Lesson 4: Tracing a Path to the Sea

Lesson Information

Summary: In this activity, students use maps to trace the watershed linking their community to the ocean.
Duration: 30 to 40 minutes
Group size: Several groups of three to five people
Materials: Local, regional, and national maps showing waterways; Resource Sheet 2: Canada's Drainage Basins.

Learning Outcomes

Students will be able to describe their community's connection to the ocean and trace their watershed link to the ocean.

Background

Water flows from land to sea through the path of least resistance. Not all water will leave your community and reach the sea directly. Some will be diverted for human use or evaporate. But most will eventually flow into one of five ocean bodies — the Pacific Ocean, the Atlantic Ocean, the Arctic Ocean, Hudson Bay, or the Gulf of Mexico — depending on which of the five main drainage basins you live in.

Every day, the average Canadian sends about 400 litres of water — and the waste it contains — down the drain and to the sea. A typical path, if you live in the country, might begin with a septic tank. In most towns and cities, sewage flows through a long maze of pipes to a purification plant, although many communities skip this step. Freshwater then flows through a serpentine network of streams, ponds, marshes, lakes, and rivers that eventually empty into the sea. Finally, vast, surging ocean currents carry this water to distant shores.

Whether or not wastes and germs are removed before water is pumped into rivers, lakes, or the ocean itself, a lot of contaminants remain. They follow the same paths as the water itself, wreaking havoc on ocean communities.

Procedure

1. Before starting the activity, obtain maps of Canada and your province or territory showing major river systems. Ask your municipality for maps of local sewage systems and outflows if you do the optional section below. Make copies of the Canada's Drainage Basins [link to Resource Sheet 2] map for each group.
2. To begin the lesson, discuss the fact that water, once used by humans, is often polluted with sewage, used motor oil, old paint, and other hazardous wastes that can have a devastating impact on aquatic habitats and the communities that depend on them. Ask what happens to sewage from your school, home, and community once it goes down the drain. Explain that the class is about to explore that question further.
3. Divide the class into groups of three to five students and give each a copy of the Canada's Drainage Basins [link to Resource Sheet 2] map, provincial or territorial maps, and a map of Canada showing major river systems. Have each group trace the route from its community to the ocean. Ensure that students know which ocean body receives the water flowing from their community.
4. As an optional step, hand out local sewage system and outflow maps. Trace the passage of wastewater from your school to a purification plant and local waterway.
5. Ask students to create a "flow chart" on a long sheet of paper — drawing and labelling the path a single water molecule or contaminants would take from drain to sewer to purification plant, local waterway, major river, and on to the ocean.
6. Discuss the following points:
• Humans and wildlife along the route are negatively affected by the contaminants coming from your school and community.
• Water and contaminants from your community will eventually go to the ocean.
• There are other ways that contaminants can travel long distances to the ocean. (For example, acids, heavy metals, and organic materials that are incinerated become air pollutants that can travel around the globe on air currents. We call this phenomenon "long-range atmospheric transport".)
• Contaminants from your community cause problems in ocean communities.
• In the next activity, your students will examine what types of pollutants go down their community's drains.

Evaluation

1. Have your students identify the drainage basin where their community is located and the ocean their wastewater flows into.
2. Have students trace the possible path of a plastic bag that enters a local waterway and ends up in the sea.
3. Have students write a story of the journey of a water molecule, from the drain in their home to the ocean.