Date of Award

Spring 1-1-2013

Document Type

Thesis

Degree Name

Master of Science (MS)

First Advisor

Joseph N. Ryan

Second Advisor

Blaine McCleskey

Third Advisor

Jeffrey Writer

Fourth Advisor

Diane McKnight

Abstract

The coupling of the stream tracer technique with transient storage modeling is a well-established approach to characterizing solute transport processes of complex stream systems. Stream tracer studies require a large number of samples and the associated chemical analyses are costly. Sampling and analytical demand would be significantly reduced if electrical conductivity - a robust, easy-to-measure, water-quality property- was used as the primary measure of tracer breakthrough and converted to bromide tracer concentrations for breakthrough curve analysis and transient storage model parameter optimization. The advantages of collecting electrical conductivity data as a surrogate for dissolved bromide tracer samples are (1) reduced cost of laboratory analysis, (2) high-frequency data collection by field instruments, and (3) well-defined breakthrough curves for enhanced transient storage model simulations.

This method was tested by collecting electrical conductivity data and dissolved tracer samples during an instantaneous sodium bromide (NaBr) injection experiment in Fourmile Creek, Boulder County, Colorado. Concentrations of bromide were calculated from electrical conductivity data using equations that relate electrical conductivity of natural waters to their chemical composition. Models of transient storage were simulated for both the tracer data derived from electrical conductivity and the measured tracer data.

Small changes in background electrical conductivity caused the highest error (%) in the breakthrough curves. The method was robust in stream reaches where changes in background electrical conductivity could be accounted for. The use of high-frequency calculated bromide data within the transient storage model provided improved parameter estimates.

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