Water is the elixir of life, and almost ⅗th of the surface of earth is covered with seawater. A small part of seawater reaches our lands by means of clouds, which are generated by the uneven heating of the Earth’s surface. The formation of clouds, their movement and dispersal through the Earth’s atmosphere are very complex and interwoven phenomena, and armies of scientists, satellites, instruments and radars are devoted to their study. This is “skywater” – the source of all groundwater in the form of rivers and lakes and underground water that has leaked into the Earth’s surface. The origin of all skywater is the oceans and the clouds that carry it in the Earth’s atmosphere. A very small fraction, less than 3%, of this flowing skywater reaches land in the form ofrain and snowfall. The techniques of cloud seeding are concerned with extracting the optimum amount of rainfall or snowfall by injecting the clouds with certain chemicals that act as catalysts. The commonly-used chemicals are silver iodide in the case of cold clouds and sodium chloride and magnesium chloride in the case of warm clouds.
The transport of these chemicals to the clouds to the height of 1 km to 6 km is done by means of aircrafts, rockets or indirectly through thermal means on the ground. Maha Varun Holi Tantra is a simple low-cost ground-based cloud seeding technique suitable for Indian monsoon conditions which consist of mostly warm clouds, and sometimes warm cold clouds. The technique consists of simply making a fire, spreading on the fire twigs of latex-bearing plants such as vad and pipal, and sprinkling common salt in a continuous way.
The formation of clouds, their movement and dispersal through the Earth’s atmosphere are very complex and interwoven phenomena, and armies of scientists, satellites, instruments and radars are devoted to their study.
Material required for each Holi Tantra Prayog: You will require a ton (10 quintals) of dry biomass such as wood, bio-briquettes etc. For samidha: about 100 kg of wet twigs of latex-bearing plants such as vad, pipal, rui, umbar, etc., any of them will do. You will also require around 200 kg of common salt (NaCl). The approximate cost of each prayog is Rs.10,000 including labour and transport
Holi Enclosure Construction: A holi enclosure can be constructed by making around 16’ diameter circular structure on the ground. It requires about 600 bricks or 300 cement blocks. The structure has ventilation holes and a passage to enter or exit.
Holi Enclosure Location: Pick a spot where, if possible, there is natural or man-made protection from wind like a school ground or river basin, or inside a dry lake or pond.It should not be set up on hilltops (with the mistaken belief that it will be near the clouds!) but at the base of hills where up currents can carry salt vapours upwards and not sideways.
Timing for Holi Tantra: There should be good dark cloud cover in about 70 to 80 % of the sky.High relative humidity and very little wind, with temperature below approximately 28⁰C. If there are Cumulonimbus clouds (shape of cauliflower) around, that is very good. A good time is around 7 AM or any time when the above conditions are present. Not effective at night when the thermals are absent.The experience of the past 4 years indicates that this results in a good rainfall over 5 km x 5 km area in 2 to 48 hours. A Doppler weather radar will be able to advise on the correct time at each location.
Tantra of Maha Varun Holi: Arrange a ton of wood inside the Holi Kund in a circular shape with small twigs below. Cover the wood with samidhas of twigs of latex-bearing plants such as vad, pipal, umbar, rui. Start the fire around 7 AM or during the day when the cloud cover is good.Let the fire continue until all the wood is exhausted. May even take a day and night. The remaining salt-containing ash, after it is cooled, should be removed and can be used for the subsequent experiments.
How many times and where? The Varun Holi Tantra should be continuously done for a period of 3 days or until the rain starts. It is more effective if it is done simultaneously at several locations spread 5 km apart. You should cover the samidhas with salt in an even manner. The number of locations can be 10, 100 or even 1000! The simultaneous performance increases the salt content in atmosphere and can even create clouds in humid conditions.The common salt is quite harmless and has no environmental side effects.
Background: How was this technique arrived at? I did a Partnership Farming Project in village Sujlegaon, district Nanded of Maharashtra in June 2009. But there were no rains until 10th August 2009. The villagers approached me as a scientist and asked if I could do anything about the situation. I did some research on artificial rainmaking techniques and in the process contacted Prof Shivaji Rao through the Internet and he sent me his book “Cloud seeding for India – An effective weapon to fight drought”.
After going through the book, I got the inspiration from James P. Espy’s suggestion in 1839 to burn large blocks of wood to create clouds. In desperation to save the crops, I made a bonfire on 19th August 2009 in Sujlegaon and sprinkled salt on flames. To my utter surprise, in about 2 hours rainfall started and we got 5 mm of rain. That saved the crops! And what was interesting was that the rainfall was restricted to about 3 surrounding villages covering an area of about 5 sq km. As the news spread quickly in the villages, another farmer Shri Deshpande from a nearby village of Navandi performed similar experiment in his village and that too resulted in rainfall. The same result was achieved in village Rudrur of nearby Nizamabad district after a couple of days. This quick succession of three results motivated me to try this technique on a larger scale in the surrounding areas.After its discovery in August 2009 in Nanded district, more than 100 experiments were done in 2009 in Nanded, Hingoli and Latur district. Almost 70% resulted in rainfall within 2 to 48 hours.
To my utter surprise, in about 2 hours rainfall started and we got 5 mm of rain. That saved the crops!
I presented the technique at the Innovation conference conducted by the Pune Chapter of IITB Alumni Association in 2010. Through the Alumni network, I met Shri Prataprao Pawar, Chairman, Sakal group in May 2010 and demonstrated the technique successfully in Lonavla. The Varun Holi Tantra has been extensively popularised in Maharashtra during 2010 monsoon through the Sakal group of publications by the enthusiastic intervention of Shri Prataprao Pawar. In June-July 2010 I made a tour of Maharashtra and have personally conducted more than 100 demonstrations which were carried out in Pune, Satara, Kolhapur and Sangli districts, and the technique received widespread publicity in all Marathi papers such as Sakal, Lokmat, and Agrowon. In 2011 I was interviewed by the Krishidarshan program on Doordarshan and received more than 5000 phone calls. Over 1000 experiments were subsequently done all over Maharashtra. In December 2012 a massive experiment of simultaneous Varun Holi Tantra in 120 villages of Malshiras taluka of Solapur district under Shivamrit Doodh Dairy resulted in 80% villages getting rainfall. Despite this vast amount of awareness in Maharashtra, it is unfortunate that very few farmers are independently using the technique.
The Science of Warm Cloud Seeding: A cloud is a two-phase system containing water vapour and water droplets. It is a viscous medium containing water vapour (size < 1 micron) and water droplets (~ 10 microns). The colour of the clouds is an indication of the water droplet density. If the density is more, less light passes through the cloud, making the cloud blacker. Raindrop size is around 1 to 2 mm. About a million small droplets have to come together to make one raindrop.The process is called Langmuir chain reaction, named after the scientist who discovered it.
Rains: Langmuir Chain Reaction: The water droplets have a random Brownian motion in the clouds.If conditions are favourable, then two drops will stick together (“coalesce”) and a new, bigger drop results.The larger droplets in the viscous condition of clouds fall faster than small droplets (mass grows as cube of radius, cross-section grows the square of radius). Hence terminal velocity of larger drops is higher. This differential rate of descent results in larger drops gobbling up smaller droplets, and becoming bigger and bigger. A chain reaction! The drops of 1 mm to 2 mm diameter reach the ground as rain, smaller droplets evaporate back into the clouds.
Why cloud seeding works: The key principle is to increase the number of drops sticking together (coalescence) when they hit each other (collision).Cloud seeding aids natural processes of rain formation and acts as a catalyst in speeding up the rate of raindrop formation.The droplets are made of ‘distilled’ water evaporated from the seas, and have a neutral electrical field around them. When salt (NaCl) goes into the clouds, it dissolves into the water-forming weak saline solution. As NaCl is an ionic substance, the positive Na ions and negative Cl ions change the electrical field and the water droplets become like electrically-charged balls.Thus when two such droplets run into each other, the chances of their sticking together and becoming bigger increases.
Over 1000 experiments were subsequently done all over Maharashtra. In December 2012 a massive experiment of simultaneous Varun Holi Tantra in 120 villages of Malshiras taluka of Solapur district under Shivamrit Doodh Dairy resulted in 80% villages getting rainfall.
Scientific Hypothesis of Varun Holi Tantra: In the fire, the latex-bearing plants start burning. The salt sticks to the leaves and ash and goes up as smoke. The smoke rises to 50-100 feet by natural convection and gets injected in the base of the naturally occurring thermals in the atmospheric boundary layer.The thermals (like gliders, birds) carry them to 3000 feet at the base of the clouds. The salt reaching the clouds acts in the manner explained earlier.This increases the chances of rain starting, and if started, the rainfall increases.
Concluding Notes: Rain drives the economies of countries like India and China where a large component of agricultural production is determined by the rainfall pattern during the monsoon season. Hence its control should form an important component of national security. The Chinese have taken important steps since 2005 and have set up the Weather Modification Authority of China which employs more than 100,000 scientists and technicians. It also has a nationwide network of Doppler radars and a vast array of airplanes and rockets and a mechanism for their deployment and use.
Alumni Support: It would be helpful if some generous alumni can take some active interest in promoting this technique in India.