This Experiment Using a Glass Cover and the Sun Can Generate Water Even in Drought Affected Areas!

In a semi-arid region of Satara district in Maharashtra, there is a plot of lush green land with about 20 fully-grown, beautiful trees – all of which were the part of a very efficient experiment. The seedlings for these trees were fed with water obtained from dry soil, with the help of solar energy.

“I did my PhD in America way back in the late 1970s. And most of my work was around solar distillation of water. I looked at everything that could possibly be done with solar energy at that time and found that if you dig a small hole in the desert, and cover it with plastic, solar energy heats the soil and you can collect a cup of water every day. This was something that remained at the back of my mind for years,” says Dr. Anil Rajvanshi, Director of Nimbkar Agricultural Research Institute (NARI) – a non-profit research and development institute based in Phaltan, Maharashtra.

In 1981, Dr. Rajvanshi returned to India with the aim of using his education to work for the development of rural India, and started establishing the energy and sustainable development work at NARI.

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Dr. Anil Rajvanshi

“I came to this very dry and partially semi-arid region. Sometime in the 1980s, the Government of India conducted a very large-scale tree plantation program. But of the many seeds that were planted, only a few resulted in fully-grown trees. Most of the seeds perished,” he remembers. So, going back to the knowledge he had gained while studying, Dr. Rajvanshi started an experiment to grow trees using water distilled with the help of solar energy, at NARI in 1988.

The basis of the experiment was that soil contains some moisture and roots of plants utilise this water with the help of osmosis – a process in which a solvent (water in this case), passes through a semi permeable membrane from a region of less solute concentration to a region of more concentration. Roots absorb water from the soil through osmosis. But in semi-arid and arid regions, the water is so tightly bound with the soil that seedlings cannot extract it because of less osmotic potential.

This is how the experiment was done:

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Five pits, each of dimensions 0.9m X 0.9m X 0.6m, were dug in a barren land in the NARI campus. These pits were covered with Soil Water Evaporation Stills (SWES) – tilted glass covers connected with water collection bottles placed beside the pits.

When sunlight fell on the pits, it heated up the soil and the water in the soil evaporated, only to be collected in the form of water droplets on the glass covers. These droplets slid into the bottles.

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Three experiments were conducted with these SWES. The water collected in the bottles everyday was given to the seedlings in the morning. In Experiment 1, the water was supplied in equal amounts to some seedlings. In Experiment 2, the water collected from SWES over a period of seven days was supplied to another set of seedlings once a week. And in Experiment 3, the seedlings were rain-fed. The growth of the trees was monitored for diameter, plant height and mortality every three months. And the results were extraordinary.

The survival rate of seedlings fed from SWES was 100% and if one SWES fed 4 plants, an average of 70-80 ml of water was given to each seedling. The growth rate of the trees in Experiment 1 was higher than in Experiment 3.

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According to Dr. Rajvanshi, the production of water from soil in arid regions is an age-old technology and has been used as a strategy for human survival in deserts. However, there is limited data on its daily use, seasonal variation, etc.

“We used to get water from the pits every day and that turned out to be sufficient for the plants. The soil would get heated and the moisture in the soil, which you could not get otherwise, we were able to extract and feed to the plants. The trees were able to grow even in the worst season. Today, we have 15-20 fully grown trees in a place that was once completely barren. They are huge now,” he says.

Dr. Rajvanshi has been working in the field of rural development for the last three decades.

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Born and brought up in Lucknow, he went to the US to pursue higher studies at the University of Florida after his Bachelor’s and Master’s degrees in mechanical engineering from IIT Kanpur. He taught at the University of Florida for over two years and then returned to India

Dr. Rajvanshi feels that with the worsening drought conditions in many regions of Maharashtra, this technique can be used in some form or the other to help people in the region. “If not to grow plants, it can be used to provide sufficient water for people to drink if we conduct a similar experiment at a large scale and think more in that direction,” he concludes.

You can contact Dr. Anil Rajvanshi by writing to him at [email protected].

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