What in the World is a Watershed?

Transcription

1 What in the World is a Watershed? LESSON GRADE LEVEL 4-9 CATEGORY Water, Wetlands and Watersheds TOPIC Watersheds and Watercycle LENGTH Part 1: a 60-minute period Part 2: two 60-minute periods SETTING Classroom or outdoors GROUP SIZE Groups of 2-4, whole class SKILLS Observation, modelling, predicting SUBJECTS Social studies, science, language arts KEYWORDS Watersheds, water cycle, drainage, earth systems MATERIALS Part 1 For each group: paper for each group, one container at least 22 cm wide, 33 cm long, and 6 cm deep (a metal baking pan will work fine), two sheets of newspaper, one sheet of thin plastic at least 20 cm larger in all dimensions than the container, one spray bottle one book, baby powder, blue food colouring. Part 2 Box construction - one sheet of plywood approximately 4 x 6 or 4 x 8 feet), 1 by 4 inch boards the same length as the plywood edges, gutter material the length of the short edge, screws or nails, plastic sheeting or silicone caulking, bricks or other materials to prop up the box, sand, stones and other materials for model landforms, sod, carpet or other materials to simulate vegetation, hand gardening tools, a watering can with a fine sprinkler. Note: for artifacts such as houses, cars, schools, hospitals, trees, etc. consider borrowing pieces from board games or Lego. Secondhand stores will likely have a selection of toys that will serve as model components. Overview The following activity demonstrates how watersheds drain into streams, rivers and eventually, lakes, and how pollutants are carried from watersheds to bodies of water. The activity also demonstrates the relationship between small and large watersheds. Students will discuss, draw, create and then make observations about watersheds in general and then their specific watershed. In the second part of this activity, students apply their understanding of watersheds and modeling to make a model that reflects their own community watershed. They will describe aspects of human-watershed interaction as they exist in the students own backyard. Objectives It is expected that students will be able to: Define and describe watersheds Explain how the water cycle affects their watershed Recognize that bodies of water are the end product of drainage from watersheds What in the World is a Watershed? 1

2 Predict where the water and pollutants will flow Observe the end results of polluting within a watershed and how it impacts bodies of water Background What is a watershed? Imagine a raindrop falling to the ground. If you were watching rain drop fall at the top of a mountain ridge, some of the raindrops would flow down one side of the mountain, while others would flow down the other side. The raindrop would then move downhill towards a stream or a lake or a river. The area of land where all water moves into a river or stream is called a watershed. It has a unique size and shape. Watersheds can be big, like the Fraser River watershed, or small, like the watershed of a puddle in the playground. Another way to model a watershed is to think of the roof of your house. At the top of the roof there is a ridge dividing the parts of the roof. Imagine a raindrop falling on one side of the roof. Watch it run down the roof area into the gutters. The gutters collect all the water from the roof. The water in the gutter then flows to the downspouts and out into your yard. In this case, the roof is the watershed, the gutters are streams, and downspouts a river flowing into the ocean. Take a look at your own roof and see a watershed! Scientists create models to study systems and make predictions about how they will react under a variety of circumstances. These models allow scientists to control and change variables without actually affecting the systems that they are studying. One way to create a simple model of a watershed is by using a piece of paper that has been crumpled into a ball and then gently opened but not flattened out completely. The highest points on the paper represent the mountains and the lowest, the valleys. To determine the watershed boundaries, one must ask If a drop of water is placed along the ridges of the paper (mountains) which way would it flow? The bowl-like drainage area where the imaginary drop flows is a watershed. Another way to imagine a watershed is to think about it as nature s version of an immense drain board with water drops flowing down the drain board into a sink. Watersheds in British Columbia have considerable diversity of ecosystems. Ecosystems are interacting complexes of living organisms (plants, fungi, bacteria, and animals) and the physical environment (soil, air, water, and bedrock) immediately affecting them. Within an ecosystem, there is a dynamic and complex interaction among organisms and their physical environment. These systems are varied in terms of topography, geological features, soil types and climate. The physical conditions in a particular watershed influence which plants and animals will be found there. Certain species may be limited to small areas of the province, while others will be found nearly everywhere. A person is usually never far from a Douglas-fir or grand fir, yet Rocky Mountain juniper is found only on Vancouver Island in B.C. Watershed ecosystems are varied from alpine meadows, estuaries, forests, valley bottoms, and wetlands. All play an important role in shaping and maintaining the health of a watershed. For thousands of years, our watersheds have provided a water-rich habitat for plants, animals and people. People use watersheds in a variety of ways. Many watersheds supply our domestic (household) water. Watersheds sometimes have forest harvesting and logging, mining or other resource extraction activities. Watersheds supply water for industrial uses from laundry-mats to factories. Different cultures and communities have different uses and views of water and watersheds. For example, the people of the Kalahari Desert often collect their water from dew and carefully use every drop. Canadians, because of our vast water supply, use 45% of their home water consumption just to flush the toilet! Only 5% of water used in Canadian households is for cooking and drinking. The Water Cycle. The water cycle connects all parts of a watershed. As water changes form as precipitation (rain/ snow), evaporation, condensation, and transpiration it travels throughout a watershed in the water cycle. Solar energy causes evaporation of water from soils, plants, oceans, lakes and streams. Gravity causes condensed water vapour to flow back to a watershed in the form of rain, snow, hail, or sleet. Energy, gravity, and plants, animals, and people all influence the water cycle in a watershed. As we gain a better understanding of our own local issues such as water use and water quality, we are better able to make informed decisions about how our actions affect our environment and others in our community. Students can integrate their understanding of watersheds and related human activities from previous activities to better understand the water that sustains them and their communities. With knowledge and understanding comes responsibility and choice. As students construct and model aspects of their own watershed, they will come to understand how their own activities directly affect their own water supply. What in the World is a Watershed? 2

3 Other Names for a Watershed A river or lake basin A drainage A catchment area A greater river valley The headwaters area (for upper watershed) A river and its tributaries Watershed Features Mountains Valleys Soils Rocks Streams and rivers Lakes and ponds Estuaries River deltas Riparian areas Forests Wetlands Cities and towns Procedure Part 1: Building Watersheds in Small Groups 1. Ask students to write down their own definition of a watershed. Have them share with a partner and then solicit possible definitions from the class. Provide these definitions to supplement students ideas: A watershed is a geographic area in which water, sediments, dissolved nutrients, and organic matter all drain into a common body of water such as a lake, stream, or ocean. A watershed is a place for all the plants, animals, and people to live in. A watershed is like a giant catch basin that catches rain and snow and funnels it into a big body of water like a lake or ocean. 2. Divide students into groups of three or four. Each group will need a container, two sheets of newspaper, one sheet of plastic, one book, some baby powder (or soil) and one spray bottle filled with water and a few drops of blue food colouring. 3. Crumple each sheet of newspaper separately and place them next to each other at one end of the container. Try to vary the shape of the two. Place the sheet of plastic over the crumpled newspaper, causing it to form hills over the high places, and streams and rivers in the low places. Put a book under the end of the container with the newspaper, which will allow water to flow down the streams and rivers and collect in the lake at the front of the container. The sides of the plastic sheet should be placed down into the container. 4. The plastic sheet represents the ground surface covering the watershed. Encourage students to study the watershed model and try to predict where the main rivers will flow. Now put the model to the test. Spray several pumps of water from the spray bottle on the model. Notice that each stream has its own watershed (the area that drains into it) and that the entire model is a larger watershed because all the water eventually flows into the pool at the bottom of the container. Have students count the number of small watersheds. After reviewing the water cycle with students, ask them to list ways in which the water cycle could affect their watershed model. 5. This watershed model represents a clean watershed. As no watersheds are completely contaminant free, have students add pollutants so as to reflect water contamination. Sprinkle a little baby powder over the model. The baby powder represents a variety of pollutants, including oil, road salt, animal manure, excess fertilizers, pesticides, tiny particles of soil and other harmful materials. Rapidly spray nine pumps of water over the upper portion of the watershed. Observe the way in which the pollutants are carried by the water and the end condition of the lake. Repeat if necessary. Part 2: Building a Class Model of a Watershed Options: 1. For younger students, you may want to make the model in advance or create the model from a water table and use it as an activity station for a small group study. 2. If you have access to a natural area, find a spot with open, sloping ground, uncovered by grass or other vegetation. A loose sand or gravel bank is ideal. Use a garden hose or buckets of water to create a landscape, letting water flow downstream across the bank. Be careful to keep the water flow quite low and gentle you are modeling a river on a small scale. What in the World is a Watershed? 3

4 Procedure Prior to the activity, you and your students may want to spend some time gathering information about your local watershed. This may involve consulting community maps, the local Chamber of Commerce, GoogleEarth, etc. Armed with research about the geography of your watershed, you are ready to begin constructing your model. For older students, combine this activity with a lesson on scale and more advanced map reading skills that will enable students to create a model that is to scale and accurate in layout. Creating the watershed box 1. Screw or nail the boards to the edges of the plywood to make a box. 2. Drill holes in one of the short boards so that water will run out of the box. 3. Attach the gutter to the short board so that it will catch water from the holes. On one side, attach the gutter at an angle to run the water into a basin. 4. Use the bricks to prop up and support the end of the box opposite the holes. 5. Line the box with plastic sheeting or seal the edges with silicone caulking. Creating the watershed 1. Use the sand or dirt and rocks to begin laying out the outline of your watershed. If you have been able to determine where there are sandy places along the watershed, use the sand to shape these areas, as well. 2. Use the sod or carpet to create green belt or riparian areas of the watershed. 3. Add human components of the watershed (schools, houses, yards, cars, etc.) and larger natural objects like trees, lakes, ponds, etc. 4. Now you can use your watering can to make it rain! Be careful, though, a downpour can sometimes wash away parts of the landscape! Have students discuss how well the model reflects actual conditions in you own natural watershed. If necessary, prompt them to consider: How does this model compare to the reality of their own watershed? What are the similarities? Differences? What possible pollutants exist in their own watershed? What could students do to improve the health of the watershed? Assessment Part One 1. Draw and label their watershed. Have them illustrate how the water cycle would affect their watershed. 2. List the features of a watershed. 3. Explain how watersheds become polluted. 4. Describe some possible solutions to keep bodies of water clean. Part Two 1. Review students written observations and conclusions and monitor class discussions to ensure that the students can describe environmental and human factors that influence the watershed. 2. Ask students to record their observations and conclusions in their notebooks. Have them describe how well their model reflects actual conditions in a natural watershed. Possible question prompts include: Where did the water flow in the model? What evidence did you see that the water changes the landscape? What was the effect of increasing the water flow? Were the effects the same in all parts of the model? 3. Have students make posters, pamphlets and/or displays identifying actions that students can take to protect natural water. Brainstorm assessment criteria with students. Criteria may include: Givens (title, name, date, proper spelling, colour, etc.) Clearly defined audience and issue Background information How to get involved/how to help resolve any issues they have identified What in the World is a Watershed? 4

5 Extensions 1. Invite a member of a community group such as a Fish and Wildlife Club, Streamkeepers or Naturalist Club into your class to discuss local watersheds and describe related stewardship activities. 2. Have students research the variety of ways that different cultures interact with their local watersheds. What kinds of cultural differences do they notice? Challenge students to examine how interactions with watersheds are affected in different regions by population, poverty, industry, religion, other. What in the World is a Watershed? 5