Snake River: A Navigation and Spawning Dilemma

The Snake River in northwestern United States is 1735 km long, the largest tributary of the Columbia River and is the 13 th longest river in the United States. The Snake River drainage basin includes parts of six U.S. states. The Snake River Plain was created by a volcanic hotspot that lies beneath Yellow-stone National Park. The previous Ice Age carved out canyons, cliffs and wa-terfalls along the middle and lower Snake River. The Missoula Flood was to the north and Bonneville Flood to the south altered the Snake River and surrounding landscape. The Snake River has a drainage basin of 282,000 km 2 in the states of Oregon, Washington, Utah, Nevada and Idaho. The Snake River drops from mountain elevations of 3000 m to its confluence with the Columbia River. The river is one of the most biologically diverse freshwater systems in the United States with trails designed to promote recreational tourism, increase use of the Snake River and create generations of people who care about the river and are willing to protect and provide environmental stewardship of the river watershed resources.


Introduction
The Snake River is the largest of the Columbia River tributaries (  Palisades Reservoir. The river leaves the mountains and crosses the broad Snake River Plain (Figure 3) of southern Idaho [2]. At the western edge of Idaho, it joins with Boise River. The Snake River turns north and forms the boundary between Idaho and Washington. At Lewiston, Idaho ( Figure 4) the Snake River then turns west to join the Columbia River south of Pasco, Washington.
The primary objective of the study is to document the major Ice Age Flooding events which created the Snake River passageway to the West which permitted United States settlement of the Northwest. The Bonneville Flood, the first of the major Ice Age flooding events eroded soils creating the Snake River Canyon and the widened Hells Canyon. These erosional events created the Snake River and

Snake River Watershed
The 279,719 km 2 Snake River watershed lies between the Columbia Plateau on the northwest and the Rocky Mountains on the east [3].            Plain just west of the Continental Divide ( Figure 12 and Figure 13).

Geology of Snake River Basin
About 42,000 years ago, lava flowing from Cedar Butte in current southeast Idaho blocked the Snake River at Eagle Rock. A 64 km long American Falls Lake formed behind the lava plug and the lake was stable for 30,000 years. Lake

Snake River Basin
The World Wide Fund (WWF) for Nature [5] divides the Snake River's watershed into two freshwater ecoregions: the "Upper Snake" ecoregion and the "Columbia Unglaciated" ecoregion. Shoshone Falls (Figure 19) has presented a   total barrier to the upstream movement of fish for 30,000 to 60,000 years, and forms the boundary between these two regions. Because the Wood River is biologically distinct from the rest of the downriver Snake the WWF placed the ecoregion boundary about 50 km downriver from Shoshone Falls to include the Big Wood River in the Upper Snake ecoregion. Only 40% of the Wood River's fish fauna and 35% of the fish fauna above the falls are shared with the Lower Snake River ( Figure 19). The mostly semi-arid climate of the Snake River watershed receives on average, less than 30 cm of rainfall per year.

Early Inhabitants
For at least 11,000 years, the Indigenous people have lived along the Snake River. Open Journal of Soil Science In eastern Snake River Plain, there is evidence of Folsom, Clovis, and Plano cultures dating back to at least 10,000 years ago. A vital food supply of the Native Americans who lived along the Snake River and downstream from the Shoshone Falls was salmon and steelhead from the Pacific Ocean and spawned by millions in the river. Historians [4] have divided the time period into three periods: 1) the "Broad Spectrum Foraging" period dating from 11,500 to 4200 years before present, and people during this time period drew on a wide variety of food resources; 2) the "Semi-sedentary Foraging" period from 4200 to 250 years BCE with an increased dependence on fish, especially salmon as well as food preservation and storage; and 3) called the "Equestrian Foragers" period, the 250 to 100 years before present, was characterized by large horse-mounted tribes that  who introduced the skill of buffalo hunting on horses, which was acquired from Europeans. For the people living downstream from Shoshone Falls, salmon and steelhead from the Pacific Ocean spawned by the millions in the river and was a vital food supply. The explorers and fur trappers change the use of the resources of the Snake River basin. By the 1850s the Oregon Trail (Figures 22-24) had become well established bring settlers to the Snake River region. Railroads and steam boats were used to move minerals and agricultural products along the river throughout the 19 th and 20 th centuries.

Horses
By 1700CE horses, originally acquired from Spanish in New Mexico and spread widely via native trade networks, reached the Shoshone of the Snake River Plain. The Nez Perce, Flathead and Cayusepeople acquired their first horses around 1730CE. The Nez Perce and Cayuse kept large herds and made annual trips to the Great Plains for bison hunting and adopted the plains culture to a significant extent, and became the main conduit through which horses and the plains culture diffused into the Columbia River region. Along with horses came aspects of the emerging Great Plains culture such as the linking of wealth and prestige to horses and war. Other tribes acquired horses and aspects of the plains culture as well.

Exploration and Settling of the Northwestern United States
The Lewis and Clark Expedition (1805-1806) was the first American group to cross the Rocky Mountains ( Figure 25) the hard way and travel down the Snake and Columbia rivers to the Pacific Ocean [8]. The party crossed the Lemhi Pass, a few kilometers from present-day Salmon, Idaho. The party was the first Europeans Open Journal of Soil Science

Oregon Trail the Settlement Pathway to Northwest United States
By the middle of the 19 th century, the Oregon Trail had been established and generally followed along the Snake River. However, settlers had to cross the Snake River when on the Oregon Trail. One ferry crossing was near present day

Steamboat Navigation on the Snake River
The Snake River was far more difficult for steamboats to navigate than the Columbia River [9]. The 320 km Snake drops over 2600 m in elevation. From the 1860s to the 1940s, steamboats traveled the Snake River from the confluence with the Columbia River to near the confluence with the Imnaha River just below Hells Canyon. Most of the steamboats stopped at Lewiston (Figure 1), located at the confluence of the Clearwater and Snake rivers. This section was the easiest to navigate, but there were still over 60 sets of rapids to traverse.

Animal and Plant in the Snake River Valley
In addition to aquatic species, much of the Snake River watershed supports large animals including numerous species of birds, mammals, reptiles and amphi- the Snake River Aquifer. The Snake Riverhead waters, inside protected areas, remain heavily forested. The Snake River watershed includes a diversity of vegetation zones both past and present. A majority of the watershed was once covered with shrub-steppe grassland. Along the length of the Snake River and its tributaries there are riparian zones, wetlands and marshes. At higher elevations, conifer (Pinophyta spp.) forests, of which ponderosa pine (Pinus ponderosa) is most common, dominate the landscape. The basin ranges from alpine to semi-desert climates, providing habitat for hundreds of species of plants. In southeastern Washington, the lowermost part of the watershed is now mostly occupied by irrigated farms. The rest of the Plateau area is characterized by dry lakes, low hills, and an arid, borderline desert, climate.

Hiking Trails in Snake River Canyon
The 330 km Idaho-Oregon Snake trail runs along the Snake River in Eastern Oregon and Southwest Idaho. This trail ends at Farewell Bend State Park, Oregon and begins at Two Island Crossing State Park, Idaho. Hells Canyon [3] provides the ultimate back packing experience. Due to rattlesnakes, poison ivy and the fact that the rim is thousands of meters above the canyon floor, there is a serious risk of a sore neck from the amount of time spent looking both upward and downward while hiking.
After Evel Knievel attempted to jump the Snake River canyon (Figure 18, Figure 27 and Figure 28) on a rock-powered motorcycle, he became a local, national and international legend and the local visitor center has an exhibit featuring Evel Knievel's jump; an improved road is being built to the jump site. The jump failed and he had to parachute safely to the valley floor. Two Island Crossing ( Figure 29) and (Figure 30) has an Oregon Trail History and Education Center with self-guided tours and group educational tours.

Salmon and Other Anadromous Fishes in Snake River
Before European settlement, the Snake River was one of the most significant rivers for the spawning of anadromous fishes that are hatched in the headwaters of rivers, live in the ocean, and return to spawn in the river. The river supported species including chinook salmon (Oncorhynchus tshawytscha), coho salmon (Oncorhynchus kisutch), and sockeye salmon (Oncorhynchus nerka), as well as steelhead (Oncorhynchus mykiss), white sturgeon (Acipenser transmontanus), and Pacific lamprey (Entosphenus tridentatus). It is known that before the construction of dams on the Snake River, there was a sockeye salmon run was about 150,000 and three major chinook salmon runs in the river totaling about 120,000. The historical barrier to fish migration on the Snake River was Shoshone Falls, a waterfall in the Snake River Plain.

Lower Snake River Dams
Starting in 1890s, 15 major dams were built on the Snake River to generate Open Journal of Soil Science     water for irrigation is pumped from the Snake River Aquifer. In 1976, the Teton Dam collapsed flooding the Upper Snake River valley. In addition to irrigation, many produce electricity, provide navigation channel and flood control. The fish passage is limited to a stretch of the Snake down river from Hells Canyon ( Figure 11).

Lower Snake River Dam Removal Proposal
A controversy has erupted since the late 20th century over the four lower Snake River dams. The primary reason being that removing the dams would allow anadromous fish to reach the lower Snake River tributaries and spawn [10]. Some agricultural groups in the Pacific Northwest have fiercely opposed removing  the four dams on the Snake River since it would create a hole in the energy grid that could not immediately be filled. Navigation on the Lower Snake River would also suffer, as submerged riffles, rapids and islands would be exposed. In southeastern Washington, irrigation pumps would also have to pump the Snake River water greater distances. In addition to arguing for restoring salmon runs the dam removal proponents argue that the power is replaceable, that only one of the four reservoirs supplies irrigation water and that the grain transportation system could be replaced by railroads.
A letter of concern [11] dated March 26, 2021 was signed by a broad coalition of ports, more than 40 agricultural groups, and other river stakeholders along the Columbia/Snake River system (Figure 1) are opposing the plan to breach four Snake River dams. The plan to protect spawning salmon was proposed by Rep. Mike Simpson of Idaho and includes compensation for farmers and others that would be hurt by the plan. The letter claims that the plan would do little to  Associates, see letter of concern [11], a wheat-export marketing organization, and all United States farmers, including those in the Great Plains produce about 1.9 billion bushels of wheat a year, which would fill 5000 Panama Canal Open Journal of Soil Science Zone-sized ships [12] a year. In the Pacific North West travel by barge on the Snake River accounts for nearly 10% of U.S. wheat exports.
The Bonneville Power Administration has pointed out that dam removal could cost the region $16 billion to replace power generated at the dams over a 20-year span using clean energy. Replacing the emissions-free hydropower with other sustainable and emission-free sources could raise electricity rates by 50 percent, and the electricity bills of average, public customer could increase by 25 percent. An additional environmental impact would be the "brown" effect of lock and dam closures which would increase emission by rail and trucks. Over 149,000 semi-trucks or 38,000 rail cars would be needed to move cargo which in addition to wheat, includes fuel products, fertilizer, wood products and large industrial components like wind turbine parts that previously went by barge in 2018. This assumes that many drivers, trucks, rail cars, and locomotives could be sourced, and highway and rail lines through the sensitive airshed of the Columbia River Gorge could be accommodate the additional traffic. The environmental impact of the dam breaching and shifting of cargo from barges to rail and trucks would result in significant annual increases in emissions. According to the letter of concern [11] the emission would total over 860,000 tons of CO 2 , 7.5 tons of PM (particulate matter), 69.7 tons of CO (carbon monoxide), 306 tons of NO x , and 7 tons of VOC (volatile organic compound).
The letter [11] concludes that 40 pro-dam associations lead by the Association of Wheat Growers "strongly support science-based salmon recovery solutions that address the myriad threats to Northwest fish runs over every part of their life cycle. Though we do not question Rep. Simpson's commitment to salmon, this proposal continues the narrow focus on four runoff-river dams with some of the highest fish passage numbers in our region. It is a speculative and costly plan that assumes we must choose between productive, fish-friendly federal projects and our Northwest salmon and steelhead runs".

Pollution of the Snake River
Throughout the 20th century agricultural runoff from ranches and farms in the Snake River Plain [13] and many other areas has severely damaged the ecology of the river. In the first decade of the 20th century after the first irrigation dams on the river began to operate much of the arable land within a few kilometers wide zone along the Snake River was cultivated or turned into pastureland. The Snake River became polluted by agricultural return water flows. Runoff from several feedlots was dumped into the river until laws made the practice illegal. Fertilizers, manure and other pollutants and chemicals washed into the river greatly increasing nutrient load, especially of fecal coliforms, phosphorus, and nitrogen. During low water, algae blooms depleted the rivers oxygen supply [13]. The Milner Dam and other dams divert water from the Snake River for irrigation, which causes many of the pollution problems in the Snake. Much of the return flows do not go directly back into the Snake River, but, rather, feed the Snake River Aquifer underneath the Snake River Plain ( Figure  Open Journal of Soil Science 13) and (Figure 14). After absorbing any surface pollutants, the water diverted from the river for irrigation re-enters the ground and feeds the aquifer. Although the aquifer has maintained its level, it has become increasingly laced with contaminants. Water in the aquiferre-enters the river as springs and eventually travels to the west side of the Snake River Plain. Throughout much of the Snake River Plain and Hells Canyon, excessive sediment is also a recurring problem. In December 2007, the U.S. Environmental Protection Agency (EPA) issued an order requiring owners of fish farms along the Snake River to reduce, by 40%, their phosphorus discharge. Pollutant levels, including that of dissolved nutrients, water temperature, and sediment, are required to meet certain Snake River standards, in Hells Canyon ( Figure 13) upstream of the Salmon River confluence.

Conclusion
The movement of the Farallon Plate under the North American plate created a hot spot with volcanic eruptions and lava flows that changed the course of the Snake River. The Bonneville Flood, the first of the major Ice Age flooding events eroded soils and scored the underlying basalt bedrock creating the Snake River Canyon and the widened Hells Canyon. The flood waters deposited huge amounts of sediment in the middle Snake River, and created and re-charged the unique Snake River Aquifer, which is used currently to irrigate farmland in the Snake River bottomlands. These erosional events created the Snake River and the passageway to the West. Without this Snake River passageway, the U.S. settlement of the Northwest would not have happened and the region may have become part of Canada. Below the Shoshone Falls, the Lower Snake River supported salmon runs prior to European and American settlement. Since the late 20 th century, the four lower Snake River dams have created a controversy. The wheat farmer needed cheap river transportation and settlers needed a source of electricial energy so dams were placed on the Lower Snake River. However, the creation of the dams, some without fish ladders, and over fishing for canneries, drastically reduced both fish spawning and fish populations.