The 'Snake River' is a major
tributary of the
Columbia River in the
U.S. states of
Wyoming,
Idaho,
Oregon, and
Washington. The river's length is 1,040 miles (1,674 km), its
watershed drains , and the average discharge at its mouth is 56,900 cubic feet per second (1,610 m³/s). The river flows from its source in
Yellowstone National Park through a series of mountain ranges, canyons, and plains.
Geography
Basin overview
The Snake River's drainage basin includes a diversity of landscapes. Its upper reaches lie in the
Rocky Mountains. In southern Idaho the river flows through the broad
Snake River Plain. Along the Idaho-Oregon border the river flows through
Hells Canyon, part of a larger physiographic region called the
Columbia River Plateau, through which the Snake River flows through Washington to its confluence with the Columbia River. Parts of the river's basin lie within the
Basin and Range province.
The Snake is the largest tributary of the Columbia River, with a mean discharge of 50,000 cubic feet per second (1,400 m³/s),
[1] or 56,900 cubic feet per second (1,610 m³/s) according to the
USGS, the 12th largest in the United States.
Geology
For much of its course the Snake River flows through the
Snake River Plain, a
physiographic province extending from eastern Oregon through southern Idaho into northwest Wyoming. Much of the Snake River Plain is high desert and semi-desert at elevations averaging around 5,000 feet (1,500 m). Many of the rivers in this region have cut deep and meandering canyons. West of Twin Falls, the plain is mainly covered with stream and lake sediments. During the
Miocene, lava dams created Lake Idaho, which covered a large portion of the Snake River Plain between Twin Falls and Hells Canyon. This large lake expanded and contracted several times before finally receding in the early
Pleistocene. In more recent geologic time, about 14,500 years ago, glacial
Lake Bonneville spilled catastrophically into the Snake River Plain. The flood carved deep into the land along the Snake River, leaving deposits of gravel, sand, and boulders, as well as a scabland topography in places. Results of this flood include the falls and rapids from Twin Falls and Shoshone Falls to Crane Falls and Swan Falls, as well as the many "potholes" areas.
[2]
The Snake River Aquifer, one of the most productive
aquifers in the world, underlies an area of about 10,000 square miles (25,900 km²) in the Snake River Plain. Differences in elevation and rock permeability result in many dramatic
springs, some of which are
artesian. The
groundwater comes from the Snake River itself as well as other streams in the region. Some streams on the northern side of the Snake River Plain, such as the
Lost River are completely absorbed into the ground, recharging the aquifer and emerging as springs that flow into the Snake River in the western part of the plain. The
hydraulic conductivity of the basalt rocks that make up the aquifer is very high. In places water exits the Snake and Lost rivers into ground conduits at rates of nearly 600 ft³/s (17 m³/s).
[3] Due to stream modifications and large-scale irrigation, most of the water that used to recharge the aquifer directly now does so in the form of irrigation water drainage.
[4]
Upper course
The Snake originates near the
Continental Divide in
Yellowstone National Park in northwest
Wyoming and flows south into
Jackson Lake in
Grand Teton National Park, then south through
Jackson Hole and past the town of
Jackson. The river then flows west through Wyoming's
Snake River Canyon, then enters
Idaho at the
Palisades Reservoir.
The Snake River flows northwest to its confluence with
Henrys Fork near
Rigby. The region around the confluence is a large
inland delta. Above Henrys Fork, the Snake River is sometimes called the South Fork Snake River, since Henrys Fork is sometimes called the North Fork Snake River.
The Snake River then swings south in an arc across southern Idaho, following the Snake River Plain. It passes the city of
Idaho Falls and a region of irrigated agriculture. North of the
Fort Hall Indian Reservation the river is impounded by the
American Falls Dam. The dam and reservoir are part of the Minidoka Irrigation Project managed by the
United States Bureau of Reclamation. The
Portneuf River joins the Snake at the reservoir. Downriver from the dam is
Massacre Rocks State Park, a site on the path of the old
Oregon Trail.
After receiving the waters of
Raft River, the Snake River enters another reservoir,
Lake Walcott, impounded by
Minidoka Dam, run by the Bureau of Reclamation mainly for irrigation purposes. Another dam,
Milner Dam and its reservoir, Milner Reservoir, lie just downriver from Minidoka Dam. Below that is the city of
Twin Falls, after which the river flows into Idaho's
Snake River Canyon (the site of
Evil Knievel's stunt) over
Shoshone Falls and under the
Perrine Bridge.
Lower course
After exiting the Snake River Canyon, the Snake receives the waters of more tributaries, the
Bruneau River and the
Malad River. After passing the
Snake River Birds of Prey National Conservation Area, the Snake flows toward
Boise and the Idaho-Oregon border. After receiving numerous tributaries such as the
Boise River,
Owyhee River,
Malheur River,
Payette River,
Weiser River, and
Powder River, the Snake enters
Hells Canyon.
In Hells Canyon the Snake River is impounded by three dams,
Brownlee Dam,
Oxbow Dam, and
Hells Canyon Dam, after which the river is designated a
National Wild and Scenic River as is flows through
Hells Canyon Wilderness. In this section of the river, the
Salmon River, one of the largest tributaries of the Snake, joins. Just across the Washington state line, another large tributary, the
Grande Ronde River joins the Snake.
As the Snake flows north out of Hells Canyon, it passed the cities of
Lewiston, Idaho and
Clarkston, Washington, where it receives the
Clearwater River. From there the Snake River swings north, then south, through southeast Washington's
Palouse region, before joining the
Columbia River near the Tri-Cities. In this final river reach there are four large dams,
Lower Granite Lock and Dam,
Little Goose Lock and Dam,
Lower Monumental Lock and Dam, and
Ice Harbor Lock and Dam. These dams, built by the
United States Army Corps of Engineers serve as hydroelectric power sources as well as ensuring barge traffic navigation to Lewiston, Idaho.
''The Tetons - Snake River'' (1942) by Ansel Adams
History
Name
The name "Snake" possibly derived from an S-shaped (snake) sign which the Shoshone Indians made with their hands to mimic swimming salmon.
Variant names of the river have included: Great Snake River, Lewis Fork, Lewis River, Mad River, Saptin River, Shoshone River, and Yam-pah-pa.
Early inhabitants
People have been living along the Snake River for at least 11,000 years. Daniel S. Meatte divides the prehistory of the western Snake River Basin into three main phases or "adaptive systems". The first he calls "Broad Spectrum Foraging", dating from 11,500 to 4,200 years before present. During this period people drew upon a wide variety of food resources. The second period, "Semisedentary Foraging", dates from 4,200 250 years before present and is distinctive for an increased reliance upon fish, especially salmon, as well as food preservation and storage. The third phase, from 250 to 100 years before present, he calls "Equestrian Foragers". It is characterized by large horse-mounted tribes that spent long amounts of time away from their local foraging range hunting bison.
[5] In the eastern Snake River Plain there is some evidence of
Clovis,
Folsom, and
Plano cultures dating back over 10,000 years ago. By the protohistoric and historic era, the eastern Snake River Plain was dominated by
Shoshone and other "Plateau" culture tribes.
[6]
Early fur traders and explorers noted regional trading centers, and archaeological evidence has shown some to be of considerable antiquity. One such trading center in the
Weiser area existed as early as 4,500 years ago. The
Fremont culture may have contributed to the historic
Shoshones, but it is not well understood. Another poorly understood early cultural hearth is called the Midvale Complex. The introduction of the horse to the Snake River Plain around 1700 helped in establishing the Shoshone and Northern
Paiute cultures.
[7]
On the Snake River in southeastern Washington there are several ancient sites. One of the oldest and most well-known is called the Marmes Rockshelter, which was used from over 11,000 years ago to relatively recent times. The Marmes Rockshelter was flooded in 1968 by
Lake Herbert G. West, the Lower Monumental Dam's reservoir.
[8]
Other cultures of the Snake River's basin's protohistoric and historic periods include the
Nez Perce,
Cayuse,
Walla Walla,
Palus,
Bannock, and many others.
Exploration
The
Lewis and Clark Expedition of 1804-1806 was the first major U.S. exploration of the lower portion of the Snake River, and the Snake was once known as the Lewis River. Later exploratory expeditions, which explored much of the length of the Snake River, included the
Astor Expedition of 1810-1812,
John C. Frémont in 1832, and
Benjamin Bonneville in 1833-1834. By the middle 19th century, the
Oregon Trail had been established, generally following much of the Snake River.
River modifications
Dams
Many
dams have been built on the Snake River and its tributaries, mainly for purposes of providing
irrigation water and
hydroelectric power and ranging in size from small
diversion dams to major high dams.
Large dams include four on the lower Snake, in Washington, built and operated by the
U.S. Army Corps of Engineers:
Ice Harbor,
Lower Monumental,
Little Goose, and
Lower Granite. These dams were built from 1962 to 1975 for hydroelectric power and navigation. They are equipped with locks, making the river as far as Lewiston an extension of the Columbia River's barge navigation system.
[9] The four dams were modified in the 1980s to better accommodate fish passage.
[10]
Upriver, in the Hells Canyon region, there are three large hydroelectric dams, operated by Idaho Power, a private utility company. Collectively named the Hells Canyon Project, the three dams are, in upriver order:
Hells Canyon Dam,
Oxbow Dam, and
Brownlee Dam. Not having fish ladders, they are the first total barrier to upriver fish migration.
In southwestern Idaho there are several large dams.
Swan Falls Dam, built in 1901, was the first hydroelectric dam on the Snake as well as the first total barrier to upriver fish migration. It was rebuilt in the 1990s by Idaho Power. Upriver from Swan Falls is another hydroelectric dam operated by Idaho Power, the
C.J. Strike Dam, built in 1952. This dam also serves irrigation purposes. Continuing upriver, Idaho Power operates a set of three hydroelectric dam projects collectively called the Mid-Snake Projects, all built in the 1940s and 1950s. They are:
Bliss Dam,
Lower Salmon Falls Dam, and the two dams of the Upper Salmon Falls Project,
Upper Salmon Falls Dam A and
Upper Salmon Falls Dam B.
Near the city of Twin Falls two waterfalls have been modified for hydropower, Shoshone Falls and Twin Falls. Collectively called the Shoshone Falls Project, they are old and relatively small dams, currently operated by Idaho Power. Above Twin Falls is
Milner Dam, built in 1905 for irrigation and rebuilt in 1992 with hydroelectric production added. The dam and irrigation works are owned by Milner Dam, Inc, while the powerplant is owned by Idaho Power.
Above Milner Dam, most of the large dams are projects of the
U.S. Bureau of Reclamation, built mainly for irrigation, some are hydroelectric as well. All part of the Bureau's Minidoka Project, the dams are:
Minidoka Dam (built 1909),
American Falls Dam (1927),
Palisades Dam (1957), and
Jackson Lake Dam on
Jackson Lake (1911). These dams, along with two others and numerous irrigation canals, supply water to about 1.1 million acres (4,500 km²) in southern Idaho.
[11]
The city of
Idaho Falls operates the remaining large dam on the Snake River,
Gem State Dam, along with several smaller associated dams, for hydroelectric and irrigation purposes.
There are many other dams on the tributaries of the Snake River, built mainly for irrigation. They are mainly operated by the Bureau of Reclamation or local government and private owners.
While the many dams in the Snake River basin have transformed the region's economy, they have also had an adverse
environmental effect on wildlife, most notably on wild
salmon migrations. Some conservation organizations and fishermen are seeking to restore the lower Snake River and Snake River salmon and steelhead by removing four federally-owned dams on the lower Snake River.
Navigation
In the 1960s and 1970s the U.S. Army Corps of Engineers built four dams and locks on the lower Snake River to facilitate shipping. The lower Columbia River has likewise been dammed for navigation. Thus a deep
shipping channel through locks and slackwater reservoirs for heavy
barges exists from the Pacific Ocean to Lewiston, Idaho. Most barge traffic originating on the Snake River goes to deep-water ports on the lower Columbia River, such as
Portland.
Grain, mostly
wheat, is the main product shipped from the Snake, and nearly all of it is exported internationally from the lower Columbia River ports.
The shipping channel is authorized to be at least 14 feet (4.3 m) deep and 250 feet (76.2 m) wide. Where river depths were less than , the shipping channel has been
dredged in most places. Dredging and redredging work is ongoing and actual depths vary over time.
[Lower Snake River Transportation Study Final Report, American Rivers]
With a channel about 5 feet (1.5 m) deeper than the
Mississippi River System, the Columbia and Snake rivers can float barges twice as heavy.
[12]
Agricultural products from Idaho and eastern Washington are among the main goods transported by barge on the Snake and Columbia rivers. Grain, mainly wheat, accounts for more than 85% of the cargo barged on the lower Snake River. In 1998, over 123 million bushels (4.3 million m³) of grain were barged on the Snake. Before the completion of the lower Snake dams, grain from the region was transported by truck or rail to Columbia River ports around the Tri-Cities. Other products barged on the lower Snake River include peas, lentils, forest products, and petroleum.
Among the negative consequences of the lower Snake River's navigational slackwater reservoirs are the flooding of historic and archaeological sites, the stilling of once famous rapids, the slowing of currents and an associated rising of water temperature, and a general decline in the ability of wild fish to migrate up and down the river.
Other information
Snake River is home to a variety of outdoor sporting activities, including fly-fishing, hiking and biking, golf, and horseback riding.
The Snake runs through a number of gorges, including one of the deepest in the world, Hells Canyon, with a maximum depth of 7,900 feet (2,410 m).
Columbia River Basin
See also
★ List of crossings of the Snake River
★ Snake River Plain
References
1. http://www.idahohistory.net/Reference%20Series/0294.pdf
2. Snake River Plain geology from Geology of the Pacific Northwest, , Elizabeth L., Orr, McGraw-Hill, 1996,
3. Snake River Plain aquifer information from Geology of the Pacific Northwest, , Elizabeth L., Orr, McGraw-Hill, 1996,
4. Upper Snake River Basin NAWQA Fact Sheet, USGS Water Resources of Idaho
5. Summary of Western Snake River Prehistory, Digital Atlas of Idaho
6. Southeastern Snake River Basin Prehistory, Digital Atlas of Idaho
7. Western Snake River Prehistory, Digital Atlas of Idaho
8. Marmes Rockshelter, HistoryLink
9. Pressure builds on Snake River dams
10. http://www.nwcouncil.org/library/2003/2003-20/hydro.htm
11. Minidoka Project, USBR
12. Harden, Blaine (1996) ''A River Lost: The Life and Death of the Columbia'', W.W. Norton & Company. ISBN 0-393-31690-4
External links
★
★ Idaho Power
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