Week 7 Blog
In Week 7, the group continued to finalize the analysis for the infiltrometer datasets and CT image scans. To begin calculating infiltration rate from the infiltrometer sensors, the calibration function was applied (see week 2 and week 6). The indirect relationship between volume of water in the sensor and sensor count value provided estimates of the volume of water infiltrated into the soil at each respective count value. The spreadsheet provided by Dr. Snehota is designed to calculate cumulative infiltration, infiltration rate, and unsaturated hydraulic conductivity for the automated infiltrometer sensors at each of the site locations.
Figure 1. Cumulative infiltration, I (cm), Infiltration rate, q (cm.min-1), versus time (min) for sensor I1 at -6 cm pressure in the St. Anne Church (week 3).
A sandstone infiltration test was conducted using a mini-disk infiltrometer at St. Anne’s Church in Vižňov (week 3). The data was analyzed by incorporating the cumulative infiltration values and time into a Decagon macro spreadsheet. The Philips equation is then solved to calculate the slope of the line and infer the unsaturated hydraulic conductivity by relating van Genuchten soil hydraulic parameters and infiltrometer dimensions.
Further analysis of the CT images from the three larger soil cores (~1540 cm3) was completed to reduce noise and highlight preferential flow paths formed by cracks, rocks, or other obstructions. The results from this section of our report will be presented in the blog post for week 8.
On Thursday, the team attempted to remove the large undisturbed soil cores collected from the Jizera Mountains and St. Anne’s Church in Vižňov so they could be prepared for a ponded infiltration test. The original objective was to remove the soil cores from the aluminum cylinders using a hydraulic jack. The samples would then be inserted into a larger cylinder and the space between the wall of the cylinder and the soil core would be filled with foam to seal any cracks that might have been created while collecting the sample. However, the sample had not dried enough, leaving the soil firmly attached to the sides of the cylinder walls. When the group attempted to remove the soil core using a hydraulic jack apparatus, the high friction resulted in soil compaction at the base of the coil column. To avoid further compression of the samples, it was decided to leave the cores in the aluminum cylinders. The top 5 cm of two of the soil cores were then removed to prepare the sample for a ponded infiltration test that will take place next Tuesday.
Figure 2: Hydraulic jack apparatus used to attempt to push the soil core out of the cylinder
On Friday, the group received a lecture by Dr. Martin Sanda on geophysics and environmental isotopes. Dr. Sanda described how geophysical profiles explain flow paths within a watershed. He then focused on how different tracers and stable isotopes are used to characterize water sources, flow paths, or age. The different isotopes present in water can be monitored over time. Several applications of this methodology can be applied to calculate residence time, paleohydrology, total balance, climate change dynamics, etc. The effects of climate change, for example, can be observed based on different isotopic combinations resulting from temperature dynamics. After the lecture, Dr. Sanda demonstrated how an isotopic water analyzer measured stable isotopes from samples he had collected in the field. The rapid and accurate measurements of the instrument allow for numerous water samples to be analyzed for isotopic variances due to water origin.
Figure 3: Isotopic water analyzer in Dr. Sanda’s lab
In addition to a final report, the group will complete a final presentation covering the various research and field experiences gained during the IRES program. This presentation will be given during an evaluation of the program next week.