GETSI Teaching Materials >Eyes on the Hydrosphere: Tracking Water Resources > Unit 2: Monitoring surface and groundwater supply in central and western US
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This module is part of a growing collection of classroom-tested materials developed by GETSI. The materials engage students in understanding the earth system as it intertwines with key societal issues. The collection is freely available and ready to be adapted by undergraduate educators across a range of courses including: general education or majors courses in Earth-focused disciplines such as geoscience or environmental science, social science, engineering, and other sciences, as well as courses for interdisciplinary programs.
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Unit 2: Monitoring surface and groundwater supply in central and western US

Jonathan Harvey (Fort Lewis College) and Becca Walker (Mt San Antonio College)


In Unit 2, students learn how the techniques for water budgeting (covered in Unit 1) can be used to monitor both groundwater (High Plains Aquifer) and surface water (western mountain watershed) systems. Students interpret time-series plots that show the impact of drought years and wet years on underground water storage in the High Plains Aquifer and on snowpack and surface runoff in the western mountain watershed. They also consider the societal implications of water deficits through a series of pre-class readings, questions embedded in the assignments, and small and whole-group discussions. This unit can involve substantial computer time during which students use Excel to view and interpret hydrologic data. An alternative version with hard-copy graphs is also provided.

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Learning Goals

Unit 2 Learning Outcomes

Students will:

  • Interpret time-series plots of hydrologic data and identify seasonal and annual patterns.
  • Identify long-term trends in groundwater and surface water using several datasets derived from traditional and geodetic methods.
  • Articulate environmental factors that influence water availability in the High Plains Aquifer and a typical western mountainous watershed.
  • Evaluate how changing water availability can present challenges for societies in semi-arid areas.

Unit 2 Teaching Outcomes

  • Cognitive: Facilitate students' consideration of multiple traditional and geodetic datasets, climatic regime, subsurface geology, and water use to make inferences about the causes of trends in the hydrologic data.
  • Behavioral: Promote skills development in constructing time-series for groundwater and surface water and interpreting variability in the data over time.
  • Affective: Provide an opportunity for students to consider how differences in water availability are influenced by environmental and anthropogenic factors and how these differences can influence water policy and infrastructure.

Context for Use

The content in Unit 2 is appropriate for introductory geology, environmental geoscience, natural hazards, climate science, and other geoscience courses; sophomore-level courses in which geodesy and/or hydrology concepts are introduced; or non-geoscience courses where water resources and/or the nature and methods of science are being investigated. Unit 2 activities could be adapted to serve small or large-enrollment classes and can be executed during class as an interactive lecture/discussion, in-class activity in which students work in small groups; or as part of a 2-3 week investigation of the use of geodesy and other methods to study water resources using the entire Water Hazards and Resources module. If the entire module will not be utilized, we recommend pairing Unit 2 with Unit 1: Exploring the Reservoirs and Pathways and Methods to Measure the Hydrologic Cycle to facilitate student understanding of water cycle reservoirs, transport pathways, and the methods used to measure them prior to working with authentic hydrosphere data. Students working on Unit 2 should have basic computer skills, including ability to navigate through folders, access MS Office (Word, Powerpoint, Excel) files, and general use of MS Word and Powerpoint for completing the assignment. Although Excel is used, Excel files are prepared such that they require only minimal previous knowledge of spreadsheets. Print outs of plots are also provided if using computers is not practical.

Description and Teaching Materials

Unit 2 is a guided exploration of prepared, multi-year hydrologic data from two different hydrologic settings in the U.S. It has two main exercises that take a total of~2-4 hours of class/lab time plus prep-homework and possibly completion time at home.

  • Unit 2.1 - Emphasis on groundwater through case study of the High Plains Aquifer
  • Unit 2.2 - Emphasis on surface water (both snow and water) through case study of Western Mountain Watershed in Colorado

These two sub-units are independent and it would be fine to do just one if needed to save time or to focus on a particular setting or part of the water system.

It is recommended that students complete Units 2.1 and 2.2 mostly in a computer lab setting with the instructor present, although once the assignment has been introduced, students may continue the work on their own. Students could work individually or in pairs.

Both of the 2.1 and 2.2 student exercises are divided into sub-sections based on investigation questions. These lettered sub-headings are NOT intended for the students to answer directly but to help the students and instructors see what topics the numbered questions (that the students should actually turn in answers to) are aiming to address.

A presentation is included to help instructors introduce the assignment and study areas. The visual aids in the slideshow would be useful for students to refer to while completing the assignment, so at least some of it should be made available to them. Because students are viewing data generated by a variety of traditional and geodetic observation techniques, it would be helpful for students to have access to materials from Unit 1 of this module. If using this unit separately from the rest of the module, instructors should look at and share some of the reference documents for Unit 1 (about these hydrologic observation techniques) with students.

Unit 2.1 - focused on the High Plains Aquifer in the central U.S.

After a small homework assignment/reading, students explore the hydrologic variability of the High Plains Aquifer by looking at multi-year datasets for two study sites (called GW1 and GW2 in the activity) of depth-to-groundwater in wells, GRACE satellite Water Equivalent Height, and GPS vertical position. In the assignment, they are asked to consider factors that lead to variability in water storage over different timescales, to compare the strengths and weaknesses of various methods of measuring water resources in the High Plains Aquifer, and to identify and consider the societal implications of drought events and long-term trends in High Plains Aquifer water storage on those who rely on the High Plains Aquifer.

Unit 2.2 - focused on an example of a Western Mountain Watershed (WMW)

After a small homework assignment/reading, students explore data from a watershed in southwest Colorado. They look at intra- and inter-annual changes in snowpack water storage as measured by SNOTEL stations and Reflection GPS, then explore stream and lake gage data from the same watershed over the same timescale to see how snowpack influences river flow. The study watershed includes a large dam and reservoir, so students must consider how such anthropogenic water storage features influence water availability for water users. In the assignment, students assess the seasonal calendar of water availability as it moves from snowpack to stream to dammed lake back to stream, identify wet and dry years, and hypothesize how changing water availability in this setting could affect water users.

Teaching Notes and Tips

Software Tips

  • Instructors should make sure their students have access to MS Word, Powerpoint, and Excel for best results.
  • Multiple issues exist with the plots if you try to use the Excel files with Google Sheets. At the time of writing, if students try to use Google Sheets, the Y-axis for the Unit 2.1 plots must be turned into the reciprocal of the values in the Excel spreadsheet in order for the curve to have the appropriate shape. In addition, the GRACE data cannot be superimposed onto the depth-to-groundwater time-series if viewing the data in Google Sheets. If students do not have Excel, the instructor should distribute printed versions of the plots ("data graphs"). However, bear in mind that this changes the way that students interact with the data, (e.g., they lose the capability to 'mouse-over' the plots to obtain specific point values).
  • If you are using Excel for the first time with your students, it would help to demonstrate 'mousing over' Excel charts to get the X- and Y-values from the cursor position.

Timing Tips

  • Although originally designed to be completed in one 3-hour lab period, this is a lengthy assignment for students who work more methodically, and Unit 2 will take even longer if instructors have a pre-lab discussion on the study areas (which is an effective way of setting the stage before students work with the data.) The module authors found that spreading Unit 2 over multiple class meetings allowed appropriate time for discussion/reflection and prevented students from cognitive fatigue from sustained screen time. One tester found that starting with the Western Mountain Watershed case study (Unit 2.2) and completing Unit 2.1 second seemed to increase the efficiency of student completion of Unit 2.1. Alternatively, one could have students complete only Unit 2.1 OR 2.2 to better fit time constraints.
  • If you are extremely limited on time, you could try a significantly abbreviated version of Unit 2. For example, half of the students receive a GW1 time-series, and the other half of the students receive a GW2 time-series. Students answer an excerpt of the questions from Unit 2.1, then pair up with a partner who was given the other time-series. The pair subsequently answers some questions together and then speculate about the difference in depth between GW1 and GW2 based on how the data look. In short, there are many options for implementing Unit 2.

Concept tips

  • Students may need some prompting on what the different methods
    • student should refer back to Unit 1
    • have a guided discussion "reading" the first graph - what are the axes, what do the numbers mean
    • maybe pop up a method slide as they start on a given method
    • particular hurdles
      • groundwater well - students forget that it is measuring from 0 at the surface to where the water table is below the surface
  • Make sure students are familiar with the concept of volume as a way to measure the amount of something (like water.) Of course, the multitude of units that can be used to measure water volume (km^3, ft^3, acre-ft, etc) can also be confusing for students. Sketching an example of each of these on the board prior to starting the Unit 2.1 exercise is helpful.
  • Unit conversions may also be challenging for introductory students. Although there are hints where unit conversion questions come up in the assignment, be prepared to help.
  • Students may need further explanation of what (and where) the Ogallala Formation is and/or how to compare it to the shallow 'gravel and sand deposits' in the Unit 2.1 High Plains Aquifer exercise.
  • Students who missed Unit 1 will be confused by references to Unit 1 notes, and probably will not know what WEH (water equivalent height) is for the GRACE questions. Be prepared to refer students back to Unit 1 when they thought about SNOTEL and encourage them to think about "fluffy" snow vs. "heavy" snow.


Formative assessment

Formative assessment can take place during the open-lab period wherein the students are completing exercises 2.1 and 2.2. Selected questions in the exercises may also be posed verbally to students during work time and used to facilitate discussion about recognizing seasonal and interannual features like drought and abundance in hydrologic data and considering the societal implications of these phenomena.

Summative assessment

The student exercises can serve as the summative assessment for the unit. If additional summative assessment questions are desired, they are provided in this document:

References and Resources

Readings related to Unit 2.1 Exercise (High Plains Aquifer):

Readings related to Unit 2.2 (Western Mountain Watershed):



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This module is part of a growing collection of classroom-tested materials developed by GETSI. The materials engage students in understanding the earth system as it intertwines with key societal issues. The collection is freely available and ready to be adapted by undergraduate educators across a range of courses including: general education or majors courses in Earth-focused disciplines such as geoscience or environmental science, social science, engineering, and other sciences, as well as courses for interdisciplinary programs.
Explore the Collection »