Delhi govt hopeful of cloud-seeding trials by month-end

Barring a few technical clearances from the Directorate General of Civil Aviation, the Delhi government has received approval for the project

New Delhi

The aim of the trials is not to assess impact on air quality, but whether rain could be induced artificially during peak pollution season. (Sanjeev Verma/HT)

The Delhi government is hopeful of conducting a pilot cloud-seeding trial by the month-end, environment minister Manjinder Singh Sirsa said on Wednesday, pointing out that barring a few technical clearances from the Directorate General of Civil Aviation (DGCA), the Delhi government has received approval for the project. The ministry of defence has allowed the government to fly a plane for the project from the Hindon Air Base in Ghaziabad.

Sirsa said that once the final clearance is in place, the government will seek a six-hour plan from the India Meteorological Department (IMD), which will analyse moisture content in the air, geographical spread of clouds and their density in the Capital.

“The good news is that the permissions we needed from the agencies and central government departments have all been received, barring a few technical clearances from the DGCA, which should be in by next week,” Sirsa said.

“We have already spoken to IMD and they will share with us a deep analysis of the atmospheric conditions. These six-hour plans will basically tell us when to fly the plane and in which areas we have suitable moisture and conditions to do cloud-seeding,” Sirsa said.

Cloud-seeding is a weather modification technique, wherein silver iodide (AgI) is released into the atmosphere to aid the formation of ice crystals and improve the ability of the cloud to create rain. “A team from IIT Kanpur met us on Tuesday night. The team will remain in Delhi and once we get the data from IMD, we can practically hold the first trial within 24 hours,” Sirsa said.

The government said the trial will take place only in the outer parts of Delhi. “The flights will avoid restricted airspace such as VIP-89 (Rashtrapati Bhawan, Parliament, PM residence), as per standard aviation protocol,” an official said.

When put to the minister that the southwest monsoon, which generally hits the Capital on June 27, was progressing at a faster-than-usual pace, Sirsa said it would not impact their plans. “We will not hold a trial on the day it is already raining, but on a day when there is sufficient moisture but less chance of natural rain,” Sirsa said.

On Wednesday, Delhi’s air quality index (AQI) was 81 (satisfactory), its lowest since it was 76 (satisfactory) on September 29, 2024.

Sirsa said testing the impact on Delhi’s air quality was not the primary aim of this trial. “We already know rain positively impacts air quality. The goal of this trial instead will be to determine whether or not this will work, how much area it can influence and how much rain is possible,” he said.

Sirsa said that according to IIT Kanpur, Nimbostratus (Ns) clouds were most suitable for seeding experiments, and these are usually at heights between 500 and 6,000 metres.

“The clouds also need to have 50% or higher moisture content.,” he said, adding IIT Kanpur custom seeding mixture, in addition to silver iodide, also contains powdered rock salt, iodized salt and a free-flowing agent that combines hygroscopic and glaciogenic cloud-seeding capabilities. “The seeding mixture requirement will vary according to moisture content.”

On May 8, Sirsa announced that the government sanctioned a project outlay of ₹3.21 crore, with five trials to cost ₹55 lakh each. The remaining ₹66 lakh would cover aircraft calibration, chemical storage, logistics, and other preparatory arrangements. “The pilot will be conducted with five flights and in a coverage area of 100 sq km. The trial will be done in northwest or outer districts of Delhi,” Sirsa had said in May.

To be sure, the state government needs clearances for trials from the Special Protection Group (SPG), the Central Pollution Control Board (CPCB), the Union ministries of environment, defence and home, the Uttar Pradesh state government, IMD, the Directorate General of Civil Aviation (DGCA), the Airports Authority of India (AAI) and the Bureau of Civil Aviation Security (BCAS).

Manindra Agarwal from IIT Kanpur said that while Delhi’s air was fairly clean at present, the trial will allow them to assess the impact of silver iodide. “A concern being raised by people was how silver iodide will impact the environment. As per our assessment, the impact is negligible. However, this run will provide us with fresh data for the same. We will collect water samples after it rains to assess the concentration of silver iodide,” he said.