Construct a rain gauge

Download this page as PDF (including the class chart)

The Global Classroom Project

This experiment will show how much rainwater that will be left in the streets and in the fields, if the rain was not able to run into the sewer or trickle into the ground. In this experiment you will see how many mm of rainwater that would be left if it is not able to run away.

This is what you’ll need to carry out the experiment:

• A container in which you can collect the rainwater
(for example a cup, bowl or a bucket). It must have a round opening.
• A scale
• A big bucket or bowl for the class to use.

How to do it, described as 4 steps below:

• Find the container with a round opening (for example a cup, bowl or a bucket)
• Measure the area of the opening
• Let it rain down throung the opening of the container
• Measure the volume of the rainwater
• Divide the volume with the area - the result will tell how high the water would have stod if this amount of rain had fell on plate with the same area as the opening of the container.

1. Measure the area of the container opening in mm²

How to do it	Example	Result
Measure the diameter (mm from side to side) of the opening	100 mm	100 mm
Multiply the diameter with the diameter	100 mm multiplied with 100 mm	10 000 mm²
Multiply this result with 3.14	10 000 mm² multiplied with 3.14	31 400 mm²
Divide the result with 4	31 400 mm² divided with 4	7 850 mm²

Now you have the area of the opening. You’ll use this result once the rainwater is collected. Write the result in the class chart (found for printing on page 3)

School chart
N a m e		R e s u l t
Student 1		7 850 mm²
Student 2		9 450 mm²
Total		17 300 mm²

2. Collect the rainwater

Place the container outdoors and let it stand there for 24 hours (for example from 7 am to 7 am)
Bring the water you have collected to school and pour it in the class bucket.

3. Measure the volume of the rainwater

Now you will have to calculate the volume of the rainwater the whole class have collected. This is how you do it.

This is how you do it	Example	Result
Weigh the water that the entire class have collected	250 g	250 g
Multiply the weight with 1 000 mm³/g	250 g multiplied by 1 000 mm³/g	250 000 mm³

4. Calculate how much rain that has fallen

Now you will find out how high the rain would have stood if it had stayed on the ground. This you do by dividing the volume of entire class collected rainwater with the sum of all areas of the container openings.

This is how you do it	Example	Result
Divide the volume of all the collected rainwater with all areas of the container openings	25 000 mm³ divided with 17 300 mm²	1.45 mm