Lab 2: What's a Watershed?
The lab activity described here was created by Betsy Youngman of Phoenix Country Day School and LuAnn Dahlman of TERC for the EarthLabs project. The hands-on activity in Part A is adapted from similar lessons by Windows to the Universe and California's Project WILD.
Summary and Learning Objectives
Students build a physical model to explore watershed features, then use Google Earth software to tie the model to a real place. By exploring several layers of map-based images and data, students develop an appreciation of the complexity of a watershed and river system in the context of a both a local and national scale.
After completing this investigation, students will be able to:
- Build a physical model of a watershed.
- Identify watershed features such as drainage divides, rivers, tributary.
- Predict streamflow patterns based on landform features.
- Use Google Earth to view watershed features.
- Discover their own watershed.
- Describe land cover and population changes within a watershed.
Context for Use
This activity builds background knowledge necessary for understanding drought. The physical model and Google Earth-based exploration of watershed data help students grasp how surface water moves across the landscape. The activity requires simple lab or household materials for Part A and the computer lab for Part B. Both parts lend themselves well to small group work. There are no prerequisite skills needed for the activity, but it may take longer if this is the first time students have used Google Earth. The activity can stand alone from the drought unit as an introduction to rivers.
Estimate of Time Required: Part A: 45 minutes; Part B: 45 to 90 minutes, depending on students' previous experience with Google Earth.
Activity Overview and Teaching Materials
In part A, small groups of students build physical models to demonstrate the concepts of watersheds and drainage divides. Each group of 2 to 4 students will need the following materials.
- Large aluminum roasting pan or paint tray
- Stack of tissue paper or newspapers
- Masking Tape
- Sheet of white plastic, slightly larger than the pan (a trash compactor bag cut into single sheet works well)
- Spray bottle
- Blue food coloring
- Absorbent cloth or paper towels
- 2 different colors of permanent markers
- Blocks of wood or a notebook to lift one end of your tray
In Part B, students use Google Earth and watershed data from USGS EDNA Watershed Atlas site to look for correlations between watershed features and landforms. They also explore population density and land cover change in a watershed of their choice. Students conclude by preparing an illustrated description of a watershed.
You may want to provide a hard copy of the Activity Sheet
Teaching Notes and Tips
The watershed models are easily built and explored in one class period. There are suggested materials to use, but there is much flexibility in the design. If you do not have squirt bottles or baking pans suggest to students to bring them in from home. Give students several days or a week's notice so that they can empty and clean an appropriate container.
Google Earth is an amazing and engaging program. Allow students sufficient time for exploration within the program will help them use it in subsequent lessons. Encourage students to access Google Earth's online User's Guide to understand how various tools and features work.
Also note that the EDNA watershed data sets from the USGS are rich sources of information for multiple investigations. Performing a practice run through the steps students will follow will help you anticipate questions that students may have.
To assess student understanding in Part A, you may ask students to draw a diagram of their watershed model and label all significant features. Additional insight into student understanding can be gained by examining their answers to the Stop and Think questions.
State and National Science Teaching Standards
Student experiences with physical models prior to work with computer-based visualizations can help them build a mental picture of watersheds.