Lesson 6 A Source of Fresh Water Wilderness Watersheds

Transcription

1 SCIENCE Lesson 6 A Source of Fresh Water Wilderness Watersheds Objectives: Students will: understand common U.S. Geological Survey map symbols including contour lines. choose a river and trace its tributaries upstream to the headwaters and its source(s). identify watershed basins for the river they have chosen. list and explain three factors which can affect water production and quality before it reaches developed urban or farm areas. explain why Wilderness areas are considered important sources of fresh water. Duration: 1 to 2 class periods Location: in the classroom Background: Wilderness areas often encompass water drainage areas know as watersheds. Mountains, and the valleys and basins that they surround, drain water toward the lowest point, which may be a lake or a river that continues to flow down to the next collection area. These water collecting areas are often the source of fresh water for human uses of all kinds. Not only do we need sources of fresh water to drink, but we use fresh water in almost everything we do. All plants and animals require fresh water. Water is the medium of all life processes. It transports nutrients as it flows through soil and living matter. Water also removes and dilutes many natural and artificial wastes. A watershed includes the mountains and hills upon which rain and snow fall, the streamlets that the water sheds into, the rivers that collect the water of the streamlets, etc. It is the rivers that people often think of when considering water conservation practices such as dams, canals, and reservoirs. We need to expand our thinking to the source - the headwaters of the streams; the basins and valleys that drain into them. It is important to realize that our supply of fresh water is based on the intricate workings of a healthy ecosystem. The oceans hold 97 percent of the Earth s water. Less than 3 percent of the Earth s water is fresh and most of that is frozen in the North and South poles. At any given time, only 0.03 percent of the Earth s water is flowing in streams or river channels readily available for human use. Page 387

2 SCIENCE Á Background continued: Most of the Earth s fresh water is underground. Groundwater fills the spaces between sand an gravel particles, or cracks in bedrock. It collects in aquifers. People sink wells into these aquifers to pump water out for drinking, irrigation and industrial use. Water from rivers and runoff often travels through layers of sand and gravel to recharge the aquifers, renewing the underground water supply. The quality of water from an aquifer is partially dependent on both the quality of water in the river, and the integrity of the watershed that supplies it. Activity 1 and 2 can be used to teach map reading skills if students have not learned these skills, or use them as a quick review and refresher before doing Activity 3. Activity 3 will apply map reading skills to identify a watershed on topographic map. Activity 1: Map Symbols Bingo Background: Map reading skills are some of the most challenging outdoor skills to learn, but they can be among the most satisfying. As with other elements of the Wilderness and Land Ethic Box, these activities are not intended to be a comprehensive curriculum in orienteering, but rather, a basic introduction to those map reading skills that will be most useful in beginning wilderness travel. A map is a reduced representation of a portion of the surface of the Earth (Kjellstrom, 1976, p. 8). A topographic map is a map that shows the three dimensional features of the land s surface in two dimensions. Topos = place; Graphein = to write or draw (Kjellstrom, 1976). Where to purchase maps - U.S. Geological Survey, and local outdoor and sporting goods stores. Materials: Í Topographic maps One copy of the Map Symbols legend, page 393 Map worksheet, pages Scissors Rulers Paper, pens A hat or other container for bingo symbols Procedure: 1) Prior to the beginning of the activity, cut up one set of symbols to be drawn out of a hat in the bingo game. Page 388

3 SCIENCE Procedure continued: 2) Introduce the Í Topographical maps by dividing students into groups, giving each group a map to look at. Ask them to tell you what they notice about this map that is different from others they have seen. Some will mention the funny brown squiggly lines, but others may point out the small pictures of bicycles, tents, or dashed lines. Highlight the symbols list on the front of the map, and go through the symbols one by one, so that students focus on them enough to learn what they stand for. Have them try to find examples of some symbols on the map itself. 3) Now it is time to play Bingo. Each student will need to draw a bingo card, four boxes wide by four boxes tall, on a piece of paper. Each student should cut out individual pictures of all the map symbols, and place any 16 in any order in the boxes, one in each box. No fair attaching the name of the symbol to the picture. The point is to learn what the symbols stand for! If you think cheating may be a problem, students can glue symbols onto boxes. 4) Select symbols randomly out of your hat in the front of the room, and read off the name of the symbol, e.g., mountain bike route, Wilderness boundary, or unsurfaced road-high clearance. Students mark an X over that symbol on their card. The winner is the first to correctly identify four symbols in a row. You might wish to play several rounds, or continue playing until everyone wins. Debrief at the end by asking if there are any symbols that anyone is still confused about. Evaluation: Test students on defining each map symbol they have learned about in the Bingo game, or use the enclosed map worksheet with a map, and evaluate. Activity 2: Reading the Land - Contours! Materials: Í Topographical maps Contour lines worksheet and quiz, pages Procedure: 1) Show students the topographic maps again, and remind them about the brown squiggly lines. Explain that contour lines are lines that represent elevation. In other words, if a person were to walk along such an imaginary line, she would never climb or go downhill. It would always be level or flat. Contour lines are a way of illustrating three-dimensional changes in topography, such as mountains and valleys, on a two-dimensional picture--a topographical map. 2) Distribute the topographic maps to small groups. Ask students to examine mountains, cliffs, ridgelines and valleys. Ask them to describe which way streams are flowing. Trace a stream all the way from its source to its exit off the map. Evaluation: Photocopy a section of a topographic map with a variety of land features. Ask students to label five to ten land features. Hand out the Contour Lines worksheet, page 376, and the Contour Line Quiz, page 399, following this lesson. Page 389

4 SCIENCE Á Activity 3: Mapping a Watershed Materials: map of a Wilderness in your region or topographic maps of the area overhead transparencies of river drainage areas, make copies from pages several highlighter markers copies of student handout Watershed, page 392 or put handout questions on an overhead or chalkboard copies of one or more river drainage areas one for every two to three students, pages Procedure: 1. Locate a map of the Wilderness nearest your school. Select a river or creek drainage, make copies for the students and overhead transparencies. 2. Introduce the topic of the lesson and the objectives. Using the overhead transparency show students how to determine the origin of the above ground water that comes from a Wilderness or other public land area. 3. Using a highlighter, find where the river is large and obvious. Find where it leaves the Wilderness. Begin to trace back upstream to the sources of the river. Highlight the lines representing rivers, streams, seasonal streams and streamlets as far as indicated on the map. Include all branches that are directly feeding the major river, i.e. trace all of the tributaries that flow into the river. See the example from the river drainage area student handout, page After highlighting all of the tributaries, go back to the map and identify the highest points around the area you have highlighted. Connect the tops of the ridges and mountains that surround the areas that contain your highlighted streamlets. The drainage for the river you have chosen is the land mass you have outlined. This entire area is the watershed for that river. Discuss the following questions with the students: Estimate how many square miles this area covers Where does the snowmelt and rainwater go? What towns or farms or other developed areas depend on this water? If not readily apparent, trace where your river travels does it lead to another river, lake or reservoir that is an important source for humans? What is the topography of this watershed? What types of ground cover are there? Ask students to repeat the exercise using the photocopied maps and handouts. Follow-up: Discuss the students answers to the questions from the Student Handout Watershed. Page 390

5 SCIENCE Evaluation: You may evaluate the students on their participation, successful completion of their handouts, thoroughness of their identification of all of the drainages on their map. Extension: Ask students to trace the origins of the water which is used in their home. This can include who the suppliers are, where their reservoirs or aquifers are, is there a different supply when levels drop in the winter, etc. Ask students to research the management of a local river or watershed. Find out how much water is removed for human purposes and what effects it has on downstream ecosystems. Have students map human settlement in their region - what habitat do humans prefer? Career Options: hydrologist, forester References: The Clark Fork Watershed Education Program, Missoula County Conservation District Understanding the Game of the Environment, USDA Forest Service Agriculture Information Bulletin No. 426 Washington, D.C Page 391

6 SCIENCE Á Activity 3: Mapping a Watershed STUDENT HANDOUT WATERSHED Directions: 1. Using a highlighter, find where the river is large and obvious. Find where it leaves the Wilderness or National Forest. Begin to trace back upstream to the sources of the river. 2. Highlight the lines representing rivers, streams, seasonal streams and streamlets as far as indicated on the map. Include all branches that are directly feeding the major river, i.e. trace all of the tributaries that flow into the river and all of the tributaries that flow into them. See the example given. 3. After highlighting all of the tributaries, go back to the map and identify the highest points around the area you have highlighted. 4. Connect the tops of the ridges and mountains that surround the areas that contain your highlighted streamlets. See the example. The drainage for the river you have chosen is the land mass you have outlined. This entire area is the watershed for that river. Answer the following discussion questions: 1. In general, are drainage areas measured in square acres or square miles? 2. For your drainage system (watershed), what is the primary source of water: rain or snow? Where does the water from your watershed end up? What is it used for? 3. Why do we take so much interest in the snowpack measurements we hear about in the news? (They are most often talked about in the early spring.) 4. How would a winter season with little snowfall affect people later in the year? 5. How would a forest fire in the fall affect the spring melt and subsequent water supply? 6. Why are water rights so strongly fought over whenever an area is being considered for inclusion into the Wilderness system? 7. Consider areas that have been developed by humans. After a strong rain there seems to be more water than our drainage systems can handle. Is this water suitable for us to use? Why? What needs to be done before it can be used? Where does the water end up after draining off your school and moving down the street? Is it recharging the aquifer? Can you think of alternatives to channeling rain water away from developed areas? How does the controlled flow of runoff in a developed area differ from runoff in a natural area? 8. Is the treated water from our gutters just as usable as the water from natural areas? 9. Do we need to preserve natural areas where rain and snow can accumulate? Page 392

7 SCIENCE- STUDENT/TEACHER INFORMATION MAP SYMBOLS Natural Resources Lake or Pond Marsh or Swamp Streams Mountain Peak or Summit Spring Cliff Human-Made Improvements Paved Road Primitive Road All Weather Road Trail Dirt Road U.S.F.S. Lookout Station 77 Arterial Road 7715 Collector Route 120 Local Route Building School Church Mine or Quarry - - Power Transmission Line E 4346 Bench Mark Location Campground Ranger Station Page 393

8 SCIENCE- STUDENT/TEACHER INFORMATION Á MAP INFORMATION SHEET 1. Map Margin Information Identify each of the following: A. Name of the map B. Names of adjacent maps C. Location of the map on the earth s surface i. Longitude, note meridians ii. Latitude, note parallels D. Date of the map Note possible changes that may have occurred since the map was drawn and field tested. E. Map scale/series Note how the scale is drawn. i. Scale ratio inches/cm. on map = inches/cm. in the field a. 1:24,000 This map is good for detailed study of a small area. 1 inch = 2,000 feet in field Approximately inches = 1 mile 1 cm. = 240 m., 4 cm. = 1 km b. 1:25,000 Used in metric series, similar to 1:24,000 scale 1 cm. = 250 m c. 1:62,500 Good general purpose map Approximately 1 inch = 1 mile in field 1 cm. = 625 m., 1.5 cm. = 1 km ii. Series a. 15" (minute) series This map covers a section of the earth s surface 15" of longitude x 15" of latitude. Note longitude and latitude marks on map to confirm size. b " series Note that it takes four " maps to equal a 15" map. c " x 15" series Metric series found only in a few areas of the United States Page 394

9 SCIENCE- STUDENT/TEACHER INFORMATION 2. General Map Details Identify the location of each detail on a sample map. A. Map symbols i. Cultural symbols symbols of human-made objects. These are represented by the color black. a. Roads b. Railroads c. Churches d. Trails e. Buildings f. Cemeteries g. Bridges h. Schools i. Quarries/mines ii. Water symbols represented by the color blue a. Lakes b. Streams (1) On " maps, for a stream width of more than 40 ft. (12 m.), both shores are shown. (2) On 15" maps, for a stream width of more than 80 ft. (24 m.), both shores are shown. c. Springs d. Marshes/swamps iii. Map directions a. True north This is the north that is shown on a map. b. Magnetic north This is the north that attracts the compass needle. Subsequent navigation lessons ( Compass: An Introduction and Combining the Map and Compass: An Introduction ) will discuss the two norths and declination in more detail. c. Place name designations Note the different styles of lettering used for area names, elevation figures, political boundaries. B. Elevation markings These are represented by the color brown. i. Contour lines An imaginary line on the ground along which every point is at the same height above sea level (Kjellstrom, 1976, p. 23). Note the altitude numbers located along some contour lines. Page 395

10 SCIENCE- STUDENT/TEACHER INFORMATION Á a. Index contour Heavier brown contour lines usually spaced at 100 ft. elevation intervals b. Intermediate contours The contour lines between index contours c. Contour interval The distance in height between one contour line and the one next to it (Kjellstrom, 1976, p. 23). Intervals vary from map to map. d. Contour shapes (1) Hills & mountains (2) Passes (3) Steep areas (4) Flat areas e. Depression contours f. Interpreting elevation change (1) Contours forming V s generally point uphill. (2) Streams which come together forming V s generally point downhill. g. Benchmarks BM represents the location of a marker in the field where altitude or distance has been verified. The number next to BM indicates altitude. Page 396

11 WORKSHEET #2 - SCIENCE MAP WORKSHEET A. NATURAL FEATURES 1. Locate a river on the map. a. What is its name? b. Name a stream flowing into it. NOTE: Dashed lines at the origin of a stream indicate that it has intermittent flow. 2. Identify: a. a spring b. a lake c. a mountain peak d. a marsh or swamp A. HUMAN-MADE IMPROVEMENTS 1. On your 1/2" scale map, identify by number:. a. an arterial road b. a collection road c. a local road d. a trail 2. Identify by name: a. a campground b. a bench mark location Page 397

12 SCIENCE - WORKSHEET #1 Á CONTOUR LINES 1. A contour line, by definition, is an imaginary line on the ground along which every point is at the same height above sea level. 2. The number on a contour line indicates elevation above sea level. Locate a contour line on Figure 2 and write it down. Write down the number of the contour line next to it. 3. The distance in elevation between one contour line and the one next to it is the contour interval. The vertical distance between the contour lines on Figure 2 is feet. 4. Contour lines indicate elevation, slope steepness, level areas, tops of hills, saddles, and ridges. 5. When contour lines cross a river or stream, they take on a V-shape, with the point of the V pointing uphill. 6. Contour lines denoting a ridge of a hill become U-shaped, with the bottom of the U pointing downhill. Figure 1 - A Landscape in Perspective x Figure 2 - The same landscape with contour lines. Page 398

13 SCIENCE - WORKSHEET #3 Contour Quiz Match the profile (A-F) with the contour lines (1-6) 1 A 2 B 3 C 4 D 5 E 6 F Page 399

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