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Page 14 WATER TALK Summer/Fall 1995 <br />etlas inesta: o <br />uc a Bally ave? <br />by Nick Rowse, USF&WS-TCFO <br />In evaluating the environmental impacts of <br />various land management proposals or <br />development projects, I may need to estimate <br />the acres of wetlands either within certain <br />counties or across the state of Minnesota. <br />Recently, I obtained digital data from. the <br />National Wetlands Inventory (NWI) office, which <br />is located in St. Petersburg. Florida. Acreage <br />figures were generated from National Wetlands <br />Inventory (NWI) digital data using ARC/INFO, a <br />geographic information system and ORACLE, a <br />database management system. I then <br />calculated, using the following procedure, <br />wetland acreages by county for the entire state <br />of Minnesota CTable 1). <br />Definition <br />The NWI <br />maps show both <br />wetland and <br />deepwater <br />habitats. <br />Wetlands are <br />defined under the <br />"Classification of <br />Wetlands and <br />Deepwater <br />Habitats of the <br />United States" as <br />lands transitional. <br />between. <br />terrestrial and <br />aquatic systems <br />where the water <br />table is usually <br />at or near the <br />surface or the <br />land is covered <br />by shallow water. <br />For purposes of <br />this <br />classification, <br />wetlands must <br />have one or more <br />of the following <br />three attributes: <br />(1) at least <br />periodically the <br />land supports <br />predominantly hydrophytes, (2) the substrate is <br />predominantly undrained hydric soil, and (3) <br />the substrate is nonsoil and is saturated with <br />water or covered by shallow water at some time <br />during the growing season of each year. <br />Deepwater habitats are permanently flooded <br />lands lying below the deepwater boundary of <br />wetlands. <br />Procedure <br />I defined wetland in my analysis to include <br />all palustrine (P) attributes and lacustrine- <br />littoral (I.2) attributes that were mapped as <br />polygons (an area enclosed with a line) on NWI <br />maps. Attributes are the alphanumeric codes <br />representing the type of wetland labeled for <br />each wetland on all NWI maps. The palustrine <br />system includes all wetlands dominated by <br />woody or emergent vegetation and shallow <br />ponds, less than 20 acres, that are lacking <br />vegetation. <br />I.acustrine- <br />littoral <br />wetlands <br />include areas <br />within lakes <br />greater than <br />20 acres that <br />have <br />nonpersistent <br />emergency <br />vegetation. <br />So, wetland <br />means all <br />palustrine (P) <br />and. (I.2) <br />habitats <br />identified on <br />NWI maps <br />covering the <br />entire state. <br />For all <br />counties <br />(Table 1), the <br />acres for <br />palustrine <br />wetlands were <br />added to the <br />acres for <br />lacustrine- <br />littoral <br />wetlands. <br />...~nYinued <br />on page 15 <br />