GEOL/CIEG 467/667 Ecohydrology Spring 2024
HW7: Groundwater Dependent Ecosystems
Learning Objectives
• Develop a model which calculates the groundwater component of ET using well hydrographs.
• Predict patterns of plant occurrence using information about hydrologic patterns.
Assignment
A template for your R scripts and necessary datasets are available for you on Canvas.
1. Quantifying ETg: The White Method
For questions A through C, use three datasets from two field sites in North America represented by the files: well_A.csv, well_B.csv, and well_C.csv. In each of these, the first column (t) is time as day of year (unit = day) and the second column (WTD) is the depth to the water table (unit = meters) collected from a pressure transducer over a growing season. Be aware that there are a few blank entries in well_B.csv for the first few days of the record. Assume a specific yield of 0.10.
a. Review the script provided for these calculations. Add comments to the code and upload the commented version of the code to the CODE assignment on Canvas. For example:
• Lines 12-13: load R libraries that will be used in this script: tidyverse for rearranging and manipulating datasets, and ggplot2 for plotting.• Line 15: define the name of all wells that will be used (A, B, and C).• Lines 16-21: load the individual csv datasets for each well, add a column to each dataset with the name of the well.• …and so on. Be careful to explain the role of commands/functions, arguments, and plotting options used. Hint: Not sure? Access the help!
b. Include a copy of the well hydrograph plot that is generated by this script (“plot_wells”). Discuss what you can infer from this plot about the hydrologic environment and drivers of each site (~2-3 sentences for each site). Annotate the plot if helpful.c. Run the R-script to analyze the records and include one or both plots of ETg over the growing season for each site (“plot_ETg1” and/or “plot_ETg2”). Comment on the results. Be sure to interpret them in relation to the hydrology you inferred from Question b and clearly annotate portions of the graph where you conclude the results are valid/invalid.d. What aspects of your script, if any, would need to change to limit the ETg timeseries to only valid values? Note: do not create a brand new script, simply describe any notable changes you would make.e. Evaluate and include plots that demonstrate the effect of uncertainty in specific yield (Sy) on your estimate. Discuss the impact of Sy uncertainty (~2-3 sentences). Note: this is the only portion of this part of the homework assignment that may require changes to the script.
2. Hydrologic Niches
Using the same water table records you were provided for Part 1, use the models presented by Henszey et al. (2004) to predict the plant frequency for three plant species: a) Symphyotrichum lanceolatum (GH), b) Sorghastrum nutans (GR), and c) Ambrosia psilostachya (GHR). Assume that each site is within the geographic range of these species.
a. Install the “pracma” package so that the script provided for these calculations will run.b. Review the script provided for these calculations. Add comments to the code and upload the commented version of the code to the CODE assignment on Canvas, as in Part 1.c. From reviewing the code and cross-checking with the Henszy publication, answer the following questions:
a. What are the species names of “plant1”, “plant2”, and “plant3”?b. Why does the value of the “d” coefficient for “plant3” not match the mean value given by Henszy et al. (2004)?
d. Include a copy of the plot of the relationship between plant frequency (%) vs. 7-day water level max models presented by Henszey et al (2004) for these species.e. Calculate the plant frequency (%) for each plant at each well and fill out the table below. You may write a few lines of codes to do this (best!) or do it manually (more annoying and prone to error, but ok if correct).
|
Plant |
Well A |
Well B |
Well C |
|
Symphyotrichum lanceolatum (GH) |
|
|
|
|
Sorghastrum nutans (GR) |
|
|
|
|
Ambrosia psifostachya (GHR) |
|
|
|
f. Discuss your results. In writing your comments, look up information about each of these three species including common name, photo, characteristics, etc.g. Discuss two other methods for articulating a species hydrologic niche. How would you apply these methods and what data would you need? Given the three groundwater data sets provided, do you see any pros or cons of your methods versus the methods presented in Henszey et al. (2004)?