Keywords: water quality, alkalinity, nitrate, pH, and biotic index; Lesson Plan Grade Level: ninth through twelfth; Total Time Required: one half-day at streams and two class periods; Setting: classroom and a local stream that passes through possible pollution areas such as cow pastures and other agricultural areas (along fields), or sewage treatment plant or urban area

Goals for the Lesson

  • Students will be able to accurately follow directions and complete water testing.
  • Students will be able to identify differences in the water quality of a stream.
  • Students will be able to collect aquatic insects and identify them using the chart and pictures and come up with an index value.
  • Students will be able to identify causes of changes and pollution in the water of a stream.

Materials Needed

  • water testing kits for testing nitrates, pH, chloride
  • thermometer suited for use in a stream
  • students who have waders or clothing suitable for wading in streams
  • gathering nets for catching aquatic insects
  • sieves, white dishpans, magnifying glasses
  • worksheets for recording information and clipboards
  • plastic jug for used water-testing chemicals
  • Biotic Index Card and key to orders of aquatic insects

State Standards Addressed: E & E: Renewable and Nonrenewable Resources (4.2); Environmental Health (4.3); Humans and the Environment (4.8)

Subjects Covered: chemistry, civics, and biology

Topics Covered: animal habitat, water quality, water testing, biotic index


Read over the lesson and understand the processes of water testing and biotic indexing. Choose a local stream that you would be able to visit and perform testing on both near its headwaters and after it has passed through agricultural land and pastures, for example. Make sure you can prepare all of the materials ahead of time.


Water quality is something that we should all be concerned with. Water is the most basic element needed for life to exist. Streams, in particular, are homes to countless kinds of wildlife, fish, and aquatic plants. They also give us a place for boating, swimming and fishing. Many streams having headwaters in forested areas are of fairly high quality near their source. However, as streams meander along their paths to rivers, bays and oceans, they are impacted (usually negatively) by humans. We are going to test the quality of this particular stream near its source and downstream after it has been impacted in various ways. We can then hopefully identify some of the causes of changes in the stream (if there are any) and come up with some ways to prevent water quality damage.


Class period before going to the stream

Determine which students will be doing what tests. Divide them out so that everyone has at least one job. Have the students who will be doing the chemical testing practice on tap water. This will give them some practice following the directions included in each testing kit and you can address any problems ahead of time. Review with students how to use the insect collecting equipment and review the aquatic insect key and biotic index card. Explain that the aquatic insects are divided up into 3 classes. Class I is the group that is most sensitive to pollution. Class III insects are the most pollution tolerant. Therefore the more insects found in the stream from Class I and II, the higher the quality of the stream. The lower the quality of the stream, the fewer the Class I and II insects, because they cannot live in that environment. Review the formula on the biotic index card and how to use it.

Visiting the stream and testing

Take the students to the stream near its headwaters and get them started on their testing. (Everyone should know what to do from yesterday.) Stress safety making sure that nobody gets hurt getting in and out of the stream. Also make sure that all used chemicals are deposited in the plastic jug (which should be labeled "toxic"). Make sure they record all of their information. Monitor the students to be sure that they are performing the tests correctly. Especially work with the students doing the biotic index helping them to ID the insects and letting them know when they have enough to count them. Collecting a total of 15-20 insects should be plenty for accuracy. After making sure all of the data is collected, load all of the equipment and head for the second testing site, which should be downstream of possible polluting areas.

Repeat all testing at the second site having the same students do the same testing. They may want to do something different, but results will be most accurate if the same ones do the same tests. Have students record all data collected. After gathering all the data and gathering up all the equipment, have all the groups share their information with each other so everyone has all of the information. They can then use the data to answer the questions on the worksheet.

Reviewing worksheet

The correct answers to the questions on the worksheet will vary with the results of the water testing and the area you live in. The pH and alkalinity may increase if the stream flows from a shale area into a limestone area. It may also change if there is some type of industry that can impact it. The temperature will most likely increase downstream, especially if the stream moves from a forested area into an open area where the sun can warm it. If the stream flows into a small dam and across an over a spillway, the temperature will also rise. This rise in temperature affects the wildlife in the stream. Trout, especially native trout, are sensitive to higher stream temperatures and this concerns many people. Students may be able to suggest planting trees and brush to shade the streams to help with this problem.

If the stream flows through agricultural areas, the nitrates may be high. Students should be able to point our fertilizers as possible sources for this. They may also be able to suggest some things farmers can do to prevent this pollution. These can include using buffer strips, avoiding over-fertilizing, avoid spreading of manure on frozen ground, and using grassed waterways.

The biotic index, then, uses nature only to gauge the quality of the stream. You will most likely see a reduction in the biotic index. After answering the questions, the students should be able to see why the reduction happened.


"This concludes testing our stream. Hopefully you can see that we do impact the quality of our streams. The biotic index alone showed that we do cause a change in the species of organisms present by our activity. I also hope that you see some of the specific causes of water quality problems and that you will do your part to minimize stream impairment."


  1. Have students fill out the worksheet after taking the water quality samples, answering all the questions.
  2. Collect and evaluate.


Swistock, Bryan and Sanford S. Smith (2001). From the Woods: Watersheds . University Park, Pa.: The Pennsylvania State University.

Sharpe, William E., William G. Kimmel, and Anthony R. Buda. Biotic Index.


James I. Over, Northern Bedford High School/ Agriculture