How is rainfall measured?

Rainfall is the most common form of precipitation. It is important for recharging groundwater, water bodies and is useful in agriculture. On the downside, heavy rainfall may cause disastrous floods and landslides. Hence, it becomes important to measure and record rainfall to plan activities of the future. Now coming to the question, how is rainfall measured?

Rainfall is measured with the help of rain gauges. There are various types of rain gauges. Some need more manual work than others. The most common is the standard rain gauge.

How is rainfall measured with the standard rain gauge?

The standard rain gauge consists of a copper cylinder with a funnel of 8 inch diameter.

How is rainfall measure?
A standard rain gauge

The shank of the funnel leads into a glass bottle or another copper cylinder placed inside the larger cylinder.
The rainfall is collected in the glass bottle and is calculated by emptying it into a graduated cylinder. The graduated cylinder generally has an accuracy of 0.01 inches.

Graduated cylinder
Graduated cylinder

In some rain gauges, the water is directly collected in the graduated cylinder.

  • The rainfall is measured every 24 hours, generally at 8.30 in the morning.
  • The gauge must be fastened and should be placed away from any structure.
  • The top of the rain gauge must be at least 0.3 metres above the ground level.

How is rainfall measured with float type (Natural syphon type) rain gauge?

  • The rainwater flows from the funnel into a chamber with a float. The float rises with the increase in water level.
  • The rainfall is recorded on the graph pasted on a rotating drum (driven by clockwork mechanism) by a pen connected to the float.
  • The chamber is emptied by a syphon arrangement.
Float type rain gauge

Quick question

Which is the coldest, windiest and driest continent?

How is rainfall measured with Tipping bucket type rain gauge?

  • In tipping bucket type rain gauge, the rainwater is collected in two buckets arranged in see-saw mechanism one by one.
  • When the water in a bucket reaches a given amount, it tips and the second bucket starts filling.
  • Each tipping activated a pen which records the rainfall on a graph pasted on a rotating drum(driven by clockwork mechanism).

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Answer to quick question

Antarctica is the coldest, windiest and driest continent.

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