiver may include the Federal Energy Regulatory Commission studies to be conducted under Docket No. E-9569 and any operational change which does not allow the flows under this chapter to be met, but which, in the opinion of the director, still provides a commensurate level of protection for instream resources.