Shoshone Falls ( ) is a waterfall in the western United States, on the Snake River in south-central Idaho, approximately northeast of the city of Twin Falls. Sometimes called the "Niagara of the West," Shoshone Falls is in height, higher than Niagara Falls, and flows over a rim nearly in width.
Formed by the cataclysmic outburst flooding of Lake Bonneville during the Pleistocene ice age about 14,000 years ago, Shoshone Falls marks the historical upper limit of fish migration (including salmon) in the Snake River, and was an important fishing and trading place for Native Americans. The falls were documented by Europeans as early as the 1840s; despite the isolated location, it became a tourist attraction starting in the 1860s.
At the beginning of the 20th century, part of the Snake River was diverted for irrigation of the Magic Valley. Now, the flows over the falls can be viewed seasonally based on snowfall, irrigation needs and hydroelectric demands. Irrigation and hydroelectric power stations built on the falls were major contributors to the early economic development of southern Idaho.
The City of Twin Falls owns and operates a park overlooking the waterfall. Shoshone Falls is best viewed in the spring, as diversion of the Snake River can significantly diminish water levels in the late summer and fall. The flow over the falls ranges from more than during late spring of wet years, to a minimum "scenic flow" (dam release) of in dry years.
Characteristics Shoshone Falls is in the Snake River Canyon on the border of Jerome and Twin Falls counties, upstream from the Snake River's confluence with the Columbia River. It is the tallest of several cataracts along this stretch of the Snake River, being located about downstream from Twin Falls and upstream from Pillar Falls.
Directly above Shoshone Falls, the Snake River narrows to less than wide and rushes over a series of rapids split by islands, before plunging over a vertical, horseshoe-shaped cliff high and wide. The appearance of the falls varies significantly with the river's flow rate. During high water, the falls appear as a single block stretching the full width of the river. In low water, the falls split into four or more separate drops; the widest, northern section is also called Bridal Veil Falls.
Flows Located in an arid region, Shoshone Falls naturally received most of its water from snowmelt in the Rocky Mountains of Idaho and Wyoming near Yellowstone and Grand Teton National Parks, and to a lesser extent springs in the Snake River Canyon above Twin Falls. A large number of reservoirs, and massive diversions for the irrigation of nearly of farmland, have greatly reduced the volume of water reaching the falls, such that the canyon springs are now the primary water source. The average Snake River flow at the Twin Falls stream gaging station is . For comparison, the average Snake River flow at Idaho Falls – upstream – is . The average flow below Milner Dam, upstream, is just , and is frequently zero in the late summer and fall.
Idaho Power's Shoshone Falls Dam is located directly upstream from the falls and diverts water to the Shoshone hydroelectric plant, further reducing the water volume. Idaho Power is required to maintain a minimum daytime "scenic flow" of from April through Labor Day, although even this small flow can be difficult to achieve due to a lack of water in the Snake River. Further complicating the issue is that most irrigation water is needed in the summer, which coincides with the peak tourist season. The Shoshone power plant draws up to of water per second; thus, the flow of the falls will only increase if the Snake River flow exceeds the combined plant capacity and scenic flow requirement. The best time to view the falls is between April and June, when snowmelt is peaking, and when water is released from upriver reservoirs to assist steelhead migration.
The highest flow ever recorded at Twin Falls was on June 10, 1914, and the lowest was on April 1, 2013. On a monthly basis, June generally sees the heaviest flows, at , and August the lowest flows, .
Geology Most of the rocks underlying the Snake River Plain originated from massive lava flows related to eruptions of the Yellowstone hotspot over many millions of years. Shoshone Falls flows over a 6-million-year-old rhyolite or trachyte lava flow that intersects the weaker basalt layers comprising the surrounding Snake River Plain, creating a natural knickpoint that resists water erosion.
The falls themselves were created quite suddenly during the cataclysmic Bonneville Flood at the end of the Pleistocene ice age, about 14,500–17,000 years ago, when pluvial Lake Bonneville, an immense freshwater lake that covered much of the Great Basin, overflowed through Red Rock Pass into the Snake River. About of water were released, 1,500 times the average annual flow of the Snake River at Twin Falls. The massive flow of water carved the Snake River Canyon in a matter of several weeks, sculpting falls such as Shoshone Falls where the local geology intersected harder underlying rock layers.
The immense Snake River Aquifer is formed in the region's porous volcanic rock and recharged each year by melting snow in the surrounding mountains. Because the Shoshone Falls canyon lies lower in elevation than the surrounding terrain, groundwater is forced to the surface via large springs in the canyon walls. Despite the almost total diversion of the river upstream from Milner Dam, these springs can provide up to of water to the falls. Spring flow varies widely depending on the season, although it has increased since the 1950s due to irrigation water on the surrounding plain percolating into the aquifer.
Ecology Due to its great height, Shoshone Falls is a total barrier to the upstream movement of fish. Anadromous fish (which live in the ocean as adults, but return to fresh water to lay eggs) such as salmon and steelhead/rainbow trout, and other migratory fish such as sturgeon, cannot pass the falls. Prior to the construction of many dams on the Snake River below Shoshone Falls, spawning fish would congregate in great numbers at the base of the falls, where they were a major food source for local Native Americans. Yellowstone cutthroat trout lived above the falls in the same ecological niche as rainbow trout below it, although their range has decreased since the 19th century due to river diversions and competition from introduced species such as lake trout.
Due to this marked difference, the World Wide Fund for Nature uses Shoshone Falls as the boundary between the Upper Snake and the Columbia Unglaciated freshwater ecoregions. The Snake River above Shoshone Falls shares only 35 percent of its fish species with those of the lower Snake River below the falls. Fourteen fish species found in the upper Snake are also found in the Bonneville freshwater ecoregion (which covers the Great Basin portion of Utah), but not the lower Snake or Columbia rivers. The upper Snake River is also high in freshwater mollusk endemism (such as snails and clams).Abell, Robin A., David M. Olson, Eric Dinerstein, Patrick T. Hurley et al. (WWF) (2000). Freshwater Ecoregions of North America: a conservation assessment. Island Press. .
History
Native peoples and explorers
The Shoshone Falls are named for the Lemhi Shoshone or Agaidika ("Salmon eaters") people, who depended on the Snake River's immense salmon runs as their primary food source, though they also supplemented their diet with various roots, nuts and large game such as buffalo. Because the falls are the upstream limit of salmon migration in the Snake River, they served as a central food source and trading center for the native peoples, who fished with willow spears tipped with elk horn. The Bannock people also traveled to Shoshone Falls each summer to gather salmon.
Although the Lewis and Clark Expedition encountered the Shoshone Indians in 1805–06, they did not pass through the Shoshone Falls area. The 1811 Wilson Price Hunt Expedition, whose goal was to scout routes for the growing fur trade, traveled down the Snake River as far as Caldron Linn, a wild rapids located near present-day Murtaugh. There, where the river drops into the precipitous Snake River Canyon, a canoe capsized and one of Hunt's Canadian boatmen was drowned. Although the party explored the canyon for several miles downstream, Hunt's journal does not mention any waterfalls as large as Shoshone Falls. Hunt then split the group to make foraging easier and they basically walked out of Idaho.Hunt, Wilson Price; Franchère, Hoyt C., editor and translator (1973). Overland Diary of Wilson Price Hunt, translated from the original French Nouvelles Annales des Voyages (Paris, 1821). Oregon Book Society. The routes they pioneered became part of the Oregon Trail, which brought many emigrants from the eastern United States to the Shoshone Falls area.
Over the next thirty years, American and British-Canadian fur trappers hunted throughout south-central Idaho and are believed to have observed Shoshone Falls. However, none of those who kept journals mentioned the feature.Beal, Merrill D.; Wells, Merle W. (1959). History of Idaho, Lewis Historical Publishing Company, Inc.
John C. Frémont passed through the Shoshone Falls area during his 1843 expedition, which aimed to map the country through which passed the western half of the Oregon Trail.Fremont, John C. Frémont (1845). Report of the Exploring Expedition to the Rocky Mountains ... The Senate Of The United States, Government Printing Office. None of his party observed the falls, however, because they left the river canyon (probably near Murtaugh) and cut southwest across a sandy plain to reach Rock Creek.Gentry, Jim (2003). In the Middle and On the Edge: The Twin Falls Region of Idaho, College of Southern Idaho. . They returned to the canyon rim where Rock Creek enters the Snake. There, he observed the Thousands Springs, which he described as “a subterranean river [that] bursts out directly from the face of the escarpment.”
They descended into the canyon with some difficulty, made some river measurements, and continued downstream. They camped about a mile below what Frémont called "Fishing Falls": "a series of cataracts with very inclined planes, which are probably so named because they form a barrier to the ascent of the salmon; and the great fisheries from which the inhabitants of this barren region almost entirely derive a subsistence commence at this place." He observed that the salmon were "so abundant that they [the Shoshone] merely throw in their spears at random, certain of bringing out fish." This stretch of the river is now known as Salmon Falls. Early encounters between Europeans and Native Americans were generally friendly, but eventually brutal conflicts broke out over land ownership. After the Snake War, some twenty years later, the Shoshone were confined on reservations elsewhere.
Pioneer traffic along the Oregon Trail through Idaho increased steadily from 1843 on, with a spurt after Frémont's journal was published and distributed. In 1847, some 4,000 emigrants passed through on their way to Oregon.Unruh, John D. Jr. (1929). The Plains Across: The Overland Emigrants and the Trans-Mississippi West, 1840-1860. University of Illinois Press. . One of the parties that year included Roman Catholic Bishop Augustin-Magloire Blanchet, who had been appointed to lead the new Diocese of Walla Walla. Traveling along the north side of the river, the group made a detour, perhaps guided by a former trapper who was familiar with the area. Blanchett then made the first known written record of seeing Shoshone Falls. Being from Quebec, Canada, he called the feature “Canadian Falls.”Blanchet, Augustine Magloire Alexander (1978). Journal of a Catholic Bishop on the Oregon Trail, Ye Galleon Press.