India and the rest of Asia are dependent on the monsoons for rains. While the South West Monsoon is the main source for India as a whole, Tamil Nadu and coastal areas of South Andhra Pradesh get the benefit of the North East Monsoon, which is just a less dependable beat on the reversal of the South West Monsoon winds.
Over the years irrigation engineers have done much to ensure maximum utilisation of available surface water resources by building anicuts and dams, excavating canals and modernising existing schemes to optimise the use of water for irrigation, adopting techno-efficient measures. Agricultural scientists are developing through research ways to meet the water requirements for crops. Agro-engineers have developed devices such as sprinklers and drip systems to economise on the transmission of the water for crops at the field level.
Meteorologists are increasingly thinking of ways to cajole passing clouds to precipitate, as irrigation sources run dry and farmers keep their fingers crossed. Thus started the attempt to seed the pregnant clouds to deliver much-needed rain at such critical times.
A pioneering cloud-seeding initiative was attempted as early as in 1970 at the Irrigation Research Station in Poondi, Chennai, where the then Director organised silver iodide spray on promising clouds by engaging an aircraft to fly low. There was limited success. But it was only a research endeavour and could not be pursued further for want of encouragement. Unfortunately this strengthened the view of the pessimists who came to the decision that cloud-seeding is a costly endeavour with uncertain success.
Cloud-seeding as an attempt at weather modification has been tried in a few States in India and in other developed and developing countries. Handsome success was achieved in the U.S. for active field research in Texas, North Dakota, California and a few other States in 2009. There is today the opinion that perhaps cloud-seeding can improve rainfall in the catchment areas and bring more inflows to the multipurpose reservoirs in rain-deficit years. Success in cloud-seeding attempts has been reported from China, Tasmania, Australia, the Philippines and monsoon-dependent East Asian countries.
In Andhra Pradesh, the Jawaharlal Nehru Technological University, Hyderabad, at its Centre for Atmospheric Sciences and Weather Modification Technologies (CASWMT) has tried cloud-seeding operations in 600 mandals, covering 12 districts during 2004-08. This was followed by good rainfall enhancement, which helped to save crops, both irrigated and unirrigated, at critical times.
This university conducted an international workshop on Weather Modification Technologies and Natural Disaster Management in 2008 at Kukatpally, Hyderabad. There was a good discussion on cloud dynamics and cloud-seeding and experiments were carried out. Results were presented by participants from Mexico, Thailand, China and South Africa, and Maharashtra. The results presented were encouraging and gave the hope that the science of weather modification would soon develop into an alternative research theme.
In the Indian perspective, cloud-seeding experiments conducted by the Indian Institute of Tropical Meteorology in Pune for more than a decade were reported to show an indication of 24 per cent enhancement in precipitation in targeted areas.
The University Research Centre at Hyderabad has developed the technique of ground-based seeding, through chemical flares and mini-rockets, in lieu of seeding by means of aircraft. The operations from 2005 onwards involved predominantly mini-rockets sent up towards promising clouds. These were loaded with chemicals which help in cloud condensation and precipitation.
Major studies have proved cloud-seeding to be effective and the process has proved helpful in critical times. Further development of this technique and its adoption may help us in water management, including in the Cauvery Delta, particularly in deficit years.
Governments ought to pay attention to the technique of cloud-seeding and encourage further research, taking necessary help from other departments, particularly the India Metrological Department.