Electronic Thesis and Dissertation Repository

Degree

Master of Engineering Science

Program

Civil and Environmental Engineering

Collaborative Specialization

Environment and Sustainability

Supervisor

Robinson, Clare

Abstract

Groundwater discharge may be an important pathway for delivering pollutants to large lakes, but this pathway is poorly understood. Understanding the potential for groundwater discharge to deliver pollutants to lakes requires an evaluation of the magnitude and spatial variability of groundwater discharge to the lake, and the history of the discharging groundwater. The first objective of this thesis was to evaluate and quantify the spatial variability of groundwater discharge to a large glacial lake, Lake Simcoe, Ontario, using the naturally occurring radon isotope tracer (222Rn). Regional scale boat surveys were conducted along 80% of the Lake Simcoe shoreline using portable radon detection equipment. Groundwater discharge hotspot areas were identified based on spatial variability in lake water 222Rn concentrations, and regional hydrogeological features were linked to these hotspot areas to develop broadly applicable understanding of the observed spatial distribution of groundwater discharge. The second objective of this thesis was to compare 222Rn-derived to model simulated estimates of groundwater discharge in two areas along the Lake Simcoe shoreline. This comparison built further confidence in the groundwater discharge estimates, and enabled the strengths and limitations of each method to be assessed. Particle tracking analysis was used to evaluate the history of groundwater discharging along the northwestern shoreline of Lake Simcoe, and the potential implications for lake water quality in this area. The findings of this thesis provide broadly applicable knowledge needed to focus efforts aimed at managing non-point pollution sources to large glacial lakes including groundwater discharge.

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