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 [Map: There is a USGS Water Science Center office in each State.] Washington Oregon California Idaho Nevada Montana Wyoming Utah Colorado Arizona New Mexico North Dakota South Dakota Nebraska Kansas Oklahoma Texas Minnesota Iowa Missouri Arkansas Louisiana Wisconsin Illinois Mississippi Michigan Indiana Ohio Kentucky Tennessee Alabama Pennsylvania West Virginia Georgia Florida Caribbean Alaska Hawaii and Pacific Islands New York Vermont New Hampshire Maine Massachusetts South Carolina North Carolina Rhode Island Virginia Connecticut New Jersey Maryland-Delaware-D.C.

National Aquifer Code Reference List

National aquifers, or principal aquifers of the United States, are defined as regionally extensive aquifers or aquifer systems that have the potential to be used as a source of potable water. The first publication of the core of the national aquifer list in a comprehensive manner was the Ground-Water Atlas of the United States (USGS Hydrologic Atlas 730 A-H), published in 13 chapters over the period 1990-1999, James A. Miller, editor.

A single combined map (Principal Aquifers) was published as part of the National Atlas in 1998, revised 2003.

Aquifers shown on the 2003 Principal Aquifers map, with some additions, were used as the first National Aquifer reference list in the USGS National Water Information System (NWIS) in the Aggregate Water Use Data System (database released in August 2001). In 2005, national aquifer was added as a field to the other components of NWIS, and to NWISWeb. Entries with a gray background are no longer valid.

Reference List
Code components
[an error occurred while processing this directive] History of National Aquifer Code
Requesting changes in the National Aquifer Code Reference List


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Aquifer Name Code Valid States Link to Aquifer Basics siteValid Date End Date Archived GIS coverage of outcrop or extent
Ada-Vamoosa aquifer N300ADAVMS Oklahoma Ada-Vamoosa aquifer (Oklahoma)20010801   Metadata Coverage
Alaska unconsolidated-deposit aquifers N100AKUNCD Alaska Unconsolidated-deposit aquifers (Alaska)20010801   Metadata Coverage
Alluvial aquifers N100ALLUVL Arkansas, Colorado, Delaware, Kansas, Kentucky, Louisiana, Maryland, Missouri, Montana, Nebraska, New Jersey, North Dakota, Ohio, Oklahoma, South Dakota, Tennessee, Texas, Utah, Virginia, West Virginia, Wyoming See note in History20010801   Coverage not available
Arbuckle-Simpson aquifer N400ABKSMP Oklahoma Arbuckle-Simpson aquifer (Oklahoma)20010801   Metadata Coverage
Basin and Range basin-fill aquifers N100BSNRGB Arizona, California, Idaho, Nevada, New Mexico, Oregon, Utah Basin and Range basin-fill aquifers (southwestern U.S.)20010801   Metadata Coverage
Basin and Range carbonate-rock aquifers N400BSNRGC Arizona, California, Idaho, Nevada, Utah Basin and Range carbonate-rock aquifers (southwestern U.S.)20010801   Metadata Coverage
Biscayne aquifer N400BISCYN Florida Biscayne aquifer (Florida)20010801   Metadata Coverage
Blaine aquifer N400BLAINE Oklahoma, Texas Blaine aquifer (Oklahoma and Texas)20010801   Metadata Coverage
California Coastal Basin aquifers N100CACSTL California California Coastal Basin aquifers20010801   Metadata Coverage
Cambrian-Ordovician aquifer system S300CAMORD Illinois, Iowa, Michigan, Minnesota, Missouri, Wisconsin Cambrian-Ordovician aquifer system (northern Midwest)20010801   Metadata Coverage
Castle Hayne aquifer N400CSLHYN North Carolina Castle Hayne aquifer (North Carolina)20010801   Metadata Coverage
Central Oklahoma aquifer N300CNRLOK Oklahoma Central Oklahoma aquifer20010801   Metadata Coverage
Central Valley aquifer system S100CNRLVL California Central Valley aquifer system (California)20010801   Metadata Coverage
Coastal lowlands aquifer system S100CSLLWD Alabama, Florida, Louisiana, Mississippi, Texas Coastal lowlands aquifer system (Gulf Coast)20010801   Metadata Coverage
Colorado Plateaus aquifers N300COPLTS Arizona, Colorado, New Mexico, Utah, Wyoming Colorado Plateaus aquifers20010801   Metadata Coverage
Columbia Plateau basaltic-rock aquifers N600CMBPLV Idaho, Oregon, Washington Columbia Plateau basaltic-rock aquifers20010801   Metadata Coverage
Columbia Plateau basin-fill aquifers N100CMBPLB Idaho, Oregon, Washington Columbia Plateau basin-fill aquifers20010801   Coverage not available
Denver Basin aquifer system S300DNVRBS Colorado Denver Basin aquifer system20010801   Metadata Coverage
Early Mesozoic basin aquifers N300ERLMZC Connecticut, Maryland, Massachusetts, New Jersey, New York, North Carolina, Pennsylvania, Virginia Early Mesozoic basin aquifers (eastern U.S.)20010801   Metadata Coverage
Edwards-Trinity aquifer system S500EDRTRN Arkansas, Oklahoma, Texas Edwards-Trinity aquifer system (Texas and Oklahoma)20010801   Metadata Coverage
Floridan aquifer system S400FLORDN Alabama, Florida, Georgia, South Carolina Floridan aquifer system20010801   Metadata Coverage
Hawaii volcanic-rock aquifers N600HIVLCC Hawaii Hawaiian aquifers (Hawaii)20010801   Coverage not available
High Plains aquifer N100HGHPLN Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, Wyoming High Plains aquifer20010801   Metadata Coverage
Intermediate aquifer system S500INTRMD Florida GW Atlas: Intermediate aquifer system (Florida)20010801   Coverage not available
Jacobsville aquifer N300JCBSVL Michigan, Wisconsin Jacobsville aquifer (Michigan)20010801   Metadata Coverage
Kingshill aquifer (Virgin Islands) N400KNGSHL Virgin Islands Kingshill aquifer (Virgin Islands)20010801   Coverage not available
Lower Cretaceous aquifers N300LCRTCS Iowa, Kansas, Minnesota, Montana, Nebraska, North Dakota, South Dakota, Wyoming Lower Cretaceous aquifers (northern Great Plains)20010801   Metadata Coverage
Lower Tertiary aquifers N300LTRTRY Montana, North Dakota, South Dakota, Wyoming Lower Tertiary aquifers (northern Great Plains)20010801   Metadata Coverage
Marshall aquifer N300MRSHLL Michigan Marshall aquifer (Michigan)20010801   Metadata Coverage
Mississippi embayment aquifer system S100MSEMBM Alabama, Arkansas, Illinois, Kentucky, Louisiana, Mississippi, Missouri, Tennessee, Texas Mississippi embayment aquifer system20010801   Metadata Coverage
Mississippi River Valley alluvial aquifer N100MSRVVL Arkansas, Illinois, Kentucky, Louisiana, Mississippi, Missouri, Tennessee Mississippi River Valley alluvial aquifer20010801   Metadata Coverage
Mississippian aquifers N500MSSPPI Alabama, Illinois, Indiana, Iowa, Kentucky, Maryland, Missouri, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia Mississippian aquifers (central and eastern U.S.)20010801   Metadata Coverage
New York and New England crystalline-rock aquifers N600NECRSN Connecticut, Maine, Massachusetts, New Hampshire, New York, Rhode Island, Vermont GW Atlas: Crystalline-rock aquifers (New York and New England)20010801   Coverage not available
New York and New England carbonate-rock aquifers N400NYNECB Connecticut, Maine, Massachusetts, New Jersey, New York, Pennsylvania, Vermont New York and New England carbonate-rock aquifers20010801   Metadata Coverage
New York sandstone aquifers N300NYSDSN New York New York sandstone aquifers20010801   Metadata Coverage
North Coast Limestone aquifer system (Puerto Rico) N400NCSTLM Puerto Rico North Coast Limestone aquifer system (Puerto Rico)20010801   Metadata Coverage
Northern Atlantic Coastal Plain aquifer system S100NATLCP Delaware, District of Columbia, Maryland, New Jersey, New York, North Carolina, Pennsylvania, Virginia Northern Atlantic Coastal Plain aquifer system20010801   Metadata Coverage
Northern Great Plains aquifer system (no longer valid) S500NGRTPL Montana, North Dakota, South Dakota, Wyoming (Includes four national aquifers but is not considered a national aquifer itself. The component aquifers are Lower Tertiary, Upper Cretaceous, Lower Cretaceous, and Paleozoic.)20010801 20050201 Metadata Coverage
Northern Rocky Mountains Intermontane Basins aquifer systems S100NRMTIB Idaho, Montana, Washington, Wyoming Northern Rocky Mountains Intermontane Basins aquifer system20010801   Metadata Coverage
Ordovician aquifers N400ORDVCN Kentucky, Tennessee Ordovician aquifers (Tennessee and Kentucky)20010801   Metadata Coverage
Other aquifers N9999OTHER All Other aquifers20010801   No map: Other aquifers is used when a local aquifer is not part of a national aquifer or aquifer system, as listed here
Ozark Plateaus aquifer system S400OZRKPL Arkansas, Illinois, Kansas, Missouri, Oklahoma Ozark Plateaus aquifer system (Missouri)20010801   Metadata Coverage
Pacific Northwest basin-fill aquifers N100PCFNWB California, Idaho, Nevada, Oregon, Utah, Washington, Wyoming Pacific Northwest basin-fill aquifers20010801   Metadata Coverage
Pacific Northwest volcanic-rock aquifers N100PCFNWV California, Idaho, Montana, Nevada, Oregon, Utah, Washington, Wyoming Pacific Northwest basaltic-rock aquifers20010801   Metadata Coverage
Metadata Coverage
Paleozoic aquifers N500PLOZOC Minnesota, Montana, North Dakota, South Dakota, Wyoming Paleozoic aquifers (northern Great Plains)20010801   Metadata Coverage
Pecos River Basin alluvial aquifer N100PCSRVR New Mexico, Texas Pecos River Basin alluvial aquifer (Texas and New Mexico)20010801   Metadata Coverage
Pennsylvanian aquifers N300PNSLVN Alabama, Georgia, Illinois, Indiana, Kentucky, Maryland, Michigan, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia Pennsylvanian aquifers (central and eastern U.S.)20010801   Metadata Coverage
Piedmont and Blue Ridge carbonate-rock aquifers N400PDMBRC Maryland, New Jersey, North Carolina, Pennsylvania Piedmont and Blue Ridge carbonate-rock aquifers (eastern U.S.)20010801   Metadata Coverage
Piedmont and Blue Ridge crystalline-rock aquifers N400PDMBRX Alabama, Delaware, District of Columbia, Georgia, Maryland, New Jersey, New York, North Carolina, Pennsylvania, South Carolina, Tennessee, Virginia, West Virginia Piedmont and Blue Ridge crystalline-rock aquifers (eastern U.S.)20010801   Coverage not available
Puget Sound aquifer system S100PGTSND Washington Puget Sound aquifer system (Washington)20010801   Metadata Coverage
Rio Grande aquifer system S100RIOGRD Colorado, New Mexico, Texas Rio Grande aquifer system20010801   Metadata Coverage
Roswell Basin aquifer system S400RSWLBS New Mexico Roswell Basin aquifer system (New Mexico)20010801   Metadata Coverage
Rush Springs aquifer N300RSHSPG Oklahoma Rush Springs aquifer (Oklahoma)20010801   Metadata Coverage
Sand and gravel aquifers (glaciated regions) N100GLCIAL Connecticut, Illinois, Indiana, Iowa, Kansas, Kentucky, Maine, Massachusetts, Michigan, Minnesota, Missouri, Montana, Nebraska, New Hampshire, New Jersey, New York, North Dakota, Ohio, Pennsylvania, Rhode Island, South Dakota, Vermont, Wisconsin Sand and gravel aquifers of alluvial and glacial origin (North of the line of glaciation)20010801   Coverage not available, web graphic
Seymour aquifer N100SYMOUR Texas Seymour aquifer (Texas)20010801   Metadata Coverage
Silurian-Devonian aquifers N400SLRDVN Illinois, Indiana, Iowa, Kentucky, Michigan, Missouri, Ohio, Tennessee, Wisconsin Silurian-Devonian aquifers (northern Midwest)20010801   Metadata Coverage
Snake River Plain basaltic-rock aquifers N600SKRVPV Idaho, Oregon Snake River Plain basaltic-rock aquifers (Idaho)20010801   Coverage not available
Snake River Plain basin-fill aquifers N600SKRVPB Idaho, Oregon Snake River Plain basin-fill aquifers (Idaho)20010801   Coverage not available
South Coast aquifer (Puerto Rico) N300STHCST Puerto Rico South Coast aquifer (Puerto Rico)20010801   Metadata Coverage
Southeastern Coastal Plain aquifer system S100SECSLP Alabama, Georgia, Mississippi, South Carolina, Tennessee Southeastern Coastal Plain aquifer system20010801   Metadata Coverage
Southern Nevada volcanic-rock aquifers N600SRNVDV Nevada Southern Nevada volcanic-rock aquifers20010801   Metadata Coverage
Surficial aquifer system S100SURFCL Alabama, Florida, Georgia, North Carolina, South Carolina Surficial aquifer system (eastern U.S.)20010801   Coverage not available
Texas coastal uplands aquifer system S100TXCLUP Louisiana, Texas Texas coastal uplands aquifer system20010801   Metadata Coverage
Upper carbonate aquifer N400UPCRBN Iowa, Minnesota

Upper carbonate aquifer (Minnesota and Iowa)

20010801   Metadata Coverage
Upper Cretaceous aquifers N300UPCTCS Montana, North Dakota, South Dakota, Wyoming Upper Cretaceous aquifers (northern Great Plains)20010801   Metadata Coverage
Valley and Ridge aquifers N500VLYRDG Alabama, Georgia, Maryland, New Jersey, New York, North Carolina, Pennsylvania, Tennessee, Virginia, West Virginia Valley and Ridge aquifers (eastern U.S.)20010801  

All(or perhaps non-carbonates): Metadata Coverage Carbonates: Metadata Coverage

Valley and Ridge carbonate-rock aquifers (No longer valid) N500VLRDGC Alabama, Georgia, Maryland, New Jersey, Pennsylvania, Tennessee, Virginia, West Virginia (Should be included in Valley and Ridge aquifers.)20010801 20050301  
Willamette Lowland basin-fill aquifers N100WLMLWD Oregon, Washington Willamette Lowland basin-fill aquifers (Oregon)20010801   Metadata Coverage
Wyoming Tertiary aquifers N300WYTRTR Wyoming Upper Tertiary aquifers (Wyoming)20010801   Metadata Coverage

Code components:

N or S, where N = aquifer, S = aquifer system
3 digit number = rock type (4 digits used for "Other" to fill out the code)
6 character identifier derived from the aquifer name [an error occurred while processing this directive] using the code derivation procedure also used for GWSI geohydrologic unit names (Note that the National Aquifer Code uses a different numeric component than the geohydrologic unit names.).

Rock types are:

100-- Sand and gravel aquifers
200--Semiconsolidated sand aquifers (not used)
300--Sandstone aquifers
400--Carbonate-rock aquifers
500--Sandstone and carbonate-rock aquifers
600--Igneous and metamorphic-rock aquifers
9999--Areas that are not a national aquifer.

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History of National Aquifer Code:

  • First publication of the core of the national aquifer list in a comprehensive manner was the Ground-Water Atlas of the United States (HA 730 A-H), published in 13 chapters over the period 1990-1999, James A. Miller, editor.
  • A single combined map (Principal Aquifers of the 48 Conterminous United States, Hawaii, Puerto Rico, and the U.S. Virgin Islands) was published as part of the National Atlas in 1998, revised 2003. Metadata and coverage contact information are available on the National Atlas page.
  • Aquifers shown on the 2003 Principal Aquifers map, with some additions, were used as the first National Aquifer reference list in NWIS, released in AWUDS v. 1.0 for the national compilation of water-use data for the year 2000 (database released in August 2001). Water-use data collected using this list of aquifers will be published in Circular 1279, Estimated Withdrawals from Principal Aquifers in the United States, 2000. The additions were:
    • Alluvial aquifers--consist of stream-valley aquifers and other aquifers of unconsolidated alluvial materials, not included in another named national aquifer, south of the limit of Quarternary continental glaciation and east of the Rocky Mountains. Note that alluvial aquifers north of the limit of continental glaciation are included in Sand and gravel aquifers (glaciated regions).
    • Intermediate aquifer (Florida)
    • New England crystalline-rock aquifers
    • (in error) Northern Great Plains aquifer system
  • Some revisions to the lists of valid States, this code, and reference list were added to the NWIS Site File and to NWISWeb with the release of NWIS 4.5 in 2005; see the memo NWIS 4.5 -- Assigning National Aquifer Codes in the Ground Water Site Inventory (GWSI) for the NWIS 4.5 Release.
  • Revisions to the reference list since it was first used by NWIS:
    • Northern Great Plains aquifer system was removed: this umbrella term includes four national aquifers but is not considered a national aquifer itself. The component aquifers are Lower Tertiary, Upper Cretaceous, Lower Cretaceous, and Paleozoic. The appropriate component aquifer should be used instead of Northern Great Plains. (February 2005)
    • Valley and Ridge carbonate-rock aquifers were removed: these now should be included in Valley and Ridge aquifers. (March 2005)
    • Surficial aquifer system: removed the following States from the valid list: Delaware, Maryland, New Jersey, Virginia. The surficial aquifer in the Coastal Plain of these States should be included in the Northern Atlantic Coastal Plain aquifer system. Surficial deposits of glacial origin (New Jersey) should be included in Sand and gravel aquifers (glaciated regions). Surficial deposits which are not of glacial origin may be coded as Alluvial aquifers. You may need to request the addition of Alluvial aquifers to the list of aquifers valid in your State. (March 2005)
    • The name of N600NECRSN was changed from "New England crystalline-rock aquifers" to "New York and New England crystalline-rock aquifers" to better reflect the geographic extent (January 2015).

Update Procedures

If you would like to request a change in the National Aquifer Code reference list, such as adding or deleting a State from the "Valid States" list or proposing a new national aquifer:

  1. Enter your request to the GNATS system. (Use the category of GW | GW-RefLists in GNATS) If you would like to discuss any issues with the proposed change with the Office of Groundwater before submitting your request, contact Linda Debrewer, (703) 648-5011.
  2. The requested change will be forwarded to the Office of Groundwater (OGW) for review.
  3. The OGW provides the NWIS maintainer with the approved content changes.
  4. The NWIS reference-list maintainer then makes the changes to the master file used by the NWIS databases, and notifies the reference list maintainers for NWISWeb and AWUDS of the changes. NWIS reference list changes are distributed quarterly to the NWIS installations. NWISWeb and AWUDS updates are on different schedules. The Office of Groundwater will update this Web page and add a note to the History section about the change.

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Page Last Modified: Monday, 18-Dec-2017 17:19:59 EST