Author: Abigail Rhodes    Major: Geology

Collecting data from a temperature logger in Copperhead spring

My name is Abby Rhodes, and I am a Geology major in the Fulbright College of Arts and Sciences. My mentor is Dr. Matthew Covington of the geoscience department, and I have been building a model to replicate temperature patterns at springs in order to better understand the geometry of a cave that feeds these springs. I plan to investigate temperature propagation in the subsurface in graduate school, with the goal of becoming a geoscientist in the geothermal energy industry.

There are thousands of caves in the Ozarks. Caves are fascinating environments to study, as the absence of light and heat prevents most plants and critters from calling it home and keeps the temperature fairly constant throughout the year. Any water residing in a cave might then stay at a fairly constant temperature too, right? Wrong! Caves and tighter passageways, or conduits, can transport water and any substances in the water quicker than in other groundwater systems. It’s basically a watery rollercoaster in the subsurface. This fast-moving water evades the natural filtration that occurs in other groundwater systems and can thus transport contaminants at greater rates and magnitudes. By measuring the propagation of temperature along a conduit, hydrogeologists can make spatial interpretations – essentially how large and long the channel is. This can help to mitigate contamination in drinking water, serving approximately 20 percent of the global population that relies on water from these aquifers. Thus my project seeks to analyze the propagation of temperature along a conduit on different timescales in order to understand the size and shape of a conduit.

I have been conducting research under the supervision of Dr. Matthew Covington of the geoscience department since the fall semester of 2018. I was amazed by the far-flung places Dr. Covington had traveled, from rappelling down glacial passages on the Greenland ice sheet to spending days underground mapping the cave channels. While initially enticed by the optics of cave exploration, I gained a tremendous amount of skills and learned a lot about myself through this research endeavor.

I spent Fall 2018 reading relevant literature, honing my project, and understanding the field methods I would be using. At my research site, Savoy Experimental Watershed, some 20 kilometers west of campus, a stream sinks underground and flows to two springs 500 meters away. My goal is to learn as much as I can about the conduits that connect the sinking stream and springs. This a small system but is excellent for analyzing the propagation of tracers. Tracers are trackable substances such as dye, salt, and temperature that can provide information on conduit geometry. I looked at the travel times of these substances over a day or so at multiple times in the year.

For all of 2019, I worked to conduct tracer tests and analyze them in Python, a programming software. I met with my professor, Dr. Covington, and mentor, Dr. Joshua Blackstock, on a weekly basis and roped in friends to help me with fieldwork. It helps to have an extra set of hands in the field, especially when your car gets stuck in the mud and you need the assistance of a rancher and their tractor to pull you out! This project introduced me to fieldwork with environmental sensors, the protocols and procedures in a wet laboratory, data collection, and programming in Python. Entering 2020, my project took a new direction: focusing more on temperature as a tracer.

As I began to amass data, I noticed very interesting temperature patterns. With a year-plus of data now, I saw a sinusoidal shape in the water temperature data appearing. The water temperature rose in the summer months and fell in the winter months. But I was also seeing a smaller sine wave nestled in this year of data – but on a daily scale, where temperatures rose with the sun and fell during nighttime. The yearly and daily temperature oscillations of the springs had noticeable differences from that of the sinking stream above ground. The thermal patterns of the springs were smaller, or damped, and occurred after, or lagged behind, the sinking stream. My advisor suggested that by looking at temperature propagation at different timescales, we could make keener estimations of conduit shape with the use of a numerical model. This past semester of funding, I’ve worked to derive a model that simulates the spring signals as a function of various geometrical parameters. So far the model has been promising in providing new insights about my system with findings I hope to submit to a hydrology journal in the summer of 2021.

The funds from my Honors College Research Grant have allowed me to buy critical water sensors for collecting data. The data I’ve amassed has given me the liberty to analyze my data from different perspectives, looking at different timescales and water properties. Where my project might have been limited to looking at a few tracers intermittently throughout the year, this funding permits me to expand the scope of my research, thereby improving my understanding of the system. I’ve also presented my findings at three geoscience conferences, with additional travel funding provided by the Honors College. I would advise those interested in research to get involved as soon as you can! The freedom of having a lot of time allowed me to be open to new questions and opportunities that present themselves after the data is collected. Time helped me to go with the flow, but in hydrology research, there really is no other way. Moving forward with research in graduate school, I’d like to give myself the gift of time. I personally benefit more from working 40 hours on one thing over 4 weeks than working 40 hours on one thing over 1 week. By allowing ideas to simmer and giving myself the ability to become acquainted with my data, I open up the door to discovery while preserving my mental well-being.

My fascination with temperature patterns and propagation in groundwater has been a passion that is all but temp….orary (temperature pun). In graduate school, I plan to investigate heat propagation in the subsurface with the purpose of extracting it for geothermal energy that heats homes and buildings.