Lesson plan Grade 6 Science
Mapping the Kirby Brook Watershed: Tracing Pollution Sources
A 50-minute grade 6 science lesson where students map a fictional watershed, sort point and nonpoint pollution sources, and argue which one a town should address first.
Objectives
- Students will label the parts of a watershed on a map and trace how water flows toward the brook.
- Students will sort pollution sources into point sources and nonpoint sources.
- Students will construct a claim, supported by map evidence, about which source a town should address first.
Vocabulary
- Watershed
- A watershed is all the land where rain that falls will drain to the same stream, river, or lake. Everyone lives in a watershed, no matter how far from the water they live.
Also: point source, nonpoint source, runoff, outfall
Teacher overview
Kirby Brook runs through the fictional town of Millhaven and picks up whatever washes off the land around it. This lesson teaches students that the land draining to a stream is its watershed, and that pollution reaches the brook from two kinds of sources: point sources, which enter at one spot such as a pipe, and nonpoint sources, which wash in from a wide area such as lawns and roads. Students map the watershed, sort the sources, and build an evidence-based argument about which source Millhaven should tackle first.
Procedure
Hook (5 min): Ask students what happens to rain that falls on a parking lot, a lawn, and a farm field. Guide them to see that the water, and anything on the ground, runs downhill toward the nearest stream. Tell them that today they will map where Kirby Brook's water, and its pollution, comes from.
Direct instruction (10 min): Define watershed as all the land that drains to a body of water. Define point source as pollution that enters at one identifiable place, such as a factory or storm drain outfall, and nonpoint source as pollution that comes from many spread-out places, such as fertilizer on lawns and oil on roads. Give one clear example of each and post the two definitions where students can see them.
Map work (15 min): In pairs, students sketch the Kirby Brook map from the site list on the Student Handout. They trace the direction water flows toward the brook, shade the watershed boundary, and mark each pollution source site with a P for point source or an N for nonpoint source. Circulate and ask pairs to justify one of their labels aloud.
Argument writing (12 min): Each student writes a short claim answering the question, "Which source should Millhaven address first to protect Kirby Brook?" They must support the claim with at least two pieces of evidence from the map, such as how close a source is to the brook or how large an area it covers.
Share and formative check (5 min): Call on three or four students to read their claim and one piece of evidence. As a quick check, confirm that at least 80% of students correctly labeled the bottling plant outfall (Site 3) as a point source and the farm field (Site 2) as a nonpoint source; reteach the two terms briefly if fewer did.
Closure (3 min): Ask the class to name one thing a town can do to reduce nonpoint pollution, and one thing it can do about a point source, then collect the written claims.
Student Handout
Kirby Brook flows from the north hills down through Millhaven to the south pond. The land on both sides slopes down toward the brook. Sketch a map of Kirby Brook flowing north to south, and label these sites on it, from north to south:
- Site 1: A forest on the north hills, where the brook begins.
- Site 2: A large farm field on the west slope, where fertilizer is spread each spring.
- Site 3: A pipe (an outfall) from a bottling plant on the east bank, which releases water at one spot.
- Site 4: A neighborhood with lawns and paved streets on the west slope.
- Site 5: A parking lot next to a shopping strip on the east slope.
- Site 6: The south pond, where the brook slows down and collects.
Answer these questions on your own paper:
- Trace the path water takes from Site 1 to Site 6. In which general direction does the brook flow?
- Which single site is a point source? Explain how you can tell.
- Which sites are nonpoint sources? Explain what they have in common.
- Write a claim naming the source Millhaven should address first, and support it with two pieces of evidence from the map.
From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.
Answer Key
Water flows from the north hills at Site 1 downhill to the south pond at Site 6, so the brook flows from north to south. Accept any answer that describes water moving downhill from the forest toward the pond.
Site 3, the bottling plant pipe, is the point source, because it releases water at one identifiable spot rather than washing in from a wide area. This is the defining feature of a point source.
Sites 2, 4, and 5 are nonpoint sources: the farm field, the neighborhood lawns and streets, and the parking lot. What they share is that pollution washes off a broad area of land during rain instead of coming from a single pipe.
Answers will vary. A strong claim names one source and supports it with two map-based reasons, such as the source being close to the brook, sitting on a slope that drains straight into it, or covering a large area. Accept either a point-source or nonpoint-source choice when the evidence is drawn from the map.
Differentiation
Support
Provide a teacher-drawn version of the map with the watershed boundary already shaded and arrows showing the flow direction, so students can focus on sorting the sources. Give sentence frames for the claim, such as "Millhaven should address ___ first because ___ and ___."
Extension
Ask students to propose a simple monitoring plan for Kirby Brook: where they would take water samples, how often, and what a change in the samples might tell them about which source is the problem. Have them explain why a spot just below Site 3 would give different information than a spot above it.
ELL supports
Pre-teach "watershed," "point source," "nonpoint source," "runoff," and "outfall" with a picture for each, showing a single pipe for a point source and rain washing off a field for a nonpoint source. Allow students to label the map and answer questions 1 through 3 with words or short phrases.