GETSI Teaching Materials >Measuring Water Resources > Unit 4: Water budget assessment of a California drought
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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 4: Water budget assessment of a California drought

Bruce Douglas, Indiana University (
Eric Small, University of Colorado (


The California Drought of 2012–2016 had significant social and economic consequences. This final unit focuses on this drought as a case study for measuring the hydrologic system so that we can better understand fluxes, variability, uncertainties, and methods to measure them. Students analyze a variety of data that are relevant to basin-scale water budget: precipitation, terrestrial water storage, and snow pack. Traditional monitoring systems used are precipitation and snow pillow sensors. The newer geodetic methods are GRACE (Gravity Recovery and Climate Experiment satellite) and Reflection GPS. The students then use these data to consider water storage changes during the drought and how these changes compare in magnitude to human consumption. The work can start during a lab period and carry over into work outside of the lab time. The student exercise takes the form of responses to questions and tasks that tests a student's abilities to synthesize information and identify challenges in monitoring the terrestrial water cycle. Students then take the step-by-step exercise results and synthesize it into a report for California water policy makers to highlight the findings and pro/cons/uncertainties for the different methods. Unit 4 is the summative assessment for the module.

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Learning Goals

Unit 4 Learning Outcomes

This unit is intended to provide the summative assessment for the entire module. As such the students should demonstrate a mastery of the learning goals for the entire module. Students will be able to:

  1. Analyze and integrate observations that describe the state of the hydrosphere at regional scales (spatial transfers/patterns, residence times, and societal needs/pressures.)
  2. Quantitatively compare and contrast different data types, and their uncertainty, for use in the context of the water balance equation.
  3. Critique/evaluate the utility of traditional versus geodetic data for quantifying fluxes and storage.
  4. Compare the magnitude of human use in the basin to deficits associated with drought.

Unit 4 Teaching Objectives

  • Cognitive: Characterize water storage reservoirs that together constitute the terrestrial water balance. Defend explanations for the spatial and temporal variations observed.
  • Behavioral: Promote skills in reading and interpreting maps and plots of precipitation and snow data, some of which illustrate snapshots in time and some of which illustrate changes over time (time-series). Facilitate a synthesis of multiple types of observational tools and basis for measurements (traditional hydrologic, GPS, GRACE, ) to make predictions about the behavior of a natural system.
  • Affective: The student will assess the critical local, regional, and climate-dependent interplay between precipitation, snow accumulation, and groundwater storage that may contribute to changes in a natural system and competition between these water gains and losses. Students will critique about the role of uncertainty in scientists' understanding of a complex system.

Context for Use

This activity is intended for use as a summative assessment for the entire module and gives students the opportunity to apply knowledge gained in the other units. This unit cannot be completed successfully without the skill and knowledge gained from previous units. Although Units 1–3 could be done without Unit 4, this unit really does provide an excellent opportunity for students to apply their new skills in a societally relevant context and introduces a new technique for measuring snow depth. The overall structure of this activity can be adapted for use in lower-level courses. This might require more group work throughout and could be heavily structured by the instructor (for example, by providing a template).

Description and Teaching Materials

Unit 4 is intended to serve as the summative assessment for the entire module, Measuring Water Resources with GPS, Gravity, and Traditional Methods. As such it includes materials and student activities that have been introduced in previous units, with one exception. This is the inclusion of an additional method of measuring and monitoring snow depth through reflected GPS signals. The unit focuses on the problem of water balance in response to drought conditions in California. Given this subject matter, there is wide opportunity to include socially relevant discussions and applications of various means of determining a water budget. The different techniques provide independent lines of working with the water balance equation. In order to give students practice in moving from thinking like students to considering how scientific analyses need to be converted to those useable by nonscientists, the final portion of the assignment requires the students to reframe what they have determined into a report useable for a California policy maker trying to determine steps to take based on findings from scientists.

The student exercise consists of sections A–H, which walk the students through data exploration and societal consideration steps.

  • A) Water Use
  • B) Precipitation
  • C) Snow data—includes both snow pillow data (which students also encountered in Unit 2) and GPS Reflection (which is new to the students in this unit)
  • D) GRACE data—students worked with gravity in Unit 2
  • E) Comparing components of the water balance—asks the students to consider the water storage changes based on different datasets within the context of the water balance equation
  • F) Water usage and drought revisited—asks the students to compare water usage in California with the deficit in precipitation and terrestrial water storage
  • G) Evaluate current monitoring network—students evaluate the pros/cons of traditional and geodetic water monitoring methods
  • H) Reflection on what they have learned

In the final activity of the unit, students synthesize the step-by-step exercise they were led through into a report intended for California policy makers.

Teaching Materials

Updating Unit 4 Data Sets

  • For more information on where and how to update the data used in this unit, please refer to the instruction sheet below:

Teaching Notes and Tips

  • Unit 4 is intended to be a synthesis of the different techniques and concepts covered in the module, as applied to a real-world scenario, emphasizing potential societal impacts. While it is hoped that the students will be able to work with a great deal of independence, it may be necessary to support students as they progress through the Unit 4 workflow and, where necessary, help them in recalling and applying previously learned material. A new technique is introduced for measuring snow depth, but it is similar to other techniques the students have been working with. This final exercise is intended to take longer than the previous units, which could be finished within a normal laboratory period and homework/write-up time (consistent with the course being one for advanced majors), but it may require additional time considering it is intended to serve as the summative assessment. As stated, Unit 4 is anticipated to require the students to work longer outside of laboratory meeting time and could be scheduled such that a second laboratory session could be used as a time when the faculty member would be available for consultation and guidance to catch misconceptions and also minimize time spent pursuing dead ends. This exercise will serve as a useful reinforcement of the technical skills already acquired by working on Units 1–3, and may add some additional technical skills.
  • Students will respond to directions for a series of tasks, including responses to questions based on information provided or in response to calculations and data table assembly that they produce based on previous exercises (comparing and contrasting to reflect on learning). Through working on these tasks, students will integrate a number of different aspects from subdisciplines within the geosciences, such as surficial processes, hydrology, and quantitative analysis and error analysis, along with various remote-sensing technology, geodetic data sets, and spatial and temporal context.
  • The student handout focuses on the 2014 water year because GRACE data from the 2015 water year were not yet available at the time of module construction. Sections C, D, and E of the handout could be adjusted to include both the 2014 and 2015 water years, or to replace the 2014 analysis.
  • The unit requires use of computers. Ideally each student will have their own computer or laptop. At least there should be one computer per work group. If it is not feasible to use computers during the class/lab period, the instructor should take extra steps to make sure that students understand what is required of them to do the exercise outside of class.
  • Students may need help with specific Excel functions such as "slope" to calculate the trend. They may also need help thinking through how to "detrend" the position data.
  • The Teaching with Spreadsheets across the Curriculum site provides support for teaching with programs such as Excel. If your students need supporting math practice, The Math You Need site provides an opportunity to brush up on skills such as graphing and unit conversion. Teaching with Google Earth provides a variety of resources for using this powerful program during teaching.


Unit 4 is the primary summative assessment for the module. Given the organization of the unit it may be easiest to make two different assessments: one based on the short responses to the directed questions and one based on the student's report with some sort of combined or weighted summed score forming the final summary assessment. The report will be based in large part on the student's responses to the directed task/questions so it could be used as the sole assessment. Instructors can modify this rubric to assign point values in a manner that is consistent with their course-grading scheme. Student metacognition is an important part of the learning process. The Unit 4 student handout includes a final section that asks the students to reflect on their own learning during this module and its personal significance. Students' responses to this section should not be included in the overall grade, but responses can be scored using the rubric included in the handout.

Unit 4 example student exercise rubric (Microsoft Word 104kB Jun10 17)

Unit 4 student final report for policy makers grading rubric (Microsoft Word 2007 (.docx) 120kB Jun10 17)

References and Resources

Reflection GPS

  • PBO H2O Data Portal - using GPS reflection data from the Plate Boundary Observatory to study the water cycle
    • Note: since the writing of this module, the active processing of the PBO H2O reflection GPS data have stopped. However the archive of data are still accessible from this link.
  • Video: Governors Award for High Impact Research - this short video overviews the significance and surprise of reflection GPS

Drought Impacts

Report Writing

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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 »