Local Hydrologic Cycle

Transcription

1 Overview: In this lesson, students review the components of the hydrologic cycle, illustrate the water cycle in their communities, and explore the impacts of climate change on local observations of the water cycle. Objectives: The student will: identify and describe the parts of the hydrologic cycle as observed in the local area; and identify at least one way that global climate change may impact the water cycle in the local area. Targeted Alaska Grade Level Expectations: Science [7-8] SA1.1 The student demonstrates an understanding of the processes of science by asking questions, predicting, observing, describing, measuring, classifying, making generalizations, inferring, and communicating. [7] SD1.2 The student demonstrates an understanding of geochemical cycles by explaining the water cycle s connection to changes in the Earth s surface. [8] SD1.2 The student demonstrates an understanding of geochemical cycles by applying knowledge of the water cycle to explain changes in the Earth s surface. Vocabulary: condensation the process by which a gas or vapor changes to a liquid by cooling or by increased pressure; this is how clouds are formed evaporation the process by which a liquid changes to a gas or vapor at a temperature below the boiling point; most of the water vapor in the atmosphere has evaporated from Earth s surface infiltration the movement of water from Earth s surface through the subsurface (soil and rock); some of this water replenishes ground water supplies called aquifers precipitation water that falls to Earth s surface in the form of rain, snow, hail or sleet runoff overland flow of water to a river, stream or ocean sublimation the process of changing from a solid to a gas without passing through an intermediate liquid phase (such as ice and snow to water vapor) transpiration the release of water vapor from plant leaves Whole Picture: The hydrologic (water) cycle is the continuous movement of water through Earth s ecosystem. The hydrologic cycle is a dynamic system that interacts with other parts of Earth s ecosystem, tying together the land, ocean, and atmosphere. Water continually changes form, moving throughout the hydrologic cycle, but the overall amount of water in the system remains fairly constant. Many factors influence the movement of water through the local environment. These include: latitude, topography, season, and human activity. Global climate change may profoundly influence the way water moves through the hydrologic cycle. Warmer temperatures can cause an increase in evaporation and transpiration. Depending on local topography this could mean increased water vapor, clouds and precipitation leading to more runoff and flooding. Other areas (further from large bodies of water) could experience drier soils, less precipitation and drought. The Arctic and subarctic regions could experience melting sea ice, rising ocean levels, flooding and decreasing ocean salinity. Increased surface temperatures can thaw permafrost causing an increase in the infiltration of water through soil, draining wetlands and lakes. All of these changes in the physical environment can cause subsequent changes in the biotic (living) community. Hydrokinetic energy is derived from harnessing the kinetic (moving) energy of rivers, streams or tides to spin a turbine and generate electricity (much the way a windmill uses moving air). Hydrokinetic turbines have been 61

2 tried in the Yukon River near the villages of Ruby and Eagle, Alaska. Although Alaska has tremendous potential for developing hydrokinetic power sources due to the abundance of rivers and tidal areas, the extreme seasons pose a considerable challenge. The presence of ice, debris, and fluctuations in flow can severely impact the functionality of a hydrokinetic system. Materials: Two ice cube trays Three clear containers of approximately equal size (at least one pint) Dirt or other loosely packed substance such as cornmeal or sifted flour (enough to fill all three clear containers to within an inch of the top) Pitcher or other vessel containing enough water to pour into the containers above Large piece of white paper Crayons and/or colored pencils or pens Two containers of equal size to fill with snow (if there is snow on the ground) Two pieces of tape STUDENT WORKSHEET: The Hydrologic Cycle in My Community Activity Preparation: 1. One week prior to this activity fill one ice cube tray (or other container) with water and place it in the freezer. Fill two of the clear containers with 1-2 inches of water and place in the freezer. 2. One day prior to this activity, place another ice cube tray in the freezer. Make sure that the same amount of water is added to each tray. Fill one of the two clear containers (now containing 1-2 inches of ice) with dirt (or other substance) and place it back in the freezer. 3. The day of the lesson, hang the large piece of white paper up in the classroom. Choose a spot that is easily accessible and visible to the whole class. Be sure the pitcher is full and accessible. Just before the lesson you will need to take the ice cube trays and the clear containers out of the freezer and fill the remaining two clear containers with dirt. You should now have: two ice cube trays (frozen), one clear container with only dirt, one clear container with ice and frozen dirt, and one clear container with ice and unfrozen dirt. 4. The morning of the lesson you will need to take students outside to collect snow samples. If there is no snow available at the time, eliminate this step. Activity Procedure: 1. If this lesson is conducted when there is snow on the ground, take students outside first thing in the morning to collect two samples of snow. For one sample, simply fill the container without packing it down. For the second sample, pack the snow as tightly as possible into the container. Label the loosely filled sample A and the tightly packed sample B. Put these samples aside until you are ready to conduct the rest of the lesson. 2. Introduce the water cycle (also known as the hydrologic cycle) as the circulation of water throughout Earth s systems. Explain the class will be working together to draw a large picture of the water cycle in their town/ village. This will be done on the large piece of white paper (see Activity Preparation). 3. With input from students, start by drawing the local topography. Include nearby hills or mountains, forest or tundra and at least one body of water (river, ocean, lake). Add the school and other important buildings and roads. 4. Ask students to come up, one at a time, and draw other places where water can be found in this picture. Examples include: clouds, rain/snow, ice, water vapor, plants, and people. 5. Ask students if the water in these places is fixed or in motion. Does the water in your town/village always stay in this area? Does the water in your body stay there? Work together to build a word bank (using the vocabulary list) to describe the movement of water through the local ecosystem and beyond. (Be sure to include: evaporation, transpiration, condensation, precipitation and runoff. Include sublimation and infiltration if students suggest them, but if not leave them off at this point. Both will be introduced and illustrated in the following demonstrations.) 62

3 6. Explain they will now investigate two less visible but important parts of the water cycle. Remove the frozen ice cube trays and clear containers from the freezer. Fill the remaining clear containers with dirt as described in Activity Preparation. 7. Begin with the ice cube trays. Ensure students have the opportunity to carefully observe each tray and ask the class to share observations. Generate predictions about any differences students observe and report. 8. After this discussion, explain that the same amount of water was placed in both trays. One tray was put in the freezer yesterday, the other one a week ago. Students should see that the tray placed in the freezer one week ago has less ice in it. Refer back to the water cycle drawing and ask students to chose a word that may describe this observation. The tray that has been frozen for a longer period of time shows evidence of sublimation. Some of the ice changed into water vapor without first changing into liquid. Ask students to add sublimation to the water cycle drawing (if it wasn t suggested initially). 9. Move on to the clear containers. Remember you should have three: one with dirt but no ice, one with ice and dirt, and one with ice and frozen dirt. Pour water into the clear container with only the dirt. Ask students to describe what they see happening. Introduce the term infiltration as the downward movement of water through soil. Some of this water pools and becomes groundwater (called an aquifer). Aquifers provide an important water source for people who tap them when they dig wells. Some of this water may seep back to the surface in the form of a spring. Sometimes groundwater is heated by magma and rises to the surface as a hot spring! Ask students to add infiltration to the water cycle drawing (if it wasn t suggested initially). 10. Pour water through the two remaining containers and ask students to share their observations. Ask students to suggest why/how this relates to the water cycle and to the Alaska landscape. The ice represents permafrost and the dirt represents the active layer (frozen in winter, thawed in summer). In areas of permafrost, water generally can not infiltrate the soil and is held in the active layer creating moist soils and wetlands. If permafrost melts (due to increased intensity and duration of summer heat), more water may infiltrate, drying soil and draining wetlands. This may change the plants and ultimately animal communities of the Arctic and subarctic regions. 11. Pass out STUDENT WORKSHEET The Hydrologic Cycle in My Community. Read aloud and complete the worksheet as a class. Extension Ideas: 1. Ask students to write a story or poem from the perspective of a water drop traveling through the water cycle in their community. 2. Find photographs of the local area and ask students to label the components of the hydrologic cycle. 3. Create a diagram illustrating the path of drinking water in your community (from the place of precipitation to the tap). This can be done individually, in small groups, or as a class. 4. If you have a plant in your classroom, lightly water it. Then loosely cover the plant (or one branch if it s a large plant) with clear plastic wrap or a paper bag. Gently secure the plastic around the pot (or base of the branch) with some tape. Make sure you tape the pot or the plastic around the branch instead of the plant itself. Wait a few days and water will start to form on the inside of the plastic. What is happening? How does this relate to the hydrologic cycle? Answers: STUDENT WORKSHEET: The Hydrologic Cycle in My Community 1. Answers will vary. Responses may include: river, well, creek or stream, catch basin, etc. 2. Answers will vary. Responses may include: bathing, drinking, cooking, brushing teeth, washing dishes and clothes, flushing the toilet, etc. 3. Answers will vary. Responses may include: fishing, travel (boat or snow machine), fish wheels, swimming, etc. 4. The compacted snow produces more melt water. This is comparable to Tsitle tu or bottom snow which is compacted by the weight of the snow above it. Top snow (or the loosely packed snow) contains a lot of air space. 63

4 5. Answers will vary. Responses may include: drinking, washing, etc. 6. Answers will vary but may include local creeks and tundra pools. 7. Answers will vary but should include: the flow of small local streams into larger rivers and eventually to the ocean; the runoff of precipitation into local streams and rivers; the sublimation of snow and ice; the condensation of clouds; the precipitation of rain and snow, etc. 8. Water can not infiltrate permafrost or frozen soil. This creates moist soils and wetlands. If permafrost thaws, more water may move through soil, draining wetlands and creating drier conditions. Different soils and fewer wetland areas will change the plants and eventually the variety animals that can live in an area. Another correct answer not necessarily covered in this lesson is warmer temperatures will result in increased evaporation and transpiration from Earth s surface. 64

5 Name: The Hydrologic cycle in my community Directions: Read the following real life water facts about three Alaska communities, then answer questions about your community. Teller s municipal storage tank is filled during the summer by truck. Water comes from the Gold Run River (20 miles away). In winter, water is delivered from a large tank at the washeteria or melt ice is used from local creeks. Coyote Creek serves as the source for the school s water tank. Total storage in Teller is 1.1 million gallons. Teller s 2005 population was around 260. White Mountain s municipal water supply is a well. Its tank holds 150,000 gallons. Water is piped to most households. White Mountain has about 220 residents (2005). Shishmaref sits on a small island and has limited freshwater resources. Although there is a central water system in place, most people still collect water by traditional methods such as collecting rain and snow and hauling ice from tundra ponds. The washeteria, is supplied from a lined catch basin in which snow is captured with the help of snow fences in winter. Three hundred thousand gallons of storage is available and Shishmaref has about 580 residents (2005). 1. In your community, where do you get water for everyday use? 2. Name at least three things everyone in your home uses water for every day. 3. Other than everyday uses in the home, what are two other uses for water in your community? Directions: Read the following description from Elder Evelyn Alexander about how water was traditionally obtained in winter. Answer the questions after each paragraph. Tsitle tu means snow water. We taught the kids to dig to the bottom to get the snow there. Yeth uga, bottom snow. Kind of little bigger than the top snow. You fill up a bucket like this, the water will be this much for the top snow. But if you get the bottom snow the water will be almost full. More water comes out of the bottom snow. Anyway they used to say clear water, cleaner than top snow. All winter we used snow water. Springtime come we use water, but sometimes we go around in canoe we look for snow drift. We get snow. We save it for drinking water until no more snow, until in June. Sometimes late June. Out in camp. We stay out in camp. They make cellar and they keep snow in the cellar. Tanana River, when ice move we put ice to shore. We cut them up and haul back to our house. Most of the people used to have cellar. We keep ice there. Òut tso k a drighila means ice cellar. Sometime when the water come it is a little bit muddy, you know. Lots of little grass, gotta settle them. Lots of little bugs sometimes. We have to boil them and settle it. I haven t seen that for a long time. We don t do that no more. If I move I ll take that snow, maybe I ll save ice. We get ice too. Clear water. Snow water, tsitl tu. We use that for tea and drinking. It tastes better than well water. 65

6 Name: The Hydrologic cycle in my community 4. Look at the samples of snow you collected earlier today. Which one do you think contains Yeth uga? Why? (If you were not able to collect snow samples, would you expect a sample of Yeth uga to produce more or less liquid water then the same size sample of top snow? Why? 5. Do you ever use Tsitle tu? If so, describe how you use it. Directions: Read the following story by Elder Robert Charlie of Minto about water and the rivers around his community. You got to have water when you re out hunting. Out from Minto when we go out traveling in the high country we never camp on top of those high ridges because there is no water there. You go down to a lower level where you can find puddles from rain or where the water has come up from the permafrost underneath. If you can t find water you can do like the animals do and kick a hole in the moss with your foot. In a little while that hole will fill up with water and you can use that to make your tea. Our ancestors learned how to do that from watching the animals. Another thing is you can look down from the top of one of those ridges and see a patch of willows and you know that a creek is there and you can find water. But you don t want to get water out of any place where there is beavers, because they make the water bad. But they re good to eat if you cook em the right way. If you are hunting or traveling in the wintertime you have tea then go a long time til you stop and rest. Then you melt snow and make tea and rest and drink as much as you can. Then you don t stop again until you get where you are going. You don t eat snow, though it is water. Snow makes you tired and makes you more thirsty. If you are chasing a moose and you see that moose licking snow up you know you are gonna get him because he is tired. If a moose leaves a hoof mark on the snow and doesn t sink in and make a hole you know he is saying, You ll never catch me! 6. Think about Elder Robert Charlie s description about where to find water when you are out traveling. Describe or draw at least one place where you could find water if you were out hunting, berry picking, or walking around your community? Identify or add this place to the large drawing of the local water cycle that you made as a class. 66

7 Name: the hydrologic cycle in my community Elder Robert Charlie also describes the water and rivers in and around Fairbanks: If you stand on top of one of those high ridges you can see how all the water is connected. Where you are is the headwaters of a little creek and that flows into a bigger stream like the Goldstream then they flow into bigger sloughs like the Chena and rivers like Chatanika and Tolovana, then it all comes down to the Tanana, then to the Yukon and that runs all the way to the ocean. It s all connected. 7. Think about the water sources your class identified on the large drawing of the local water cycle. How are they connected? If your drawing contains a river, does the river flow into the ocean or a larger river? 8. Describe at least one way global climate change could affect the water cycle in your community. 67