Groundwater interaction with a kettle-hole lake: Relation of observations to digital simulations

Abstract

Observations made on a small, fully penetrating, kettle hole lake are used to test predictions made using digital stimulation about the exchange of water between lakes and groundwater systems. On the upgradient side of Lower Nashotah Lake, groundwater inseepage decreases exponentially away from the shore. Water exchange on the downgradient side is controlled by the presence and strength of a groundwater mound, but that mound and its effects are ephemeral. When the mound increases in strength, it generates a local groundwater flow cell beneath it which contains water of chemical composition distinct from deeper, regional groundwater. The growing mound also causes local inseepage of groundwater to the lake in an expanding zone along the downgradient shore. All of these phenomena occur as they have been predicted in published studies where digital simulation of relatively simple groundwater-lake systems has been carried out. The field observations thus confirm the validity of the simulation studies and their usefulness as a tool for understanding water exchanges in unmonitored systems.