Effects of Great Lake water level fluctuations on groundwater and forests in ridge and swale ecosystems

Imbalances in Great Lake water inputs and outputs cause Great Lake Water Levels (GLWLs) to fluctuate at annual and decadal time scales with an observed range of ~2m for Lake Michigan-Huron since 1860. These GLWL changes cause groundwater (GW) fluctuations in coastal aquifers and interact in complex ways with local, intermediate, and regional GW flow systems. Coastal ridge and swale forested wetlands are GW-dependent ecosystems that rely on shallow GW to maintain their ecological health. They are an ideal system for investigating the effects of climate induced GLWL fluctuations on coastal GW systems and forests because they are not only vulnerable to GLWL changes, but they also record historic GW conditions in the annual growth rings of individual trees. The objective of this project is to quantify the impact of changing GLWLs on GW storage, GW flow patterns, Lake-GW interactions, evapotranspiration and forest productivity to better understand spatial variability in vulnerability to GLWL fluctuations both within and among in ridge and swale systems along Wisconsin’s Lake Michigan coast. To accomplish this, we will create an Ecohydrologic Observatory at the Ridges Sanctuary to monitor GW response to two years of GLWL fluctuations and infer historic shifts in GW flow patterns by measuring annual tree ring growth and remotely-sensed ET to understand how local, intermediate, and regional GW inputs differentially impact GW regimes and forest growth. We will regionalize the remotely- sensed ET and dendroecological methods throughout Door County, WI to understand differential vulnerability of these systems to future environmental change. The collaboration proposed in this work will not only further the understanding of Wisconsin’s groundwater resources but advance the professional development of early career researchers including associate investigator D. Ciruzzi, PhD student E. Kastelic, and undergraduates at UW Platteville and Madison.