The Snake River Aquifer is a large reservoir of

groundwater Groundwater is the water present beneath Earth's surface in rock and Pore space in soil, soil pore spaces and in the fractures of stratum, rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit ...

underlying the

Snake River Plain The Snake River cutting through the plain leaves many canyons and Canyon#List of gorges">gorges, such as this one near Twin Falls, Idaho The Snake River Plain is a geologic feature located primarily within the U.S. state of Idaho. It stre ...

in the southern part of the

U.S. state In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its sove ...

Idaho Idaho ( ) is a U.S. state, state in the Pacific Northwest region of the Western United States. To the north, it shares a small portion of the Canada–United States border with the province of British Columbia. It borders the states of Monta ...

. Most of the water in the aquifer comes from rain and melting snow that flows onto the plain from the

Snake River The Snake River is a major river of the greater Pacific Northwest region in the United States. At long, it is the largest tributary of the Columbia River, in turn, the largest North American river that empties into the Pacific Ocean. The Snake ...

Big Lost River The Big Lost River is a major river in the U.S. state of Idaho, about long.U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map, accessed May 4, 2011 Description The river starts in the Rocky Mountai ...

and other

lost streams of Idaho There are two rivers in Idaho named "Lost", the Big Lost River and the Little Lost River. They are often considered separate streams, but both flow into the same depression and become subterranean, feeding the Snake River Aquifer. The rivers ar ...

Bruneau River The Bruneau River is a U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data. tributary of the Snake River, in the U.S. states of Idaho and Nevada. It runs through a narrow canyon cut into ancient lava flows in sout ...

, and other watercourses of southern Idaho. Measuring about from east to west, it is an important water source for agricultural irrigation in the Plain. The Snake River Aquifer is commonly defined as two separate parts, separated by

Salmon Falls Creek Salmon Falls Creek is a tributary of the Snake River, flowing from northern Nevada into Idaho in the United States. Formed in high mountains at the northern edge of the Great Basin, Salmon Falls Creek flows northwards ,U.S. Geological Survey. ...

: the Eastern Snake River Plain Aquifer and Western Snake River Plain Aquifer.

Eastern Snake River Plain Aquifer

The Eastern Snake River Plain Aquifer north of the Snake River is a remarkable aquifer of great resource and economic significance. It is not a single homogeneous geologic formation. Rather it consists of a volcanic pile of the

Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.58 million year ...

Snake River Group

basalt Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90 ...

s. In eastern Idaho, these basalts may be about thick. The individual flows are thick with the upper consisting of a very permeable rubble zone.

Interbedded In geology, interbedding occurs when beds (layers of rock) of a particular lithology lie between or alternate with beds of a different lithology. For example, sedimentary rocks may be interbedded if there were sea level variations in their sedi ...

alluvial Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. ...

sediments are also found between many of the flows. In the eastern Snake River Plain, the Snake River lies near the southern edge of the plain, about southeast of the ranges of central Idaho. The rivers in the ranges north of the plain all disappear into the surface of the Snake River Plain near the mountain front. The

Little Lost River The Little Lost River is a river in the central part of the U.S. state of Idaho. It is approximately longU.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map, accessed May 4, 2011 and drains an arid f ...

is a typical example. For about 100 miles downstream from Milner Dam in the vicinity of Twin Falls an estimated total volume of approximately of water enter the Snake River from gigantic springs on the north side of the canyon. This is the well-known Thousand Springs area. Groundwater flows to the southwest through the Snake River Plains aquifer which is consistent with the overall tilt to the southwest of the basalt

strata In geology and related fields, a stratum ( : strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as e ...

. The channel of the Snake River cuts through the aquifer. Consequently, the gravity and weight of the water in the basalt layers north of the river drives the huge springs.

References

Aquifers in the United States Snake River Bodies of water of Idaho {{Idaho-geo-stub