GS Paper III

News Excerpt:

The Indian Institute of Tropical Meteorology (IITM) reported that the CAIPEEX experiment showed rainfall could be enhanced by up to 46±13% at certain locations and an average of 18±2.6% over a 100 square kilometre area over the rain shadow region of Solapur.

About Cloud Aerosol Interaction and Rainfall Enhancement Experiment (CAIPEEX):

• The first phase of CAIPEEX began in 2009. The second phase was in 2010-11, the third in 2014-15, and then came the fourth phase in Solapur in 2017-19.
• CAIPEEX IV, was one of the largest experiments in cloud seeding attempted anywhere in the world.
• It was conducted over two years to test the feasibility and effectiveness of cloud seeding to create rain.
• IITM evaluated samples of 276 clouds to test the effectiveness of cloud seeding.
• The latest report said the first three phases consisted of research and studies on clouds and airborne observations of clouds and rain.
• Their outcomes helped scientists at the IITM to design cloud seeding experiments for the fourth phase.
• The report concluded, that cloud seeding under suitable conditions could effectively enhance rainfall in a region.
• All measurements were done using a wide network of state-of-the-art equipment such as automatic rain gauges, radars, radiometers, and aircraft.
• The results showed robust statistical significance above the 95% confidence level.
• The IITM experiment laid down elaborate protocols for state governments and others for doing cloud seeding.

Cloud seeding:

• According to the IITM report, cloud seeding is a technique in which cloud-forming particles are used to increase rainfall.
• The clouds are spotted using radars and once a cloud is identified, the base of the cloud is pumped with the chemicals.
  • Most cloud seeding operations use a compound called silver iodide (AgI)
• It can be done in two ways, hygroscopic and glaciogenic.
  • Hygroscopic seeding is done at the base of warm clouds, using seed particles with an affinity for water vapour.
    • During monsoon, hygroscopic seeding is more advantageous in enhancing rainfall and ensuring longevity of the clouds.
  • Glaciogenic seeding, is carried out in cold clouds by seeding near the top of the cloud, using silver iodide particles, which may form ice particles in the clouds.

National and Global Practices:

• IITM tried hygroscopic seeding in the 1970s. Subsequently, several states, such as Maharashtra and Karnataka, from time to time attempted creating rains artificially, but with limited success.
• More than 56 countries practise cloud seeding to create rain.
• Some of them are Australia, China, Russia, Thailand, the United Arab Emirates, and the United States.

Challenges:

• Practically cloud seeding can only happen in the monsoon months, as you need some amount of moisture in the clouds that can then be enhanced through seeding.
• Cloud seeding can’t happen in clear blue skies.
• That is one reason why cloud seeding cannot be the right solution to bring down Delhi’s pollution in winter.
• Cloud seeding cannot mitigate large-scale droughts.
• It just brings rain to a village facing water scarcity.
• The IITM Report said that currently most of the technology and equipment required for cloud seeding were imported.

Way forward:

• Earth Sciences Minister has said that cloud seeding will be used only in extreme circumstances.
  • Scientist also agrees with it and have said it should be attempted in places like perennially water-deficit areas such as Telangana or Vidarbha.
  • Meanwhile, the centre at IITM should facilitate the indigenisation of technologies for cloud seeding aligned with the Make in India vision.
• A much simpler way would be to conserve rainwater, because India get around 1,000-1,100 mm of rainfall in a year and it don’t need artificial rain except perhaps in extreme conditions.
  • Studies show that of India’s annual rainfall, 35-55% is the run-off rate in different regions.
  • The environmental flow requirement is a minimum of 10 to 15%, while the rest can be used by creating water infrastructure or artificial groundwater recharge.
• The priority should be groundwater recharge, as this is where water is extracted from, and groundwater is the primary source of water in India.