v From last time: Describe the purpose and function of a rain barrel, and make quantitative calculations to estimate how a rain barrel is involved in the water budget of a residential property in Chicago.

v New this time: Use concepts of length, area, volume, and flow rate to quantify hydrologic variables.

v Solve a hydrologic problem in a sequence of logical steps, using reasonable units, significant figures, and dimensional analysis.

Our agenda today:

Teams get together to go over their calculations

Compare answers between teams:

How big is the property? How does the area compare to an acre?

Describe how big an acre is in non-technical terms.

How much of the property is in garden plots?

What is the area of the roof?

If there are differences between answers, what accounts for them?

What is a typical rainfall in Chicago? (cite your sources)

What depth annual precipitation do we get in Chicago?

What volume annual precipitation do we get in Chicago?

Problem-solving: See "Hints for Solving Quantitative Problems".

Now let's move on to the rest of the questions. Answer them using dimensional analysis and paying attention to significant figures:

How much rain will the roof collect in a typical rainfall?

Are two barrels enough to store water from a typical rainfall?

Are two barrels enough for me to store water to irrigate my entire garden?

--------------------------------------------------------

Groups that finish early should consider these questions:

- If the rain falls at a rate of 1 inch per hour, how long would it take to fill a rain barrel?
- How heavy would a
full rain barrel be?

How big are the differences between answers? How much difference indicates "the same amount", and how much difference indicates a "real" difference?

Homework: For Tuesday, as a group (one set of answers for the whole group), complete Homework #1.

Department of Earth Science | Northeastern Illinois University

*© 2009 Laura L. Sanders.
Last updated January 15, 2009.*