Information Resources and Technology Management

Data Layer: WETLANDS

You are invited to read the definitions of terms used in this data standard.

Wetlands Data

Digital wetland maps created by the U.S. Fish and Wildlife Service, Division of Ecological Services, Branch of Geospatial Mapping and Technical Support, National Wetlands Inventory.

The FGDC Steering Committee endorsed the revision of the Wetlands Classification Standard in summer 2013. The revised FGDC Wetlands Classification Standard has been formatted to be consistent with more recently endorsed FGDC Standards. The text has been edited, refined, clarified, and rewritten as necessary. Some portions were rewritten because the scientific foundation upon which the original classification (Cowardin et al. 1979) was developed has advanced. Changes were thoroughly vetted in the wetlands community.   The Wetlands Classification Standard is available here -

NOTE: The FGDC endorsed the Wetlands Mapping Standard in July 2009. The purpose of this standard is to support accurate mapping and classification of wetlands, while ensuring mechanisms for their revisions and update as directed under OMB Circular A-16, Revised. It is designed to direct the current and future digital mapping of wetlands. This mapping standard will be used for all wetland mapping nationally including Federal Agencies, States, Tribes, especially if that mapping data will be uploaded into NWI/The National Map as a data layer. Specifically, if Federal funding is involved, then use of the proposed Standard is required. For all other efforts, use of the standard is strongly encouraged. More information about the Wetlands Mapping Standard is available here.

National Standards and Quality Components For Wetlands, Deepwater and Related Habitat Mapping. 2004. U.S. Fish and Wildlife Service, Division of Habitat and Resource Conservation, Branch of Habitat Assessment, Arlington, VA. 18 pp.
Historical Data For information on past versions of this standard, contact the Chief Data Officer

Classification of Wetlands and Deepwater Habitats of the United States - U.S. Fish and Wildlife Service Data Standard.

Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 2013.  Classification of Wetlands and Deepwater Habitats of the United States 2nd Edition.  U.S. Fish and Wildlife Service, FWS/OBS-79/31, Washington, D.C. 85 pp.

Coordination of Wetlands Data Collection:
• National Wetlands Inventory:  A Strategy for the 21st Century. 2001.  U.S. Fish and Wildlife Service, Branch of Habitat Assessment, Arlington, VA. 13 pp.
• National Standards and Quality Components For Wetlands, Deepwater and Related Habitat Mapping.  2004. U.S. Fish and Wildlife Service, Branch of Habitat Assessment, Arlington, VA. 18 pp.
Data Collection Requirements and Procedures for Mapping Wetland, Deepwater and Related Habitats of the United States. Division of Habitat and Resource Conservation (version 2),  Dahl, T.E., J. Dick, J. Swords, and B.O. Wilen. 2015. National Standards and Support Team, Madison, WI. 92 p.

National Wetlands Inventory Home Page - online maps, map information, wetland information, and more!

Use Instructions

The Service’s topical wetland maps are graphic representations of the type, size and location of wetlands and deepwater habitats in the United States. These maps, produced from the analysis of high altitude imagery, collateral data sources and field work, represent reconnaissance level information on the location, type, and size of wetlands habitats. Published wetland maps, at the nominal scale of 1:24,000 for the conterminous U.S. and 1:63,360 for Alaska, comply with National Map Accuracy Standards. Due to the margin of error inherent in the use of imagery, detailed on-the-ground inspection of any particular site may result in revision of the wetland boundaries or classification established through image analysis.

The accuracy of image interpretation depends on the quality of the imagery, experience of the image analysts, amount and quality of the collateral data, and extent of ground truth verification conducted in the field. Metadata should be consulted to determine the date of the source imagery and any problems that may have occurred during the mapping process.

Wetlands or other mapped features may have changed since the date of the imagery and/or field work. There may be occasional differences in polygon boundaries or classifications between the information depicted on the map and the actual conditions on site. 

Wetlands Master Geodatabase (MGD):  Development of a MGD stems from the Service’s need to expand and improve the availability of digital wetlands data. With the advent of computer technologies that allow the integration of large relational databases with spatial information, the MGD provides an opportunity to capitalize on years of data collection by developing scientifically sound, technologically relevant tools for analyzing, distributing, archiving and updating aquatic resource information. The MGD provides a seamless layer of digital wetlands and deepwater habitat data in a geodatabase format, i.e., a single standard projection (Albers Equal-Area Conic Projection) with horizontal planar units in meters, the North American Datum of 1983 (NAD83), and minimum coordinate precision of one centimeter. The MGD also accommodates upland(s), riparian habitats and hydrogeomorphic coding of features within the data set and provides technologically advanced mechanisms to edit, store, distribute and archive resource inventory data.
The Wetlands Data Verification Toolset is designed to automate the quality control functions necessary to ensure the data in the Wetlands geodatabase is accurate. It has been designed to address geopositional errors, digital anomalies, and logic checks. This toolset was created using Environmental Systems Research, Incorporated's (ESRI) ModelBuilder, is compatible with ESRI's ArcDesktop 10.0 software suite, only works on File Geodatabases, and replaces previous custom Wetlands Verification Tools. The Wetlands Data Verification Toolset, installation instructions, and user information are available for download at

The Wetlands Mapper application, developed in collaboration with the USGS,promotes a greater awareness of wetlands map data applications and delivers easy-to-use, map-like views of America's wetland resources in a digital format. For ease of viewing the map information, wetland types are displayed in aggregation with similar classifications (e.g., all freshwater emergent wetlands are displayed as a single color category). The Wetlands Mapper currently serves wetland data for all of the conterminous 48 States, Hawaii, Puerto Rico, the Virgin Islands, Guam, the major Northern Mariana Islands and 35 % of Alaska.

FWS Created & Adopted
Approval Date
June 26, 2006
Validation Date
September 4, 2015
Data Steward
Mitch Bergeson, Division of Ecological Services, Branch of Geospatial Mapping and Technical Support.


Last updated: May 9, 2019