In early August, torrential rains battered districts on Karnataka’s coast and along the Western Ghats, swelling rivers and submerging large tracts of land. Between August 1 and August 10, the coastal districts received over 1,000 mm of rain.
In the same period, some 350 km inland, Raichur and its neighbouring districts had received less than 20 mm in 10 days, and its residents were anticipating the seventh year of drought this decade. Radars scanned the skies and two planes hovered over arid landscapes looking for rain-bearing clouds that could be ‘nudged’ into precipitation in these areas.
Karnataka had been blindsided by the floods, but for drought, administrators had been prepared with a desperate trick up their sleeves: weather modification.
Since July 25, planes have taken off to ‘seed’ clouds over Karnataka’s drylands as part of a Rs-45-crore cloud-seeding project to enhance monsoonal rainfall. This year, Maharashtra is also implementing a project to induce rainfall over the drought-hit Marathwada region for Rs 30 crore. This is the largest public investment in operational cloud-seeding in India to date.
In a cloud-seeding project, radars on the ground guide airplanes towards rain-bearing clouds over areas with a rainfall deficit or high soil-moisture stress. The planes then ignite chemical flares of potassium chloride or calcium chloride for warmer clouds, whose bases are above the freezing point1, and silver iodide or other ice-forming particles when the cloud’s base is below the freezing point2. Water vapour condenses around these particles until they become heavy enough to fall to the ground as rain.
But chasing these clouds is not easy, and the variability of the monsoons that cloud-seeding is supposed to help deal with has become a significant hurdle. In Maharashtra’s case, officials have struggled to find “seedable” clouds.
Karnataka has been implementing a more sophisticated and well-coordinated system, but the results are only slightly better. Between July 25 and September 12, two planes that could potentially have flown 97 seeding sorties undertook only 53, according to data from the Rural Development and Panchayati Raj (RDPR) department. In 21 cases, the planes were grounded due to an absence of suitable clouds.
“This year, the monsoons have seen intense short spells of rain or long [lull] periods in these dry areas,” H. Prakash Kumar, chief engineer of water and sanitation at RDPR, said. “We can’t seed if suitable cloud formation doesn’t take place.”
Their preliminary data suggests at least 650 mm of rain was received in a few hours after the clouds were seeded. Kumar believes much of this can be attributed to the seeding operation.
“The precipitation due to seeding cannot be separated from the natural precipitation,” Thara Prabhakaran, a project director at the Indian Institute of Tropical Meteorology, Pune, added. The World Meteorological Organisation (WMO) has suggested “statistical evaluation with randomised experiments and physical experiments to demonstrate seeding’s effects on precipitation.”
J. Srinivasan, a distinguished scientist at the Divecha Centre for Climate Change, IISc, Bengaluru, was more cautious. “We don’t have an identical unseeded cloud whose precipitation can be compared to a seeded cloud. These are complex systems. The numbers showing increase in rainfall” aren’t entirely reliable, he said.
Karnataka and Maharashtra aren’t alone in their support for this engineering fix. Politicians in many other states, especially those with large drought-prone areas, are eager to follow suit. In response to multiple questions in the Lok Sabha earlier this year, Ashwini Kumar Choubey, the then minister of Earth sciences, said IITM will draft cloud-seeding protocols for use in the rain-shadow regions of the Western Ghats.
At least 56 countries have attempted some sort of weather modification, for purposes ranging from hail suppression to fog dispersal and rainfall enhancement. India has the world’s fifth-highest investment in weather modification.
China in particular has been pushing geoengineering to its limits. After having kept the rain away from the Beijing Olympics in 2008, its government is now working on the world’s largest weather-modification programme in Tibet. In 2018, it spent millions to install 500 burners to produce enough silver iodide to induce up to 10 billion cubic meters of rain – a volume of water equal to 7% of the country’s total consumption. India is right to worry about how this will affect the Brahmaputra.
Cloud-seeding in India is over 60 years old, with the first experiments conducted at IITM Pune. These endeavours culminated with the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) in 2009.
However, states have attempted to use this technology at different times: Tamil Nadu in 1984-1987 and then in 2003; Andhra Pradesh in 1998; Karnataka in 2003 and 2009; and Maharashtra in 2015. There has been renewed interest since 2017, when Karnataka launched its cloud-seeding project, called Varshadhare, at a cost of Rs 35 crore.
Under Varshadhare, operational weather modification had scientific oversight for the first time in the country. Scientists and meteorologists, working together in a monitoring committee, tracked clouds through three ground radars. The state’s disaster monitoring centre provided data about moisture-stressed regions while 6,000+ rain gauges spread across the state provided post-seeding rainfall data.
In a paper published a year after seeding, in May 2019, IITM researchers revealed that, on average, areas the clouds over which had been seeded received 27.9% more rain compared to an estimated ‘normal’ value. This is roughly an additional 2.1 billion cubic feet of water.
“The results … [could help] establish a long term policy for cloud seeding in the state of Karnataka,” the paper concludes.
More research needed
For now, the Earth sciences ministry has said it is not considering any cloud-seeding proposals but that it has increased its expenditure on CAIPEEX experiments.
IITM has focused the CAIPEEX experiments on understanding monsoon clouds better and has also supplied technical guidance to state governments. It expects its experiments will conclude in 2019.
Experts from the WMO have noted that while water shortage motivated the first cloud-seeding initiatives, climate change added a renewed urgency – so much so that there have been many instances of seeding undertaken without rigorous study or on the back of empty promises.
This in turn has brought on more complexity and uncertainties. “Seedable clouds are available only at selected time and at selected places. Cloud-seeding is not an answer to ensure better distribution of rainfall,” Prabhakaran said. “Cloud-seeding can be adopted at small scales and in select catchment areas, once a scientific basis is in place.”
The Karnataka government has clarified that cloud-seeding is just another arrow in its quiver against drought, and not the sole arrow. It is also implementing rainwater harvesting, tank rejuvenation, large-scale drinking water pipeline projects from perennial rivers, and other schemes. And irrespective of Varshadhare’s success this year, the state is committed to supporting the project next year as well. The RDPR department has also asked for a long-term seeding policy to be followed by a separate department with its own human, technical and monetary resources.
R.S. Sharma, former deputy director general of metrology at the India Meteorological Department, who was involved with Maharashtra’s cloud-seeding experiments in 2015, believes the technology can be an “important” tool with which to manage water. However, he is also wary of states adopting it simply to score political points with farmers without paying more or any attention to whether it will pan out.
“If done properly, with technical and scientific oversight, we may see positive results,” Sharma said. “But human errors are common in such an unpredictable ecosystem. Unsatisfactory results could lead to adverse public opinion.”
For example, funding in the US for research into weather modification fell from $19 million a year in the 1970s to $0.5 million by 2000 after scientists over-promised solutions and politicians became cynical. India should be working around this, according to Sharma, by waiting for CAIPEEX’s results before future plans are made.
Then again, even within the extant set of protocols, cloud-seeding can’t be a long-term solution to manage drought, according to Srinivasan of IISc. His objection stems from the economics: after all, success is not guaranteed.
“You are not going to get a significant increase in rainfall every time. The cost per litre generated in the long-run will be prohibitive compared to more efficient ways of conserving water,” Srinivasan explained. “Research in the US and Australia has shown it is not economically viable.”
Clouds also have a fixed amount of water, so if clouds in one area are made to rain down, the question arises if this is water stolen from another area. Farmers in the West, where the solution has been in use for a longer time, have taken seeders to court over such issues. Srinivasan agreed this is possible but added that there was no way to be certain. One 2015 study recorded cloud-seeding chemicals spreading to areas 200 km downwind of where they were first injected, with potential consequences for regional water balance.
Mohit M. Rao is an independent journalist in Bengaluru interested in environment, wildlife and their socioeconomic intersection. He tweets at @mohitmrao.