POMEROY, Wash. – The Walla Walla District of the U.S. Army Corps of Engineers is improving both adult and juvenile fish passage at Lower Granite Lock and Dam to help endangered salmon and steelhead migrate in the lower Snake River. Two significant new fish passage improvements are in progress:
First, to prepare for potential high water temperatures this summer and help upstream-migrating adult salmon and steelhead pass Lower Granite Dam, the Corps completed installing a permanent adult fish ladder water cooling system in February. This new Adult Fish Ladder Temperature Improvement System was built in response to unusually hot weather the past several years throughout the Columbia-Snake river basin. Hot weather raised temperatures in the “tailwater” just below Lower Granite Dam in summer to more 68 degrees Fahrenheit, which is above acceptable limits. Hotter water promoted development of a “thermal barrier” in the adult fish ladder, hindering upstream migration of adult salmon and steelhead to their spawning grounds. Sockeye salmon were most affected in summer 2015, though the Corps used temporary pumps to cool the fish ladder in 2014 and 2015. This permanent system will cool fish ladder water starting this summer.