The Snake River

Snake River is part of the larger Columbia River system. The natural ecology of the Snake River has been altered by the placement of dams on the river, altering the way Salmon move through the entire region and raising a number of questions about whether the dams are doing more harm than good. The Snake River is the main tributary of the Columbia River and extends some 1028 miles through both Yellowstone National Park and Grand Teton National Park. The river originates in Wyoming. The river empowers a number of hydroelectric plants along its route and so is a vital energy source for the country. The ecology of the Snake River has changed as a result of many of the projects along the length of the river, including the aforementioned series of dams and possible pollutants from the hydroelectric plants as well as from other environmental challenges in the region.

The Snake River

The Snake River was first discovered by whites when the Lewis and Clark Expedition crossed it early in the nineteenth century. The name of the river is a source of some speculation, with one theory being that it derives from an S-shaped snake sign that the Shoshone Indians made with their hands to mimic swimming salmon. Other names used for the river inlcude the Great Snake River, Lewis Fork, Lewis River, Mad River, Saptin River, Shoshone River, and Yam-pah-pa.

The Columbia River system drains a 259,000-square-mile basin covering territory in seven states (Oregon, Washington, Idaho, Montana, Nevada, Wyoming, and Utah) and one Canadian province (Columbia River 2005). This river is probably the most significant environmental force in the Pacific Northwest, flowing more than 1,200 miles from the base of the Canadian Rockies in southeastern British Columbia to the Pacific Ocean at Astoria, Oregon, and Ilwaco, Washington. Human beings have inhabited the region along the river for more than 10,000 years, but modern engineering in the 19th and 20th centuries has dramatically altered the Columbia River, so much so that some scientists today believe that the river is environmentally threatened and that drastic action should be taken to reverse the changes made to the Columbia over the last 150 years.

Human beings were present in the region beginning 10,000 years ago, as noted, and they first followed trails across the land made by migrating wildlife. This would have included elk and bison. Long-term residenc=y was not possible given the harshness of the winters, but nomadic tribes would move through the region at different times of the year. It was only in the 1890s that people made the area a year-round residence in the Grand Teton region. Erarlier momadic groups made use of the valley to harvest its meadoes for wild plants and edible roots, and the big game population was not large enough to support more than occasional hunting. Thes eearly peoples left the region between AD 1000 and 1600, to be replaced by tribes of Shoshone, Crow, Gros Ventre, and Blackfeet, groups that were also infreqeunt visitors to the Grand Tetons. Lewis and Clark passed through and returned to the east in 1806, after which expedition member John Colter returned to join a group of hunters looking for beaver along the upper Yellowstone River. A survey expedition came to the area in 1840 led by Jim Bridger, gatehring information on native tribes, farming and mining possibilities, and potential railroad routes. In 1872, President Grant named Yellowstone the first national park, beginning the tourism industry in the area and drawing many people who decided to stay.

The Homestead Act of 1862 contributed to the move of some into these kinds of area, with many settling around Jackson Hole in spite of poor grazing and farming conditions. In 1943, President Roosevelt named 221,000 acrs east of the Snake River the Jackson Hole National Monument. After years of contention, the federal government reimbursed owners for the land being aded to the monument and settled the issue (Human history in the Tetons 2001).

Comments on the mechanics of the Snake River have been made for dedcades, with early references noting the turgidity of the waters in some reagions and considering the issue of sedimentation. The changes that have been made in the river have also contributed to shifts in the patterns of sedimentation, and it was recently noted that some 100 to 150 million cubic yards of sediment have been deposited upstream of the four lower Snake River dams since the Ice Harbor project became operational in the early 1960s, meaning that one million cubic yards of sediment will cover a section of land (one square mile) to a depth of approximately 1 foot as a result. It has been determined that a breach in the four lower Snake River dams would allow approximately 50% of the previously deposited materials to be eroded and transported by the Snake River within the first few years after dam breaching. It is likely that the eroded materials would then be redeposited in Lake Wallula between the Snake River and Wallula Gap. McNary Dam's backwater pool extends up to Ice Harbor Dam, meaning that the very coarsest cobble materials could then be left in the vicinity of Ice Harbor Dam, although they could be subject to resuspension and further transport downstream to Lake Wallula at a later date by floods at a higher level than existed at the time they were first deposited (Lower Snake River Sedimentation 2005).

In this process, the coarsest sediments would be deposited first, with the sediment deposits becoming progressively finer as they are transported further downstream into Lake Wallula. At one time, these materials were deposited behind the lower Snake River dams. Because the flow velocities in Lake Wallula are generally lower than those in the Snake River, it is likely that most of these sediments will be deposited in Lake Wallula rather than being transported downstream of McNary Dam. The problem could increase because the rest of the sediments deposited earlier upstream of the lower Snake River dams and not eroded within the first few years of dam breaching would now be affected by long-term erosion by wind and rain. These could also be transported downstream in time by the Snake River to Lake Wallula, again adding to the deposits in that body of water (Lower Snake River Sedimentation 2005).

The Columbia River system includes the watershed, from which it is ecologically inseparable. The watershed is defined as the land area around the river that delivers runoff, sediment, and dissolved substances to the river and its tributaries. How healthy the watershed may be affects the temperature, flow rate, aquatic life, and other physical components of the river itself (The Columbia River Basin watershed and its ecosystems 2005). The watershed for the Columbia system covers seven states and one Canadian province, with the northernmost reach found in the high glaciers of the Canadian Rockies. The main body (or stem) of the Columbia River then runs over a thousand miles to empty into the Pacific, and as the river runs south and west, it is fed by many smaller rivers before being joined by the Snake River in Pasco, Washington. The Columbia River turns sharply west near there and forms a natural border between Washington and Oregon. The Snake is the largest of the rivers feeding into the Columbia River, and indeed the streams and small rivers feeding into the Snake represent 49% of the Columbia River Basins watershed below the Canadian border. The watershed covers nearly 260,000 square miles (The Columbia River Basin watershed and its ecosystems 2005).

High rates of rain from the hydrologic cycle give the watershed a seasonal supply of water. The rain that does not soak into the ground becomes runoff, and the runoff from the watershed fills the rivers, streams, wetlands, and lakes of the region. Some of the rain that seeps into the ground evaporates, but gravity draws other water deeper into the earth, at times creating an underground river. This groundwater gathers in layers of underground rock and eventually becomes an aquifer, of which there are many in the Columbia River Basin (The Columbia River Basin watershed and its ecosystems 2005).

These rivers are also involved with what is called the riparian zone, meaning the border of moist soils and plants found next to a body of water. This zone may consist of gently sloping shores, steep banks, or other types of terrain. As one travels down the river, such forces as geologic differences, altitude, varied river flow, and the types of organisms and vegetation that can survive and thrive from area to area cause changes in the nature of the river and the species which migrate to it. In the area downstream, the channel widens, the gradient flattens, and the water slows, and in such areas, more permanent plant species can survive, such as tree and shrub communities and specialized grasses and forbs (non-grasslike herbs). In turn, these plant species serve to provide food and shelter for the rich diversity of wildlife living along the riverbank. Among the animals found in these relatively lush riparian zones are elk, deer, bear, sheep, and mountain lions. In addition, smaller animals that live and feed along this biologically vital corridor may include birds (like the ring-necked pheasant, grouse, geese, falcons, great blue herons, hummingbirds and warblers), small mammals (such as longtail weasel and striped skunk), reptiles (garter snake and the western painted turtle), and amphibians (red-legged frog and the Pacific giant salamander). The flora and fauna often include many threatened, endangered, or sensitive species, among which could be the bald eagle, peregrine falcon, and kit fox (The Columbia River Basin watershed and its ecosystems 2005).

The plant life along the river can also has an effect on the health of the species living in the river by maintaining the health of the river by influencing the amount and kind of sediment in the river. The vegetation along the side of the river achieves this by anchoring soil, catching silt, filtering out pollutants, and absorbing nitrogen and phosphorus. This vegetation also provides shade to cool the water and so makes a habitat for insects and their predators (The Columbia River Basin watershed and its ecosystems 2005).

When there is too much sedimentation, which may occur when vegetation along riverbanks is removed by flooding or any other means, the river can become obscured. This occurs as sediment washes back into the water to cause turbidity, meaning that the sediment is stirred up and suspended in water. A river in this condition can impair the respiration of fish or other aquatic organisms. Such conditions can also cause sediment to cover gravel used for fish-spawning, raise the temperature of the water, and bury submerged plants (The Columbia River Basin watershed and its ecosystems 2005). This is the situation along much of the Snake River, some of it caused or exacerbated by the damming of the river. However, it is not clear if breaching the dams, as has been suggested, would be sufficient to alter the situation significantly given that breaching the dams would change the sedimentation but perhaps add to the turbidity.

Changes to the River

Many of the hydroelectric projects along the river alter the balance and can contribute to the sedimentation process. It is really the dams built for this purpose that cause the problem, and this includes dams built for other reasons, of which there are many. Specific ecosystem impacts are possible and are influenced by several variables, as follows:

the size and flow rate of the river or tributary where the project is located, the climatic and habitat conditions that are current, the type, size, design, and operation of the project, and whether cumulative impacts occur because the project is located upstream or downstream of other projects.

Dams create reservoirs or lakes, and these can significantly slow the rate at which water moves downstream. Because surface temperatures tend to become warmer as the slower moving or "slack," water absorbs heat from the sun, this can affect the nearby ecosystem. At the same time, the colder water sinks to the bottom because it has a higher density, and this in turn causes a layering effect called stratification, with the bottom layer the coldest and the top layer the warmest. There is also an ecosystem effect because the colder water that sinks toward the bottom contains reduced oxygen levels, and when water is released from the colder, oxygen-depleted depths, downstream habitat conditions change because of the reduced oxygen level in the water (How a hydroelectric project can affect a river 2005).

A related problem is cased by the accumulation of sediments, which are fine organic and inorganic materials that are typically suspended in the water but that can collect behind a dam because the dam itself is a physical barrier. Man-made and natural erosion of lands adjacent to a reservoir may cause sediment build-up behind a dam. The ecosystem can then be affected by the fact that 1) downstream habitat conditions can decline because these sediments no longer provide important organic and inorganic nutrients; and 2) because where sediment builds up behind a dam, "nutrient loading" can cause the supply of oxygen to become depleted because more nutrients are now available so that more organisms populate the area to consume the nutrients, using more oxygen. Gravel can be trapped behind a dam in the same way as sediment, and this can affect the ecosystem if there is a movement of gravel downstream (How a hydroelectric project can affect a river 2005).

According to a study conducted in 1991 by the U.S. Geological Survey, the water and sediment in the Snake River contains contaminants, found in streambed sediment and aquatic biota tissue. In 1992, fourteen sites in the upper Snake River Basin in Idaho and western Wyoming were analyzed, and mercury was identified as a contaminant in aquatic biota, representing contamination from natural or anthropogenic sources. Mercury enters the system from natural sources, including through the weathering of minerals and rocks. It also comes from human activities associated with mining, agriculture, and industry. Cinnabar is the most common natural source, and this is a mineral ore comprising mercury and sulfur. In streams, mercury occurs at higher concentrations in bed sentiment and biota than in the surrounding water. Microorganisms can synthesize inorganic mercury compounds into methylmercury, which is both the most bioavailable form of mercury and the most toxic form because concentrations accumulate in organisms and are then magnified in the food chain. Mercury is also a known mutagen and a carcinogen, capable of adversely affecting reproduction, growth and development, behavior, and the metabolism of the organism. The highest concentration of mercury was found in northern squawfish from the Columbia River Basin, thought to be caused by the presence of extensive natural cinnabar deposits and to mercury from mining in the basin. The elevated levels of mercury raise concerns because of the direct threat to human health from ingestion of these fish (USGS 2004).