Application of Rn-222 for Identification and Quantification of Groundwater Discharge to Lake Simcoe

Session: 56. - Science for a Healthy Lake Simcoe

Hayley Wallace, University of Western Ontario, [email protected]
Clare Robinson, The University of Western Ontario, Civil & Environmental Eng., [email protected]

Abstract

Groundwater discharge may be an important pathway for delivering pollutants to Lake Simcoe, but this pathway is not well understood. To understand the potential impact of groundwater inputs on lake water quality, the volume of groundwater discharge and the spatial distribution of this discharge must be quantified. The first objective of this study was to evaluate the use of the naturally-occurring radon isotope tracer (Rn-222) for identifying areas of high groundwater discharge. Regional scale boat surveys were conducted along the Lake Simcoe shoreline using portable radon detection equipment. Spatial variability in Rn-222 lake water concentrations allowed groundwater discharge hotspot areas to be identified. The location of hotspot areas were linked to regional hydrogeological features to develop broadly applicable understanding of the observed spatial distribution of groundwater discharge. The second objective of the study is to investigate uncertainties associated with using Rn-222 as a tracer, including the influence of environmental factors (e.g., wind speed, precipitation) on lake Rn-222 concentrations, and aquifer heterogeneity on groundwater Rn-222 concentrations. The study findings provide a more refined and reliable method for evaluating groundwater discharge to Lake Simcoe, and other large lakes, as required to focus efforts aimed at managing non-point pollution sources including groundwater discharge.

1. Keyword
Lake Simcoe

4. Additional Keyword
Groundwater discharge

5. Additional Keyword
Groundwater- surface water interactions

6. Additional Keyword
Natural tracer