| Supplemental information |
The Ground Water Atlas of the United States (GWA) chapters include additional information that may be relevant to the use of this map layer, such as maps of alluvial and glacial aquifers that overlie the aquifers in this map layer, as well as other information described below. The areal extent of the aquifers, as shown in this map layer, represents the area in which a named aquifer is the shallowest of the principal aquifers. These aquifer areas are not necessarily the only areas in which ground water can be withdrawn, for two reasons: 1) The aquifers shown may have a larger areal extent than is represented here. The boundaries in this map layer generally represent an interpretation of the surface location (outcrop), or near-surface location (shallow subcrop) of the uppermost principal aquifer for the area. An aquifer may extend beyond the area shown, but be overlain by one or more other aquifers, and (or) low-permeability material. 2) There may be areas of water-bearing surficial material not shown in this map layer. Major alluvial aquifers that occur along main watercourses are not shown. Significant unconsolidated sand and gravel aquifers, that are not indicated in this map layer but are important sources of water, may occur locally in glaciated regions. The user of this map layer is advised that to get complete information regarding areas that serve as sources of water, more information about surficial aquifers needs to be obtained, particularly in glaciated areas. This map layer was constructed by combining data created for or from the regional GWA chapters. Minor aquifers that are important local sources of water were mapped in some regions, so the regional maps in the GWA may show more detail than this map layer. The data were reviewed, adjusted, and published based on new information provided by national, State, and local scientists. The juxtaposition of regionally mapped aquifers has led to some instances where an aquifer outcrop or shallow subcrop is bounded by a State line. This is a result of the regional mapping and national categorization methods used and is not meant to imply a hydrogeologic change coincident with a State boundary. The aquifer outcrop and shallow subcrop boundaries represent broad, regional categories and should not be interpreted as site-specific. Comments regarding the names of aquifers or the hydrogeologic interpretation of the aquifers can be directed to the U.S. Geological Survey, Water Resources Division, Office of Ground Water, ogw_webmaster@usgs.gov. This map layer was used as part of the effort to publish a 1:5,000,000- scale 'Principal Aquifers' map in the National Atlas of the United States of America series of printed maps. The printed map can be considered a representation of this map layer with the exceptions of: the smaller scale, slight differences in the coastline due to generalization, base and cultural information, and delineation of the glacial-deposit area. These data were developed in conjunction with the publication of the GWA. For documentation purposes, areas are referred to by their corresponding GWA chapter letter, or by State. This list shows the relationship between State names and GWA chapters: >HA 730-B Segment 1-California, Nevada >HA 730-C Segment 2-Colorado, Utah, New Mexico, Arizona >HA 730-D Segment 3-Kansas, Missouri, Nebraska >HA 730-E Segment 4-Texas, Oklahoma >HA 730-F Segment 5-Arkansas, Louisiana, Mississippi >HA 730-G Segment 6-Alabama, Florida, Georgia, South Carolina >HA 730-H Segment 7-Idaho, Oregon, Washington >HA 730-I Segment 8-Montana, North Dakota, South Dakota, Wyoming >HA 730-J Segment 9-Iowa, Michigan, Minnesota, Wisconsin >HA 730-K Segment 10-Illinois, Indiana, Kentucky, Ohio, Tennessee >HA 730-L Segment 11-Delaware, Maryland, New Jersey, North > Carolina, Pennsylvania, Virginia, West > Virginia >HA 730-M Segment 12-Connecticut, Maine, Massachusetts, New > Hampshire, New York, Rhode Island, Vermont >HA 730-N Segment 13-Alaska, Hawaii, Puerto Rico, and the U.S. > Virgin Islands Refer to <http://capp.water.usgs.gov/gwa/gwa.html> for a graphic depiction of the GWA chapter regions, as well as more information about the GWA. It may be helpful to refer to the printed GWA chapters when using the Data, however, there are significant differences between this national map layer and the printed chapters. Because the GWA regional chapters were written by different authors, there were areas of different interpretations and category delineations, aquifer names, etc., that became apparent when combining the regions. The following listings show the differences between aquifer names in the GWA chapters and the aq_name and aq_code used in this map layer. See the Entity and Attribute Information section for definitions of the data attributes. >GWA chapter HA 730-B >Name from fig 11, page B4 aq_code-aq_name >____________________________________________________________ >Basin and Range volcanic- 601-Southern Nevada >rock aquifers volcanic-rock aquifers > >Coastal Basins aquifers 103-California Coastal Basin > aquifers > >Northern California Basin 104-Pacific Northwest >fill aquifers basin-fill aquifers > > >GWA chapter HA 730-C >Name from fig 11, page C4 >____________________________________________________________ >Names and categories the same > > >GWA chapter HA 730-D >Name from fig 5, page D4 aq_code-aq_name >____________________________________________________________ >Mississippi embayment 109-Mississippi River Valley >aquifer system alluvial aquifer > >Great Plains aquifer 304-Lower Cretaceous > aquifers > >Confining unit 999-Other rocks > >Dune sand 107-High Plains aquifer > > >GWA chapter HA 730-E >Name from fig 4, page E3 aq_code-aq_name >____________________________________________________________ >EDWARDS-TRINITY AQUIFER SYSTEM >Edwards-Trinity aquifer 501-Edwards-Trinity aquifer > system > >Edwards aquifer 501-Edwards-Trinity aquifer > system > >Trinity aquifer 501-Edwards-Trinity aquifer > system > >Confining unit 999-Other rocks > > >GWA chapter HA 730-F >Name from fig 7, page 4 aq_code-aq_name >____________________________________________________________ >MAJOR AQUIFER SYSTEMS >Surficial aquifer system 109-Mississippi River Valley > alluvial aquifer > 203-Mississippi embayment > aquifer system > 501-Edwards-Trinity aquifer > system > 999-Other rocks > >Mississippi embayment 109-Mississippi River Valley >aquifer system alluvial aquifer > 203-Mississippi embayment > aquifer system > 204-Southeastern Coastal > Plain aquifer system > 999-Other rocks > >Tokio-Woodbine aquifer 999-Other rocks > >Ouachita Mountains aquifer 999-Other rocks > >CONFINING SYSTEMS AND CONFINING UNITS >Western Interior Plains 999-Other rocks >confining systems > >Confining unit 109-Mississippi River Valley > alluvial aquifer > 203-Mississippi embayment > aquifer system > 999-Other rocks > > >GWA chapter HA 730-G >Name from fig 3, page 3 aq_code-aq_name >____________________________________________________________ >Sand and gravel aquifer 201-Coastal lowlands aquifer > system > >Piedmont and Blue Ridge 611-Piedmont and Blue Ridge >aquifers crystalline-rock aquifers > >Appalachian Plateaus 310-Pennsylvanian aquifers >aquifers > >Interior Low Plateaus 503-Mississippian aquifers >aquifers > >Confining unit 999-Other rocks > > >GWA chapter HA 730-H >Name from fig 5, page H4 aq_code-aq_name >____________________________________________________________ >Unconsolidated-deposit 101-Basin and Range basin-fill > aquifers aquifers > 104-Pacific Northwest > basin-fill aquifers > 105-Northern Rocky Mountains > Intermontane Basins > aquifer system > 112-Puget Sound aquifer system > > >Pliocene and younger 606-Snake River Plain >basaltic-rock aquifers basaltic-rock aquifers > 610-Pacific Northwest > basaltic-rock aquifers > >Miocene basaltic-rock 606-Snake River Plain >aquifers basaltic-rock aquifers > 607-Columbia Plateau basaltic-rock > aquifers > 610-Pacific Northwest > basaltic-rock aquifers > >Aquifers in pre-Miocene 401-Basin and Range >rocks carbonate-rock aquifers > 999-Other rocks > > >GWA chapter HA 730-I. See Process Description regarding >differences between this data and the printed Ground Water >Atlas chapter in Western Montana >Name from fig 7, page I4 aq_code-aq_name >____________________________________________________________ >Quaternary volcanic and 610-Pacific Northwest >sedimentary rock aquifers basaltic-rock aquifers > >Upper Tertiary aquifers 105-Northern Rocky Mountains > Intermontane Basins > aquifer system > 107-High Plains aquifer > 314-Lower Tertiary aquifers > 316-Wyoming Tertiary aquifers > >Lower Tertiary aquifers 107-High Plains aquifer > 314-Lower Tertiary aquifers > >Upper Cretaceous aquifers 301-Colorado Plateaus > aquifers > 315-Upper Cretaceous > aquifers > >Lower Cretaceous aquifers 301-Colorado Plateaus > aquifers > 304-Lower Cretaceous aquifers > >Confining unit 301-Colorado Plateaus > aquifers > > >GWA chapter HA 730-J >Name from fig 7, page J4 aq_code-aq_name >____________________________________________________________ >Cretaceous aquifer 304-Lower Cretaceous > aquifers > >MISSISSIPPIAN AQUIFER >Carbonate rocks 503-Mississippian aquifers > >Sandstone 311-Marshall aquifer > >Crystalline-rock aquifer 999-Other rocks > >Confining unit 312-Cambrian-Ordovician > aquifer system > 999-Other rocks > > >GWA chapter HA 730-K >Name from fig 5, page K4 aq_code-aq_name >____________________________________________________________ >Blue Ridge aquifers 611-Piedmont and Blue Ridge > crystalline-rock aquifers > >MISSISSIPPI EMBAYMENT AQUIFER SYSTEM >Upper Claiborne, middle 109-Mississippi River Valley >Claiborne, middle Wilcox, alluvial aquifer >and lower Wilcox 203-Mississippi embayment > aquifer system > >McNairy-Nacatoch 204-Southeastern Coastal > Plain aquifer system > >Pennsylvanian aquifers 999-Other rocks > >Confining unit 999-Other rocks > > >GWA chapter HA 730-L >Name from fig 7, page L4 aq_code-aq_name >____________________________________________________________ >NORTHERN ATLANTIC COASTAL PLAIN AQUIFER SYSTEM >Surficial aquifer 111-Surficial aquifer system > 205-Northern Atlantic > Coastal Plain aquifer > system > >Chesapeake aquifer 205-Northern Atlantic > Coastal Plain aquifer > system > >Castle Hayne-Aquia aquifer 418-Castle Hayne aquifer > >Severn-Magothy aquifer 205-Northern Atlantic > Coastal Plain aquifer > system > >Peedee-upper Cape Fear 205-Northern Atlantic >aquifer Coastal Plain aquifer > system > >Potomac aquifer 205-Northern Atlantic > Coastal Plain aquifer > system > >PIEDMONT AND BLUE RIDGE AQUIFERS >Aquifers in early Mesozoic 308-Early Mesozoic basin >basins aquifers > >Carbonate-rock aquifers 417-Piedmont and Blue Ridge > carbonate-rock aquifers > >Crystalline-rock aquifers 611-Piedmont and Blue Ridge > crystalline-rock aquifers > >Valley and Ridge 416-New York and New England >carbonate-rock aquifers carbonate-rock aquifers > 505-Valley and Ridge > carbonate-rock aquifers > >APPALACHIAN PLATEAUS >Permian and Pennsylvanian 310-Pennsylvanian aquifers >aquifers > >Not a principal aquifer 611-Piedmont and Blue Ridge > crystalline-rock aquifers > > >GWA chapter HA 730-M >Name from fig 10, page M5 aq_code-aq_name >____________________________________________________________ >SANDSTONE AQUIFERS >Mesozoic sandstone and 308-Early Mesozoic basin >basalt of the Newark aquifers >Supergroup > >Lower Paleozoic 309-New York sandstone > aquifers > >CRYSTALLINE-ROCK AQUIFERS >Adirondack 999-Other rocks > > >GWA chapter HA 730-N >Hawaii name from fig 35, >page N14 >Puerto Rico name from >fig 71, page N24 aq_code-aq_name >____________________________________________________________ >Volcanic rock aquifers 608-Hawaiian Volcanic-rock > aquifers > 609-Hawaiian Sedimentary > deposit aquifers > >MINOR AQUIFERS >Coastal embayment aquifers 999-Other rocks >Volcaniclastic-, igneous-, >and sedimentary-rock aquifers > >Confining unit 999-Other rocks > >NORTHCOAST LIMESTONE AQUIFER SYSTEM >Upper aquifer 419-Puerto Rico North Coast Limestone > aquifer system > >Lower aquifer 419-Puerto Rico North Coast Limestone > aquifer system > Related Spatial and Tabular Data Sets A map layer showing the areal extent of sand and gravel aquifers of alluvial and glacial origin north of the line of Quaternary continental glaciation is included in the online, interactive National Atlas of the United States. This map layer ends at the southern limit of glaciation in the United States; areas north of the limit line contain significant sand and gravel glacial deposits that are important sources of water for local areas. For additional information on principal aquifers, please see the Aquifer Basics page at <http://capp.water.usgs.gov/aquiferBasics/index.html.> The final data are being served to the public in the following formats: Spatial Data Transfer Standard (SDTS), Arc/INFO Export, or ArcView Shapefile.
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