Bengaluru

New device measures rate of evaporation in minutes

In what is touted to be a more efficient and inexpensive alternative to existing methods, a team of scientists from the Indian Institute of Science (IISc.) has developed a device that can measure the rate of evaporation within a couple of minutes.

Apart from being an integral process in the water cycle, evaporation plays a major role in regulating water loss in plants through a process called transpiration, an IISc. release explained. “Being able to measure the evaporation rate is useful for farmers to gauge water requirements for their fields and in weather stations to characterise the local atmospheric conditions. It is also widely used by botanists to study the dynamics underlying transpiration by plants,” said IISc. in the release.

Currently, pan evaporimeters – resembling large pans that are filled with water – are the most commonly used devices to measure evaporation rates. The change in water level over a day gives the evaporation rate from that area for that day.

“The disadvantages are that the evaporation rates are for one whole day, and over a large area, one square metre. One needs an open ground to place the device. But we have a simple method of directly measuring evaporation from a small surface – at the order of a couple of centimetres, and over a short period of time. Our method allows you to get a much more realistic measure of transpiration from plants and evaporation from soil,” the release quoted Jaywant H. Arakeri, Professor in the Department of Mechanical Engineering, IISc., and senior author of the study, which was recently published in the Journal of Hydrology, as saying.

The proposed device consists of a filter paper connected to a capillary tube that takes water from a reservoir to the filter paper, wetting it and mimicking an evaporating water surface. By measuring the distance travelled by the lower meniscus in the capillary tube over a couple of minutes, the evaporation rate is estimated. The innovation lies in being able to measure the very small amount (about 1 microlitre) of water that is lost in evaporation from the surface in a minute, the release explained.

As the evaporation rate is affected by a number of factors such as temperature, wind velocity and humidity, the device can show the evaporation rate within a niche environment. It would be useful to scientists studying the physiological process of transpiration in plants because of its ability to measure the evaporation rate over small areas over short periods of time.

The authors also suggest that it could be used in oceans to study changing evaporation patterns in the open sea and in weather stations to estimate evaporation rates in the atmosphere, an important parameter that is currently not measured.

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Printable version | Jan 23, 2021 7:26:27 PM | https://www.thehindu.com/news/cities/bangalore/new-device-measures-rate-of-evaporation-in-minutes/article33252840.ece

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