National Wetlands Inventory
Ecological Services

Frequently Asked Questions

About the Wetlands Data

How do I view the wetlands data?
Visit our wetlands mapper. The mapper hosts the most current digital wetlands data held by the U.S. Fish and Wildlife Service, National Wetlands Inventory.
How do I download wetlands data?

The Get Data button on the Wetlands Mapper will open a new dialog box with options for downloading seamless wetlands data as viewed on the Wetlands Mapper. The Wetlands Mapper provides users enhanced access to the wetlands data with the capability to download geospatial wetland map data by state and watershed (HUC8) in shapefile and file geodatabase format; and to connect to the wetlands dataset via web services (WMS, KMZ and REST). Connecting to Web services allows users to dynamically interact with the data on their desktop and web-based applications.  You can view the Shapefiles by using ESRI's ArcGIS Explorer free software among others. Geodatabases require a full ESRI ArcDesktop license.


By Watershed - The Download by Watershed option allows users to select individual watersheds in the mapper for data download. This tool gives you the option of downloading a Shapefile or File Geodatabase.

By State - You can also download data by State. Each State data download is available as either a compressed File Geodatabase or a Shapefile.

Web Services – Web Services option allows direct connection to the NWI web map service, for either wetlands data, wetlands status, or riparian data. For detailed information on how to connect to these services please visit our website at:

What software do I need to view downloaded data?
Shapefiles can be viewed using most GIS software applications, including ESRI's free ArcGis Explorer software. Geodatabases will require ESRI software (version 10.*) to view.
What do the wetland map codes mean?

The wetland classification codes are a series of letter and number codes that have been developed to adapt the national wetland classification system to map form. These alpha-numeric codes correspond to the classification nomenclature that best describes the habitat. (for example, PFO1A).

The Service provides extensive documentation of this Cowardin Classification System. 

Why do I get an error when I try to unzip my downloaded data?
If an error occurs during your download, or if your downloaded file(s) is corrupted, we strongly recommend the use of a download manager. A download manager is a computer program dedicated to the task of downloading files from the Internet for storage. The typical download manager at a minimum provides means to recover from errors without losing the work already completed. 

There are several download manager programs available, including some that are free. We use Xtreme Download Manager (Open Source software); it works really well. 

Note: Due to their size, State files can not be sent by email.


About the Wetlands Mapper

Can the wetlands mapper be used for regulatory purposes?

The wetlands displayed on the Wetlands Mapper show wetland type and extent using a biological definition of wetlands. There is no attempt to define the limits of proprietary jurisdiction of any Federal, State, or local government, or to establish the geographical scope of the regulatory programs of government agencies.

Persons intending to engage in activities involving modifications within or adjacent to wetland areas should seek the advice of appropriate federal, state, or local agencies concerning specified agency regulatory programs and proprietary jurisdictions that may affect such activities.

For information about regulations that may affect wetlands or development on your property, contact the U.S. Army Corps of Engineers office nearest you:

Why is the wetlands mapper not displaying data?

This problem could be caused by old internet addresses in your browser and/or computer DNS cache. To clear both, please do the following in this order:

1. Open a Command Prompt window (Start button, Search box, type Command Prompt). 
2. tyoe  ipconfig /flushdns  and press Enter. (if unsuccessful, you may have to do this with Admin rights). 
3. Restart your computer. 
4. Open your browser, then clear your cache memory. 
5. Open the mapper from here:

What are areas of interest?

The Areas of Interest layer was designed to highlight wetlands that exhibit unique or important ecological characteristics. It currently includes sites located throughout the United States. It includes Wetlands of International Importance (Ramsar sites) as well as state natural areas, National Parks and National Wildlife Refuges. Each site is marked with a geographic location and includes a link to additional information about that particular wetland. Additional site and information may be added in the future.

How do I cite digital data or hard-copy maps in publications?

For wetland digital data downloaded from our website:

U. S. Fish and Wildlife Service. Publication date (found in metadata). National Wetlands Inventory website. U.S. Department of the Interior, Fish and Wildlife Service, Washington, D.C.

When were wetlands in my area mapped?

The Service's topical wetland and riparian maps are graphic representations of the type, size and location of the wetlands, deepwater or riparian habitats in the United States. These maps have been prepared from the analysis of high altitude imagery in conjunction with collateral data sources and field work.

The date a given wetland polygon is valid is based on the imagery that was used for the interpretation. This imagery information is visible when you click on a wetland polygon in the Wetlands Mapper. A display box containing information about the selected polygon will appear including 'Image Date(s)' which identifies the year(s) of imagery used. For a more general view of when the wetlands in a larger area were mapped display the' Data Source - Image Year' layer on the Wetlands Mapper.

How do I save and print a map?

The Print button allows users to print the current map view.  Use the Panning and Zoom controls to center map to desired extent. After entering a title, selecting the print button will add the map to the print jobs queue. 


Selecting an individual print job will open an Adobe PDF document with a rendition of the previously displayed map. The generated map will be approximately .5MB. The generated PDF document can be saved and/or printed.

How do I find the date of the mapper base imagery?

There are several options for base maps including aerial and satellite imagery, street maps that show transportation routes, topographic maps provided by ESRI, and U.S. Geological Survey digital raster graphics of topographic mapping. Click on the desired base map type button to switch views. Please allow a few seconds for the view to refresh.

A list of Basemap contributors can be found at:

Metadata for this imagery service can be found at: 

Why doesn't my location work on my mobile device?
The zoom to location will not work on your mobile device unless the location services are turned on. Each device may have different ways to accomplish this. For Apple devices, follow this link. For Android devices, please follow this link. Certain browsers have specific location settings: for Safari, please follow this link; for Chrome, please follow this link.
How do I enter latitude and longitue coordinates?
The 'Find Location' tool in the Wetlands Mapper accepts decimal degrees for coordinates separated by a comma in Long/Lat format (e.g. -89.4676, 43.0568). 
Is data available for historic wetland coverage?

Historic wetlands data is available in IA, IN, WI, and portions of MN and SD, and more information about how this layer was developed and its suitability is available at Product-Summary.html.

The wetlands mapper also shows areas with available historic wetlands data, which will be included when downloading data by either state or watershed.

Why is there a difference between mapped wetlands and ground conditions?

It is likely the base imagery date is different than the date of the imagery used for photointerpretation, and interim changes in the landscape since the wetland was mapped may result in mismatch when comparing newer imagery with ground conditions.

The wetlands mapper defaults to ESRI base imagery. More information can be found at:

Imagery can also be viewed in theESRI map viewer to determine image dates for specific areas of interest.

In addition, not all wetlands are wet throughout the year. Some wetlands may appear dry during certain times of the year while still supporting hydric soils and wetland plants characteristic of wetland areas.

How often is the mapper updated?

​Wetlands data is typically updated twice a year; in the spring and fall. The best way to check for updates is by using the projects mapper viewer link on the right of the main mapper page (, which shows recent data updates as well as active mapping projects.

How do I sign up for email updates pertaining to NWI?
To subscribe to our Listserv for email announcements, or change your existing subscription, visit this website:
Who do I contact when I have a question?
Please visit our Contacts web page for more information.



Last updated: May 12, 2017