How To Read a Rain Gauge

Rain gauges are primarily used for the measurement of rainfall level in a specified area within a particular duration. Majority of rain gauges measures precipitation using the millimeter unit. Sometimes, rainfall level is reported in centimeters or inches.  The amounts of rainfall collected by the rain gauge can be read manually or through the Automatic Weather Station or AWS.  

There are some countries that are willing to provide weather forecasting institutions with a vast volunteer network to help obtain rainfall data.   This instrument is very important, as it provides relevant data to gardeners, scientists, and weather professionals. Information on rainfall level is also significant for agricultural purposes such as harvest season and irrigation systems.

Regardless of the reason for rainfall data collection, it would be beneficial if you know how to properly read rain gauges. Here’s how:

  • Check rain gauge. Get your rain gauge and make sure that it is empty even before the rainfall you are planning to measure pours. A useful tip or practice is to see to it that you empty the instrument right after a precipitation reading.
  • Read rain gauge on eye level.  Once the rainfall has occurred, examine the filled rain gauge.  You can either stoop down to check or you may lift the instrument up.  Just make sure that the gauge’s water line is within eye level.  This is to make sure that you are interpreting the readings accurately.
  • Record water’s height.  Do the recording of the water level’s height.  The water’s surface will be curved slightly due to surface tension which makes water stick within the container’s sides.  This is commonly referred to as meniscus.  Carefully read the water’s height within the meniscus’ base.  Rain gauges usually have numeric figures which are divided by tenths of several inches.

    For example, when the rain gauge has been filled up to the line marked .50; it is read as .5 of an inch, which translates to half inch rain fall.  In cases when the gauge has collected very little water or no water at all even if the rainfall is already finished, put on record that there was a precipitation “trace” only.

  • Empty gauge.  To prepare for your next measurement, empty the gauge. While rain gauges are useful measuring instruments, put in mind that they also have limitations.  Rain data collection during hurricanes is nearly unreliable because the winds are so extreme.  Remember also that rain gauges could only measure rainfall within localized areas.  Another problem that you can encounter in using rain gauges is during freezing weathers.  During this time, your gauge can collect frozen water, and this will not allow the passing through of subsequent rain. To maintain the accuracy of your rain gauge, you also have to maintain it properly.  

Rain gauges must be placed within an unobstructed, open area.  Avoid putting rain gauges in spaces where there are trees or buildings which can block rainfall.  This also aims to prevent water collected on buildings’ roofs or trees’ leaves after rain from dripping to your rain gauge. This may result in erroneous and inaccurate readings.


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