The Minnesota Department of Natural Resources has completed a 10-year effort to provide much more accurate maps of Minnesota’s wetlands. The update of the state’s National Wetlands Inventory (NWI) used new technologies to produce a clearer picture of Minnesota’s wetlands, lakes, rivers and streams.
The updated NWI gives resource managers and landowners a vital tool to aid wetland protection and restoration. “These new maps are much more accurate, capture more detail and provide more information than the original NWI maps,” said Steve Kloiber, the DNR manager of the NWI update project.
The new statewide GIS dataset reveals that there are 14.2 million acres of combined lake and wetland area in Minnesota. Of this total, 12.2 million acres are wetland, which are distinguished by having relatively shallow water or saturated soils with permanent vegetation under normal conditions.
The U.S. Fish and Wildlife Service originally mapped wetlands in Minnesota in the late 1970s and early 1980s as part of the National Wetlands Inventory. The just-completed DNR mapping project is the first time the NWI has been updated in Minnesota. The new maps reflect the latest technology in remote sensing and mapping, including high-resolution aerial imagery and Light Detection and Ranging (LiDAR) data.
The new wetland map data are available through an interactive mapping application on the DNR’s website (https://arcgis.dnr.state.mn.us/ewr/wetlandfinder/) and can also be downloaded, free of charge, for use in geographic information system applications through the Minnesota Geospatial Commons (https://gisdata.mn.gov/).
Besides showing the location, size and type of each wetland, the updated map data include information on other wetland characteristics, such as depth, duration and frequency of flooding, and how the wetland is situated in the overall landscape. That information is useful in assessing wetland benefits such as water quality improvement, flood storage, and fish and wildlife habitat. The map data are widely used by landowners, local governments and state and federal agencies for land use planning, wetland permit screening and natural resource management.
As noted by Dillon Hayes, Mille Lacs County environmental resources manager, “We use wetland maps for many of our county functions, like water and transportation planning, shoreland management and wetland permitting. Having accurate, up-to-date wetland map data will be very helpful to the county.”
While the new wetland map data are an improvement over the original NWI and are useful for planning and identifying the potential need for wetland permits, they are not sufficiently accurate on their own to determine all applicable wetland regulations.
Landowners considering work that may affect wetlands should contact their county soil and water conservation district or the DNR for advice on determining whether wetlands are present and the exact location of the regulated wetland boundary.
It is not possible to accurately compare the updated wetland data to the original NWI, because of the significant advances in remote imagery and mapping techniques. A 1984 University of Minnesota study based on soil analysis estimated that Minnesota has lost about half of the wetlands that existed prior to European settlement. Recent monitoring conducted by the DNR shows that the state’s wetland acreage has been holding steady since 2006, although there has been a net conversion of higher quality, vegetated wetlands to open water ponds.
The NWI update project was funded by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources. Other partners included the U.S. Fish and Wildlife Service, the University of Minnesota, St. Mary’s University, Ducks Unlimited and the St. Croix Watershed Research Station.