Hanford Reach Salmonid Entrapment Research The Hanford Reach stretches from Priest Rapids Dam 82 kilometers downstream to Richland, Washington. The topography, river dynamics, and climate of the area create a unique habitat for wildlife and fish populations. The Hanford Reach supports the larger of the only two remaining healthy naturally spawning fall chinook salmon (Oncorhynchus tshawytscha) populations in the Columbia River System. This population is a primary source of ocean and freshwater sport, commercial, and in-river tribal fisheries and is a primary component of the Pacific Salmon Treaty between the United States and Canada. River flows for this section of the Columbia River are controlled by discharge from Priest Rapids Dam. Flow fluctuations from Priest Rapids Dam can occur rapidly due to changes in hydroelectric power generation, irrigation, water storage, and flood control. These fluctuations have been observed to cause stranding and entrapment of juvenile fall chinook salmon on gently sloped banks, gravel bars, and in pothole depressions in the Hanford Reach area of the Columbia River. Stranding of juvenile fall chinook salmon occurs when the fish are trapped on or beneath the unwatered substrate as the river level recedes. Entrapment occurs when the fish are separated from the main river channel in depressions as the river level recedes. Fish mortality in entrapments occurs from stranding, thermal stress, and piscivorous, avian, and mammalian predation. The impact of river fluctuations due to operation of hydroelectric facilities on rearing salmonids has been assessed on numerous Columbia River tributaries and other river systems but limited research has been conducted on the Hanford Reach prior to 1997. In 1997, the Washington Department of Fish and Wildlife (WDFW) was contracted through the Bonneville Power Administration (BPA) and the Grant County Public Utility District (GCPUD) to perform an evaluation of juvenile fall chinook salmon stranding on the Hanford Reach. The multi-year study was developed to assess the impacts of water fluctuations from Priest Rapids Dam on rearing juvenile fall chinook salmon, other fishes, and benthic macroinvertebrates of the Hanford Reach and for directing the future management of flows from Priest Rapids Dam.

Reports 2004 Evaluation of Juvenile Fall Chinook Salmon Entrapment in the Hanford Reach of the Columbia River Paul Hoffarth 2003 Evaluation of Juvenile Fall Chinook Salmon Stranding in the Hanford Reach of the Columbia River Paul Hoffarth, Andrew Fowler and Wendy Brock 2003 Field Summary Report: Assessment of Losses of Juvenile Fall Chinook in the Hanford Reach of the Columbia River in Relation to Flow Fluctuations Paul Hoffarth 2002 Evaluation of Juvenile Fall Chinook Salmon Stranding on the Hanford Reach of the Columbia River John Nugent, Paul Hoffarth and Wendy Brock 2001 Evaluation of Juvenile Fall Chinook Salmon Stranding on the Hanford Reach of the Columbia River John Nugent, Todd Newsome, Paul Hoffarth, Michael Nugent, Wendy Brock and Michael Kuklinski, Jr. 2000 Evaluation of Juvenile Fall Chinook Salmon Stranding on the Hanford Reach of the Columbia River John Nugent, Todd Newsome, Mike Nugent, Wendy Brock, Paul Hoffarth and Paul Wagner 1999 Evaluation of Juvenile Fall Chinook Salmon Stranding on the Hanford Reach of the Columbia River John Nugent, Todd Newsome, Wendy Brock, Mike Nugent, Paul Hoffarth and Paul Wagner