CONTRIBUTION OF GROUNDWATER DISCHARGE IN DELIVERING POLLUTANTS TO NEARSHORE WATERS OF LARGE LAKES

ABSTRACT: Groundwater discharge is a potentially important pathway for delivering pollutants into the nearshore waters of large lakes, yet this pathway remains poorly understood. Predicting pollutant inputs from groundwater to lakes is complex as loading is controlled not only by the specific pollutant sources and groundwater flow paths, but also by dynamic groundwater-lake interactions that affect water and pollutant exchange across the sediment-water interface. These groundwater-lake interactions also set up an important geochemical reaction zone near the interface that can ultimately control the amount and timing of pollutant inputs to the lake. This presentation will provide an overview of current understanding and approaches used to understand groundwater discharge to nearshore waters of large lakes. This will include i) regional-scale field studies focused on identifying groundwater discharge hotspots to nearshore lake waters, and ii) local-scale field investigation focused on detailed evaluation of groundwater-lake interactions along shorelines and how these interactions govern inputs of a variety of different pollutants to lakes including nutrients, metals and fecal contaminants. Finally, science gaps that need to be addressed to better quantify the influence of groundwater-lake interactions on nearshore water quality will be discussed.