Tehran is running out of water. Rationing has begun in Iran’s capital city, with some of the approximately 10 million residents experiencing “nightly pressure cuts” between midnight and 5 am. The entire country is in an unprecedented drought, facing its driest — and hottest — autumn in nearly 60 years. Tehran has received no rain at all since the start of September, and no rainfall is expected for the foreseeable future.The city depends on five major reservoirs for its water supply. One has dried up completely, with another below 8 percent capacity. The managing director of the Tehran Regional Water Authority told state media last week that the Karaj Dam has only two weeks of drinking water left. The drought extends beyond the city, too. The water reserves of Mashhad, the second largest city in the country, have dropped below 3 percent capacity, putting 4 million people at imminent risk. This story was first featured in the Future Perfect newsletter.Sign up here to explore the big, complicated problems the world faces and the most efficient ways to solve them. Sent twice a week.But if nothing changes, Tehran may soon face Day Zero — or when a municipality can no longer supply drinking water to its residents and taps run dry. In October, President Masoud Pezeshkian claimed that Tehran could no longer serve as the country’s capital, citing the water crisis as a major factor. “If it doesn’t rain in Tehran by late November, we’ll have to [formally] ration water,” Pezeshkian told Iranian state media on Thursday. “And if it still doesn’t rain, we’ll have to evacuate Tehran.”While it’s unlikely evacuation will happen any time soon, Tehran’s water crisis is not made equal. When the taps run dry, more affluent Tehranis purchase mineral water or rely on water tankers, a prohibitively expensive option for many. The rest must rely on charity, or they will die of thirst.How did things get this dire?Water use in Tehran is quite high, even for cities. But Iran’s water problems go deeper than this record-breaking drought. The country is uniquely isolated and subject to numerous sanctions, crippling the economy and making it very difficult for Iran to obtain state-of-the-art water technologies. It’s an enemy state to many of its neighbors, as well as regional leaders in desalination technology — Israel, Saudi Arabia, and the United Arab Emirates. But desalination is largely irrelevant in an Iranian context, often coming at a high environmental cost. According to water issues analyst Nik Kowser, Iranians are under the thumb of a “water mafia” — a shadowy and well-connected network driving these megaprojects for their own gain. “Iran faces water bankruptcy, with demand far outstripping supply,” Kowsar wrote in Time. “The collapse of water security in Iran has been decades in the making and is rooted in a mania for megaprojects — dam building, deep wells, and water transfer schemes — that ignored the fundamentals of hydrology and ecological balance.” Iran is also particularly vulnerable to the effects of climate change: Over 82 percent of the country is arid or semi-arid, and Iran is sixth on the list of countries most prone to natural disasters. The country grows thirsty crops, and its quest for food security and self-sufficiency is a tremendous driver of its water bankruptcy. The agricultural sector comprises up to 90 percent of the country’s total water withdrawals. But Iran’s environmental crisis does strain existing geopolitical tensions both inside and outside of the country. Water is sometimes transported from one region of the country to supply another, driving fears that certain ethnic populations are intentionally being deprived at the expense of others. Yale University historian and Iran expert Arash Azizi, who is also a contributing writer for The Atlantic, told me that despite the tremendous humanitarian cost of continued sanctions, they are very unlikely to be removed in response to the water crisis. The future of urban livingTehran joins many, many other cities that have approached Day Zero, and it certainly will not be the last. São Paulo in Brazil and Cape Town, South Africa, had similar crises that ended with rainfall. Tehran might not be so lucky in terms of its weather forecast, though. So, let’s loop back to the idea of evacuating Tehran.It is, of course, incredibly unpopular. Iranians balked at the idea when the president mentioned the possibility. Former Tehran Mayor Gholamhossein Karbaschi said this was “a joke… Evacuating Tehran makes no sense at all.” Azizi thinks it’s unlikely that Iran will end up moving its capital anytime soon. The majority of jobs are in Tehran. And evacuating a city of upward of 10 million people would be an incredible logistical challenge. More importantly, relocation won’t fix the immediate issue of water access. But the current strategy of trucking in supplies, rationing water, and praying for rain is woefully inadequate to meet the moment. And water rationing is a stopgap measure. “Actually cutting off the supply to households or to individual neighborhoods de facto reduces their consumption,” said David Michel, senior fellow for water security at the Center for Strategic and International Studies. “But the underlying demand is still there.”However, there are other kinds of strategies cities like Tehran could employ. Michel argued that cities have to prioritize business models that provide the resources and revenues needed for water systems to operate, maintain, and expand to serve new customers.“That challenge has put many city water systems around the world into this very challenging spiral where lots of municipal water systems’ revenues don’t cover the costs of operations and maintenance, much less expanding supply,” Michel said. Economic incentives like volumetric tariffs, where the cost of water is proportional to the amount consumed, could be beneficial. The more you use, the higher price you pay, essentially, with the hope of reducing pressure on the poorest consumers. Relief can’t come to Tehran soon enough. American cities in California and the southwest, with similarly arid climates and dwindling water supplies, should take heed. And everyone should pay attention when the president of Iran says the residents of its capital city may have to evacuate in a few months’ time. “You can imagine the psychological effect,” Azizi said. And that could be “the future of everywhere in the world.”