Overview
This conclusion can be used after a field trip to Tule Ponds and Tyson Lagoon, or performed without the field trip. If students were unable to attend the field trip simply omit parts pertaining to the trip.

The discussion begins with an overview of the project. An experiment will then be performed to demonstrate water filtration. A concluding discussion will focus on ways students and their families can help keep our bays clean. Students will create posters to illustrate their knowledge of our bays and why we should be concerned about their cleanliness. These can be performed during a long science class, or split between two periods.

Background Information

Water drains into the Tule Ponds and Tyson Lagoon from many surrounding neighborhoods. These neighborhoods contain a diverse mixture of old and new homes and farmland. Students should have noticed that water entered the ponds from several points. Not all of these inlets dumped into Pond #1, as was originally planned. Inlets entering into other ponds were not allowed the same settling time as had been planned to allow for the removal of impurities.

As water percolates through the ground, impurities are often left behind in the sediment. Gravel, sand, activated charcoal and other substances can be used to filter water. Wetlands naturally allow this to happen. The creation of ponds, such as the Tule Ponds, employs this principal.

Student Discussion

Prepare an overhead of the map showing the areas that drain into the Tule Ponds. Trace how the water flows into the ponds and the pathway the water takes to the bay.

Prepare an overhead of the map showing the Tule Pond/Tyson Lagoon system. Ask the students to show you where the inlets dump water into the ponds. Remind the students that the ponds are designed to settle out the impurities in the storm water. Ask them what is wrong with the water not entering the system at Pond #1. (Ans. The water is suppose to travel through the three ponds so that the impurities have time to settle out. If they enter the system at the end or in the middle, settling will be limited.)

Water Filtration Experiment

Students will observe how impurities are filtered out of water.

Before beginning this experiment, you will need to prepare the filtration bottles.

Materials (per group)
student lab sheets (one per student)
3, 2 liter bottles or 3 plastic water bottles
3 pie tins
gravel
sand
water
dirt
blue food coloring

Procedure:

1. Poke many holes into the bottom of the bottles. This can be easily done by heating a nail and pushing it through the bottom of the bottles.
2. Label the bottles 1-3.
3. Into bottle #1 add 4 inches of gravel. Into bottle #2 add 4 inches of sand. Into bottle #3 add 2 inches of gravel and then 2 inches of sand.
4. Mix some dirt and food coloring with water. This water will be used to filter, so prepare enough for the entire class.
5. Each group needs three prepared bottles setting in separate pie tins.
6. Place a container of polluted water at each groups site. Include a 250 ml. graduated cylinder.

1. Which bottle cleaned the water the best?
2. What would be the best material(s) to line the bottom of settling ponds with in order to clean the water?

Review the results with the class. Elicit a discussion based on question #2 and relate it to the Tule pond system. Impress upon them that although the water exited cleaner than it went in, some impurities do get through. This is why it is so important to keep impurities out of our waters in the first place.
 

Keeping the Bay Clean
 

Discuss with the students the following main points about the San Francisco watershed:
 

• A watershed is an area of land that water flows over or through on its way to a river, bay, or ocean. The San Francisco Bay is one large watershed. Fremont has two main watersheds. The northern areas drain into the Alameda Creek, and the southern areas drain through sloughs below the Dumbarton Bridge. Tule Ponds and Tyson's Lagoon form an even smaller watershed. This watershed drains the areas discussed earlier and eventually enters the bay through the Mowry Slough.
• Water that drains inside buildings, including your home goes into the sanitary sewer system. This water is treated and cleaned before going to the bay.
• Water that drains from street gutters enters the storm drain system and drains directly to the bay.
• Watersheds are home to plants and animals. They also provide us with fresh water and recreation areas.
• Only we can keep our watershed clean. We can keep it clean by  picking up litter, washing cars on the lawn so the soap filters through the ground before entering the storm drain, recycling motor oil, avoiding the use of pesticides, and participating in creek clean-up projects.

Working in groups, have the students design large posters, illustrating the importance of our watershed. They may wish to focus on how to prevent pollution, or the importance of clean water. Display the posters around the classroom or school.

 4-6 Watershed Curriculum