These data represent critical habitat designated (September 2, 2005, 70 FR 52630) under the Endangered Species Act for the Middle Columbia River steelhead DPS.

Critical habitat includes the stream channels within the designated stream reaches, and includes a lateral extent as defined by the ordinary high-water line (33 CFR 319.11). In areas where ordinary high-water line has not been defined, the lateral extent is defined by the bankfull elevation. Bankfull elevation is the level at which water begins to leave the channel and move into the floodplain and is reached at a discharge which generally has a recurrence interval of 1 to 2 years on the annual flood series. Critical habitat in lake areas is defined by the perimeter of the water body as displayed on standard 1:24,000 scale topographic maps or the elevation of ordinary high water, whichever is greater. See the final rule (70 FR 52630) for descriptions of areas excluded from this critical habitat designation. Excluded Indian lands were not clipped out of the data.