AGCI Insight

Intern Showcase: Soil Moisture Across the Landscape

August 31, 2022
Rachel (left) and AGCI staff Elise (right) take soil moisture measurements using a hand-held probe at the Spring Valley iRON site, July 2022. Image Credit: Lauran Garcia.

About the Intern: Rachel Buchler graduated from the University of Denver in 2022 with degrees in Geography and Studio Art, and a minor in Sustainability. Rachel is passionate about water resources and food systems and has an interest in dendrochronology.

This summer under the guidance of AGCI staff, Rachel investigated soil moisture conditions across the Roaring Fork Watershed. She read literature about comparing soil moisture values across soil types and the role of soil moisture in the water cycle, conducted transects to collect soil moisture measurements across a broader scale at each AGCI iRON site, and generated maps to visualize her findings. Additionally, Rachel helped with other field work needs at iRON stations and contributed to staff discussions on global change relevant topics.

Soil moisture values across site transects

The main objective of this project was to better understand the state of soil moisture in the Roaring Fork Valley. This was done by measuring and mapping soil moisture values at two depths (4.8 and 8in) at each of the 10 AGCI soil moisture monitoring iRON sites using a handheld device. Measurements gathered from this handheld device were used to gain a clearer picture of the heterogeneity of soil moisture in the area in which each station is located.

Soil moisture data were collected using a handheld FieldScout 150 Soil Moisture sensor. At each site, data were collected along 4 transect lines, each 50m in length and oriented in the cardinal directions. These transects began 2m from the iRON station, and soil moisture was sampled every 5m, along with GPS coordinates. Date and time was also recorded for the start of each transect.

Future work on this study may include taking additional readings under multiple conditions at each site and comparing soil moisture variations with other factors, such as topography and vegetation.

Some examples of the GIS maps generated using these data can be seen below:

This map shows soil moisture measurements overlaying a topographic map for the Spring Valley site on July 7, 2022 at a 4.8in depth. The iRON station is at the center of the transect cross. Soil moisture values are represented in percent of saturation, with saturation values drawn from highest soil moisture values on record for the iRON station from this site (saturation type being the point at which no more water will be taken up by the soil and pooling may occur). The soil type at this site is clay.
This map shows soil moisture measurements overlaying a topographic map for the Smuggler Mtn site on the morning of July 26, 2022 at a 4.8in depth. The iRON station is at the center of the transect cross. Soil moisture values are represented in percent of saturation, with saturation values drawn from highest soil moisture values on record for the iRON station from this site (saturation type being the point at which no more water will be taken up by the soil and pooling may occur). The soil type at this site is sandy loam. Some points stray from a direct transect line when trees were in the way. Proximity to large trees often correlated with wetter soil moisture readings at this site.
This map shows soil moisture measurements overlaying a topographic map for the Sky Mtn site on August 2, 2022 at a 4.8in depth. The iRON station is at the center of the transect cross. Soil moisture values are represented in percent of saturation, with saturation values drawn from highest soil moisture values on record for the iRON station from this site (saturation type being the point at which no more water will be taken up by the soil and pooling may occur). The soil type at this site is loam.
This map shows soil moisture measurements at a 4.8in depth overlaying a topographic map for the Independence Pass site on July 28, 2022 during a light drizzle. The iRON station is at the center of the transect cross. Soil moisture values are represented in percent of saturation, with saturation values drawn from highest soil moisture values on record for the iRON station from this site (saturation type being the point at which no more water will be taken up by the soil and pooling may occur). The soil type at this site is sandy loam.
This map shows soil moisture measurements at a 4.8in depth overlaying a topographic map for the Northstar Aspen Grove site on August 4, 2022. The iRON station is at the center of the transect cross. Soil moisture values are represented in percent of saturation, with saturation values, with saturation values drawn from highest soil moisture values on record for the iRON station from this site (saturation type being the point at which no more water will be taken up by the soil and pooling may occur). The soil type at this site is sandy loam.