The Role of Lake Expansion in Altering the Wetland Landscape of the Prairie Pothole Region, United States.

Interannual variation in lake extent is well documented in the Prairie Pothole Region, but the role of surface-water expansion, including lake expansion, in merging with and subsuming wetlands across the landscape has been minimally considered. We examined how the expansion of surface-water extent, in particular, the expansion of lakes across parts of the Prairie Pothole Region can alter landscape-level hydrologic connectivity among substantial numbers of previously surficially disconnected wetlands. Temporally static wetland, lake, and stream datasets were fused with temporally varying Landsat-derived surface-water extent maps (1990-2011) to quantify changes in surface-water connectivity. Under deluge conditions, lakes were found to create significantly larger complexes of surficially-connected wetlands relative to non-lake surface-water connections (e.g., only wetlands or wetlands and streams). Analysis of three specific lakes showed that lakes can merge with and subsume wetlands located kilometers to tens of kilometers from the National Wetland Inventory defined lake perimeter. As climate across the Prairie Pothole Region is highly variable, understanding historic patterns of surface-water expansion and contraction under drought-to-deluge conditions will be integral to predicting future effects of climate change on wetland function, loss and influence on other aquatic systems, including downstream waters.