How much did it rain today?

"It rained almost one inch yesterday. Good. We need more rains." It was monsoon time and Harish was talking to his friend over the phone. For his daughter, Kaavya, who was overhearing the convesations, that "one inch" was confusing. "After all, how can one measure 1 inch of rain??"

After the telephonic conversation was over, Kaavya asked her dad "Dad, inch is measurement of length, right? It is used to measure rain too??"

"Yes Honey.." Harish replied. And as we all konw, kids are always prepared. She went to her desk, got a scale. "Daddy, common, lets measure rain."

"Well, your scale can't measure the rain, my dear. But we can measure rains. Lets do it."

Rain is measured as 'rain received in a column of 1 square inch area.' So, 1 inch rain is, 1 cubic inch of rainwater.

This is what Harish did:

Measure rainfall

Take a Jar having the same diameter from top to bottom. The wider the jar, better the measurement. If you choose a small jar, and if it rains much, the jar may overflow. So, make sure you use a deeper jar.

Now, go to your terrace and place the jar in such a way that it is not very near to any shade.

After a day, or say "24 hours" get that jar back to your home. If it rained that day, the jar will contain the water collected in it during last 24 hours. Now you need to do two things:

Measure the collected water in ML (milliter)

Measure the diameter of the jar's opening, because now it is time for some number crunching.
We have collected rains in "ml". And so, we need to convert the "ml" in "cubic inch". If you search the Internet, you will come to know that:

1 cubic inch = 16.387 ml. So, if your jar (having opening area of 1 sq inch) collected 16.387 ml of rainwater, you can say, it was 1 inch of rainfall.

But we had used wider jar, which collected much more water. So, it is time to reduce the "ml" accordingly.

For example, If your jar's area is 10 square inch, and it has collected 163 ml of rainwater, so we need to divide the figure by 10. Because, collection area is 10 times larger. To find how much rain water you would have collected in 1 square inch, apply following formula:

water collected in 1 sq inch = water collected in jar / area of jar-opening (1)

Now to convert the ML in INCH, apply following formula:

Rainfall in inch = rainfall in ml (1) / 16.3

Here you are. You just measured rainfall in your terrace, without using a rain gauge. Simple, isn't it? But this method is "home use" method. It will not work in all conditions, like:

• It rains only for 1 - 2 minutes, and then bright sunlight for remaining day. The collected water will get evaporated.


• It rains so much that it completely fills the jar and water starts spilling out of the jar.


• You may get inaccurate results if rain is accompanied by a heavy winds.


• You can't measure whole season's rainfall at one go.

But, again, no problems. We are not weathermen. We just wanted to be with our kid and give him/her assurance that "my daddy (or mom whoever is reading this blog) knows everything". And you successfully did that.