Datasets
National Wetlands Inventory
Domain: Land Cover
Spatial Resolution: 1:24,000
Temporal Frequency: irregular
Temporal Coverage: 1977 - 2021
Spatial Extent: CONUS; AK; HI; PR; VI; Pacific Trust Islands
Source: USFWS
Update Type: Dynamic
Update Frequency: irregular
Update Detail: append and modify
Access Details:
Access is by State, for larger area contact the Wetlands Team ( wetlands_team@fws.gov ) to request a custom download.
Description:
The National Wetlands Inventory (NWI) was established by the US Fish and Wildlife Service (FWS) to conduct a nationwide inventory of U.S. wetlands to provide biologists and others with information on the distribution and type of wetlands to aid in conservation efforts. To do this, the NWI developed a wetland classification system (Cowardin and others 1979) that is now the official FWS wetland classification system and the Federal standard for wetland classification (adopted by the Federal Geographic Data Committee on July 29, 1996: 61 Federal Register 39465). The NWI also developed techniques for mapping and recording the inventory findings. The NWI relies on trained image analysts to identify and classify wetlands and deep water habitats from aerial imagery. NWI started mapping wetlands at a small scale (1:250,000 map which covers an area the size of 128-1:24,000 USGS topographic maps or approximately 7,400 square miles). Eventually, large-scale (1:24K scale) maps became the standard product delivered by NWI. As computerized mapping and geospatial technology evolved, NWI discontinued production of paper maps in favor of distributing data via on-line “mapping tools” where information can be viewed and downloaded. Today, FWS serves its data via an on-line data discovery, the Wetlands Mapper. GIS users can access wetlands data through an on-line wetland mapping service or download data for various applications (maps, data analyses, and reports). The techniques used by NWI have recently been adopted by the Federal Geographic Data Committee as the federal wetland mapping standard (FGDC Wetlands Subcommittee 2009). This standard applies to all federal grants involving wetland mapping to insure the data can be added to the Wetlands Layer of the National Spatial Data Infrastructure. NWI also produces national wetlands status and trends reports required by Congress.
Citation:
Cowardin, L.M., Carter, V., Golet, F.C., and LaRoe, E.T., 1979. Classification of Wetlands and Deepwater Habitats of the United States: U.S. Department of the Interior, Fish and Wildlife Service, Washington, DC. FWS/OBS-79/31, https://www.fws.gov/program/national-wetlands-inventory