IMPROVING REGIONAL GROUNDWATER RECHARGE MODELS WITH A NETWORK OF HIGH-RESOLUTION TEMPERATURE RECORDING BUTTONS

Much of the annual groundwater recharge flux in northern, semi-humid climates occurs during the spring and fall seasons. In northern-lower Michigan, the presence of spatially-variable ground frost can inhibit infiltration of the spring snowmelt while storage of heat within the regions' many large deep lakes enhances evaporation during the fall months. Modeling regional groundwater recharge during these critical seasons depends on an accurate representation of time-variant temperatures in near-surface soils and in deep inland lakes.

We deployed an extensive network of approximately 160 high-resolution temperature recording buttons across the Grand Traverse Bay and Muskegon River watersheds in northern lower Michigan from winter 2006 through summer 2007. Temperature data were collected from groundwater wells, shallow soils, air, and lakes. We combine these data with collocated soil moisture probes, pressure transducers, and publicly available weather station data to model ground frost formation and large lake evaporation. These explicit process models will be added to a comprehensive surface and near-surface suite of hydrologic models we have developed called the Integrated Landscape Hydrology Model (ILHM). The ILHM is used for regional, high-resolution water cycle modeling, including the spatially-explicit calculation of groundwater recharge and evapotranspiration.