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Clarification of Cowardin Classification and Circular 39 Wetland Types 1, 1L, 2, 3 and 7 By � Franklin J. Svoboda Svoboda Ecological Resources 2477 Shadywood Road, Suite 100 Excelsior, MN 55331 (952)47]-1100 franks C>gpsinnovations.com Introduction The National Wetland Inventory (NWI) mapping process completed in Minnesota between 1979 and 1982 developed a wetlands inventory map far the�state of Minnesota utilizing remotely sensed color infrared photography that was visually interpreted. The interpretation process hierarchically classified wetlands using, at the time, the recently published Cowardin classification system (Cowardin et al 1979). The wetland interpretation and classification process was ground verified using selective plots and locations but was field verified to only a limited extent. Consequently, the published NWI paper copies carry the disclaimer that these maps are to be used for advisory purposes only and actual classifications are to be based on ground verification. Visual interpretation from remote sensed imagery has some limitations particularly with regard to the water regime modifier. Year to year variation in precipitation cycles along with the occurrence of precipitation events at the time that the imagery was acquired, even if all acquisition occurred during the spring season, can result in variations in modifier categorization. Accurate classification becomes critical when regulatory decisions are being made with regard to the wetland type and the amount of de minimum fill that is permissible. Also, it is a matter of scientifically accurate consistency with regard to adherence to the various technical publications and regulatory guidance documents. Circular 39 was authored by Shaw and Fredine and published by the U. S. Fish and Wildlife Service (USFWS) in 1956. The intended purpose of Circular 39 was an effort at classifying and inventorying wetlands on a national scale in order to assess the wetland base and related waCerfowl production potential. The classification process was never intended to serve as a classification system for wetland regulatory purposes. However, since it was the first national effort of its kind and as wetland regulatory intentions materialized, this was the only method available to differentiate between wetlands of different types. The Board of Water and Soil Resources (BWSR) cross-reference table (8420.0549 subp. 2.) indicates that Circular 39 Type 3 wetlands have a "C" water regime modifier. This is an