Slick of edible oil on pond water surface can reduce evaporation by 70%

One forward-thinking farmer in the Vikarabad district of Telangana, has devised a method that can reduce water evaporation by up to 70%. The technique entails pouring a few litres of edible oil onto the water, which forms a sheet cover on the water due to its lower density.

Farmers dig small ponds, especially in rainy areas, to collect rainwater and save it for the rabi season. Though farmers commonly use tarpaulin sheets in pond beds to prevent seepage, they still lose up to 2-4 inches of precious water per week due to evaporation, especially during the March-June period when temperatures rise dramatically.

The oil sheet shields water from direct heat and prevents water molecules from escaping from the surface. During the summer, farmers lose up to one-fourth inch to half-inch of water level in a farm pond per day, according to estimates.

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‘You will lose 25,000 to 50,000 gallons of water per year for a normal sized pool,’ MS Subrahmanyam Raju, a progressive farmer from Jingurthi village in Thandur mandal of Vikarabad district, explained.

‘This is not a novel situation. Previously popular, the technique faded into obscurity over time,’ he explained. He did warn, however, that this method should only be used in agricultural ponds and not in ponds used to draw drinking water.

There is also no need to use fresh edible oil, which is currently around ₹ 150 per litre. ‘They can just use the oil that was once used and sold by hotels and restaurants for around ₹ 50 per litre. The cost-benefit analysis favours the farmer, according to Raju, General Secretary of Go Aadharitha Prakriti Vyavasayadarula Sangham (an association of farmers who practise farming with cow products).

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He has tested this technique on two ponds and alleges that the results are promising. ‘A 1,000-square-meter pond will require 25 litres of oil. After a month, you should top it up with another 13 litres,’ he explained.