Karst Hydrogeology and Geomorphology: A virtual field experience using Google Earth, GIS, and TAK
This activity incorporates and builds upon the material covered in Karst Hydrogeology: A virtual field introduction using Google Earth and GIS. If you have already completed the introductory activity, use your results from that activity and continue onto this activity, doing step 2.d. and then skipping to continue from step 3.f.
Skills and concepts that students must have mastered
Topographic map reading
Geologic map reading
Previous experience with Google Earth preferred
Previous experience with GIS preferred
How the activity is situated in the course
Activity Length1-2 days
Content/concepts goals for this activity
Analog vs. digital topographic map interpretation to determine drainage patterns.
Effective field strategy planning to address an original hypothesis.
Higher order thinking skills goals for this activity
Analyze digital and analog data to draw conclusions about landscape-associated hazards.
Compare and contrast analog with digitally automated analyses.
Formulate hypotheses using analog and digital data.
Develop an experimental strategy to test these hypotheses.
Other skills goals for this activity
Geologic history construction
Navigating Google Earth
searching the WWW and/or USGS's EarthExplorer website
manipulating data in a GIS for analysis and presentation
oral presentation or video presentation
teamwork synchronously and asynchronously
Description and Teaching Materials
Prior to beginning this activity, students need access to an Internet enabled laptop. They will need to download and install the following software packages: Google Earth on web or desktop (https://www.google.com/earth/versions/); a GIS (QGIS is a free and open source option: https://www.qgis.org/en/site/); Topographic Analysis Kit (free, open source software package available at github: https://github.com/amforte/Topographic-Analysis-Kit)
Students may work in groups or independently to complete the activity and presentation. Final reports should be written and submitted independently.
1. Background. Students are first encouraged to review background information on karst and on the source of the digital elevation model (DEM) data they will use in this activity. Background information on karst:
https://kgs.uky.edu/kgsweb/olops/pub/kgs/ic04_12.pdf, https://en.wikipedia.org/wiki/Karst, http://www.igme.es/boletin/2016/127_1/BG_127-1_Art-9.pdf. Background on the Shuttle Radar Topography Mission (SRTM) to acquire the data used in the DEMs recommended in this activity: https://www2.jpl.nasa.gov/srtm/
2. Data acquisition.
2.a. For an overview of karst aquifers on Earth, students refer to the World Karst Aquifer Map (WOKAM), available at https://www.whymap.org/whymap/EN/Maps_Data/Wokam/wokam_node_en.html. They can use WOKAM to select an area of interest or browse Google Earth searching for karst landforms.
2.b. As a base layer for their GIS mapping of their karst area, they should load the WOKAM shapefiles so that they can see their focused area in the context of its broader karst region. WOKAM shapefiles can be found at https://produktcenter.bgr.de/terraCatalog/OpenSearch.do?search=473d851c-4694-4050-a37f-ee421170eca8&type=/Query/OpenSearch.do or in the attached zipped folder.
2.c. Once students have selected their focused karst landscape, they need to acquire topographic and geologic map information. For locations in the United States, Earth Explorer is a good source for SRTM DEM files (https://earthexplorer.usgs.gov/). Students who choose sites outside of the US can still find their DEM data, but may need to do additional internet searching to obtain it.
2.d. Acquire geologic map data. Inside of the US, the National Geologic Map Database project should have what they need (https://ngmdb.usgs.gov/ngmdb/ngmdb_home.html). Outside of the US, it will vary country by country and more internet searching will be needed. Geologic information can be in a file format ready for import to a GIS or as a scanned image or pdf file.
3. Data processing.
3.a. The DEM file then needs to be uploaded to a GIS. Check the properties of your DEM raster layer to see what coordinate reference system (CRS) it loaded in. For many DEMs, you will need to find the appropriate CRS and reproject the raster. For a review of the Universal Transverse Mercator System, here is a link to the USGS fact sheet (https://pubs.usgs.gov/fs/2001/0077/report.pdf) and a world map of UTM zones (https://maptools.com/tutorials/grid_zone_details). Another option is to use an interactive online map (https://mangomap.com/robertyoung/maps/69585/what-utm-zone-am-i-in-) to help determine the coordinate system for their location. The reproject task is performed by selecting the layer for the DEM raster data. Then click on the "raster" drop down menu. Go to "projections," and select "Warp (reproject)..." Then select a complete path for output and give a name to the output file for the reprojected map data.
3.b. After their project is in the correct CRS, they can then choose a color scheme (right click on the layer > "properties" > "style" > "render type" > "singleband pseudocolor" > "generate a new color map" > select the desired color band > "classify") and make a Hillshade layer to better visualize the topography. To generate a Hillshade layer, again use the "raster" menu. Go to "Terrain analysis" > "Hillshade..."
Questions for students: What karst aquifer region did you select? What UTM Zone is this field site in? What colorband worked best for your visualization of the topography? What does the Hillshade function do? How is it helpful?
3.c. The next layer to upload to GIS is geologic map information.
If the geologic map data is in a proper file format for GIS, it will most likely need to be reprojected to the same CRS as the elevation data (see step 3a).
If the geologic map data is a scanned image, students have two options:
Import the image to the GIS and Georeference it to align it with the map. The procedure for georeferencing analog images is covered in this webinar (https://www.youtube.com/watch?v=WbMdNvQcCOs); or
Work side-by-side comparing the information from your geologic map with that on the GIS. This is less precise, but if students are careful they can make it work.
3.d. To better understand the drainage patterns of this landscape, extract a set of topographic contour lines. Again use the "raster" menu. Go to "Extraction" > "Contour..." A good interval to start with a 20. If the contour lines end up looking too crowded or too spread out, students can make new contour layers with different intervals.
3.e. Now that students have detailed topographic maps with contour intervals, they may want to revisit the rule of V's for determining flow paths over land surfaces (http://uncivilengineer.net/2017/07/14/watercourses-and-ridges-on-topographic-maps-why-the-vs/). This is also attached as a pdf. If students have access to a printer, they can print out a paper copy of the map they built and draw the drainage patterns in with a pencil. There are two digital options for drawing in the water flow paths. For the first, students can export the image of their map in QGIS as png format. To do this they go to the "Project" menu and select "Save as Image..." They can then use a photo editor to draw flow paths on their maps. Students with more GIS experience may want to work directly in the GIS and make new vector layers to create their surface flow paths.
Questions for students: Describe the flow paths you drew on your map. What was your reasoning for electing to draw the flow paths you did? What challenges or obstacles did you encounter while determining the routes water would take? How did you overcome the challenges/obstacles to determine the routes?
3.f. To determine flow paths more objectively, use a software designed with flow-routing algorithms. Here we will use Topographic Analysis Kit (TAK). You first need to give the software the output files name prefix and select the output directory. Then load the Reprojected DEM (tif file) into TAK. If it gives you an error regarding whole numbers, your file has loaded correctly. Check the box labeled "Resample" and then click "Run MakeStreams." This is as far as this activity goes as far as using TAK, but it is a powerful tool for doing geomorphological analysis. If you are curious, I recommend you check out the documentation at Github and explore it on your own.
3.g. From the TAK output file folder, drag and drop your new shapefile into the GIS. If you do not see your streams overlaying the topography, right click on your streams vector layer name. Go to "Properties" > "General" > "Coordinate Reference System." Select the appropriate CRS. Click on "Update extents", "Apply", "OK."
4. Data analysis.
4.a. Compare the stream network predicted by TAK with the one you drew in step 11. Questions for students: What similarities or differences do you see between the two networks? Which one do you think is more accurate? Why?
4.b. Using your observations of the geology, the topography, and the hydrology, construct a geologic/geomorphic history of your study area. Questions for students: What was the sequence of events at this site? Be sure to consider in particular depositional, tectonic, and erosional events. How did the stream network (or lack thereof) evolve?
5. Hypothesis formulation.
5.a. Some events in your above history will be more hypothetical than others. Please state which events need additional testing to be able to defend them.
5.b. What environmental or natural-disaster hazards do you think might be issues in this landscape? Why do you think this? Write these ideas in the form of additional hypotheses about this landscape.
6. Experimental design.
6.a. What data would you need to collect to support or refute your hypotheses? Please speculate as to the kinds of results that may be obtained for different types of data and what implications those might have for each hypothesis.
6.b. What field, laboratory, or numerical techniques would be required to obtain the data you need? Please be specific as if you were planning for field work, lab work, or numerical modeling.
Student Handout for Karst Hydrogeology and Geomorphology: A virtual field experience using Google Earth, GIS, and TAK (Microsoft Word 2007 (.docx) 29kB May15 20)
World Karst Aquifer Map GIS files (Zip Archive 20.1MB May15 20)
World Country Outlines GIS files (Zip Archive 5.1MB May15 20)
Technology NeedsThis activity works best with an Internet enabled laptop or other computer. Modifications for smartphone are described below in detail.
Google Earth works equally well for this activity in desktop, web, or mobile versions.
QGIS desktop version needs to be downloaded and installed.
TAK is only available for desktop and needs to be downloaded from GitHub and installed.
While the main goal of this exercise is to virtually explore and develop hypotheses about a karst field site, almost as important is to build students' skills with digital topographic and geologic analysis. However I realize that not all students have access to a laptop, and GIS tools in mobile devices may not offer full functionality. One option for a fully mobile-based activity is to bypass the GIS steps and TAK steps. In this modified activity, students use their mobile device to directly access google Earth, topographical maps, and geologic maps. Apps are often changing, so there is a legacy issue in promoting specific apps. However, USGS has created a great tutorial video (closed-captioning embedded in the video) for how to access topo maps from a mobile device: https://www.usgs.gov/media/videos/using-us-topo-and-historic-topo-maps-your-mobile-device. For this approach, students complete a modified workflow--steps 1, 2a, 2d, 3e, 4b, 5a, 5b, 6a, 6b extracted from the above activity--following the procedure in the USGS video (also attached as an mp4). It is not the complete activity, but will still give the student an opportunity to achieve the scientific thinking outcomes, learn about karst, and enhance their ability to use a smartphone as a scientific tool.
Teaching Notes and Tips
A walk-through for this activity, including screenshots for each step, is included in the uploaded documents.
Teaching Notes for Karst Hydrogeology and Geomorphology: A virtual field experience using Google Earth, GIS, and TAK (Microsoft Word 2007 (.docx) 14.1MB May15 20)
Grading Rubric for Karst Hydrogeology and Geomorphology: A virtual field experience using Google Earth, GIS, and TAK (Microsoft Word 2007 (.docx) 20kB May15 20)
Sharing our science:
1. After completing the exercise as individuals or as small groups, students share their findings with the whole class. This can happen virtually or in person as circumstances dictate. Each presentation can happen as a slideshow or as a video made by the student(s) and played for the group.
2. Each student writes a formally structured report (Title, author's name, date, abstract, introduction, methods, results, discussion, conclusion). Within the report or as a separate document, they should reflect on their experience with this activity and assess their level of understanding before and after the activity of a.) Google Earth, b.) GIS, c.) UTM CRS, d.) topographic map interpretation, e.) TAK, e.) karst hydrogeology, f.) geologic history construction, g.) hypothesis formulation, and h.) scientific experiment design.
An assessment rubric is included in the uploaded documents to aid in the instructor's grading of these two student expressions of learning.
References and Resources
Hands-on supplementary activity if students want to get a 3D feel for the concept of a karst aquifer: https://www.usgs.gov/science-support/osqi/yes/resources-teachers/paper-model-karst-topography.