Local-scale variability in groundwater resources: Cedar Creek Watershed, Wisconsin, U.S.A.

A local-scale groundwater flow model representing an unconfined aquifer at the Cedar Creek Watershed in Wisconsin, U.S.A. was constructed to determine the effects on groundwater resources due to anthropogenic activities, climate variability, Lake Michigan stage, and finally, the treatment of surface water. The importance of this aquifer lies in its location on the sub-continental divide, which separates the Mississippi River Basin from the Great Lakes Basin, and its proximity to one of the largest surface water bodies, Lake Michigan. The groundwater aquifer model incorporating 4 layers and 18 different geologic zones simulated the influence of recharge on the local-flow regime by utilizing recharge estimates from the Soil-Water-Balance Code. The steady-state simulation revealed that groundwater head in general was decreased toward the Lake Michigan with local variation caused by stream networks. In response to 2012 drought event, groundwater drawdown was not rehabilitated until spring 2013, implying that the aquifer required approximately 3–4 months until responding to meteorological drought. Additionally, variation in recharge caused to change in groundwater table throughout the entire aquifer simultaneously, but the effect of Lake Michigan stage on groundwater table was relatively minimal. Finally, a certain portion of streams in the Cedar Creek Watershed could be ephemeral. Switching from the RIVER to the DRAIN package for the implementation of ephemeral river and stream cells resulted in significant reduction of both groundwater head and flux, implying that realistic distribution of present groundwater head would resemble one simulated between RIVER and DRAIN packages.