The Hanford Reach Fall Chinook Protection Program and How Hydroelectric Development May Contribute to Increased Productivity

The Hanford Reach of the Columbia River is located in southeastern Washington State (USA) and extends from Priest Rapids Dam (Rkm 639) to the head of McNary Pool (Rkm 557). This 82 kilometer reach supports one of the largest spawning populations of fall Chinook salmon in the Pacific Northwest, which is highly valued for its ecological function and contribution to sport, tribal, and commercial harvest in local, regional, and international fisheries. The importance of this population led to intense scrutiny during the recent relicensing of the Priest Rapids hydroelectric project. A new operating license was issued in 2008 and several conditions of the license related to investigating the effects of hydroelectric operations on fall Chinook that spawn in the Hanford Reach. A group, consisting of stakeholders and fisheries managers, was developed to act as a consulting body for license conditions relating to fall Chinook. During the early stages of development and implementation several controversial issues emerged. Issues ranged from data quality and quantity to perceptions of the effects of dams on habitat and mortality. A total of 25 different studies were proposed by stakeholders, however, it became clear that most stakeholders were not considering protections or evaluations in a population context. A comprehensive assessment of life-stage specific productivity had not been completed to identify whether protections or evaluations for particular life stages are necessary, effective, or the most efficient. This could lead to an imbalance between the needs of the hydroelectric system and fall Chinook salmon in the Hanford Reach. Recent stock-recruitment analyses indicate this population is among the most productive in the Pacific Northwest and several evaluations were implemented to investigate the cause. One explanation could be increased survival from spawning through emergence. Field and lab studies of egg-to-fry survival are ongoing and modeling of spawning habitat was completed for the Hanford Reach. A hydrodynamic model was combined with Hanford Reach-specific spawning habitat data to generate annual estimates of the amount of suitable habitat. Area of suitable spawning and incubation habitat were compared for three eras including pre-hydroelectric development (1917-1932), hydroelectric development (1933-1984), and post-hydroelectric development with flow constraints to protect fall Chinook (1986-2010). Preliminary analyses indicate hydroelectric development decreased spawning habitat availability but increased area of suitable incubation habitat. Flow constraints to protect fall Chinook further increased area of suitable incubation habitat.