Snake vs block 40 or more challenge5/16/2023 Three years later, when a screen at the outlet of Wallowa Lake was removed to allow an estimated 5 million fish to migrate to the ocean, most of the fish later were discovered in irrigation ditches short distances downstream. By then, sockeye in Wallowa Lake had lost their migratory instinct and become adapted to the lake environment. Two weeks after the dam was blown out, the Wallowa County Chieftain newspaper of Enterprise, Oregon, reported: “It is hoped that the removal of the dam, by opening the river to migratory fish, will make angling better than ever in streams and lakes of this county.”īut the hope never was realized. Eggs from Wallowa River salmon were incubated and the smolts released from the Bonneville Fish Hatchery at Eagle Creek several hundred miles downriver on the Columbia to feed the commercial fishing industry, but the dam had decimated the Wallowa River fishery. The dam had been in place since 1905, when it was constructed with the hatchery to trap salmon returning to spawn. The dam was constructed in 1904 at the Minam Fish Hatchery, and on June 4, 1914, in a late-season snow storm, the dam was dynamited. One of the first, if not the first, to be removed over salmon impacts was one across the Wallowa River in northeastern Oregon. But for the Indians, it was a catastrophe.”Īlthough dams were known to impact salmon, few dams ever were removed. McDonald later wrote: “It was a sad day for the settlers who had grown to depend on the salmon as one of their staple foods. In 1915 Long Lake Dam, with no fish ladder, was completed on the Spokane River four miles above Little Falls Dam (completed in 1911, also without fish passage facilities), effectively ending salmon and steelhead passage some 30 years before Grand Coulee Dam would finish off Spokane River salmon and all other upriver anadromous stocks. Other tributary dams wiped out salmon runs long before mainstem Columbia and Snake river hydropower dams were built. Splash dams brutalized many salmon and steelhead spawning streams. Once a pool formed behind a splash dam, more logs would be dropped into the pool and, when it was full, the dam would be dynamited and the logs and water would sluice down the tributary to the main river and be floated to sawmills. Splash dams were nothing more than piles of logs that backed up small, temporary reservoirs on tributary streams of a larger river. Between 18, for example, loggers built 56 splash dams in the western Washington portion of the Columbia River Basin, and 55 more in the Willamette and Deschutes watersheds of Oregon. The impacts of dams on salmon and steelhead began practically as soon as the first dams were constructed. These are not all recent impacts, and the impacts are not limited to those from hydroelectric dams. Not until the 1990s did fishery officials and the public utility that owns and operates the dam devise an agreement to regulate its outflows, and others upstream, to protect the fish. For years after the dam was completed, water levels rose and fell with power generation at the dam, and egg nests (redds) and newly hatched juvenile salmon sometimes were stranded as water flooded and then retreated from low-lying shoreline areas. In the Hanford Reach of the Columbia, the most productive, and natural, fall Chinook spawning habitat remaining in the Columbia River Basin, water levels are affected by water releases from Priest Rapids Dam immediately upstream. By altering historic river flow patterns dam operations also led to changes in the Columbia River plume into the ocean, an important rearing area for juvenile salmon and steelhead. Dams also changed the food web in rivers by impounding reservoirs, as well as by altering the ecology downriver of dams through, for example, changes in sediment transport. Reservoirs also slow the flow of water and, through insolation, can cause its temperature to rise to levels that are lethal to salmon and steelhead. Inundation of shoreline areas in some parts of the Columbia River Basin, the Umatilla Reach of the Columbia behind John Day Dam and Hells Canyon of the Snake River, for example, wiped out historically productive spawning habitat for fall Chinook salmon. More than 40 percent of the spawning and rearing habitat once available to salmon and steelhead in the Columbia River Basin is permanently blocked by dams.ĭams also altered habitat by creating reservoirs. Where fish passage is not provided the blockage is permanent. Dams impact salmon and steelhead in a number of ways, from inundating spawning areas to changing historic river flow patterns and raising water temperatures.ĭams block passage of salmon and steelhead between spawning and rearing habitat and the Pacific Ocean.
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