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Utilizing National Wetland Inventory (NWI) shape file datasets for import into MyWorld

National Wetlands Inventory, Wetlands Data
This DataSheet was created by Mike Taber of Colorado College in conjunction with the Project WET Team at the 2007 AccessData Workshop

The Dataset

The NWI provides data in ESRI Shape file format. The datasets are queried by state and 100K or 25K USGS quadrangle. Data fields include freshwater emergent wetland, freshwater forested/shrub wetland, freshwater pond, lake, riverine, and other
Image info:
http://www.fws.gov/wetlands/Data/Mapper.html The image is a clickable map of the US states.

Use and Relevance

The NWI dataset provides basic information on the location of freshwater wetlands. The target audience is primarily resource managers who need information on the location, status, extent, and characteristics of wetlands.

Use in Teaching

This data can be used for determining locations of wetlands for determining impact on land use change.


  • Wetland Inventory
  • Hydrology
  • Land use
  • Geographic Information Systems (GIS)


Use data to conduct spatial queries.

Exploring the Data

Data Type and Presentation

Data is presented in ESRI Shape file format.

Accessing the Data

Users primarily use the Wetlands Mapper (interactive interface at http://www.fws.gov/wetlands/Data/Mapper.html) or by using the extraction tool (http://www.fws.gov/wetlands/Data/CustomDataExtractions.html) for users who know the state and quadrangle for the location they desire.

Manipulating Data and Creating Visualizations

Users can create graphs using the Wetlands Mapper. Selected data can be downloaded as ESRI shape files.

Tools for Data Manipulation

The NWI site provides an online GIS mapping tool. In addition, there is an ArcIMS server for use with ArcGIS or MyWorld.

Acronyms, Initials, and Jargon

NWI = National Wetland Inventory
USFWS = US Fish and Wildlife Service

About the Data

Collection Methods

Original stable base hard copy maps of wetland and deepwater habitats were created based on USGS state and quadrangle boundaries. These maps were converted to digital files using various software packages (WAMS, ARC and others). The digital files were stored as ESRI Import/Export files corresponding to a single 1:24,000 USGS quadrangle. These digital files were imported and converted to ESRI Coverage format and checked for topological and attribute errors. All coverages were converted from a UTM map projection to an Alber's Equal Area map projection and the horizontal datum was converted from NAD27 to NAD83 were necessary. Polygons attributed as "Uplands" were removed from the dataset and polygons were merged at quadrangle boundaries where the quadrangle line divided polygons with the same attribute. The data was loaded into a seamless SDE geodatabase for the conterminous United States. These steps were conducted using both Arc Macro Language (AML) and ArcMap editing tools. All point data from the original ESRI Coverages were buffered by 11.28 meters (1/10 of an acre) and incorporated into this polygon feature class. Linear features from the original ESRI Coverages were merged at quadrangle boundaries where the quadrangle line divided lines with the same attribute. Linear data is stored in a separate feature class.

Limitations and Sources of Error

There is a margin error inherent in the use of imagery, thus detailed on-the-ground inspection of any particular site, may result in revision of the wetland boundaries or classification, established through image analysis.

References and Resources

Education Resources that Use this Dataset

Project WET (Water Education for Teachers) curriculum at http://www.projectwet.org/

Other Related Scientific References

Related Links

Related links scattered above.