How Did a City of 10 Million People Nearly Run Out of Water?
Tehran’s near–“Day Zero” crisis and the global warning it carries
In late 2025, Tehran—Iran’s vast capital of nearly 10 million residents, expanding to more than 15 million across its metropolitan region—stood on the edge of an unthinkable precipice: running out of water. Reservoirs dwindled to single-digit capacity, tap pressure collapsed across much of the city, and senior officials openly warned that parts of the capital could become uninhabitable. President Masoud Pezeshkian described the situation as an “ecological catastrophe,” even raising the once-unthinkable idea of relocating the capital itself.
This was not a sudden disaster. Tehran’s water emergency was the inevitable outcome of decades of environmental mismanagement, explosive urban growth, agricultural overreach, and the accelerating force of climate change. Like Cape Town in 2017 and Chennai in 2019, Tehran became a case study in how modern megacities can stumble toward “Day Zero” not because water disappears, but because governance fails to respect its limits.
The Crisis Timeline: How Close Tehran Came to Day Zero
By November–December 2025, Tehran’s main reservoirs had fallen to roughly 10–11% of capacity after six consecutive years of drought and the driest autumn in more than half a century. Rainfall during late November and early December was nearly 90% below historical averages, leaving dam inflows negligible.
Key reservoirs told the story starkly:
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Lar Dam: ~1% full
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Latyan Dam: ~9% full
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Amir Kabir (Karaj) Dam: ~8% full
Water pressure was halved across nearly 80% of households, causing high-rise buildings to lose supply entirely while ground-level homes struggled with intermittent flow. Authorities urged residents to cut consumption by at least 20%, publicly discouraging car washes, lawn watering, and non-essential use. A one-day national holiday was declared to reduce industrial and office demand, with discussions of extending it to a full week.
Officials warned that if winter rains failed, emergency evacuations could not be ruled out. Although rainfall eventually arrived and provided temporary relief, experts stressed that the underlying system remained fundamentally broken.
Climate Change: The Accelerator, Not the Sole Cause
Iran sits in one of the world’s most climate-vulnerable regions. The Middle East is warming at nearly twice the global average, intensifying drought cycles and reshaping precipitation patterns.
Historically, Tehran depended on snowpack in the Alborz Mountains, which slowly melted to recharge rivers, reservoirs, and aquifers. That system is unraveling:
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Snowpack has declined sharply.
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Rainfall increasingly arrives in short, intense bursts.
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Water runs off rapidly instead of soaking into the ground.
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Aquifers fail to recharge, even during wet episodes.
This shift mirrors what scientists observed in Cape Town before its crisis and in Chennai before its reservoirs ran dry: climate change doesn’t just reduce rain—it breaks the natural timing and storage of water.
But climate change alone did not bring Tehran to the brink. Human decisions did.
From Ancient Sustainability to Modern Overreach
Iran’s water history is paradoxical. Few civilizations understood arid-region hydrology better than ancient Persia. For over 2,500 years, Iranians built qanats—underground tunnels that gently tapped aquifers and delivered water by gravity. These systems were self-limiting: they could never extract more water than nature replenished.
At their peak, Iran had an estimated 70,000 qanats, stretching more than 250,000 miles in total. Tehran itself relied heavily on them until the mid-20th century.
The break came with modern development. From the 1950s onward, deep wells replaced qanats. Pumping ignored recharge rates. After the 1979 revolution, promises of abundance—symbolized by slogans like “free water”—encouraged waste. Iran became one of the world’s most aggressive dam-builders, constructing dozens of dams on small rivers. While intended to boost food and energy security, many dams increased evaporation, disrupted downstream recharge, and provided only short-term gains.
As sanctions tightened in the 2000s and 2010s, Iran pursued food self-sufficiency at all costs. Irrigated farmland doubled since 1979, often in arid regions unsuitable for water-intensive crops like wheat and rice. Agriculture now consumes about 90% of Iran’s water while contributing barely 10% of GDP.
Groundwater Collapse and a Sinking City
Groundwater became Tehran’s hidden lifeline—and its silent killer.
Iran has lost more than 210 cubic kilometers of stored water since 2000, largely from aquifers. Nationwide, 32 of the world’s 50 most over-exploited aquifers are in Iran. Around Tehran, water tables have dropped by several feet per year.
The physical consequences are dramatic:
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Land subsidence of up to 10 inches annually in parts of the capital
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Cracking roads, damaged pipelines, destabilized buildings
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Permanent loss of aquifer storage as underground structures collapse
Experts now describe the situation as “water bankruptcy”—damage so severe that even if rains return, the system cannot fully recover.
Urban Explosion Without Limits
Tehran’s population surged from 700,000 in the 1940s to around 10 million today, driven by industrialization and rural collapse. More than 12,000 villages across Iran have been abandoned since the early 2000s due to water shortages, pushing migrants into already-stressed cities.
Infrastructure never kept pace. Leakage in pipes wastes up to 30% of urban water, while informal settlements strain networks further. Wealthier residents install rooftop storage tanks and private pumps; poorer neighborhoods wait for tankers. Inequality becomes embedded in scarcity.
Social, Economic, and Political Consequences
Water stress has become a multiplier of instability:
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Public health risks rise as sanitation falters.
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Food prices increase due to agricultural failures.
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Dust storms from dried land worsen respiratory disease.
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Protests erupt, echoing earlier unrest in Khuzestan and other regions.
Experts warn that by 2050, up to 50 million Iranians could face severe water shortages, triggering one of the largest internal displacement crises in the region’s history.
Government Responses: Emergency Measures and Radical Ideas
Authorities responded with rationing, pressure reductions, tanker deliveries, pipeline redistribution, and expanded wastewater reuse. Cloud seeding and desalination pipelines from the Persian Gulf were accelerated, though they remain expensive and energy-intensive.
Most striking was the renewed discussion of relocating the capital—possibly to the Makran coast. Estimated costs exceed $100 billion, and critics argue it treats symptoms, not causes.
Structural reform—especially agricultural water use, groundwater regulation, and corruption in infrastructure projects—has lagged behind rhetoric.
What Could Still Be Done
Despite the damage, pathways remain:
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Agricultural reform could free enormous volumes of water.
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Leak reduction and efficiency gains offer fast returns.
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Managed aquifer recharge using floodwaters can slow collapse.
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Reviving qanat principles, if not systems themselves, could restore sustainability.
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Capping urban growth and pricing water realistically may be unavoidable.
Other cities—Las Vegas, Phoenix, even Istanbul—are now openly discussing growth limits and moratoriums. Tehran’s crisis shows why.
A Global Warning
Tehran’s near–Day Zero moment is not an anomaly. It is a preview.
From ancient Mesopotamia to Angkor to the Maya cities of Tikal, history shows that civilizations rarely collapse from drought alone. They collapse when growth outpaces water, when leaders treat nature as negotiable, and when short-term gains eclipse long-term survival.
Tehran’s lesson is blunt:
Water scarcity is often man-made—and therefore preventable.
But only if societies act before the taps run dry.
