Out of the many compounding catastrophes happening in the world, including the ones in Sudan and in Gaza, one is happening in Iran. Tehran is a gulp away from thirst.
Iran’s President Masoud Pezeshkian warned, “If it doesn’t rain in Tehran by late November, we’ll have to ration water. And if it still doesn’t rain, we’ll have to evacuate Tehran.”
With forecasts showing no rain for days and weeks, people in Tehran could runout of water in the next two weeks. Iran has been on the boil for some years. In July this year, 52.77 C was recorded in the city of Shabankareh.
During the 12-day Iran-Israel war, Israel bombed water infrastructure. In summer, water reserves plummeted to their lowest in a century. On August 29, 2024, a weather station near Qeshm Dayrestan Airport in southern Iran recorded a staggering heat index of 82.2C (180F), potentially marking the highest temperature index ever documented on earth. The heat index combines air temperatures and humidity to estimate how hot it feels.
From 2,50,000 a hundred years ago, Tehran’s population increased to 9.8 million now. A witch’s brew of climate change, corruption, overdrawing of reservoirs and inequity has since parched the land.
So, where does India figure?
“Our condition is quite different in the sense that we are facing more wet versus dry kind of pattern,” said Amey Pathak, assistant professor at IIT-Kharagpur. Pathak is an expert on hydro-climatology, monsoon and weather extremes.
India has short-duration, intense bursts of rainfall, coupled with prolonged drought events “which are things that are alarming, actually”.
Rainfall is the main source that fulfils our demands of water. Around 70 per cent of freshwater is consumed in agriculture. The regions where agriculture is dependent on good monsoon are likely to be hit hard if monsoon tanks. Total rainfall in the last 30 years remains more or less the same. However, the inter-annual variability, what is happening within a season in terms of extremes, has become volatile.
For example, in Maharastra this year, many places got hit by intense rain, causing a lot of damage. In contrast, prolonged drought continues to bake and bruise the Bundelkhand region, parts of Madhya Pradesh, rain shadow regions of Western Ghats, and in Marathwada.
Most of the rain for India comes from the Indian Ocean. During the summer the Intertropical Convergence Zone (ITCZ), also called the equatorial trough, moves over the Indian subcontinent. It births a zone of low pressure, called the monsoon trough, which draws moisture from the Indian Ocean towards the landmass, bringing in the southwest monsoon from June to September.
Pathak said the Indian Ocean is warming at an alarming rate, especially the Arabian Sea branch. This is resulting in more frequent extreme rainfall events. Although the total rainfall numbers may not vary much, these intense bursts are damaging in nature. Moreover, storing these waters is not feasible; they are lost as run-off.
In the context of climate change, researchers have argued that in the near future, there are two competing factors that lead to rainfall in India. One is the dynamic effect that leads to the transport of moisture: warm pools of water evaporate more; along with wind, moisture gets transported toward the landmass.
The other is the thermodynamic effect that is temperature-dependent: warmer oceans mean more evaporation. The critical question here is whether the it is coming back in the form of precipitation.
Pathak refers to 2024 paper which analyses the relationship between water vapour and rainfall during the Indian monsoon. The paper states: “Most climate models have shown that the Indian Summer Monsoon Rainfall (ISMR) will increase on account of global warming. The primary reason is the increase in column water vapour (CWV). The rainfall increase is not, however, proportional to the increase in column water vapour; for a given amount of CWV, rainfall will be lower in the future, according to model simulations. This suggests that other there are factors are at play.”
The researchers talk about lapse rate, which is the rate at which atmospheric temperature drops with height. If an air bubble goes up, it gets cooled down at a certain height in the upper layer of the atmosphere. If the upper layers are getting warmer, then it will be difficult for the water parcel or air bubble to get condensed quickly.
“So, even though the evaporation is more, or the total column water vapour is more, it is still not leading to higher precipitation,” said Pathak.
Earlier, researchers mostly attributed India’s precipitation to the dynamic effect. “But now we are experiencing that both effects (dynamic as well as thermodynamic) play important roles. And what we get as a rainfall will be the combination of that,” said Pathak.
These effects are not abstract; they directly determine how much water is available and for how long; whether it can meet year long domestic and agricultural needs.
Tier-one and two cities are bursting with people, as in Tehran and elsewhere. Demand for freshwater and drinking water has increased as has the drawing of the groundwater.
Back in 2018, Cape Town was inching towards Day Zero. Transparency, information and behavioural change saved Cape Town. In 2024, Mexico City averted Day zero with the rain gods saving it. Tehran awaits a miracle.
