Earlier this month Tehran, a city of 10 million people, was questioning its viability. After six years of drought and the driest autumn in over 50 years, the reservoirs that supply the city fell to around 10 percent of capacity, and in some cases lower still. In late November and early December rainfall was down by roughly 90 percent, compared with historic averages. City residents faced rolling water cuts, sharply reduced tap pressure and pleas from officials to limit washing.
Iran’s president, Masoud Pezeshkian, announced in November that if rains did not come, parts of the city would need to be evacuated. Thankfully, rain eventually fell around Tehran, easing immediate pressure on water supplies. But the city came too close to disaster. There is no reprieve from the danger of taps running dry, and the prospect of more rain appears grim.
Tehran is just the latest major city to come perilously close to Day Zero — a term popularized in 2017, when the water supply in Cape Town fell so low that city officials considered a plan to shut off water taps and ask residents to collect water rations from distribution points. Cape Town, along with São Paulo, Brazil, in 2015 and Chennai, India, in 2019, recovered after nearly running out of drinking water, but all are getting by in ways that are expensive and ultimately unsustainable.
In a rapidly warming world, it is only a matter of time before luck runs out in Tehran or the dozens of other drought-prone cities. When it does, the lesson from the past is not that cities must simply find more water, but that they must also confront their limits.
Any proposal to relocate a city is a distraction from the fact that restricting growth and water use — however politically difficult — is often more prudent than trying to engineer ever more elaborate workarounds. Cities that survive ecological stress are those that adapt their scale and behavior to their environment, not those that assume technology can endlessly override natural limits.
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The drought conditions in Iran are in part a result of climate change: Much of the Middle East, including Iran, is warming twice as fast as the global average, and climate change is altering precipitation cycles across the Iranian plateau. Winters are becoming shorter and drier; snowpack in the Zagros and Alborz mountains — critical natural reservoirs that once fed rivers and aquifers during spring and early summer — is shrinking. When rain does fall, it increasingly comes in intense bursts that run off hardened ground rather than soaking in, doing little to recharge groundwater.
Global warming, though, is only part of the problem. The Iranian water infrastructure has long suffered from a lack of investment as well as from the illegal drilling of hundreds of thousands of wells that sustain agriculture and industry. The Iran Water Resources Management Company estimates that its workers seal around 13,000 illegal wells each year, or 250 a week, without making a major dent in the problem.
Other factors may contribute even more to the crisis: rapid urbanization, growing population and rising water use. Tehran’s population, for example, has risen from 700,000 during the 1940s to around 10 million today.
Such rapid growth is unsustainable, Mr. Pezeshkian has said, which is why he suggested the best course of action was to move the country’s capital to the Gulf of Oman coast.
I have my doubts about whether the government is up to such a herculean logistical task. There is the question of money: relocating a capital demands tens of billions of dollars of investment in infrastructure, housing, transport and services. Iran is already cash-strapped by sanctions, inflation and competing social needs. But the real problem is that such an effort would absorb scarce resources that might otherwise be directed toward addressing the underlying water crisis: getting serious about water management, pricing, agriculture’s overuse and urban growth.
We have seen what happens in other cities when authorities fail to address these deeper issues. India’s tech capital, Bengaluru, formerly known as Bangalore, cannot meet its demand for water with local resources and instead relies on fleets of private tankers from outside the city, which charge varying rates for water, draining people’s savings and exacerbating inequality. Istanbul has invested in reducing water leakage and improving efficiency and conservation, buying it time from its own crisis. But these measures have not altered the basic arithmetic of finite supply and growing demand. As cities continue to grow and aquifers are depleted, the distances, costs and social tensions involved rise sharply — which ensures that emergency solutions only temporarily delay the reckoning to come.
Cities have come and gone throughout history. Many of the greatest urban centers of the past — Lagash and Uruk in Mesopotamia, Angkor in Cambodia, Tikal in Guatemala — were eventually undone in part by failures to manage water. Once the ecological balance tipped, even the most sophisticated societies struggled to recover.
To avoid the fate of Lagash and Angkor, Tehran and other modern cities must do something radical by contemporary political standards: accept that living within ecological boundaries is not optional. That means setting hard limits on urban expansion, aligning population and consumption with available resources and treating water not as an endlessly flexible input but as a defining constraint.
Even cities long built on the assumption of limitless growth are beginning to confront this reality: places such as Las Vegas and Phoenix, which have been historically reluctant to cap expansion, are now debating moratoria, tighter planning rules and growth management. Water scarcity has exposed the costs of assuming that physical limits do not apply, and that all problems can be solved by human ingenuity or by throwing money at them.
Like all species, humans depend on equilibrium with the natural world. Our ingenuity allows us to bend the rules — but not forever. In the long run, the bank always wins.
Peter Frankopan is a professor of global history at Oxford and the author of five books, including “The Silk Roads: A New History of the World.”
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