Chapter 2:

The Problem:

Some places in the world the only local source of drinking water is the rain that fall on their roof. This is called rainwater catchment. I'd like you to make a stack plot of our water usage (for you for the year) and one that illustrates how much water falls in a year on your roof (presumably in Jefferson or Crook County). Compare your stack plots in the way that David MacKay describes and determine whether you can easily meet your needs from rain water, there's not a chance of pulling this off, or is it a near thing (within 25% or so).

Hints:

There are several things that you will need to think about to do this. I recommend that you break your water usage up into categories like drinking water, bathroom water, washing water, and kitchen water. Make reasonable estimates of the liters that you use (1 gal = 4 lt for our purposes) and add them up. For the rainfall you may find table 1 at this link

[ http://www.ocs.oregonstate.edu/county_climate/Crook_files/Crook.html ]

[ http://www.ocs.oregonstate.edu/county_climate/Jefferson_files/Jefferson.html ]

helpful. This is inches of rainfall in different parts of Jefferson or Crook County. Remember 1 inch is 2.54 cm and 1 liter is 1000 cm3. When you figure the size of your room (in cm2) you will need to notice that the effective size of your roof when it comes to gathering rain is just the size of the footprint of your house. The slope of the roof appears to increase it's area but it doesn't change the size of the target for the falling rain. I would recommend calculating the volume of water in cm3 and then dividing by 1000 to get liters.

The next time we meet you will have 15 min to consult with your classmates about your solution but until then I ask that you work on this problem alone to test your understanding/mastery of the subject.

I know this is a challenging problem in some ways. I hope the concept is clear enough and that you are willing to try to work your way slowly through to find the answer. The people of California were starting to wonder about this exact question in recent years.