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Metadata Ecoregions

Level III Ecoregions of the Conterminous United States in BASINS

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Originator: U.S. Environmental Protection Agency/Office of Water/OST
Publication_Date: 20070611
Level III Ecoregions of the Conterminous United States in BASINS
Publication_Place: Washington, D.C.
Publisher: U.S. Environmental Protection Agency
For BASINS model and data <>
For further documentation and information on ecoregions <>
The ECOREG coverage provides polygon coverage of the Level III ecoregions for the conterminous United States. The coverage is stored in the EPA Spatial Data Library System (ESDLS). The ecoregions shown here have been derived from ecoregions of the conterminous United States and from refinements of Omernik's framework that have been made for other projects. These ongoing or recently completed projects, conducted in collaboration with the U.S. EPA regional offices and with state resource management agencies, involve refining ecoregions, defining subregions, and locating sets of reference sites. These are designed to serve as a spatial framework for environmental resource management.

For distribution with BASINS v.2.0, the data layer was prepared in Arcview shape file format.

This coverage provides a valuable data layer for BASINS that require Arcview shape file format in an unprojected form.

Ecoregions denote areas within which ecosystems (the type, quality, and quantity of environmental resources) are generally similar. The most immediate needs are to develop regional biological criteria and water quality standards and to set management goals for nonpoint source pollution.


Intended_use_of_data: This data set was prepared to support the U.S. EPA BASINS (Better Assessment Science Integrating Point and Nonpoint Sources) System.

Limitations_of_Data: None

Procedures: The approach used to compile these data is based on the premise that ecological regions can be identified through the analysis of the patterns and the composition of biotic and abiotic phenomena that affect or reflect differences in ecosystem quality and integrity (Wiken 1986, Omernik 1987, 1995). These phenomena include geology, physiography, vegetation, climate, soils, land use, wildlife, and hydrology. The relative importance of each characteristic varies from one ecological region to another regardless of the hierarchical level. Because of possible confusion with other meanings of terms for different levels of ecological regions, a Roman numeral classification scheme has been adopted for this effort. Level I is the most coarse level, dividing North America into nine ecological regions. Level II, the continent, is subdivided into 32 classes. Level III further subdivides the continent into 78 classes. For portions of the United States, the ecoregions have been further subdivided to Level IV. The Applications of the ecoregions are explained in Gallant et al., (1989) and in reports and publications from state and regional projects. The National Geographic Information Services (NGIS) Team at Environmental Protection Agency's (EPA) Systems Development Center (SDC) reprojected the coverage to North American Datum 83 (NAD83) and added the ecoregion names to the data set.

a. All ecoregion and subregion coverages are digitized from the USGS 1:250,000 base maps. Prior to digitizing, each base map must be initialized to orient the map and relate it in geographic coordinates to the surface of the earth. When the registration tics are entered at the start of digitizing, a transformation error of <0.003 must be achieved in order to ensure a high level of registration accuracy. The person responsible for digital data entry completes a data sheet describing coverage name, date of entry, and whether a topology for the coverage is established.

b. After each 1:250,000 base map has been digitized, a topology for each coverage is established. This function creates unique identities for each polygon.

c. Next, each base map is tested for polygon errors through an internal editing function. Errors are corrected for unlabeled polygons, unclosed polygons, or polygons with more than one label. Topology is re- established for each coverage and tested again until no errors are indicated.

d. The digital coverage is then plotted at the same scale as the original base map. This coverage is overlaid on a light table with the original and visually inspected for replication of original lines with digitized lines. Two individuals independently inspect the coverage for accuracy.


SDC Product Assurance (PA) applied these reviews to the data set: a. Verified coverage existence and spatial extent. b. Verified the addition of ecoregion names to the data set. c. Verified spatial index existence and the use of NAD83 projection.

References_Cited: Gallant, A.L., T.R. Whittier, D.P. Larsen, J.M. Omernik, and R.M. Hughes. 1989. Regionalization as a Tool for Managing Environmental Resources. EPA/600/3089/060. U.S. Environmental Protection Agency, Environmental Research Laboratory, Corvallis, OR. 152p.

Gallant, A.L., E.F. Binnian, J.M. Omernik, and M.B. Shasby. (draft map and report). Ecoregions of Alaska Report prepared jointly by the U.S. Geological Survey, the U.S. Environmental Protection Agency, and Colorado State University.

Omernik, J.M., U.S. EPA, NHEERL, 200 SW 35th Street, Corvallis, OR 97333 (phone: 503-754-4458).

Omernik, J.M. 1987 "Ecoregions of the Conterminous United States." Map (scale 1:7,500,000). Annals of the Association of American Geographers 77(1):118-125.

Omernik, J.M. 1995. "Ecoregions: A framework for environmental management." in: Biological Assessment and Criteria: Tools for Water Resource Planning and Decision Making. W. Davis and T. Simon (eds.) Lewis Publishers, Chelsea, MI.

Wiken, E. 1986. Terrestrial Ecozones of Canada. Environment Canada. Ecological Land Classification Series No. 19. Ottawa, Canada.

Notes: Source Data Information 1. Original data were compiled at 1:3, 168,000, 1986. 2. Unknown number of revisions between 1986 and 1994. (Est. 6-8) 3. 2 new ecoregions (77-North Cascades and 78-Klamath Mountains) were added to reflect changes with the subregion project in Oregon and Washington. 3/95 4. Revised lines reflecting changes in subregions in Oregon and Washington. 8/95 5. Revised lines reflecting changes in subregions in Pennsylvania, the Blue Ridge Mountains, Ridge and Valley, and Central Appalachians of EPA Region 3. 11/95 6. Revised lines reflecting changes in subregions in North Dakota, Indiana, and Ohio. Ecoregion 42 (Northwestern Glaciated Plains) was enlarged to include the area of ecoregion 45 (Northeastern Great Plains). Ecoregion 45 was deleted. A new ecoregion 45 (Piedmont) was added in the southeast US. 1/96

Beginning_Date: 1986
Ending_Date: 1994
Currentness_Reference: 19960930
Progress: Complete
Maintenance_and_Update_Frequency: As needed
West_Bounding_Coordinate: -167.0
East_Bounding_Coordinate: -65.0
North_Bounding_Coordinate: 71.0
South_Bounding_Coordinate: 17.5
Theme_Keyword_Thesaurus: None.
Omernik Ecoregions
Conterminous United States
Coast Range
Puget Lowland
Willamette Valley
Sierra Nevada
Southern and Central California Plains and Hills
Central California Mountains
Southern California Mountains
Eastern Cascades Slopes and Foothills
Columbia Plateau
Blue Mountains
Snake River Basin/High Desert
Northern Basin and Range
Southern Basin and Range
Northern Rockies
Montana Valley and Foothill Prairies
Middle Rockies
Wyoming Basin
Wasatch and Uinta Mountains
Colorado Plateaus
Southern Rockies
Arizona/New Mexico Plateau
Arizona/New Mexico Mountains
Southern Deserts
Western High Plains
Southwestern Tablelands
Central Great Plains
Flints Hills
Central Oklahoma/Texas Plains
Edwards Plateau
Southern Texas Plains
Texas Blackland Prairies
East Central Texas Plains
Western Gulf Coastal Plains
South Central Plains
Ouachita Mountains
Arkansas Valley
Boston Mountains
Ozark Highlands
Central Irregular Plains
Northern Montana Glaciated Plains
Northwestern Glaciated Plains
Northwestern Great Plains
Nebraska Sand Hills
Northern Glaciated Plains
Western Corn Belt Plains
Lake Agassiz Plain
Northern Minnesota Wetlands
Northern Lakes and Forests
Northern Central Hardwood Forests
Driftless Area
Southeastern Wisconsin Till Plains
Central Corn Belt Plains
Eastern Corn Belt Plains
S. Michigan/N. Indiana Drift Plains
Huron/Erie Lake Plains
Northeastern Highlands
Northeastern Coastal Zone
Northern Appalachian Plateau and Uplands
Erie/Ontario Lake Hills and Plain
North Central Appalachians
Middle Atlantic Coastal Plain
Northern Piedmont
Southeastern Plains
Blue Ridge Mountains
Central Appalachian Ridges and Valleys
Southwestern Appalachians
Central Appalachians
Western Allegheny Plateau
Interior Plateau
Interior River Lowland
Mississippi Alluvial Plain
Mississippi Valley Loess Plains
Southern Coastal Plain
Southern Florida Coastal Plain
North Cascades
Klamath Mountains
Place_Keyword_Thesaurus: Geographic Names Information System
Place_Keyword: Conterminous United States of America (CONUS)
Place_Keyword: Alabama AL
Place_Keyword: Arizona AZ
Place_Keyword: Arkansas AR
Place_Keyword: California CA
Place_Keyword: Colorado CO
Place_Keyword: Connecticut CT
Place_Keyword: Delaware DE
Place_Keyword: District of Columbia DC
Place_Keyword: Florida FL
Place_Keyword: Georgia GA
Place_Keyword: Idaho ID
Place_Keyword: Illinois IL
Place_Keyword: Indiana IN
Place_Keyword: Iowa IA
Place_Keyword: Kansas KS
Place_Keyword: Kentucky KY
Place_Keyword: Louisiana LA
Place_Keyword: Maine ME
Place_Keyword: Maryland MD
Place_Keyword: Massachusetts MA
Place_Keyword: Michigan MI
Place_Keyword: Minnesota MN
Place_Keyword: Mississippi MS
Place_Keyword: Missouri MO
Place_Keyword: Montana MT
Place_Keyword: Nebraska NE
Place_Keyword: Nevada NV
Place_Keyword: New Hampshire NH
Place_Keyword: New Jersey NJ
Place_Keyword: New Mexico NM
Place_Keyword: New York NY
Place_Keyword: North Carolina NC
Place_Keyword: North Dakota ND
Place_Keyword: Ohio OH
Place_Keyword: Oklahoma OK
Place_Keyword: Oregon OR
Place_Keyword: Pennsylvania PA
Place_Keyword: Rhode Island RI
Place_Keyword: South Carolina SC
Place_Keyword: South Dakota SD
Place_Keyword: Tennessee TN
Place_Keyword: Texas TX
Place_Keyword: Utah UT
Place_Keyword: Vermont VT
Place_Keyword: Virginia VA
Place_Keyword: Washington WA
Place_Keyword: West Virginia WV
Place_Keyword: Wisconsin WI
Place_Keyword: Wyoming WY
Access_Constraints: None
None. Acknowledgement of the U.S. Environmental Protection Agency would be appreciated.
Arcview shape files on Window 95 PC.

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Polygon and chain-node topology present.
See Supplemental_Information
The Arc/Info export file was downloaded from the EPA FTP site ( and was converted from Albers Conic Equal Area projection to geographic decimal degrees projection using Arc/Info. The coverage was then converted to Arcview shape file using the Arc/Info ARCSHAPE command.

For distribution with BASINS 2.0, the data layer was divided by EPA regions (i.e. distribution by CD). Other form of data distribution (e.g. by cataloging unit) is available through the web <>

Process_Date: 19980218
Contact_Organization: Tetra Tech, Inc.
Address_Type: Mailing Address
Address: 10306 Eaton Place, Suite 340
City: Fairfax
State_or_Province: Virginia
Postal_Code: 22030
Country: USA
Contact_Voice_Telephone: 703-385-6000
Contact_Instructions: See Distributor_Information

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Latitude_Resolution: 0.0001
Longitude_Resolution: 0.0001
Geographic_Coordinate_Units: Decimal Degrees
Horizontal_Datum_Name: North American Datum of 1983
Ellipsoid_Name: Geodetic Reference System 80
Semi-major_Axis: 6378137
Denominator_of_Flattening_Ratio: 298.257

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Entity_Type_Label: ecoreg.dbf
Entity_Type_Definition: Ecoregion primary attribute table.
Entity_Type_Definition_Source: USEPA
Attribute_Label: AREA
Attribute_Definition: Area of poly/region in square coverage units.
Attribute_Definition_Source: Computed
Enumerated_Domain_Value: 12
Enumerated_Domain_Value_Definition: Floating value
Enumerated_Domain_Value_Definition_Source: Assigned
Attribute_Label: PERIMETER
Attribute_Definition: Perimeter of poly/region in coverage units.
Attribute_Definition_Source: Computed
Enumerated_Domain_Value: 10
Enumerated_Domain_Value_Definition: Floating Value
Enumerated_Domain_Value_Definition_Source: Assigned
Attribute_Label: Ecoreg_
Attribute_Definition: ARC/INFO internal value
Attribute_Definition_Source: Computed
Enumerated_Domain_Value: 4
Enumerated_Domain_Value_Definition: Integer value
Enumerated_Domain_Value_Definition_Source: Assigned
Attribute_Label: Ecoreg_id
Attribute_Definition: User-assigned feature number.
Attribute_Definition_Source: User-defined
Enumerated_Domain_Value: 4
Enumerated_Domain_Value_Definition: Integer value
Enumerated_Domain_Value_Definition_Source: USEPA
Attribute_Label: Eco
Attribute_Definition: Ecoregion ID
Attribute_Definition_Source: USEPA
Enumerated_Domain_Value: 2
Enumerated_Domain_Value_Definition: Integer value
Enumerated_Domain_Value_Definition_Source: USEPA
Attribute_Label: Name
Attribute_Definition: Indicates the name of the ecoregion.
Attribute_Definition_Source: USEPA
Enumerated_Domain_Value: 40
Enumerated_Domain_Value_Definition: character ID value
Enumerated_Domain_Value_Definition_Source: USEPA

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Contact_Organization: USEPA/Office of Water/OST
Address_Type: Mailing Address
Address: 1200 Pennsylvania Ave., NW (4305T)
City: Washington
State_or_Province: District of Columbia
Postal_Code: 20460
Country: USA
Contact_Voice_Telephone: 202-566-0400
Contact_Facsimile_Telephone: 202-566-0409
Although these data have been processed successfully on a computer system at Tetra Tech, Inc., no warranty expressed or implied is made regarding the accuracy or utility of the data on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. This disclaimer applies both to individual use of the data and aggregate use with other data. It is also strongly recommended that careful attention be paid to the contents of the metadata file associated with these data. The U.S. Environmental Protection Agency nor Tetra Tech, Inc. shall not be held liable for improper or incorrect use of the data described and/or contained herein.
Environmental Systems Research Institute (ESRI) ArcView Shapefile
Network_Resource_Name: <>
Offline_Media: CD-ROM
Recording_Format: ISO 9660
Fees: None
When requesting data by phone or mail, please inquire about spatial data sets that work with Better Assessment Science Integrating Point and Nonpoint Sources (BASINS). The BASINS web page has instructions for downloading datasets. It also has a link to The National Center for Environmental Publications and Information (NCEPI), from which BASINS CD-ROMs may be ordered. Each CD-ROM contains the BASINS v2.0 Application and this data set along with others covering the spatial extent of an EPA Region.

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Metadata_Date: 20070611
Contact_Organization: USEPA/OW/OST
Address_Type: Mailing Address
Address: 1200 Pennsylvania Ave., NW (4305T)
City: Washington
State_or_Province: District of Columbia
Postal_Code: 20460
Country: USA
Contact_Voice_Telephone: 202-566-0400
Contact_Facsimile_Telephone: 202-566-0409
Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata
Metadata_Standard_Version: 19940608


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Generated by USGS mp on Thu Sep 10 11:05:23 1998 Exit

Ecoregion Text Version(1 pg, 21 K)