12 March Science 8 Watersheds and Simulated rivers

Have you done this: Make a cartoon: Where does the water you use come from? Where does it go? What happens along the way?

What is your response to these “competing” claims?

“The water coming out of your kitchen tap is four billion years old and might well have been sipped by a Tyrannosaurus rex.” <http://www.thebigthirst.com/the-book/>

“The earth’s oceans, ice caps, glaciers, lakes, rivers, soils and atmosphere contains about 1.5 billion cubic kilometers of H2O. It has been estimated that all the earth’s water is split by plant cells and reconstituted by the biota about every 2,000,000 years.” (The Oxygen Cycle by Preston Cloud and Aharon Gibor in theU special issue on The Biosphere September, 1970.)

Be sure you have the previous blogpost marked. And be sure you have examined the many links. http://rfrazier.msblogs.aes.ac.in/2018/03/07/8-march-science-8/

Today–work in assigned groups, if you were not here during the last class you will be assigned.

Learn how to set up the stream table. Begin the 3 activities below. (Hint: Make a reference grid for your stream table so that you can mark the changes in time and space. Use photographs made at regular intervals. Video can be useful but requires time to watch. You might try time-lapse.)

  1. Learn how to operate the siphon.
  2. Learn how to make observations:
  • Depth at head, middle, mouth of stream
  • Width at head, middle, mouth of stream
  • Ratio of Depth to Width at head, middle, mouth of stream
  • Velocity (distance/time—small floating object moving with the current)
  • GradientValley side angle—cross section
  • Stream type / Stream age
  • Keep full and complete records/notes/data/reasoning/lists of questions (including images, sketches, and short video clips) on how you set-up and run each trial and what you observe happening in your streams. Your group will make a multimedia presentation on your investigation of streams. (See below)
  • Pay attention to how the water and sand move at both smaller and larger scales.
  • Identify any landforms/riverforms and note what leads to their appearance, modification, and disappearance (alluvial fan, canyon, waterfall, meander, etc.)
  • Link patterns of development as well as particular features you observe in your streams with real streams.

Activity 1 – Flat, Inclined Terrain Model

  1. Create a slightly inclined plane.
  2. Predict what will happen when the water is turned on. Turn on the water so that it pours in a steady, moderate stream.
  3. Record observations in 5-minute intervals for about 20 – 30 minutes. Include sketches and photos at each interval. You may try 30-second video segments, too. Try to make a time lapse record.
  4. Turn the water off after 20 – 30 minutes. Discuss the similarities or differences between the two models. What were their observations? Did each model have the same result? How did the landscape influence the course of the river?
  5. Refill the water jug to prepare for the next experiment.

Activity 2 – Hills and Valleys Landscape Model

  1. Remold the sand in the tray to create a surface with several hills and valleys.
  2. Predict what you think will happen in this scenario. Will the same river formation happen? Turn on the water so that it pours in a steady, moderate stream. Table is at same inclination as model 1.
  3. Record observations in 5-minute intervals for about 20 – 30 minutes. Include sketches and photos at each interval. You may try 30-second video segments, too. Try to make a time lapse record.
  4. Turn the water off after 20 – 30 minutes. Discuss the similarities or differences between the two models. Did each model have the same result? How did each landscape influence the course of the river? How were the results different or the same, compared to the flat and inclined model?

What’s Happening?
If you’ve been in mountains and seen a spectacular waterfall, you probably were looking at the beginning of a river. Most rivers begin on top of mountains where water from rain or melting snow collects. Under the influence of gravity, this water flows downhill to form brooks, streams or rivers. As the stream or river flows downhill, it can change the landscape by eroding rocks and depositing sediments.

Some observations that can be made by comparing both models are:

  • The speed of the water flowing downhill will be affected by the degree of incline, and any structures or topographical features in its path.
  • The faster the water flows, the more erosion occurs.
  • Water flowing downhill moves and deposits sand at the bottom of the river. The faster the water flows, the more sand will be deposited at the bottom. A delta at the mouth of a river forms in the same way.

Although the formation of the “rivers” in this activity appeared very quickly, in reality rivers can take millions to billions of years to form a path from land to sea.

More Discussion

  • How would the river formation be affected if the water continued to flow for one hour, two hours or three hours?
  • How would the river formation or pattern be affected if the sand were replaced with soil?
  • How can the stream table be used to simulate a landslide? What variables could be changed to induce a landslide?
  • What are some kinds of man-made structures or human activities that can affect a river system? Name rivers in India and in home countries that are being affected in these ways.
  • Name an important Indian and and important home country river that does not originate in mountains.

Extended Activity 3
Extend the activity by changing some of the variables to observe how it affects the river’s path and speed, or the erosion and deposition of sand. Students can create their own variables to test or try one of the following:

  • Place other objects in the sand, such as small pebbles, stones or small plastic houses or trees.
  • Build a dam in the middle the river.
  • Place two or three water jugs next to each other and turn all spigots on at the same time.
  • Mold the sand into a valley. Compare the differences when the water flows directly down the middle, to what happens when the water flows from the inclined section of the valley (the long side of the tray).

Presentation:

You and your group will need to decide how to illustrate, describe, and explain your stream simulation investigation in a multimedia presentation. Judicious use of photos, videos, diagrams, graphs, and data are an important part of the presentation. Be sure to attend to the following:

  • Experimental methods
  • Control of variables
  • Repeated trials
  • Observables (descriptive, quantitative—counts and measures)
  • Analysis and Interpretation
  • Explaining the observed simulated river landforms—their origin and development–principles and mechanisms of the effect of flowing water on the landscape and the effect of the landscape on the way water flows)
  • Links to actual river landforms
  • Tests of the explanations (evidence is gathered to support or challenge explanations)
  • Organization and display of data
  • Clarity, completeness, and accuracy of the presentation
  • Big ideas—significance of watershed to the water cycle; importance of people understanding watersheds with regard to human impact on the environment

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