Iran faces an extreme drought, prompting the president to suggest a possible evacuation of Tehran. To mitigate the situation, cloud-seeding aircraft will start operations on November 15, set to persist through the rainy season until May. However, experts caution that this method is complex and unlikely to significantly alleviate the water crisis on its own.

How critical is the drought in Iran?

Iran’s rainfall is down by 85 percent, with Tehran registering only 1 mm this year. Local reservoirs are reported to be in a dire condition, with 32 dams barely holding 5 percent of their capacity. Satellite imagery shows some areas completely parched.

Residents of Tehran have cut their water usage by approximately 10 percent, yet this reduction falls short. Water pressure has diminished overnight, and officials are preparing to fine households and businesses that exceed their water limits. The president indicated that if rains do not increase by December, 14 million people in Tehran might need to relocate.

What are the causes of drought?

Experts attribute the drought, which has persisted for five years, to climate change. This autumn is the driest Iran has seen in 50 years, with temperatures reaching above 15°C (59°F) in Tehran, a city usually experiencing snowfall in November.

However, mismanagement is largely to blame. Kave Madani, a former environmental ministry official, labels Iran a “water bankrupt.” The government has expanded agriculture in arid regions excessively, stressing water resources. A staggering number of illegal wells—around half a million—have been drilled by desperate farmers, draining groundwater supplies.

What exactly is cloud seeding?

Cloud seeding originated in the 1940s with scientists like Bernard Vonnegut, brother of author Kurt Vonnegut. The process involves dispersing particles that encourage water droplets in clouds to precipitate as rain. While some studies have experimented with salt, the focus has generally been on spraying silver iodide into upper-level mixed-phase clouds. When supercooled liquid droplets encounter this crystalline material, they crystallize into ice that ultimately falls as rain or snow.

Determining the amount of precipitation caused by cloud seeding can be challenging, especially in the absence of cloud formation.

“The natural variability of clouds is significant, making it tough to quantify their impacts,” says Andrea Frosman from the University of Clermont-Auvergne, France. “Externally, clouds appear, but not all of them bring rain.”

A 2014 experiment conducted in Wyoming indicated that cloud seeding could enhance precipitation by 5 to 15 percent.

Is there hope for resolving the drought?

Previously, Iran blamed Israel and the United Arab Emirates for “stealing” rain via cloud seeding, but it’s now taking matters into its own hands. It plans to deploy cargo planes, drones, and a “ground generator”, which is essentially a smoker’s oven, commonly located in mountainous regions.

On November 15, clouds formed over the watershed surrounding Lake Urmia, which has been barren for over two decades, now reduced to a salt flat littered with decaying boats. Initial reports suggest that areas west of the lake received up to 2.7 centimeters of rain the following morning, as indicated by a precipitation map from the University of California, Irvine.

Success in cloud seeding depends on the presence of moisture-rich clouds, which might be sparse in arid Iran, where large bodies of water are limited.

“Cloud seeding becomes particularly challenging during droughts, owing to the extremely dry atmosphere that may not support moisture-laden clouds,” notes Karen Howard, a scientist with the U.S. General Accounting Office.

Yet, in recent days, numerous rain clouds have poured into Iran from the Black Sea, causing localized flooding in regions such as Iram and Kurdistan on November 16.

Cloud seeding might help “extract a few additional droplets” from these weather systems, according to Armin Sorooshian at the University of Arizona. “While it won’t create flooding or completely solve the drought issue, it may provide a minor benefit.”