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Video by Chief Petty Officer Matthew Cole

River Cooling System

U.S. Army Corps of Engineers Walla Walla District

July 24, 2020 | 3:23

he U.S. Army Corps of Engineers has developed and constructed fish cooling systems at Lower Granite and Little Goose dams to alleviate warming water concerns.

Warm water temperatures above 68 degrees aren’t good for salmon and steelhead in the Columbia and Snake river system, and records show that 2015, 2016 and 2017 were the hottest years on record.

When summer temperatures spiked, the Walla Walla District’s scientist, biologists and engineers responded by developing fish cooling systems at Lower Granite Dam and Little Goose Dam on the Snake River.

While building four dams on the lower Snake River between the 1950s and 1980s, the U.S. Army Corps of Engineers constructed adult fish ladders to allow passage of upstream-migrating adult salmon and steelhead (salmonids) on their way to their natal spawning areas. Since construction, the Corps has made both facility and operational improvements to assist adult salmonid migration as needed.

Historically, the Snake River is known to have experienced high summer water temperatures in years prior to construction of dams. In summer 2013, elevated water temperatures began to occur in Columbia-Snake basin river reaches with and without dams due to unusually hot weather dominating the basin. At Lower Granite Lock and Dam’s adult fish ladder, longer-duration elevated water temperatures began to form a “thermal barrier” to upstream migrating salmon and steelhead, slowing and/or stopping adult fish migration upstream.

During 2015 fish perished throughout the West in rivers with and without dams due to elevated water temperatures. A total of 510,705 sockeye that originated in numerous watersheds passed Bonneville Dam on the lower Columbia River. Snake River-born sockeye comprised about 4,069 of the more-than-510,000 sockeye run, or less than one percent of the total run, as confirmed by Passive Integrated Transponder (PIT) tag analysis.

By the time the survivors of those initial 4,069 Snake River sockeye reached Ice Harbor Dam, the first dam encountered on the lower Snake River, 74.1 percent had perished in the lower Columbia River, and their numbers were reduced to 1,052 Snake River sockeye to migrate up the Snake River.

In response, the Corps developed both an interim solution to the thermal barrier in 2014-2015, and installed permanent cooling systems at Lower Granite Dam in 2016 and at Little Goose Dam in 2017.