HYDROLOGIC RESPONSE OF KETTLE LAKES TO EXTREME PRECIPITATION EVENTS

Ten years ago, during summer 2008, record precipitation contributed to widespread flooding across southern Wisconsin. Clear and Duck Lakes, two of the thousands of groundwater-fed kettle lakes in the glaciated Upper Midwest, were unique in their response to the extreme precipitation events. Lake levels did not begin to rise until spring 2009, and then the lakes remained in flood conditions for two full years. This lagged response is known as groundwater flooding. Lake levels finally dropped during summer 2012, when southern Wisconsin experienced severe drought conditions. Average lake levels resumed in 2013 and continued through summer 2018. Because groundwater-fed kettle lakes like Clear and Duck Lakes respond slowly to changes in hydrologic conditions, long term measurements are necessary to fully understand their water budgets and to predict their potential future response to extreme hydrologic events. Lake seepage measurements made in summer 2012 were repeated in summer 2018 to extend the record of hydrologic conditions. Groundwater samples were also collected and are being used to calculate nutrient loading associated with groundwater flooding conditions versus average lake levels.