The San Diego Bay Watersheds Common Grounds Project was created to incorporate data from water quality monitoring programs and integrate this data on a watershed level using a web-based interactive application to serve as a broad communication, education and decision-making tool; and to further develop the region's capacity to understand and assess processes affecting our water resources.

San Diego Bay Watershed Lesson

The San Diego Bay Watershed Lesson teaches students what a watershed is, where watersheds are located in San Diego , and why they are important to learn about. Because San Diego is heavily populated, humans have a considerable effect on the watersheds. Though this lesson, students will learn how individuals affect the watersheds.


Watershed (wa·ter·shed)

1. A region or area bounded

peripherally by a divide (ie: mountain

range) and draining ultimately to a

particular watercourse or body of water


2. An area of land which drains all rain

that falls within it to a common body of

water such as a creek, lake or ocean. (from


Watershed Information:

• A watershed is the area of land where all of the water drains to the same place - this
includes water that flows on the surface and water located underground. Watersheds
come in all shapes and sizes. They cross county, state and national boundaries. No
matter where you are, you're in a watershed! (from This site also has a nice diagram of a model watershed.

• For this unit, the smaller watersheds in the San Diego region will be discussed and presented to students. The explanation of varying watershed names is provided to prepare educators in case students find these different names when doing independent research. The general idea of a watershed is consistent no matter what the scale; “watershed” is more a concept than a rigidly defined term.

• Watersheds also include water located underground (groundwater).

• The major understanding that students should take away from this Investigation is that watersheds are areas where all of the water in a geographic area, both above and below ground, ends up in the same place. Dams can be confusing, but the “watershed concept” holds true. If overflowed, the water from dams flows downhill to the same place.

Lesson/Activity 1: Defining Watersheds

1. Work with students to begin to define a watershed (to this point the word watershed hasn't been used with students). Use the following points to help your students to begin to form an understanding of watersheds.

• Imagine 3 raindrops that don't dry up and evaporate. One lands in Clairemont, one lands in Mira Mesa and one lands Downtown. Where will each of them end up? ( In the Bay) Have students explain their thinking even if their answer is incorrect.

• Now imagine a raindrop falls on the East side of San Diego 's mountains, will it also end up in the Bay? ( no, it will roll down the east side of the mountain- water doesn't flow uphill )

• What do you think determines where the raindrops end up? (It depends on the landforms- the shape and slope of the land determines where water flows)

• Do you suppose that scientists might have a term for the area where all water flows to the same place? ( yes )

• They do! The term is watershed. You know what water is, what does shed mean in this word? ( shed in this word means to “cast off”. Think of your pets fur shedding or falling off )

• Try sketching a watershed in your notebooks. Give students a few minutes.

• What are the features of your watershed?

• How does the water flow in your drawing? (downhill)

  • Can you explain why it flows that way? (Students should mention that water flows downhill around some landforms and forming others due to the force of gravity)

. What landforms do you have in your sketch? Students should have some elements of landforms/topography, hills, mountains and canyons, in their drawings

Where does the water in your sketch flow to? (The water all ends up in the same place. Sketches perhaps include a river, lake, or the ocean.

• A watershed is an area where all of the water ends up in the same place.

• The boundaries of a watershed are based on topography/landforms, such as hills, ridges, and mountains. Compare this to the sketches students made in their notebooks. What did students represent in common with the drawing and what elements did they leave out in their sketches?

• No matter where precipitation (rain, snow, etc) or water from sprinklers falls within a watershed it all goes the same place.

Have students re-sketch a generic watershed in their student science notebooks. They need to label water features (lakes, rivers, creeks, oceans, etc) at this time. Circulate and ask students to explain their sketches.

Lesson/Activity 2: Identity San Diego Bay Watersheds

San Diego Bay contains 3 watersheds: Otay, Sweetwater and Pueblo

A key understanding from this experience is that no matter where you are on land, you are in a watershed!

Teachers: Make a transparency of the San Diego Bay Watershed (found on Common Ground Web site homepage)

1. Divide the class into 3 groups, each with a San Diego Bay Watershed.

2. Tell students that today they will become “experts” on different watersheds in San Diego. At the end of the lesson each group of experts will share some of the things that they have learned about watersheds.

3. Tell students that the goal of this activity is not to memorize every single thing about their particular watershed. The goal is to learn about the general features of San Diego Bay 's watersheds, and particularly to understand some of the pollution problems in our watersheds.

Questions for the students to think about:

• Where is your watershed located?

• Where does your water in your watershed end up? (what is the receiving body?)

• What are some of the specific problems in your watershed?

• What are some of the causes of problems in your watershed?

• What is the water in your watershed used for?

• What kinds of organisms (plants and animals) live in your watershed?

• Are there any important natural areas that are undisturbed by humans in your


• What suggestions could you make to help solve some of the problems in your


Lesson/Activity 3: Modeling Pollution in San Diego Watersheds

In this last lesson, students become familiar with San Diego 's watersheds and some of the pollution issues related to them. This lesson is intended to show students how pollution in one part of a watershed affects other parts of the watersheds.

1. Have students create models of watersheds.

2. Conduct experiments to demonstrate how pollution moves through watersheds.



*1 box of food colors per group

*clay +stream tables

*glitter +basins for wastewater

*dish soap /water source

*cotton balls /Newspaper (table protection)

*Optional: leaves, dirt, twigs


1. Ask students what they learned about San Diego watersheds in the last lesson. Be sure that all students understand what a watershed is and can describe some of the features of watersheds. Ask students where all of San Diego 's water drains after it passes through our watersheds ( ocean or bay ). This will be a key concept when thinking about pollution issues in our watersheds.

2. Tell students that they will be creating a model watershed using their stream tables. Then they will have a chance to design an experiment to show how pollution can affect watersheds.

3. Distribute the Watershed Maps and Informational Packets to students.

4. Ask students to create a model watershed in their stream tables. Tell them to make it resemble a San Diego watershed (ending in the ocean or bay). Set a time limit of about 10 minutes (the models don't need to be perfect!).

5. Now ask students what kinds of pollution they think might be a problem in San Diego . ( some ideas are: litter, animal waste, pesticides and fertilizers, motor oil or other automobile “drippings” and chemicals, etc ). Chart their ideas.

Teacher Note: San Diego 's watersheds and topography are complex, so it isn't realistic for students to create an exact model of their San Diego watershed, just encourage them to do the best that they can within the allotted time and focus on the main features of their watershed.

6. Now that students have generated some ideas about pollution, tell them that they will be able to model how pollution might affect their watershed by designing their own setup. Students should follow this procedure:

a) First decide what types of pollution you want to model and where you want to locate them. Here are some suggestions on how to represent different pollutants, but you and your students can choose different representations if you'd like:

Green food coloring=fertilizer Red food coloring=chemicals

Glitter=litter Blue food coloring=pet waste

Yellow food coloring=automotive waste Soil, leaves, etc=yard waste or erosion

b) Add the pollutants to your watershed model. For the solid pollutants (glitter and dirt or leaves) students can place them in their watershed model. For the liquids, students should press a cotton ball down into the sand/clay mixture, but leave a bit of it showing, then put at least 10 drops of food coloring on the cotton ball.

c) Run water through your polluted watershed model. Students should move the water source around the model to mimic what happens when it rains (if the water source is left stationary very little will happen).

d) Immediately observe and record in your notebook what happens as water flows through the polluted watershed model. Make sure to look at the water in the catch basin to see what it contains.

7. Have students share their observations of their experiments with the class. Here are some questions that you might want to address with students:

• How did the pollutants move through your model watershed?

• What did the water in the catch basin look like?

• What does the catch basin represent? ( the ocean or bay )

8. Have students write what they learned about pollution in San Diego Watersheds. Be sure to remind them to cite their evidence when they make observations and or conclusions.

Wrap-up: Review the experiment emphasizing that it is a model of how pollution moves through a watershed. Ask students to tell you where much of the pollution from around San Diego ends up (in the ocean or bay). Tell them to think about that problem for your next science meeting.


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