July 3 - 9
This week the team began finalizing results from the five infiltrometer field tests collected in weeks 3 and 4: -6 cm pressure head test from St. Anne Church in Vižňov, -6 cm and -3 cm pressure head tests from All Saints Church in Heřmánkovice, -6 cm and -3 cm pressure head tests from the Jizera Mountains. First, the raw data was downloaded from the infiltrometer sensors and estimates of cumulative infiltration (cm) were calculated using the sixth order polynomial relationships described by the infiltrometer calibration from week 2. Using an excel spreadsheet provided by Dr. Snehota, the team was able to calculate the infiltration rate for each of the sensors for each respective infiltrometer field test. Next week, the results will be completed and added to the final report.
Image 1. The infiltrometer set-up from St. Anne in Vižňov.
Additionally, the computer tomography (CT) images (see week 5 blog post) from Central European Institute of Technology (CEITEC) were analyzed using ImageJ. ImageJ is written in Java script and is an open source image processing program designed for analyzing scientific multidimensional images. Some of the benefits of ImageJ include extendibility with thousands of plugins and scripts for performing a variety of tasks and it has a large user community. We specifically used SoilJ, a new plugin by John Koestel that is particularly helpful for analyzing soil cores. To analyze the 3D images, the raw files were converted to .tif and the results are stored as multi-slice .tif images, which is an elegant way of storing CT datasets. We visually assessed the presence of stones, macropores, and the intactness of the core itself looking for any fractures, cracks and/or space between the soil and walls of the cylinder.
Image 2. One of the large soil cores collected in the Jizera Mountains and scanned using CT imaging in week 5.
The team also evaluated the three ponded infiltration test datasets collected in the Jizera Mountains. The Philips equation (reviewed in week 1, lecture provided by Dr. Ray) was used to calculate the cumulative and actual infiltration rates. The flow rate, according to Philips equation, is equal to the change in volume over the change in time multiplied by the cross-sectional area. Preliminary results indicate steady state infiltration to be approximately equal to 260 mL/sec for Test 1, 40 mL/sec for Test 2 and 160 mL/sec for Test 3. The variability in infiltration rate in space is most likely due to preferential flow paths within the measurement volume, caused primarily by the tree roots and large stones observed at the field site.
Image 3. Jessica recording infiltration rates during one of the infiltration tests in the Jizera Mountains.
Figure 1. Graph of Infiltration Rate vs. Time for Test 1.
Lastly, the team continued to write their final report. A final outline for the report was agreed upon and we will be including a literature review, methodology from the various experiments and field sites, final results, discussion, conclusions and other activities we participated in while at CVUT.