Snake River ecosystem
The Snake River Ecosystem is a vital component of the broader Columbia River watershed, spanning approximately 173,984 square miles across parts of Wyoming, Idaho, Washington, and Oregon. As the longest tributary of the Columbia River, the Snake River stretches about 1,078 miles and has been significantly shaped by geological events such as volcanic activity, flooding, and glaciation. The river supports diverse habitats, hosting a wide array of flora and fauna, including critical species like salmon and steelhead, which are integral to the local ecosystem and cultural heritage of Indigenous peoples such as the Nez Perce and Shoshone.
Historically, these fish have been essential for sustenance and have influenced the cultural practices of communities along the river for millennia. However, the ecosystem faces significant challenges due to human activities, particularly the construction of hydroelectric dams that impede fish migration and disrupt natural river flows. The dams have resulted in increased mortality rates for juvenile fish and have led to calls for their removal to restore fish populations and fulfill treaty obligations to Indigenous peoples. Climate change is also a looming threat, with potential reductions in water runoff and increased pollution impacting the river's health.
Overall, the Snake River Ecosystem is a complex interplay of natural processes and human impacts, with ongoing efforts to balance environmental sustainability, cultural heritage, and modern development.
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Subject Terms
Snake River Ecosystem
Category: Inland Aquatic Biomes.
Geographic Location: North America.
Summary: The Snake River and its peoples are defined by fish, especially salmon, and the struggle continues to provide safe, clean habitat in the face of dams and climate change.
The mighty Columbia River in the Pacific Northwest region of the United States has more than 60 tributaries, and the Snake River is its largest and most important. The Snake River watershed of 173,984 square miles (280,000 square kilometers) is larger than the state of Idaho, with an average discharge of over 53,000 cubic feet (1,500 cubic meters) per second. The Snake River itself is approximately 1,078 miles (1,735 kilometers) long, and flows through forests, mountains, and plains in Wyoming, central Idaho, southeast Washington, and northeast Oregon. Throughout its long history, volcanoes, flooding, and glaciers have shaped the river and its shores.
The Snake River plain was created by a volcanic hot spot beneath Yellowstone National Park, which holds the headwaters and origin of the river. Flooding as the glaciers retreated after the ice age created the current landscape, including eroded canyons and valleys. Mountains and plains are typical terrain along the river. The Snake River has more than 20 major tributaries, most of them in the mountains; Hells Canyon is the deepest river gorge in North America.
The Snake River is home to salmon and steelhead, which were central to the lives of the Nez Perce and Shoshone, the dominant tribal nations before the Europeans came. People have lived along the Snake River for over 15,000 years. The river may have been given its name when European Americans misinterpreted a Shoshone hand signal representing fish to reference a snake.
Flora and Fauna
The areas near the Snake River contain diverse flora, and the river basin itself was once home to broad shrub-steppe grassland. Riparian, wetland, and marsh habitats are found along the Snake River today, and thus a broad range of plants inhabit the area. At higher elevations, Ponderosa pine, Douglas fir, and other conifers are dominant. In drier areas, sagebrush and desert plants are the widely distributed dominant vegetation.
Salmon remain perhaps the most important animal species of the Snake River. Portions of the watershed have the largest, highest, and most intact salmon habitats in the continental United States. Anadromous steelhead, chinook salmon, and sockeye salmon are born in the Snake River watershed, swim downstream, grow and live in the Pacific Ocean, and return to the river to breed, spawn, and die. The river is also home to the bull trout, which overwinters there, and other year-round species of fish.
Through their life cycle and migrations, anadromous fish such as salmon and steelhead transfer nutrients from the oceans to inland rivers, tributaries, forests, and mountains. These fish also provide one of the primary foods of killer whales in coastal waters, and of the grizzly bear, gray wolf, wolverine, lynx, and other carnivores inland. More than 200 bird species also benefit from salmon, including birds of prey such as eagles and falcons. Other notable fauna in the Snake River biome include several species of frogs, such as the inland tailed frog, Northern leopard frog, and Columbian spotted frog, as well as reptiles including the western toad.
Threats
Pressures began to mount upon salmon in the 19th century, with the establishment of commercial fisheries and canneries on the river. Up until the 1930s, native people continued to live on the river and fish year round, moving with the seasonal and migratory patterns of the fish.
The most significant impact occurred in the 20th century, with the widespread construction of hydroelectric dams along the Columbia River and all its tributaries, including four dams on the lower Snake River. The Lower Snake River Project resulted in four locks and dams—Ice Harbor Dam, Lower Monumental Dam, Little Goose Dam, and Lower Granite Dam—being constructed in Washington State. These dams became operational between 1961 and 1975. They are run-of-river facilities; this means the dams have limited storage capacity in their reservoirs, and water passes through the dam at about the same rate and volume as it enters the reservoir. The dams provide inexpensive hydropower, irrigation, navigation, and recreation to the region, but have had devastating impacts on fish and fish habitat.
Dams affect salmon and steelhead in many ways; they flood spawning areas, change historic river flow patterns, and raise water temperatures. Dams block the passage of fish between their spawning and rearing habitat and the Pacific Ocean. If no artificial fish passage is provided, that blockage is permanent. Dams block the passage of both adult and juvenile fish. Adult fish passage has more recently been addressed through the creation of fish ladders.
The more significant problem is the need for juvenile fish to go through or around the dams. Juvenile fish that are drawn into the dam turbines can be killed or injured. The intense water pressure alone can kill the fish. If turbine passage is the only way past a dam, 10 to 15 percent of the fish that go through each dam’s turbines will die. With that much mortality at each dam, fish that pass multiple dams—fish from the Snake River must pass through up to eight dams—have a statistically high probability of dying before they reach the ocean.
Environmental groups and scientists have requested the federal government to remove the four lower Snake River dams, arguing that mortality of juvenile fish would significantly decrease and that overall fish populations would recover after this removal. They also argue that these species are more likely to adapt to and survive climate change if these dams are removed. Salmon and steelhead require clear, cold water. The mountainous areas of the Snake River are likely to stay cool, and could be sanctuaries for salmon and steelhead populations throughout the region as global warming pushes up temperatures in the lower altitudes.
The dam removal could also be consistent with federal government obligations to native peoples in the Pacific Northwest. These groups signed treaties in the 19th century for rights to fish for salmon and steelhead in their usual and accustomed places. Government mainly failed in its obligation, as federal dams are the major cause in the decline of these fish. Therefore, the removal of these dams would be consistent with fulfilling federal treaty obligations.
Anticipated climate change impacts along the Snake River are likely to be felt mostly in the form of reduced snowfall, which will decrease the amount of water runoff into the river system. This in turn may affect the availability of water, especially during the summer months, to keep habitats fully supportive of native plants and animals. Some research has found that recent sharp increases in the amount of zinc and other toxic metals in the upper Snake River streams—quite damaging to fish and other creatures—is apparently tied to warmer average air temperatures. Scientists are attempting to pinpoint the processes involved, but suspect lower levels of water to filter out metals is one aspect, as plants draw up more water when evaporation rates increase. In addition to lower filtration rates, more rock surface exposed to sunlight, air, and wind—because of lower stream levels—allows faster weathering and movement of metals into the water.
Bibliography
Berwyn, Bob. “Global Warming May Be Upping Snake River Metals Pollution.” Summit County Voice, September 12, 2012. http://summitcountyvoice.com/2012/09/12/global-warming-may-be-upping-snake-river-metals-pollution/.
Lovell, Mark D. and Gary S. Johnson. Assessment of Needs and Approaches for Evaluating Ground Water and Surface Water Interactions for Hydrologic Units in the Snake River Basin. Moscow: Idaho Water Resources Research Institute, 1999.
Slaughter, Richard A. and Don C. Reading. “Snake River Case Study: Institutions, Adaptation, the Prior Appropriation Doctrine, and the Development of Water Markets.” Climate Impacts Group, University of Washington. http://cses.washington.edu/cig/res/sd/snakecasestudy.shtml.
Storch, Adam J., et al. "A Review of Potential Conservation and Fisheries Benefits of Breaching Four Dams in the Lower Snake River (Washington, USA)." Water Biology and Security, vol. 1, no. 2, 2022. DOI: 10.1016/j.watbs.2022.100030. Accessed 1 Sept. 2022.