Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Engineering Science

Program

Civil and Environmental Engineering

Supervisor

Robinson, Clare

2nd Supervisor

Power, Christopher

Abstract

It is well recognized that groundwater-surface water interactions influence the quantity and quality of various hydrogeological systems (rivers, lakes, streams). Groundwater-stream systems are an important investigative area for understanding fate and transport of nutrients and chemicals within the stream. While traditional methodologies are established to provide measurement and mapping of the spatial distribution of groundwater-stream interactions and exchange fluxes across a streambed, many can be invasive, labour intensive and suffer from low sampling density. The complexity in such systems is due largely to the heterogeneous nature both spatially and temporally. Given the strong control by streambed lithology on groundwater-surface water interactions, an improved measure of the spatial and temporal variations is desired. Geophysical techniques of DC-IP are an intriguing option as they can provide rapid, non-invasive and continuous information about the subsurface. The overall thesis objective was to evaluate the potential of 3D DC-IP for characterizing the structural heterogeneities within a streambed to inform assessment of groundwater-stream water interactions. High-resolution 3D DC-IP surveys were conducted in a 50m long headwater stream reach located in Kintore, Ontario. The resulting 3D distributions of resistivity and chargeability highlighted the heterogeneous nature of the streambed. Traditional characterization techniques were employed to evaluate the performance of DC-IP for mapping streambed composition and its associated influence on groundwater-stream exchanges. Strong concordance between DC-IP imaging and all the other traditional methods were determined, providing increased confidence in the ability of DC-IP to provide a valuable, non-invasive site tool to improve characterization of streambed heterogeneity and interpretation of groundwater-stream exchange patterns.

Summary for Lay Audience

Groundwater and surface water interact nearly everywhere on earth. These interactions take place in rivers, lakes, streams and more. It is understood that through these interactions the quality and quantity could be affected in either water body. Groundwater-stream systems are of particular interest to understand how nutrients and contaminants may transport across streambeds. Investigations of groundwater and stream water systems have been long established and traditional techniques are used to determine the interactions involved. However, many of these traditional techniques have various limitations, such as: being labour intensive, destructive and invasive to the stream or subsurface and do not provide characterization throughout an entire investigative site. The difficulty with understanding groundwater-stream water systems is that the conditions affecting the interactions change with regards to space and time. The specific changes in the sediments of a streambed or aquifer are thought to heavily affect the interactions and exchanges between groundwater and stream water. Therefore, an improved way of measuring these changes in space and time are desired. This was achieved using geophysical techniques, which use electrical current to produce an image of the subsurface. This can be done to better seen inside/beneath a streambed, similar to an x-ray, but of the ground. This study used geophysical techniques to create 3D images of the subsurface of a stream located in Kintore, Ontario. These images were used to help understand the interactions involved in the groundwater-stream water system.

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