|
Rosenshein (1988, p. 174) defines a type of alluvial aquifer, “alluvial-valley aquifers”, to be long but narrow aquifers that “are in hydraulic connection with associated streams”, and that “are of limited areal extent in comparison to most aquifer systems, [but] they are among the most intensively used.” Heath (1984), in distinguishing between alluvial basins and alluvial valleys, defines alluvial valleys to be “thick sand and gravel deposits beneath floodplains and terraces of streams” (Heath, 1984, p. 58).
The Principal Aquifers map (U.S. Geological Survey, 2003) does not have a “stream-valley aquifers” unit mapped. However, in many instances, stream-valley aquifers are accounted for by being combined with other alluvial aquifers. A large part of the western conterminous U.S.—the region west of the Rocky Mountains and the Colorado Plateau, but extending as far east as the Rio Grande basin, and also including the Northern Rocky Mountains Intermontane Basins Aquifer System—contains numerous structural and erosional basins partially filled with alluvium. Stream-valley aquifers are abundant in this region, but generally are hydraulically connected with basin-fill aquifers and also generally not separable on a regional scale from basin-fill aquifers because of lithologic and hydraulic similarities.
Stream-valley aquifers are also numerous in the region north of the limit of Quaternary continental glaciation and east of the Rocky Mountains. Stream-valley aquifers here are essentially reworked glacial materials, and generally are hydraulically connected with glacial aquifers and generally not separable from them on a regional scale.
Stream-valley aquifers in the remainder of the U.S. often are less well represented on the Principal Aquifers map (U.S. Geological Survey, 2003). However, many stream-valley aquifers are mapped in the subregional chapters of the Ground Water Atlas of the United States (Miller, 2000).
Bibliography
|
