Identification Information

Title Aquifers

Date 2008-11-18

Date Type Publication

Cited Responsible Party

Organization Name U.S. Geological Survey

Role identify

Presentation Form vector digital data

Abstract This map layer contains the shallowest principal aquifers of the conterminous United States, Hawaii, Puerto Rico, and the U.S. Virgin Islands, portrayed as polygons. The map layer was developed as part of the effort to produce the maps published at 1:2,500,000 in the printed series "Ground Water Atlas of the United States". The published maps contain base and cultural features not included in these data. This is a replacement for the July 1998 map layer called Principal Aquifers of the 48 Conterminous United States.

Purpose These data are intended for use in publications, at a scale of 1:2,500,000 or smaller. Due to the small scale, the primary intended use is for regional and national data display and analysis, rather than specific local data analysis.

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 These aquifer areas are not necessarily the only areas in which ground water can be withdrawn, for two reasons: 1) The aquifers shown may have a larger areal extent than is represented here.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.

Data Set Credit This map layer was created and modified over a period of at least five years by several staff members of the U.S. Geological Survey Water Resources Discipline, Cartographic and Publications Program in Madison, Wisconsin. Completion of this map layer and associated metadata was funded, in part, under a cooperative joint funding agreement between the U.S. Geological Survey and the U.S. Environmental Protection Agency.

Status Complete

Point of Contact

Individual Name

Organization Name U.S. Geological Survey

Position Name

Role Point of contact

Voice 608-238-9333

Facsimile

Address

Delivery Point 505 Science Drive
City Madison
Administrative Area WI
Postal Code 53711-1061
Country USA

Electronic Mail Address

Maintenance and Update Frequency As needed

Descriptive Keywords Aquifer, Groundwater, Hydrogeology, Geohydrology

Access Constraints None

Use Constraints None. Acknowledgment of the Ground Water Atlas of the United States and (or) the National Atlas of the United States of America would be appreciated in products derived from these data.

Language English

Topic Category inlandWaters

Extent

Geographic Bounding Box

West Bound -160.236053332639
East Bound -64.5661622435395
North Bound 49.3856196512481
South Bound 17.6746926217151

Temporal Extent

DateTime 2003-10

Data Quality Information

Logical Consistency Report Polygon and chain-node topology are present. Each polygon is closed and has one label point.

Completeness Report This map layer includes aquifer information for the 48 conterminous United States, the District of Columbia, Hawaii, Puerto Rico, and the U.S. Virgin Islands.

Lineage

Source Information

Source Citation

Source Scale Denominator 2500000

Type of Source Media Stable-base material

Source Time Period of Content

DateTime 1995
Source Currentness Reference publication date

Source Citation Abbreviation GWA HA 730-B

Source Contribution Aquifer data for California and Nevada

Source Information

Source Citation

Source Scale Denominator 2500000

Type of Source Media Stable-base material

Source Time Period of Content

DateTime 1995
Source Currentness Reference Publication date

Source Citation Abbreviation GWA HA 730-C

Source Contribution Aquifer data for Arizona, Colorado, New Mexico, and Utah

Source Information

Source Citation

Source Scale Denominator 2500000

Type of Source Media Stable-base material

Source Time Period of Content

DateTime 1998
Source Currentness Reference Publication date

Source Citation Abbreviation GWA HA 730-D

Source Contribution Aquifer data for Kansas, Missouri, and Nebraska

Source Information

Source Citation

Source Scale Denominator 2500000

Type of Source Media Stable-base material

Source Time Period of Content

DateTime 1996
Source Currentness Reference Publication date

Source Citation Abbreviation GWA HA 730-E

Source Contribution Aquifer data for Oklahoma and Texas

Source Information

Source Citation

Source Scale Denominator 2500000

Type of Source Media Stable-base material

Source Time Period of Content

DateTime 1998
Source Currentness Reference Publication date

Source Citation Abbreviation GWA HA 730-F

Source Contribution Aquifer data for Arkansas, Louisiana, and Mississippi

Source Information

Source Citation

Source Scale Denominator 2500000

Type of Source Media Stable-base material

Source Time Period of Content

DateTime 1990
Source Currentness Reference Publication date

Source Citation Abbreviation GWA HA 730-G

Source Contribution Aquifer data for Alabama, Florida, Georgia, and South Carolina

Source Information

Source Citation

Source Scale Denominator 2500000

Type of Source Media Stable-base material

Source Time Period of Content

DateTime 1994
Source Currentness Reference Publication date

Source Citation Abbreviation GWA HA 730-H

Source Contribution Aquifer data for Idaho, Oregon, and Washington

Source Information

Source Citation

Source Scale Denominator 2500000

Type of Source Media Stable-base material

Source Time Period of Content

DateTime 1996
Source Currentness Reference Publication date

Source Citation Abbreviation GWA HA 730-I

Source Contribution Aquifer data for Montana, North Dakota, South Dakota, and Wyoming

Source Information

Source Citation

Source Scale Denominator 2500000

Type of Source Media Stable-base material

Source Time Period of Content

DateTime 1992
Source Currentness Reference Publication date

Source Citation Abbreviation GWA HA 730-J

Source Contribution Aquifer data for Iowa, Michigan, Minnesota, and Wisconsin

Source Information

Source Citation

Source Scale Denominator 2500000

Type of Source Media Stable-base material

Source Time Period of Content

DateTime 1995
Source Currentness Reference Publication date

Source Citation Abbreviation GWA HA 730-K

Source Contribution Aquifer data for Illinois, Indiana, Kentucky, Ohio, and Tennessee

Source Information

Source Citation

Source Scale Denominator 2500000

Type of Source Media Stable-base material

Source Time Period of Content

DateTime 1997
Source Currentness Reference Publication date

Source Citation Abbreviation GWA HA 730-L

Source Contribution Aquifer data for Delaware, Maryland, New Jersey, North Carolina, Pennsylvania, Virginia, and West Virginia

Source Information

Source Citation

Source Scale Denominator 2500000

Type of Source Media Stable-base material

Source Time Period of Content

DateTime 1995
Source Currentness Reference Publication date

Source Citation Abbreviation GWA HA 730-M

Source Contribution Aquifer data for Connecticut, Maine, Massachusetts, New Hampshire, New York, Rhode Island, and Vermont

Source Information

Source Citation

Source Scale Denominator 2500000

Type of Source Media Internal file

Source Time Period of Content

Beginning Position 1990
Ending Position 1993
Source Currentness Reference Publication or compilation date

Source Citation Abbreviation National aquifers file

Source Contribution Preliminary aquifer map of the 48 conterminous States.

Source Information

Source Citation

Source Scale Denominator 2000000

Type of Source Media Online

Source Time Period of Content

DateTime 1998
Source Currentness Reference Publication date

Source Citation Abbreviation Atlas-State boundaries

Source Contribution Coastline and international boundary

Source Information

Source Citation

Source Scale Denominator 2500000

Type of Source Media Online

Source Time Period of Content

DateTime 1998-07-01
Source Currentness Reference Publication date

Source Citation Abbreviation Atlas-principal Aquifers_1998

Source Contribution Aquifer data for the conterminous United States.

Source Information

Source Citation

Source Scale Denominator 1000000

Type of Source Media Stable-base material

Source Time Period of Content

DateTime 1999
Source Currentness Reference Publication date

Source Citation Abbreviation GWA HA 730-N-HI

Source Contribution Aquifer data for Hawaii.

Source Information

Source Citation

Source Scale Denominator 500000

Type of Source Media Stable-base material

Source Time Period of Content

DateTime 1999
Source Currentness Reference Publication date

Source Citation Abbreviation GWA HA 730-N-PR

Source Contribution Aquifer data for Puerto Rico and the U.S. Virgin Islands.

Source Information

Source Citation

Source Scale Denominator 2000000

Type of Source Media CD-ROM

Source Time Period of Content

DateTime 1998
Source Currentness Reference Publication date

Source Citation Abbreviation PP 1424-D

Source Contribution Dividing line between the Puget Sound Aquifer system and the Willamette Lowland basin-fill aquifers.

Source Information

Source Citation

Source Scale Denominator 250000

Type of Source Media CD-ROM

Source Time Period of Content

DateTime 1998
Source Currentness Reference Publication date

Source Citation Abbreviation PP 1424-B

Source Contribution Dividing line between the Puget Sound Aquifer system and the Willamette Lowland basin-fill aquifers.

Source Information

Source Citation

Source Scale Denominator

Type of Source Media CD-ROM

Source Time Period of Content

DateTime 1998
Source Currentness Reference Publication date

Source Citation Abbreviation PP 1418

Source Contribution Name change for the Marshall aquifer.

Source Information

Source Citation

Source Scale Denominator 500000

Type of Source Media CD-ROM

Source Time Period of Content

DateTime 1997
Source Currentness Reference Publication date

Source Citation Abbreviation WRIR

Source Contribution Aquifer data for the Cambrian-Ordovician Aquifer System extension in Illinois.

Source Information

Source Citation

Source Scale Denominator 2500000

Type of Source Media Internal file

Source Time Period of Content

DateTime 2000
Source Currentness Reference Compilation date

Source Citation Abbreviation Hawaii aquifers

Source Contribution Aquifers for Hawaii.

Source Information

Source Citation

Source Scale Denominator 2500000

Type of Source Media Internal file

Source Time Period of Content

DateTime 2000
Source Currentness Reference Compilation date

Source Citation Abbreviation Caribbean aquifers

Source Contribution Aquifers for Puerto Rico and the U.S. Virgin Islands.

Source Information

Source Citation

Source Scale Denominator 2500000

Type of Source Media Internal file

Source Time Period of Content

DateTime 2001
Source Currentness Reference Compilation date

Source Citation Abbreviation Principal aquifers 2001 intermediate file

Source Contribution Aquifer data for the conterminous United States.

Process Step

Process Description Aquifer outcrop line work for each GWA chapter was compiled on mylar at a scale of 1:2,000,000, and reduced to 1:2,500,000 for further production work. For chapters HA 730-G, -H, and -J, the outcrop lines were scribed at a line width of 0.006 inch. Film positives made from the scribed materials were scanned on a drum scanner, vectorized, and converted to Arc/INFO coverages. For chapters HA 730-B, -C, -D, -E, -F, -I, -K, -L, and -M, the aquifer compilation was either hand digitized, and (or) scanned on a drum scanner, vectorized and converted to Arc/INFO coverages. The data were then checked, cleaned up, and attribute creation was done. The Arc/INFO coverages were plotted and checked against the source compilations. Polygons were attributed using Arcedit. The coverages for GWA chapters HA 730-B, -C, -D, -E, -F, -I, -K, -L, and -M were used to generate output files that were imported into Adobe Illustrator for map publication. Each completed map, at a scale of 1:2,500,000, was reviewed for content and accuracy by the chapter lead cartographer, Water Resources Discipline Geohydrologic Map Editor, and chapter author. Individual chapter coverages were appended into one continuous coverage. Arcedit was used for edgematching and to remove duplicate labels. No DISSOLVE was done on the coverage; an equivalent of a DISSOLVE was done manually in Arcedit in conjunction with attribute checking, by removing arcs that divided adjacent polygons with the same attributes. Several iterations of editing were performed. These mostly involved ensuring all polygons had labels and aquifer information and ensuring polygons had correct aquifer information. No polygons were removed for generalization.
Source Used Citation Abbreviation GWA HA 730-B
Source Used Citation Abbreviation GWA HA 730-C
Source Used Citation Abbreviation GWA HA 730-D
Source Used Citation Abbreviation GWA HA 730-E
Source Used Citation Abbreviation GWA HA 730-F
Source Used Citation Abbreviation GWA HA 730-G
Source Used Citation Abbreviation GWA HA 730-H
Source Used Citation Abbreviation GWA HA 730-I
Source Used Citation Abbreviation GWA HA 730-J
Source Used Citation Abbreviation GWA HA 730-K
Source Used Citation Abbreviation GWA HA 730-L
Source Used Citation Abbreviation GWA HA 730-M
Process Date 1993
Process Time
Process Contact

Process Step

Process Description Plots of the national aquifers file were made at 1:2,500,000, covering the areas of the regional GWA chapters. Each plot was compared to the printed GWA chapter aquifer maps. Where applicable (chapters HA 730-B, -C, -D, -E, -F, -I, -K, - L, and -M), an Adobe Illustrator file of the coverage data was compared on-screen with the Illustrator file used to print the published map. Discrepancies between the coverage file and print file were noted, and the coverage updated to match the published map. Where a line appeared to shift noticeably (approximately 1/8 inch at a scale of 1:2,500,000) across the boundary of two adjacent GWA chapter regions, the line was adjusted for a smoother appearance. The adjustments may have been made on one or both sides of the region boundary, depending on a cartographic assessment of the instance. Coastline Location The 1:2,500,000 principal aquifer maps in the Ground Water Atlas publications used a coastline and international boundary, derived either from the map separates from the National Atlas of the United States of America (published 1970), or from the Digital Line Graph (DLG) data created from the 1970 National Atlas. GWA chapters HA 730-G, -J, and -H used coastline and boundary filmwork photo-mechanically reduced from the 1:2,000,000 National Atlas map separates. The remaining chapters used coastline and boundary data from the DLG's. A revision of the DLG data took place in 1997, after the creation of the chapter aquifer map data. After the edgematching, a decision was made to replace the coast and international boundary of this national-level aquifer data with one derived from a newer version of 1997 DLG data. State boundary data from the National Atlas was used to provide the coastline and two aquifer boundaries that coincide with State lines. The existing outline (coastline and international boundary line) was removed, the new outline added to the coverage, and the remaining aquifer contact lines snapped to the new outline. The coverage was re-cleaned, data categories checked onscreen and with plots, and corrected. Line and labeling corrections, such as undershoots, overshoots, and improper labels were corrected in Arcedit. There are some slight locational differences between this map layer and the printed GWA chapters. For example, there are several small differences in the number of small islands in coastal areas and the categorization of these small islands was assigned to either the nearby principal aquifer category or as Not a principal aquifer, depending on the location and categorization of similar small islands in the printed GWA chapters. There are other differences in the categorization of some land/shoreline-related features. For example, an area symbolized as a bay in a GWA chapter may be land in this map layer. Western Montana During the review of a printed map made from this national-level aquifer data, the compiler, James A. Miller, requested a change in the representation of aquifers in western Montana. The area affected is in the following counties: Lincoln, Flathead, Sanders, Lake, Mineral, Missoula, Powell, Ravalli, Granite, Lewis and Clark, Deer Lodge, Silver Bow, Jefferson, Broadwater, Gallatin, Beavershead, and Madison. These areas fall under the Northern Rocky Mountain Intermontane Basins Regional Aquifer Systems Analysis (RASA). With one exception, the aquifers, as shown in GWA chapter I, figure 7 in the listed counties were removed and replaced with unconsolidated-deposit areas as shown in GWA chapter HA 730-I, figure 6. The exception is an area in northern Flathead county, listed as an Upper Tertiary aquifer in GWA chapter I, figure 7, that was retained as an area but reclassified as a Lower Tertiary aquifer.
Source Used Citation Abbreviation National aquifers file
Source Used Citation Abbreviation GWA HA 730-B
Source Used Citation Abbreviation GWA HA 730-C
Source Used Citation Abbreviation GWA HA 730-D
Source Used Citation Abbreviation GWA HA 730-E
Source Used Citation Abbreviation GWA HA 730-F
Source Used Citation Abbreviation GWA HA 730-G
Source Used Citation Abbreviation GWA HA 730-H
Source Used Citation Abbreviation GWA HA 730-I
Source Used Citation Abbreviation GWA HA 730-J
Source Used Citation Abbreviation GWA HA 730-K
Source Used Citation Abbreviation GWA HA 730-L
Source Used Citation Abbreviation GWA HA 730-M
Source Used Citation Abbreviation Atlas-State boundaries
Process Date 1997
Process Time
Process Contact

Process Step

Process Description Aquifer data was taken from digital files created in Adobe Illustrator for Ground Water Atlas chapter HA 730-N of Hawaii, Puerto Rico, and the U.S. Virgin Islands. Where polygons ended at the shoreline, National Atlas State boundaries were used. The final Illustrator file was exported into a DXF file. The DXF file was converted to a coverage. Using the TRANSFORM command, the coverage containing the aquifer lines was rubber-sheeted to the coverage containing registration tics, and was then projected from geographic coordinates to Albers Equal-Area Conic projection for verification purposes. The aquifer coverage was cleaned, the topology was built, and labels were added. Attributes were added as necessary.
Source Used Citation Abbreviation Atlas-State boundaries
Source Used Citation Abbreviation GWA HA 730-N-HI
Process Date 2000
Process Time
Process Contact

Process Step

Process Description Aquifer data was taken from digital files created in Adobe Illustrator for Ground Water Atlas chapter HA 730-N of Hawaii, Puerto Rico, and the U.S. Virgin Islands. Where polygons ended at the shoreline, National Atlas State boundaries were used. The final Illustrator file was exported into a DXF file. The DXF file was converted to a coverage. Using the TRANSFORM command, the coverage containing the aquifer lines was rubber-sheeted to the coverage containing registration tics, and was then projected from geographic coordinates to Albers Equal-Area Conic projection for verification purposes. The aquifer coverage was cleaned, the topology was built, and labels were added. Attributes were added as necessary.
Source Used Citation Abbreviation Atlas-State boundaries
Source Used Citation Abbreviation GWA HA 730-N-PR
Process Date 2000
Process Time
Process Contact

Process Step

Process Description The Principal Aquifers map published in 1998 was reviewed and modified, resulting in 57 aquifers, 36 of which were the same geographically as in the 1998 publication. Aquifers were aggregated, divided, renamed and updated from more recent publications, using a variety of techniques, which include scanning, importing unpublished digital data and paper compilation at 1:2,500,000 scale. The updated Adobe Illustrator aquifer data was exported into a DXF file. The DXF file was converted to a coverage. Using the TRANSFORM command, the coverage containing the aquifer lines was rubber-sheeted to the coverage containing registration tics, and was then projected from geographic coordinates to Albers Equal-Area Conic projection for verification purposes. The aquifer coverage was cleaned, the topology was built, and labels were added. Attributes were added as necessary.
Source Used Citation Abbreviation Atlas-principal Aquifers_1998
Source Used Citation Abbreviation GWA HA 730-B
Source Used Citation Abbreviation GWA HA 730-C
Source Used Citation Abbreviation GWA HA 730-D
Source Used Citation Abbreviation GWA HA 730-E
Source Used Citation Abbreviation GWA HA 730-F
Source Used Citation Abbreviation GWA HA 730-G
Source Used Citation Abbreviation GWA HA 730-H
Source Used Citation Abbreviation GWA HA 730-I
Source Used Citation Abbreviation GWA HA 730-J
Source Used Citation Abbreviation GWA HA 730-K
Source Used Citation Abbreviation GWA HA 730-L
Source Used Citation Abbreviation GWA HA 730-M
Source Used Citation Abbreviation PP 1424-D
Source Used Citation Abbreviation PP 1424-B
Source Used Citation Abbreviation PP 1418
Source Used Citation Abbreviation WRIR
Process Date 2001
Process Time
Process Contact

Process Step

Process Description The Principal Aquifers coverages of Hawaii, Puerto Rico, and the U.S. Virgin Islands were merged with the coverage of the conterminous United States. The coverage was read into ArcGIS and both a personal geodatabase and a shapefile were created.
Source Used Citation Abbreviation Principal aquifers 2001 intermediate file
Source Used Citation Abbreviation Hawaii aquifers
Source Used Citation Abbreviation Caribbean aquifers
Process Date 2003
Process Time
Process Contact

Aquifers

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