National Wetlands Inventory (NWI) Overview

The National Wetlands Inventory (NWI) was established by the U.S. Fish and Wildlife Service (FWS) to conduct a nationwide inventory of the wetlands and deepwater habitats of the United States and to produce national wetlands status and trends reports required by Congress.  This information is used by Federal, State and local agencies, academic institutions, and private industry for various management, research, policy development, education and planning activities.

To accomplish this task, the NWI developed a wetland classification system (Cowardin et al. 1979) that is the FWS and Federal standard for wetland mapping, monitoring and reporting.  The mapping techniques used by NWI have been adopted by the Federal Geographic Data Committee as the federal wetland mapping standard (FGDC Wetlands Subcommittee 2009). This standard applies to all federal funds involving wetland mapping to ensure data is consistent and can be incorporated into the NWI dataset and served to the public.

The NWI website provides users with various methods for viewing and downloading wetlands data as well as important information about Federal wetland mapping standards and wetland status and trend studies.

Viewing and Downloading Wetlands Data

NWI wetlands data is available on-line via the Wetlands Mapper. This application has a user-friendly interface that provides an interactive environment for users to view, query and print wetlands data displayed on imagery, street and topographic maps.  GIS users can access wetlands data through online wetland mapping services or by downloading the data by state or watershed.  

NWI Wetlands Data Verification Toolset & Wetlands Website Search Engine

The USFWS National Wetlands Inventory is pleased to announce the release of an Updated Wetlands Data Verification Toolset and a new Wetlands Website Search Engine.

The Wetlands Data Verification Toolset is designed to automate the quality control functions necessary to ensure wetlands data is accurate and conforms to requirements for data inclusion into the USFWS Wetlands geodatabase.  It has been designed to address geospatial errors, digital anomalies, and logic checks.  The tool should be run multiple times by photo interpreters while mapping wetlands and as an interim and final quality control step.

The toolset was created using Environmental Systems Research Institute’s (ESRI) ModelBuilder, is compatible with ESRI’s ArcDesktop 10.3.1 software suite and replaces previous versions of the Wetlands Verification Tools.  Modifications to this 10.3.1 tool include: the most recent, expanded and up to date wetland code list from June 2016, the addition of quad boundaries to improve the performance of the Upland Slivers tool, the use of ESRI topology to improve performance of identifying Overlapping Wetlands, and the insertion of a compact geodatabase and repair geometry functions before every tool is run to reduce the occurrence of lost data after an edit session due to an ESRI bug.   

Note: This ESRI bug has not been resolved in 10.3.1 or earlier versions so be sure to make backup copies on the data often and check polygon counts before and after edit sessions and running models.   When loss of data is observed, exporting and reloading the data from that feature class has shown to force the geodatabase to read the missing features and they reappear. There is also an ESRI’s ArcDesktop 10.2.2 version available that includes the most recent, expanded and up to date wetland code list from June 2016.

To download the latest tool, go here

NWI has also developed a new Wetlands Website Search Engine created with Google Custom Search Engine technology (CSE). This Search Engine greatly improves users ability to find topic specific wetland information on our website and document library.  It has the same search index technology that powers, with accurate, fast results and spell checking capabilities.  It allows users to search not only the contents of our website (site search), but also focus on a particular topic from other sites.

Google CSE is complemented by Google Search Console and Google Analytics.  Refinements created with Google CSE and Google Search Console will also enhance all general searches requested by users using Google Search from any browser or mobile device.

Use the new Wetlands Website Search Engine here

Wetlands Code Classification

Extensive documentation pertaining to the Federal wetland mapping standard as well as the Federal wetland classification Standard is available through the NWI website.  Users are also encouraged to use the Wetland Code Interpreter tool that provides detailed habitat descriptions for a specific wetland code as well as the NWI Water Regime Restriction Table to aid in wetland code compliance.

Status and Trends

The FWS is congressionally mandated to conduct status and trends studies of the nation’s wetlands at 10 year intervals. Data from these studies dating back to the 1950’s provides important information about the overall status of the nations’ wetlands as well as an accurate record to assist in future restorations. In addition to the national reports the FWS has also conducted numerous state and regional reports.

Google Earth

The NWI website provides a way to view wetlands data with Google Earth. One advantage of this is that NWI data can be seen on current as well as recent historic images. This can be a great tool for viewing recent changes in and around wetlands.  Some historic wetland data is also available via the Wetlands Mapper for specific areas of the country.

Contribute Data

Federal mandate states that all data produced using federal funding must comply with federal standards. Other organizations and individuals not using federal funding are encouraged to contribute their wetlands data to the national dataset. The benefits of contributing to the NWI geospatial data layer include data hosting, visibility, distribution and recognition of your mapping efforts. For information on how to contribute your data, visit the contributed data page.

For more information please visit the NWI website at: