Amid the escalating protests over water shortages in Iran’s oil-producing Khuzestan province, government officials in Tehran are unable to fall back on the old excuse that nobody could have seen the crisis coming. They themselves did.

In 2015, Isa Kalantari, a former Iranian agriculture minister, warned that water scarcity would force 50 million Iranians — 60 percent of the population — to leave the country. He complained that officials in Tehran had for too long ignored the problem, adding: “And now that they understand it, it’s a little late.”

Two years later, this Cassandra was given the opportunity to do something about the calamity he had prophesied: Kalantari was appointed the Islamic Republic’s vice president for environmental protection — effectively, its environment minister. Since then, he has done little more than pronounce even more dire auguries. At the start of this summer, he predicted a “water war” that would spread in the countryside, putting Iran in danger of being “wiped out.”

This is hardly reassuring to Iranians in the provinces that have been parched by what Kalantari’s colleague, Energy Minister Reza Ardakanian, has described as the driest summer of the past 50 years. But the sun-baked villages of Khuzestan are not taking up arms against one another: Their anger is directed at the government in Tehran. Across the province, protesters are calling for the downfall of the regime and of Supreme Leader Ali Khamenei.

And it’s not just about the lack of water, either. The scarcity is only one manifestation of the central government’s failure to provide basic services for a province that has been aggressively exploited for its resources. There is also an ethnic dimension to the demonstrations: Khuzestan is home to most of Iran’s ethnic Arab minority, who feel ignored — and sometimes regarded with suspicion — by Tehran.

This combustible combination is set alight every summer; the resulting conflagration grows hotter yearly and spreads wider. Tehran invariably responds with brute force, inflicted by the police, the Islamic Revolutionary Guard Corps and the Basij militias. If the protesters persist, the violence will likely escalate next month with the elevation of the new president, the hardline cleric Ebrahim Raisi.

There are other pressing problems awaiting Raisi: Iran’s economy is in parlous condition, negotiations to lift American sanctions have stalled and the country is experiencing a new wave of COVID-19 cases and deaths. The new president also faces questions about his political legitimacy — his election, after all serious rivals had been disqualified, was undermined by Iran’s lowest-ever turnout.

But the water crisis is arguably the most intractable of Raisi’s challenges. Climate change trends point to hotter, drier summers in the years ahead, and Iran’s groundwater sources are already depleted to a dangerous extent. Like Khamenei, Raisi believes the Islamic Republic, in order to insulate itself from international pressures, must have a “resistance economy,” the key pillar of which is agricultural self-sufficiency. That is obviously impossible while the country faces what environmentalists have described as an impending water bankruptcy.

Ironically, the water scarcity is to a considerable extent the result of the regime’s desire for agricultural independence. Tehran has for decades encouraged widespread cultivation of essential crops, incentivizing farmers to use any and all the groundwater they can get. As a result, environmentalists reckon the aquifers in 12 of Iran’s 31 provinces will run dry in the next 50 years.

Water above the ground is growing scarcer, too. Excessive damming of Khuzestan’s rivers has dried up the province’s lakes.

The political fallout of all this is not hard to predict: Climate migration on an epic scale. If Kalantari’s predicted number, 50 million, seems high, huge numbers of Iranians already are moving from the countryside to urban centers, where they are swelling the ranks of the unemployed — and the angry.

The leadership in Tehran won’t need reminding of what happened the last time this occurred. The dissatisfaction of the urban underclass was the kindling for the 1979 revolution that created the Islamic Republic. The fire next time could burn it down.