Date of Award

8-2018

Degree Name

Master of Science

Department

Geosciences

First Advisor

Dr. Donald M. Reeves

Second Advisor

Dr. Duane Hampton

Third Advisor

Dr. Dan Cassidy

Access Setting

Masters Thesis-Campus Only

Restricted to Campus until

8-2020

Abstract

Quantifying groundwater discharge across the sediment—surface water interface remains a challenge due to streambed heterogeneity and the integration of disparate measurements over a continuum of spatial and temporal scales. In this study, mini-piezometers are first used to identify areas of groundwater discharge in lakes and streams, and micro-pulses of fluorescein dye are released at precisely known shallow depths as a conservative tracer. The use of fluorescein dye allows for visual dye detection regardless of light conditions, and measurements of dye concentrations over time using a fluorometer are used to generate high resolution breakthrough curves. Accurate determination of groundwater velocity and dispersivity are obtained by fitting dye breakthroughs to the classical advection-dispersion equation. Study results indicate that time to visual breakthrough is highly non-linear with depth. Consistent with the majority of solute transport studies, calculated dispersivities increase with transport depth. Traditional measurements are used to compare tracer-obtained velocities to Darcy-based velocities, with Darcy velocities underestimating velocity. These results suggest that the proposed dye tracer method is advantageous over traditional Darcy methods due to the high degree of heterogeneity associated with fluvial systems and associated measurement error propagated through multiple parameters.

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