Water is a vital natural resource that all living things depend on to survive, but water quality is being affected by human activity. In this lesson, students explore how humans have impacted the quality of our water resources, and consider ways to avoid further pollution. Students first examine the causes of water pollution, then investigate the quality of their community's water supply. They conclude with an exploration of ways to make water safe for human consumption.
- Identify different human activities that can pollute our water resources
- Use scientific equipment to test water quality
- Compare the quality of different water samples taken from the local watershed
- Describe local community impact on water resources
- Consider ways to better protect and conserve our freshwater supplies
Grade Level: 6-8
Two to three class periods
- Pollution Along the Rhine River QuickTime Video
- Water Treatment Plant QuickTime Video
- Earth Water Filter QuickTime Video
- Map of your local watershed (See the U.S. Environmental Protection Agency's Surf Your Watershed page for maps.)
- Aquatic Organisms Identification Chart PDF Image
- Provide a text on water quality factors, or go to the following Web site: Important Water Quality Factors
- For each group of two or three students:
- containers with caps for collecting water samples
- water samples from three or four locations along the local watershed
- dissolved oxygen kit
- four pH sensor or test strips
- water quality test kit (optional) (It can be ordered from Hach Company or 1-800-227-4224.)
- colored markers
∗Provide water samples only if students will not be collecting their own samples.
For each group of two or three students:
- Directions for how to make an Earth Water Filter HTML Document
- pitcher of water
- cotton (like cotton balls, a bandana, or an old sock)
Before the Lesson
The water quality observations activity (Part II) in this lesson can be done as a field trip or as an in-classroom activity. If you will be taking students on a field trip to collect their own samples, select three or four locations along the local watershed prior to the trip. Try to include locations of contrast. For example, you may want to take them to an area near heavily fertilized lawns and industry, as well as to more natural and less polluted areas upstream of these locations.
If students will be doing the activity as an in-classroom observation, collect water samples to bring to class. Select varied locations, as described above. Also, be sure to record information about each sample that students will not be able to observe in the classroom, such as:
- water temperature
- amount of dissolved oxygen
- types of organisms present in the water and under rocks
- other observations (e.g., visible signs of pollution near the water; human-made structures or sites located near each area — for example, factories, homes, or farms; plants or algae growing in or near the water; bare spots along the banks where you would expect to see plants; holes from animals in the banks; dirt or rocks falling/crumbling into the water)
Part I: Getting Acquainted with Your Local Watershed
1. Tell the students that they will be investigating the quality of the water in their community. To begin, they will discuss possible causes for pollution. Use the following questions to guide the discussion:
- What could pollute water?
- What are some ways that pollutants could get into the water? Is the source always visible?
- Can a substance get into the water in one place and travel to another? What are some examples?
- Can you think of any examples of pollution that you've heard about? Any examples of clean-up efforts?
- If you were given a water sample, how might you determine if it was polluted?
2. Display the watershed map and ask students to think about what could cause the water to be polluted in their area. For example, students can look for industry and housing developments along the watershed. List students' ideas on the board for later discussion.
3. Show the Pollution Along the Rhine River QuickTime Video and ask students to read the background essay that accompanies the resource. Have students add to the list any new ideas about causes of water pollution. (Remind them to include pesticides on their list if they do not include it on their own.) Also, discuss the following questions:
- How has the Rhine River since been cleaned up? What methods were used?
- Do you think the same problems occur in your local community? Why or why not?
Part II: Examining Pollution Levels in Your Local Watershed
4. Tell students that they are going to observe water from three or four different locations throughout the local watershed. Discuss what factors they should observe in order to accurately measure the quality of water in these locations. Have students construct a data table to collect these observations.
5. If students will be collecting their own samples, take them to the locations you have chosen along your local watershed. At each location, have students work in groups of two or three to collect water samples and record the following information:
- water temperature
- water clarity and color
- amount of dissolved oxygen
- types of organisms present in the water and under rocks. For reference, check out the Aquatic Organisms Identification Chart PDF Image
- other observations (e.g., visible signs of pollution in or near the water; human-made structures or sites located near each area, such as factories, homes, or farms; plants or algae growing in or near the water; bare spots along the banks where you would expect to see plants; holes from animals in the banks; dirt or rocks falling/crumbling into the water)
If students are doing an in-classroom observation, provide them with the water samples and observational information that you collected. Have students work in groups of two or three to observe the water clarity and color of each sample. They should observe the water when it is still, then shake it up to see if any particles had settled. Students can also look for any organisms present in the water.
6. In the classroom, have students test the pH level of each water sample. Discuss with students what these measurements tell them about the quality of the water samples.
(Optional: Have students use water quality test kits to test their samples for lead, bacteria, pesticides, and other contaminants. Be sure to instruct students not to taste their samples, to wear goggles while handling them, and to wash their hands after concluding their tests.)
7. Once they have finished collecting data, have students compare the differences in water quality among the different samples. To help students interpret their data, provide a text on water quality factors, or go to the following Web site: Important Water Quality Factors. Discuss the following:
- What, if any, differences did you observe in water temperature, number and type of organisms, and water clarity among the different samples?
- What could have caused differences in the amount of dissolved oxygen, types of organisms present, water color, etc.?
- Is there a difference in water quality upstream and downstream of a city or industry?
- Is there a difference in water quality where humans have had an impact?
8. Using the watershed map from Surf Your Watershed, have students mark the areas that they observed and color code them for water quality. Ask students what relationship they see between human population and water quality in their community.
Part III: Making Water Resources Safe
9. Water pollution affects the environment in several ways. It can be harmful to plants and animals that depend on the water as their habitat, and it can also limit the amount of water that humans have for drinking. Ask students to consider how water from lakes, streams, and other sources can be made safe for people to use. Show the Water Treatment Plant QuickTime Video and discuss the following:
- Why is it important to treat water before sending it to homes?
- What methods were used to purify water for human consumption?
- What is removed from water to make it safe for drinking?
- Fresh water is becoming more contaminated and scarce. What can people do to protect and conserve water supplies?
10. Sand and gravel may seem unlikely choices for materials to use to clean water, yet water has been filtering through these substances underground for millions of years. The result is spring water, some of the cleanest water on Earth. Show students the Earth Water Filter QuickTime Video and discuss the following questions:
- How effective were the filters at cleaning the water?
- What other materials could be used to filter water if you were on a deserted island?
- What other filtering materials could you use if you were going to do this experiment in your classroom?
- Divide the class into small groups and have them create their own water filters. For Directions, go to Earth Water Filter HTML Document.
If time allows, give students the opportunity to continue their study of local water quality. Have students conduct research to find out where their drinking water comes from and what happens to it between the source and the faucet. If they discover any potential sources for pollution, they can write a letter to a city or town official to share their findings and offer suggestions for ways to reduce or remove the source of pollution.
Check for Understanding
- Does the water quality in your local watershed vary depending on the proximity to human populations? Give specific examples.
- What are some sources of pollution in your local watershed and in global water resources?
- What steps can be taken to clean up existing pollution and prevent future pollution of local watersheds?
The Digital Library for Earth System Education (www.dlese.org) offers access to additional resources on this topic.