What's in the Water? Lesson 1: Water Cycle and Watersheds

Kelsey Bitting, Environmental Studies & Center for the Advancement of Teaching and Learning

Jessica Merricks, Biology

Elon University

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In this lesson from "What's in the Water?" PFAS Contamination Unit", students collaboratively explore water and contaminant cycling through the natural environment. They identify pathways each may follow, driven by solar energy and gravity, and consider the distinction between point source and nonpoint source contamination. Students use these ideas to guide their observations and hypotheses about PFAS contamination sources and pathways in a local town plagued by drinking water contamination.

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This activity has been used in an introductory-level university course in environmental science that enrolls both majors and non-majors, as well as a summer intensive science course for high school students, both in North Carolina where the unit is set. It could easily be adapted to other locations where PFAS contamination is present, as well as to geology or biology courses.

Skills and concepts that students must have mastered

Students in the course in which this unit was initially taught have some experience with biogeochemical cycling, by virtue of having studied the carbon cycle in the previous unit. Similarly, during the prior unit we discussed the challenges of evaluating source material found on the internet, and introduced the CRAAP framework as a useful approach to that process. If your students are not familiar with either of these ideas, additional scaffolding and discussion may be useful.

How the activity is situated in the course

This is the first instructional lesson of the "What's in the Water?" PFAS Contamination Unit". Prior to this lesson, students will have been introduced to the unit-long Community-Engaged Project, met the community partners to understand the local PFAS contamination situation and the community partner's needs, and completed the Benchmarking Activity to take stock of their prior knowledge of water and water contamination.


Content/concepts goals for this activity

  • Students will be able to diagram the hydrologic cycle and explain how water and contaminants move from one reservoir to another.
  • Students will be able to describe the anthropogenic threats to freshwater reservoirs of different types.
  • Students will be able to define the concept of watershed and analyze a watershed for possible contaminant sources.

Higher order thinking skills goals for this activity

  • Synthesizing information from multiple sources
  • Evaluating the quality and relevance of sources of information
  • Forming hypotheses based on observations

Other skills goals for this activity

  • Collaboration
  • Convergent decision-making (coming to agreement on a rank-ordered list of possible answers using an evidence-based rationale)

Description and Teaching Materials

In this lesson, students begin to unpack how water and contaminants cycle through the natural environment, including identifying the complex pathways both may follow, recognizing the sun and gravity as the drivers of the hydrologic cycle, and discussing the difference between point source and nonpoint source contamination (and the relevance of that distinction in mitigating contamination). These concepts are framed within the local context of Pittsboro, NC, the nearby town experiencing a PFAS water contamination crisis where the community partner is located. This framing is introduced via the following guiding questions:

  • Where does Pittsboro's drinking water come from?
  • How does the probability of contamination presence/type vary by freshwater source?
  • How does the geographic concept of "watershed" and the chemical designation of "point source vs. nonpoint source contamination" help us narrow down possible sources of Pittsboro's drinking water contamination?

Pre-Class Homework
Before class, students complete an independent homework assignment in which they investigate a single reservoir in the hydrologic cycle, including identifying the processes by which water and different types of contaminants move into and out of that reservoir.

Activity 1
In the first activity during class, students convene in groups based on which reservoir they were assigned, compare notes to prepare a brief report about that reservoir for the class, and describe their collective understanding. Small group sharing on each reservoir leads the class to develop a diagram of the full water cycle together, which the instructor can sketch on a whiteboard or projector. This can then be followed by guiding questions like, what drives the water cycle? What processes tend to remove contaminants, and what processes simply pass them along or add new ones, and why?

To create a bridge to the second activity, the instructor should introduce the concept of point source vs. nonpoint source contamination. If time allows, this might be done by collaboratively brainstorming a list of water pollution sources and then asking groups to find ways to classify them and what the value of a given classification system would have for prevention or remediation. The instructor should also introduce the concept of a watershed, and how watersheds determine where and how far inputs of water and contaminants go and where they end up.

Activity 2
Once students understand these guiding concepts, the second activity challenges them to explore possible point sources for the PFAS contamination in Pittsboro, and rank them in terms of likelihood. This can be done using a whiteboard or Google Slide per team, or by asking students to input and up/downvote likely contamination sources in Padlet or another similar technology. The goal of this activity is NOT for students to identify the correct source of PFAS contamination, since they do not yet have sufficient information to do so. Instead, the goal is to connect the concept of watershed and point sources (i.e., contamination sources must be upstream of the area experiencing contamination issues) and to uncover and begin to complicate students' assumptions about water contamination (e.g., how far can contamination travel? What kinds of personal or industrial activities result in water contamination? Do all contaminants come from all polluters, in equal amounts?).

What's in the Water Lesson 1 Class Plan and Timeline (Microsoft Word 2007 (.docx) 13kB Nov3 21)
What's in the Water Lesson 1 Pre-Class Homework Assignment (Microsoft Word 2007 (.docx) 9kB Nov3 21)
What's in the Water Lesson 1 Instructor Slides (PowerPoint 2007 (.pptx) 2.8MB Nov3 21)

Teaching Notes and Tips

  • During the first in-class activity, students may be tempted to compare notes at a superficial level. To encourage deeper processing, we recommend the instructor circulate among breakout groups or throughout the room, asking teams to think critically, re-evaluate ideas, and decide which ideas are most logical/meaningful/useful and why. This can also be done with framing before the activities, and often needs to be repeated in different forms over time to shift student habits and foster deeper engagement.
  • To ensure equitable group work, the instructor can assign roles (discussion facilitator, note-taker, time-keeper, reporter, and/or "outside the box" thinker) and ask students to rotate through all roles several times during the unit. This can be done by providing a spreadsheet that assigns roles on each date of the unit within the team, or asking students to fill out such a spreadsheet to record their activity in different roles. In our experience, simply asking students to rotate roles without accountability is rarely effective.
  • Providing a reporting template such as a worksheet, Google Slide, Google Doc, or even a whiteboard that students write on while working helps to keep teams on-task, and can be collected or photographed using your/their phones to allow you to review their work in more detail and give credit for attendance or participation.
  • In teaching this class, we asked students to save all their activities and assignments to a Google Drive folder, which served as an impromptu portfolio for feedback and allowed them to archive their work and review it before completing the end-of-unit Benchmarking Activity . Please modify the submission guidelines for activities as suits your own approach to collecting and giving feedback on student work.
  • Between this class and the next, we ask students to read https://www.theassemblync.com/long-form/silent-waters/ about our area's PFAS contamination crisis, and share in a discussion forum one quote that stuck out to them and why. If you can locate a similar article for your area, you might do the same.


  • Assessment within the lesson is formative. All groups report back after activities, and the instructor facilitates deeper thinking or revision via supportive questioning. Whole-class discussion and brief mini-lecture between activities helps students identify misconceptions or recognize additional complexity to add to their conceptual understanding.
  • Ultimately, new or revised understandings from all lessons in the unit should be reflected by student answers to the Benchmarking Activity completed at the conclusion of the unit, which can be used for summative assessment purposes.

References and Resources