List of unconsolidated sand and gravel aquifers

Science Center Objects

Unconsolidated sand and gravel principal aquifers of the United States, which are characterized by intergranular porosity and all contain water primarily under unconfined, or water-table, conditions.

To learn more, visit the Unconsolidated and Semiconsolidated Sand and Gravel Aquifers webpage for an overview, or access more extensive information from the Ground Water Atlas of the United States (USGS Hydrologic Atlas 730) by clicking on an individual region/chapter below.
 

Basin and Range basin-fill aquifers

Map showing Basin and Range aquifers

The Basin and Range aquifers consist of primarily unconsolidated basin-fill sand and gravel, but fractured carbonate rocks also underlie some basins and form important aquifers.

 

Rio Grande aquifer system

Rio Grande aquifers

The Rio Grande aquifer system extends through parts of three States, and it is the principal source of groundwater in much of the area. Sediments consisting of alluvial deposits of the Santa Fe Group and floodplain deposits form the most permeable part of the Rio Grande aquifer system.

 

California Coastal Basin aquifers

Map of California Coastal Basin aquifers

The California Coastal Basin aquifers occupy a number of basins in coastal areas of California. These basins are in structural depressions filled with marine and alluvial sediments. Nearly all of the large population centers in California are located in the coastal basins and the available groundwater is used primarily for municipal supplies.

 

Central Valley aquifer system (California)

Map showing the Central Valley aquifer system

The Central Valley aquifer system is located in a large strutural trough in central California. The aquifer system is divided into three subregions on the basis of surface-water basins.

 

Pacific Northwest basin-fill aquifers

Map showing the Pacific Northwest basin-fill aquifers

Unconsolidated-deposit aquifers, which consist primarily of sand and gravel, are the most productive and widespread aquifers in Idaho, Oregon, and Washington.

 

Puget Sound aquifer system

Map showing the Puget Sound aquifer system

The Puget Sound aquifer system is used extensively for ground-water supplies. Unconsolidated-deposit aquifers predominate.

 

Willamette Lowland basin-fill aquifers

Map showing the Willamette-Lowland basin-fill aquifers

The Willamette Lowland basin-fill aquifers are used extensively for ground-water supplies. Unconsolidated-deposit aquifers predominate.

 

Columbia Plateau basin-fill aquifers

Map showing the Columbia Plateau basin-fill aquifers

The Columbia Plateau basin-fill aquifers consist of unconsolidated deposits that overlie basalt formations. The unconsolidated-deposity aquifers are a principal source of water for many wells.

 

Snake River Plain basin-fill aquifers

Map showing the Snake River Plain basin-fill aquifers

Unconsolidated-deposit aquifers predominate in the western plain.

 

Northern Rocky Mountains Intermontane Basins aquifer system

Map of the Northern Rocky Mountain Intermontane Basins aquifer system

Northern Rocky Mountain Intermontane Basins aquifer system is in Idaho and western Montana. Unconsolidated Quaternary deposits and Tertiary rocks are aquifers in narrow basins; less-permeable rocks underlie mountain ranges that separate the basins.

 

High Plains aquifer

Map showing the extent of the High Plains aquifer system

The High Plains aquifer underlies an area of about 174,000 square miles that extends through parts of eight states. The aquifer is the principal source of water in one of the major agricultural areas of the United States.

 

Sand and gravel aquifers of alluvial and glaical origin

 

Pecos River Basin alluvial aquifer (Texas and New Mexico)

Map showing the Pecos River Basin alluvial aquifer

Thick alluvial deposits in the Pecos River Basin yield large quantities of water mostly to irrigataion wells.

 

Mississippi River Valley alluvial aquifer

Map of the Mississippi River Valley alluvial aquifer

The thickness of the Mississippi River Valley alluvial aquifer ranges from about 25 to more than 150 feet. The aquifer is more than 75 feet thick in most locations.

 

Seymour aquifer (Texas)

Map showing the Seymour aquifer

Isolated patches of alluvial deposits in 20 counties in north-central Texas form the Seymour aquifer. The deposits are erosional remnants of the Seymour Formation.

 

Surficial aquifer system (eastern U.S.)

Map showing the Surficial aquifer system

The Surficial aquifer system extends throughout large areas in the Coastal Plain of Florida, Georgia, and South Carolina. The Surficial aquifer is the uppermost aquifer in the Northern Atlantic Coastal Plains aquifer system. The surficial aquifer extends over large parts of the Delmarva Penninsula and the eastern coastal plain of North Carolina.

 

Unconsolidated-deposit aquifers (Alaska)

Map showing the Unconsolidated-deposit aquifers - Alaska

Coarse-grained alluvial and glacial out-wash deposits of Quaternary age are present in many of the lowland areas of Alaska and are known to yield large quantities of water in such places as Fairbanks and Anchorage. These coarse-grained deposits are likely to yield water in other places, if the deposits are unfrozen.

 

South Coast aquifer

Map showing the South Coast aquifer (Puerto Rico)

The South Coast aquifer is an alluvial aquifer that underlies the broad coastal plain that extends from Patillas westward to Ponce in southern Puerto Rico. The alluvium that composes the aquifer was deposited mostly in a number of coalescing fan-deltas that built seaward from the mouths of major streams.