- Measure the square footage of the roof
- Determine the collection potential from an inch of rain
There are some areas of the country that get enough rainfall annually that measuring the potential is irrelevant. But in northern Wyoming where the first Edible Learning Lab was established, it’s a different story.
Rainwater is far better suited for plant development than tap water or even creek water which is abundant at the base of the Bighorns. But will there be enough to foster all the plants in the Lab from seed to harvest?
The first step in answering that question – and the same applies to any Edible Learning Lab – is to determine the collection potential of the system. If the collection potential and storage capacity are known then a calculation can be made based on a specific amount of rain. Knowing how much rainwater you will be able to harvest can then be used to determine the carrying capacity based on usage.
Though this may seem like a lot of numbers, knowing how much water you need and how much you might have access to will allow you to plan for the Lab operations in a more comprehensive way.
Teach the Teacher
Tools & Materials
- Paper and pencil
- Tape measure
- Collection potential
- Efficiency factor
Introduction (10 minutes)
Begin the lesson by explaining that a 1000 sq ft roof will yield 623 gallons from a single inch of rain. Ask the question “How many gallons do you think our roof will yield? More or less than 623 gallons?”
Activity (20 minutes)
The first step is to calculate the square footage of the roof. This can be done by measuring the length and width of the building. Be sure to consider where the water is transported by the gutter and downspouts. Your building may have downspouts on both sides. If that is the case, calculate the area of the roof for just the side that will supply rainwater for your system.Using the square footage of the roof, calculate the collection potential of the roof.
Discussion (10 minutes)
How many gallons would we get if only a half inch of rain fell? What about 2 inches of rain? How much rain would it take to fill our system?
Assessment (5 minutes)
Use the following questions to assess the Students before and after the lesson. Tally the responses of the group in the Assessment Tracking Log for comparison:
- By a show of hands, how many of you know the amount of water that we could collect from our roof if it rained an inch?
- Know that you know how to calculate the collection potential for our system, how many of you think you could calculate the potential for the roof on your home?
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