AGCI Insight

Intern Reflection: Early winter soil moisture

August 21, 2023

About the Intern: Henry Hurd is a Summer Research Intern at the Aspen Global Change Institute. A rising junior at Aspen High School, Henry is passionate about environmental science and math and is pursuing independent river temperature research focused on protecting the aquatic ecosystem in the Roaring Fork Watershed. Henry is thrilled to be a part of the ACGI team this summer, where he is enjoying assisting with field work and examining the relationship between soil moisture saturation at various Roaring Fork Observation Network sites and naturalized streamflow.

Several people erect a 6ft hight metal structure for science in an opening in the aspen trees.
Henry Hurd (front) helping to install a USGS cosmic ray station alongside USGS and AGCI staff. Image Credit: Elise, Summer 2023.

As a summer intern at AGCI, I have had a wide array of growth opportunities. I experienced the process of science real-time, engaging in activities ranging from hands-on field work (such as helping install USGS cosmic ray neutron sensors and replacing soil moisture sensors and rain gauges) to analyzing and graphing soil moisture data over time. In doing so, I got a taste of what it might be like to pursue a career as an environmental scientist! I also had the opportunity to learn about the crucial role of soil moisture within the interconnected system of mountain hydrology–and its important implications for our high mountain watershed ecosystem and our water supply.

A typical view at the Glenwood Springs site, June 2017. Image Credit: Elise, AGCI.

In addition to the new scientific knowledge I gained this summer, I experienced the thrill of participating in the creation of knowledge and also learned about the importance of perseverance in that endeavor! An experience that particularly highlighted this for me was our Glenwood Springs field visit. The field visit began like any other field day, as we started our routine station maintenance, adjusting the snow depth sensor and tightening cables around the station. Our next objective was to conduct a soil moisture transect (carrying out measurements across a landscape), but what seemed like a straightforward process soon transformed into a task requiring navigation of a challenging obstacle course. The dense scrub oak obstructed our path, causing constant scrapes and scratches and the need to crawl and maneuver around and under sharp branches. The unforgiving Glenwood summer heat compounded our difficulties. Despite the adversity faced by the AGCI field team, we pressed on, determined to accomplish our mission. We successfully completed all ten measurement points required for our transect, and I finished with a sense of accomplishment—as well as heightened awareness of the intensity of the sun at high altitudes! Through this experience, I learned that field science could be challenging at times, but incredibly rewarding as well!

Balancing out my time in the field, I also spent a fair amount of time this summer examining soil moisture saturation data gleaned from seven of the Roaring Fork Observation Network sites (also known as “iRON”) with varying elevations to try to add to our understanding of the pivotal role of soil moisture in mountain hydrology. My main objective was to try to recognize patterns that might be useful for a subsequent follow-on study connecting selected metrics (e.g., soil moisture at specific times of year, rain, or snow) with run-off stream flows. I chose to examine soil moisture data at an 8 inch depth because it tends to be more sensitive to short-term changes (due to a rainstorm, for example) than the 20 inch depth but less prone to rain-induced fluctuations than a 2 in depth. I then examined soil moisture saturation percentages for each site for various November windows from 2016-2022. I plotted the data for one day, one week, a half month, and the full month of November, and saw that the data were surprisingly stable across the month of November—a seemingly simple observation, but one that packed a big punch as it enabled me to recommend the use of a monthly November soil moisture saturation data window for future studies. 

As I investigated the soil moisture saturation data across the seven iRON sites, I considered and attempted several possible analyses to try to uncover correlations in the data. For example, I examined the percentage difference from median for each year, attempted a quartile or “bin” analysis, and also considered the plotting of first derivative slope values; unfortunately, none of these approaches yielded a clear pattern. Upon further considering the plotted data, however, an interesting observation did surface: the sites at the same elevation zones were behaving somewhat similarly, and that behavior was different from the other elevation zones. The Shrublands sites (Glenwood Springs and Spring Valley, at elevations of 6,200’ and 7,100’ respectively) had the most highly correlated soil moisture saturation percentages across the seven years studied. The Montane sites (with elevations ranging from 7,780’ to 8,380’) were a bit more heterogeneous in their behavior, but they still behaved more like each other than any of the other sites. Lastly, the Independence Pass site (elevation 12,080’), which was the sole Alpine zone, presented entirely differently from the sites in the other two elevation zones. The importance of elevation zone as well as ecological features of the various iRON sites to soil moisture saturation was highlighted by this study, which hopefully may aid in the design of future studies tying soil moisture saturation to naturalized streamflow. 

Graph showing soil moisture patterns in November across 4 sites
A graph showing month average November soil moisture for six years at four of the iRON sites reveals similarity of soil moisture behavior at Sky Mountain and Northstar Transition Zone, two sites located in Aspen Groves within montane elevation range. Credit: Henry Hurd.

My experience with data analyses echoed my experiences in the field in that I learned that the process of science is very iterative—it’s a process driven by trial and error, with each new effort being a creative new iteration that builds upon past learnings. Discussing my findings with my mentors at AGCI was also a crucial part of the scientific process. Together we were able to dig deeper into the story conveyed by our data, identify key drivers, and brainstorm further studies that would continue to advance our understanding of soil moisture.

Henry Hurd taking soil moisture reading with a Field Scout sensor at the Independence Pass station, July 5, 2023. Image Credit, Elise, AGCI.

This internship provided me with a lot of new content knowledge and hands-on experience–but the most important thing it taught me was this greater understanding of the nature of science. I am hopeful that,  through this iterative process, my contribution to our understanding of soil moisture in our high mountain watershed will be built upon by others in the future, and I’m eager to see what those future studies hold!

I’m so grateful for the wide array of learning opportunities I’ve had this summer and for my incredible mentors at AGCI!