A hydrogeomorphic lake classification system for lake assessment and management

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• Webster, K.E., University of Maine, Orono, (207)581-2542, katherine.webster@umit.maine.edu
• Soranno, P.A., Michigan State University, East Lansing, (517)432-4330, soranno@msu.edu
• Bremigan, M.T., Michigan State University, East Lansing, (517)432-3831, bremigan@msu.edu
• Cheruvelil, K.S., Michigan State University, East Lansing, (517)353-9528, ksc@msu.edu
• Asplund, T., Wisconsin Department of Natural Resources, Madison, (608)267-7602, tim.asplund@dnr.state.wi.us
• Bacon, L.C., Maine Department of Environmental Protection, Augusta, (207) 287-7749, linda.c.bacon@maine.gov
• Bell, K.P., University of Maine, Orono, (207)851-3156, kathleen.p.bell@umit.maine.edu
• Connor, J., New Hampshire Department of Environmental Services, Concord, (603)271-3414, jconnor@des.state.nh.us
• Downing, J.A., Iowa State University, Ames, (515)294-8880, downing@iastate.edu
• Renwick, W.H., Miami University, Miami OH, (513)529-1362, renwicwh@muohio.edu
• Vaux, P.D., University of Maine, Orono, (207)581-3256, peter.vaux@maine.edu

Across broad spatial scales, lake trophic status is a function of lake-specific features, landscape setting, and anthropogenic drivers. However, regional-scale studies examining the influence of human activities on lakes often focus on geographic areas with relatively uniform hydrogeomorphology, limiting extrapolation. We used a diverse set of ~2500 lakes in the Northeast (Maine and New Hampshire) and the Midwest (Michigan, Wisconsin, Iowa and Ohio) to examine how broad and interacting gradients in land cover and hydrogeomorphic features influenced lake trophic status. Increasing intensity of agriculture from northeast to southwest combined with gradients in runoff and topographic relief generates spatially complex variation in natural and anthropogenic drivers. We developed a hierarchical classification system that accounted for variation at the both the regional and local lake scales. After removing regional variation in total phosphorus (TP), the most important local features defining classes were lake maximum depth and catchment area. We tested the classification system by examining relationships between land cover type and nutrient concentration within classes. We found strong relationships between TP residuals and percent agriculture in the 500m buffer around the lake that differed in intercept among classes. Our results suggest that this hierarchical approach is a useful approach for understanding heterogeneity at the landscape scale and for developing tools for important management goals like setting reference conditions.