At the time of writing, Tehran’s reservoirs are estimated to hold just nine more days of drinking water. If it does not rain soon, president Masoud Pezeshkian has warned, the capital city – home to 10 million people – may have to be evacuated.

The crisis is national and extraordinary. In the northeastern city of Mashhad, the second largest in Iran, reservoirs are down to less than three per cent of capacity. In all, the energy ministry said on Tuesday, 19 of the country’s major dams are on the brink of running dry.

Archaeologists have even warned that the aquifer beneath Persepolis itself has been so thoroughly drained that the ancient city – Darius’s tomb and all – could soon collapse into the ground.

. . . Thoughtless development has drained the aquifers, and Tehran has been allowed to grow so fast and so chaotically that its landscape simply cannot support the modern population, he argued. The capital’s institutions, he said, will have to move to another part of the country – probably the south. The vast civilian population possibly evacuated. And worst of all, he complains, there is almost nothing that can be done about it.

The situation is now “beyond” a crisis, says Kaveh Madani, a former deputy head of Iran’s environment department. Both the “checking account” of rain-filled mountain reservoirs, and the “savings account” of groundwater, which has traditionally got the country through dry years, are exhausted. “Now, we are in the sixth year of drought.