Evaluation of Inundating Salmoid Habitat by Increased Winter Impoundment at Wynoochee Reservoir, Washington

摘要

A change in the storage operation of Wynoochee Reservoir has been proposed to provide greater hydropower potential. Under the proposal, there would be a permanent increase in wintertime elevation from 762.5 feet to 776.1 feet. Presently, the reservoir is held at elevation 762.5 from about November 1 to March 15 of each year. From mid-March until the beginning of June, the reservoir is filled to elevation 800, and then progressively drafted to 762.5 during the summer and early fall to augment downstream flows for municipal, irrigatio, and fisheries purposes. The proposed increase in wintertime reservoir elevation would permanently inundate tributaries to the Wynoochee Reservoir that are now only seasonally inundated during the period of refilling and gradual drafting from approximately mid-March until early fall, and briefly inundated during winter flood events. The principal tributaries impacted would be the Wynoochee River, and beaver, Scatter, and Sixteen Creeks. Permanentr inundation of the lower reaches of these tributaries would flood aavailable spawning and reating habitat for anadromous and resident fihs. Chinook, coho and sttelhead bound for the upper Wynoochee are annually trapped below the project and hauled to a release point in the Wynoochee River above the Reservior to complete their life cycle.