Watersheds and Surface Water Runoffs

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Watersheds and Surface Water Runoffs
Diffusion Impacts the Environment
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Functions in the Real World

• Were now going to explore one of the countless
  areas in which scientists use functions, their
  graphs and their equations, to model data and
  make predictions that impact our lives in a
  significant way every day.

Photo from Tropical Storm Allison Recovery Project
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Diffusion in the Environment

• The area we are going to focus on is diffusion
  and its effects on the environment. Since these
  are numerous and far reaching, we need to limit
  our investigation further. What well be
  concentrating on is diffusions impact on water
  quality when it rains no - not just when it
  rains, but when it FLOODS!

Photo from Tropical Storm Allison Recovery Project
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Diffusion

• Lets begin with some definitions, so everyone
  will understand exactly what is meant by the
  particular terms that well be using.
• Diffusion is defined as the process where
  molecules move from a high concentration to a low
  concentration. Diffusion simulation
• For example, spray a squirt of cologne in a room.
  There will be a strong scent where you sprayed
  it, but it will diffuse and become a weaker scent
  as it moves from the area where it was first
  sprayed until it is the same concentration
  throughout the room. This movement of molecules
  in order to maintain an equilibrium is known as
  homeostasis.

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Diffusion in Water

• Following a rain, runoff occurs. Runoff is water
  from rainfall which is not absorbed by the soil
  as it flows downhill, where it eventually drains
  into the local drainage system and ultimately
  into a creek, bayou, stream, river or other body
  of water.

Photo from Tropical Storm Allison
Recovery Project
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Diffusion in Water Continued

• As the water flows downhill, it picks up
  insoluble material. This is material that will
  not dissolve in the water. Topsoil is an example.
• Even things like decomposing animals or oil that
  has spilled or leaked onto streets and highways
  can become part of the runoff.
• The runoff can also pick up contaminants like
  toxic chemical fertilizers and pesticides.

Photo from Tropical Storm Allison Recovery
Project
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Diffusion in Water Continued

• These contaminants may create serious water
  quality problems because they will diffuse,
  allowing the harmful substances to pollute all
  the bodies of water the runoff empties into as it
  flows.

Photo from Allison Tropical Storm Allison
Recovery Project
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Significance of Diffusion in Runoff

• Therefore, it is extremely important to be able
  to predict the amount of runoff a particular area
  will experience during a storm, for this can help
  in the prevention of major water pollution
  problems.
• This is especially true in flood prone regions
  where high levels of contaminants exist.

Photo from Tropical Storm Allison Recovery
Project
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Watersheds

• A watershed is the total of all the land area and
  smaller bodies of water whose rainfall ultimately
  drains into a specific body of water.
• Example The total region of land, creeks and
  streams whose runoff flows into the Colorado
  River is called The Colorado River Watershed

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Watersheds continued

• Later in our study, we will use a computer model
  to examine the amount of runoff in various
  watersheds in Harris County, Texas following
  Tropical Storm Allison which hit the Houston area
  June 5-9, 2001.
• But before we can do that, we need some more
  information.

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Assignment Part I

• Go to Surface Water Runoff and click on
  Background Science.
• Read
• Why is it important to model runoff water?
• How is surface water runoff determined?
• What is a hydrologic soil group?.
• Answer the Part I questions given on the next
  slide on your own paper. When you have completed
  Part II of the assignment, you will turn in your
  work to your teacher. You may also choose to use
  Word to complete your assignment and email your
  work to your teacher.

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Questions Part I

• 1. How does the addition of fertilizers affect
  the entire ecosystem of a body of water?
• 2. What is currently the most appropriate and
  authentic numerical model in use by soil
  scientists?
• 3. In the graph on Runoff Curves,
• a. Which axis is the independent variable and
  what does it represent?
• b. Which axis is the dependent variable and what
  does it represent?

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Questions Part I continued

• 4. What is a predictive model?
• 5. The runoff curve number depends on what four
  factors?
• 6. How are soil groups classified?
• 7. Describe the four soil groups.

Tropical Storm Allison Recovery Project
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Questions Part II

• Go to Surface Water Runoff and click on
  Mathematics. Read through this section.
• Then answer the following questions on the same
  page as the responses to Questions Part I.
• Turn the completed assignment in to your teacher.

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Questions Part II

• 1. Give the equation used to calculate runoff and
  identify each variable.
• 2. Define initial abstraction and infiltration of
  the variables.
• 3. What is the runoff curve number (CN) and its
  range of values?
• 4. Which equation that was specifically
  formulated through the use of data compiled from
  the study of many small watersheds?

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Assignment Part II Continued

• 5. Fill in the missing step.

a.
? ? ? ? ? ? ? ? ? ? ?
b.
c.
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Questions Part II Continued

• 6. In the equation given above,
• a. Name the type of function.
• b. Write the function in functional notation.
• c. Identify the independent variable.
• d. Identify the dependent variable.
• e. What would be a reasonable domain?
• f. What would be a reasonable range?

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