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Snake River Plain

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NameColor on MapEPA Code‡
Treasure Valley12a
Lava Fields12b
Camas Prairie12c
Dissected Plateaus and Teton Basin12d
Upper Snake River Plain12e
Semiarid Foothills12f
Eastern Snake River Basalt Plains12g
Mountain Home Uplands12h
Magic Valley12i
Unwooded Alkaline Foothills12j

† Status: ✓ = Complete ○ = Needs Image … = Incomplete ∅ = Stub Only

This code refers to the US EPA's Level 4 ecoregion codes for the continental U.S., see here.


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About the Snake River Plain

The Snake River Plain is a crescent-shaped basin located mostly within southern Idaho, stretching slightly into Oregon and barely reaching a tiny portion of Wyoming. As the name suggests, the region is a plain centering around the Snake river.

The climate is a semi-arid steppe climate with strong seasonality of both temperature and precipitation. Summers are warm to hot, and have little rainfall, whereas the remainder of the year is slightly wetter, with precipitation peaking in May. Temperatures decrease moving from west to east, owing to a gradual increase in elevation to the east. The frost-free period varies from 50 to 170 days.

Terrain consists of plains, low hills, and alluvial valleys, with scattered lava fields.

Naturally this area was covered with sagebrush steppe, with dominant plants being Wyoming sagebrush, bigbasin sagebrush, mountain sagebrush, bluebunch wheatgrass, Idaho fescue, Indian ricegrass, rabbitbrush, and fourwing saltbush. Vegetation on lava fields is sparse.

The areas closest to the Snake river have been heavily developed for agriculture, using the river for irrigation. Canals and reservoirs have altered the natural structure of waterways. The main crops grown here include sugar beets, potatoes, alfalfa, various small grains, and assorted vegetables. There are also cattle feedlots and dairy farming. Farther from the river, rangeland is common.

Although Idaho is not the most populous state, this region is the most urbanized portion of it, containing all but one of the state's largest cities: Boise, Meridian, Nampa, Idaho Falls, Pocatello, Caldwell, and Twin Falls are all located in this plain.

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1. Wiken, E., Griffith, G. "North American Terrestrial Ecoregions - Level III", Commission for Environmental Cooperation, (2011) Web.