Water in Iran

Iran is living through the region's largest water reckoning. Half a century of dam-building and subsidised pumping built an agricultural economy on roughly 90 BCM of annual use, most of it groundwater now being mined. The bill is visible from orbit. Plains are subsiding up to about 25 cm a year, Lake Urmia nearly died before its partial rescue, and rivers like the Zayandeh Rud and Karun no longer reliably reach their cities. Water protests recur from Isfahan to Khuzestan. The compound droughts of 2021–25 pushed Tehran itself into emergency rationing debates.

By late 2025 the reckoning had arrived: the driest autumn in 50 years, the sixth consecutive drought year, and nineteen major dams effectively empty. In November 2025 President Pezeshkian warned that Tehran, a city of 10 million, might face rationing and even evacuation if the rains failed again.²⁵ Parts of the western Tehran plain subsided more than 25 cm a year between 2003 and 2017, and about 3.5% of the national territory is sinking.³¹³⁰

A quick-reference dashboard for Iran: headline economy and water indicators⁶⁴⁶⁵, water stress against the scarcity thresholds, non-conventional supply, and the institutions behind the sector. The commercial picture, with buyers, deal structures and the project pipeline, is in the market brief.

One interactive map of Iran's water, built from real geodata. Climate & drought maps the aridity gradient (WorldClim) with warming projections. The WRI Aqueduct layers, covering overall water risk, water stress and flood risk (plus groundwater decline where the trend is significant), shade every river sub-basin by its 0–5 risk score. Demand shows where the population, and the water demand, concentrate. Infrastructure brings the physical system together: rivers, dams (FAO AQUASTAT), treatment plants, desalination and the major conveyors. Hover any sub-basin or marker for detail; sources are cited under each view.

Iran is a high plateau ringed by mountains. About 52% of the country is mountain or desert, and some 16% lies above 2,000 m.²⁴ The Zagros, the largest massif, runs from the north-west down to the Gulf coast and on to the far south-east.²⁴ The Alborz follows the Caspian shore. Its peak, Damavand, reaches 5,600 m, while the Caspian Sea lies about 28 m below sea level.¹ Between the chains, the Central Plateau covers more than half the country, partly salt flats and partly sand or stone.²⁴

The national communication divides the land into six main basins. The Central Plateau basin alone covers about 824,000 km², roughly half the basin area. The Persian Gulf and Oman Sea basin covers about 423,000 km².¹ The Caspian, Eastern border, Lake Urmia and Ghareh-Ghom basins make up the rest.¹

Rainfall

Rain is scarce and unevenly spread. Annual rainfall ranges from under 50 mm in the deserts to 2,275 mm at Rasht near the Caspian.²⁴ National estimates of the average range from 228 mm to about 240 mm, and about 90% of the country is arid or semi-arid.²⁴¹ Half of the rain falls in winter, 23% each in spring and autumn, and only 4% in summer.²⁴ About 30% of precipitation comes as snow.¹ Of 417 billion m³ of precipitation a year, 299 billion m³, or 72%, evaporates.¹

Single years swing hard. From October 2024 to 7 March 2025, official data showed 93.8 mm of rain against a long-term average of 157.8 mm for the period.⁶ Hormozgan was 77% below normal and Sistan-Baluchestan 72% below.⁶ By early November 2025 the country had received only 2.3 mm, 81% below the historical average.²⁵

Heat and drought

The climate is strongly continental. Away from the coasts, the annual temperature range is about 22–26 °C.¹ Summer temperatures in the interior have passed 55 °C, and winter lows reach −30 °C in the north-west.²⁴ Heat now strains power and water together. In July 2024, with temperatures above 50 °C in some regions, Tehran declared a public holiday to save electricity and water.⁷

Drought has become the norm. Human-induced warming made the 2020–2023 drought in Iran 16 times more likely, an attribution study found. Heat, not falling rain, drove the change.³ By 2025 the country was in its fifth consecutive drought year, the worst on record.⁴ A year-long drought like that of July 2024 to June 2025 is now expected about once a decade. In a world 1.3 °C cooler it would come once every 50 to 100 years.⁴

Projections and the coast

Models agree on heat far more than on rain. The World Bank’s CMIP6 ensemble shows small rainfall changes of either sign, as the table below sets out. Under high emissions, Iran would have about 69 more days a year above 35 °C by 2080–2099, nearly double the 74 days of 1995–2014.² Its hottest day of the year would be 6.8 °C hotter.² The national communication estimates that a 2 °C rise cuts groundwater recharge by 20% and snowfall by 5%. Snowmelt comes a month earlier and the snow line rises by 200 m.¹ Under its pessimistic scenarios, runoff falls in every basin, by up to 65.5% in the Bandar Abbas–Sedij basin.¹

The Gulf coast faces the sea as well as the heat. Tide gauges show sea level at Bandar Abbas rising by 2.34 mm a year.¹ The worst scenario for 2100 would flood low-lying coast in Khuzestan and parts of Hormozgan, and could affect groundwater.¹ Under high emissions and without major adaptation, about 184,700 people a year could be affected by coastal flooding in 2070–2100.¹

Rainfall and temperature in numbers

Averaged over the whole of Iran, ERA5 reanalysis gives about 289 mm of rain a year and a mean temperature of 18.3 °C for 1991–2020. About 46% of that rain falls in January, February and March. Since 1971 the country has warmed by about 0.54 °C a decade. Average rainfall in 1993–2022 was about 4% lower than in 1951–1980, and single years swing widely around that.

Projected change

Source: World Bank Climate Change Knowledge Portal, retrieved September 2026. ERA5 0.25° reanalysis for the annual series (1950–2022) and the monthly climatology (1991–2020); CMIP6 0.25° multi-model ensemble median for the projections, as change against 1995–2014. These are national averages, which hide the gap between wet highlands and dry interiors, and reanalysis rainfall over deserts carries wide uncertainty.

Groundwater is the story. Discharge from wells, qanats and springs rose from less than 20 billion m³ a year in the early 1970s to more than 74 billion m³ around 2000.²⁴ Over the same period the number of wells grew fivefold, from just over 9,000 to almost 45,000.²⁴ FAO put groundwater depletion at 3.8 billion m³ a year, mostly in the central basins where surface water is scarce.²⁴ Qanats, the tunnels that tap aquifers by gravity, still run from about 100 m to 120 km in one Yazd system.²⁴

The large rivers lie on the edges of the plateau. About 24.7 billion m³ a year flows from the Karun into the Shatt al-Arab just before the sea.²⁴ One report cited by the Washington Institute says 45% of the Karun’s flow has been diverted from its natural course.⁴⁶ Dams regulated 34 billion m³ of surface water in 2006, of which 20.51 billion m³ was used.¹

The main rivers

The table ranks the rivers of Iran by the largest natural flow they reach inside the country. Natural flow is the modelled long-term average before any withdrawals. For a heavily used river it measures what the river could carry, not what arrives today.

Sources: Grill, Lehner, Thieme et al. (2019), Mapping the world’s free-flowing rivers, Nature 569, dataset under CC BY 4.0, for length, natural flow (WaterGAP, 1971–2000) and free-flowing status, meaning the share of the river’s length inside Iran still classed as free-flowing. No flow figure is given below 20 m³/s, where a global model is too coarse to rank small rivers. Dams from the FAO AQUASTAT regional inventories, matched to the nearest river reach, so a dam on a tributary close to a main stem can be counted against the main stem. The same rivers are drawn on the water map above under Rivers & lakes.

Iran withdrew about 93.3 km³ of water in 2004, FAO estimated: 53.1 km³ from groundwater, 40 km³ from surface water and 0.2 km³ from desalination. Agriculture took about 92%, the same share as in 1993.²⁴ Withdrawals equalled almost 68% of renewable resources, and groundwater was being depleted by 3.8 km³ a year.²⁴ In the year to March 2025 more than 90% of supply still went to agriculture, which produced about 12% of GDP. Households are believed to use less than 8%.²⁵

The pumping boom

Groundwater discharge rose from less than 20 km³ a year in the early 1970s to more than 74 km³ around 2000.²⁴ The area equipped for irrigation grew from 7.26 million ha in 1993 to 8.13 million ha in 2003, about 62% of it fed from groundwater.²⁴ Efficiency stayed low. Surface methods covered 91.4% of the irrigated area in 2003, and national irrigation efficiency averaged about 33%.²⁴ In 1995 farmers paid US$0.2–0.8 per 1,000 m³ of delivered water, while pumping groundwater cost US$5–9.²⁴ Food policy locks the pattern in: Iranian law requires 85% of domestic food to be produced at home.²⁵

Dams and transfers

In 2006 Iran operated 94 large dams with 31.6 km³ of storage, with 85 more under construction.²⁴ It became the world’s third-largest dam builder after China and Japan.²⁷ Transfers move the conflict between provinces. Farmers in Isfahan have protested transfers of Zayandeh Rud water to Yazd since at least 2012, and the river has had no permanent flow since 2006.²⁷²⁸ Desalination is growing on the coast. State media reported 95 plants producing about 233 million m³ a year in 2023, and pipelines carry Gulf water inland to provinces including Isfahan, Kerman and Yazd.²⁹

Sinking plains

The deficit shows in the ground. A national satellite survey for 2014–2020 found about 56,000 km², 3.5% of Iran, subsiding, mainly because of irrigation. About 3,000 km² sinks faster than 10 cm a year, and parts of the central plateau faster than 35 cm.³⁰ The western Tehran plain subsided at more than 25 cm a year between 2003 and 2017.³¹ Around Isfahan the rate ran from 5 to 100 mm a year in 2014–2019.³² At Rafsanjan, groundwater overdraft rose about sixfold between 1969 and 1999, and the water table fell about 28 m.³³

Lake Urmia

Lake Urmia peaked in 1995. Over the next two decades its level fell more than 7 m and it lost about 90% of its area.³⁴ By 2013 its volume had fallen sixtyfold, to 500 million m³.³⁵ A restoration programme launched that year had cost about US$1 billion by 2021. It worked to move farmers off sugar beet and began diverting up to 600 million m³ a year from the Little Zab.³⁵ A 2025 study attributes about 66% of the fall in river inflows to agricultural water use, as irrigated land grew more than fourfold between 1985 and 2020.³⁶ The lake hit a record low below 1,270 m in September 2023.³⁷ Officials reported 1,270.70 m in April 2026, still 3.4 m below its ecological level.³⁸

Tehran in 2025

Drought brought the crisis to the capital. By early November 2025 the country had received 81% less rain than the historical average, in its sixth consecutive dry year.²⁵ Nineteen major dams, about a tenth of the reservoirs, were effectively empty.²⁶ Tehran’s Lar reservoir held 2% of capacity and Latyan about 9%.²⁶ On 7 November President Pezeshkian warned that without rain the city of 10 million might have to be rationed or even evacuated.²⁵

Withdrawals over time

FAO’s AQUASTAT estimates put Iran’s freshwater withdrawals at 45.0 billion m³ in 1975 and 93.0 billion m³ in 2022. Agriculture’s share of the total moved from 92% in 1994 to 92% in 2022.

Source: FAO AQUASTAT via the World Bank World Development Indicators, retrieved September 2026. AQUASTAT revises national figures irregularly and fills the years between surveys, so a jump between two adjacent years usually marks a new national estimate rather than a change on the ground.

Dams carry the system. In 2006, 94 large storage dams with a capacity of 31.6 billion m³ were operating. Another 85, holding 10 billion m³, were under construction.²⁴ Building goes on. In August 2025 the head of the Planning and Budget Organization said 88 dams under construction would regulate about 7.5 billion m³ a year.¹⁰ Silt is a hidden cost. Sedimentation averages 10 tonnes per hectare a year in Iran, against under two tonnes worldwide.¹

Reservoirs under drought

The dams are only as full as the rain allows. In mid-November 2025, official figures showed reservoirs holding 17.12 billion m³, 33% of capacity. A year earlier they held 22.92 billion m³.⁸ Inflows since late September were 1.48 billion m³, half the previous year’s 3 billion.⁸ Nineteen dams were below 5% of capacity, and Tehran’s five supply dams averaged about 10%.²⁵ About 70% of the capital’s water comes from those five dams.⁷ Winter brought only partial relief. On 20 February 2026 the major dams were 41% full, but Tehran’s five held just 132 million m³ between them.⁹

Moving water to the plateau

Transfers now move water over long distances. On 6 December 2025 the president inaugurated a project that carries desalinated Gulf water to the central plateau, on a route from Sirjan to Isfahan.¹¹ The 800 km pipeline took two years and cost 350 trillion rials, about US$320 million.¹²¹¹ Built with major support from Mobarakeh Steel, it supplies industry in Isfahan Province.¹² A 339 km branch began trial deliveries of about 700,000 m³ a month to the Isfahan refinery in July 2025.¹³ The Taleqan transfer system, opened in November 2025, brings drinking water to Tehran and Alborz.¹⁴

Desalination

Desalination is growing from a small base. Installed capacity was about 590,500 m³ a day in 2002.²⁴ Operational capacity is now estimated at about 1 million m³ a day, only 4% of the Gulf Cooperation Council total.²⁹ More than 90% of plants sit in Bushehr, Hormozgan, Khuzestan and Sistan-Baluchistan.²⁹ Pipelines also serve Isfahan, Kerman, Khorasan Razavi, South Khorasan and Yazd. In all, Gulf desalination supplies some 30 million people, a third of the population.²⁹ New plants remain modest. The Assaluyeh unit opened in September 2026 at 1,000 m³ a day, toward a design of 5,000 m³.¹⁵ It covers 58 litres a second of the town’s 237 litres a second drinking-water deficit.¹⁶

Networks, sewers and irrigation

Supply networks reach almost everyone, but sewers came late. In 2011, 98% of urban and 90% of rural residents had an improved water source.¹ By 2000, only 15% of cities, home to 24% of the population, treated their domestic wastewater.¹ A 2005 World Bank loan financed sewers and network upgrades in Rasht, Anzali, Sari and Babol.⁵ The Robat Karim treatment plant in Tehran Province opened in November 2025.¹⁴

On farms, dam-fed canal systems cover 1.56 million ha. The rest of the irrigated land relies on traditional canals built by farmers.²⁴ Officials say 40% of farmland now uses modern irrigation technology, against 60% in Europe.¹⁷ Measurement lags behind. In August 2026 only about 125,000 of some 416,000 authorised farm wells had volumetric smart meters.¹⁸

War damage

War has become an infrastructure risk. The energy minister blamed part of the 2025 supply strain on damage from the 12-day war with Israel in June.²⁵ In 2026 strikes hit water reservoirs in Sirik county and desalination plants on the Hormozgan coast.⁶⁰⁴⁴ The plant in Bonji village, in Jask county, was hit and cut off water to 10,000 people.⁴⁴ By August, UNICEF had delivered water and sanitation equipment to nine war-affected provinces. The supplies included 26 solar-powered disinfection systems.²¹

The asset base in numbers

Sources: FAO AQUASTAT regional dam inventories (CC BY 4.0), which list large dams with a published capacity and can lag recent construction; the MENA Water Review major projects register, where each record cites its source on the project page. The database follows large contracted projects, not the whole asset base.

Salinity follows the diversions. On the Karkheh, conductivity at Hamidiyeh rose from about 600 µS/cm in 1988 to 2,500 µS/cm in 2002. Irrigation return flows and sewage drove the rise.³⁹ The Gotvand Dam on the Karun, completed in 2012, was built on salt beds that made its reservoir water unfit for irrigation.²⁷ At Sayhan on the Shatt al-Arab, dissolved solids averaged 2,408 mg/L in 2011, against an FAO irrigation guideline of less than 450.³⁹ The delta held about 18 million date palms in the 1970s, and more than 80% were gone three decades later.³⁹

Soils and aquifers carry the long-term damage. FAO put the area affected by salinity and waterlogging at about 15.5 million ha, 9.4% of the country.²⁴ Wells in the Tehran–Karaj aquifer supply up to 80% of the water for more than 18 million people. Between 2007 and 2018 their nitrate ranged from about 6 to 150 mg/L, up to three times the drinking standard.⁴¹ Lake Urmia’s exposed bed now produces aerosols that harm human health.⁴²

Wastewater and the 2026 war

Treatment came late. In 2001 Iran had 39 wastewater plants with a capacity of 712,000 m³ a day, serving 3.8 million people, and raw sewage was used directly for irrigation in some towns.²⁴ The 2026 war added new contamination. Strikes on Tehran’s oil depots on 7 March contaminated drainage and raised alarms about surface water and groundwater.⁴³ A wastewater treatment plant in Bandar Abbas was also hit.⁴⁴

The reported indicators

Sources: WHO/UNICEF Joint Monitoring Programme via the World Bank; SDG 6.3.1 and 6.3.2 from the UN Statistics Division SDG database, retrieved September 2026. Safely managed means an improved source on the premises, available when needed and free from priority contamination. SDG 6.3.2 rests on each country’s own monitoring network, so a high share can mean few water bodies were assessed, and values move when methods change between reporting rounds.

Iran sends about 10 km³ a year to Iraq through the Tigris tributaries, and about 24.7 km³ of Karun water reaches the Shatt al-Arab near the sea.²⁴ To the east it shares the Helmand and the Harirud with Afghanistan and Turkmenistan.

Iraq and the Shatt al-Arab

Iran and Iraq signed a frontier treaty in Baghdad on 13 June 1975, after the Algiers communiqué. It fixed the boundary on the Shatt al-Arab along the thalweg, the median line of the main navigable channel.⁴⁵ A separate agreement on frontier watercourses divided streams such as the Wand, and Iraq has since expressed reservations about it.⁴⁰ No water agreement covers the Shatt al-Arab, the Karun or the Karkheh.³⁹

Iranian dams now shape the Tigris tributaries. The Gavoshan Dam on the Diyala headwaters was built between 1992 and 2004 with 550 MCM of storage.⁴⁰ The 48 km Nosoud tunnel, completed in 2013, diverts Sirwan water inside Iran. The Daryan Dam followed in 2018, 28 km from the Iraqi border.⁴⁶⁴⁷ In August 2020 the director of Iraq’s Darbandikhan Dam said Iran had cut the Sirwan’s flow by 75–80%.⁴⁷ The Sirwan and Little Zab together supply roughly a quarter of the Tigris’s annual flow in Iraq.⁴⁶ In December 2003 Iran also agreed to supply Kuwait with Karkheh water for 30 years. The scheme’s status was unclear by 2013.³⁹

The Helmand

The Helmand dispute dates to the 1870s, and a 1939 treaty was never ratified by Afghanistan.⁴⁸ The 1973 Helmand River Treaty gives Iran an average 22 m³/s, plus 4 m³/s “for goodwill and brotherly relations”, cut proportionally in dry years.⁴⁹ Its implementation has always been disputed. The flow to Iran was choked off under the Taliban from 1998 to 2001.⁵⁰ One 2020 analysis argues that Iran has received 40% more than its right in normal years since 1973.⁵¹

Afghan dam building sharpened the dispute. President Ghani inaugurated the Kamal Khan Dam on 24 March 2021, with 52 million m³ of storage. He said Iran should give oil for water beyond its quota.⁴⁸ On 18 May 2023 President Raisi accused the Taliban of restricting the flow. On 27 May guards exchanged heavy gunfire on the border, and at least two Iranian guards and one Afghan guard were killed.⁵² Iran’s ambassador said Iran had received only 4% of its share the previous year, while Afghanistan blamed low rainfall.⁵³ Iran’s parliament says 25–30% of Sistan’s population has left in two decades because of water shortages.⁵³

The Harirud

On the Harirud, Iran and Turkmenistan share the Doosti Dam, the basin’s largest, with an effective capacity of 980 MCM.⁵⁴ Afghanistan inaugurated the Salma Dam upstream in 2016, which Iranian reporting says cut flows to Iran and Turkmenistan by an estimated 73%.⁵⁵ The Pashdan Dam near Herat began filling in December 2024.⁵⁶ No treaty covers the river. In January 2026 Iran’s energy minister called for talks with Afghanistan over its water rights.⁵⁷

Water in the 2026 war

The war brought desalination into the line of fire. On 7 March 2026 Iran’s foreign minister accused the United States of striking a desalination plant on Qeshm Island, cutting water to 30 villages. The United States and Israel denied it.²⁹⁵⁸ The next day Bahrain said an Iranian drone had damaged one of its desalination plants, which Iran denied.⁵⁸ On 13 March President Trump threatened to destroy Iran’s power and desalination plants, and Iran later threatened the Gulf’s water infrastructure.²⁹⁵⁹ In June Iranian authorities said US strikes had destroyed two reservoirs in Sirik County serving more than 20,000 people.⁶⁰ In July a strike on the Bunji desalination plant cut water to 20 villages, and Iran struck Kuwaiti power and desalination plants on consecutive nights.⁶¹⁶²

The record

Shared river basins

The register also places small areas of Iran in the Astara Chay basin, too little to carry here.

Cooperation and conflict on the record, 1948 to 2008

The International Water Events Database scores every reported interaction between riparian states on the Basins at Risk scale, from formal war over water to voluntary unification. Cooperative and conflictive events add up to less than 100% because neutral events are counted too.

Source: Transboundary Freshwater Dispute Database, International Water Events Database, Oregon State University, as compiled by the Transboundary Waters Atlas. The series ends in 2008; every later dispute and agreement is outside it and is covered in the text above.

The agreements

Source: Master Treaties Database of the Transboundary Freshwater Dispute Database (February 2023 edition), via the Transboundary Waters Atlas. Titles as recorded, with spelling normalised. Colonial-era boundary instruments appear because they fixed water rights on rivers that later became international.

Joint bodies

• Dostluk Commission (DOCO)Harirud · 2007 · Iran, Turkmenistan
• Helmand River Delta Commission (HRDC)Helmand · 1950 · Afghanistan, Iran

Source: the river basin organisation database of the Transboundary Freshwater Dispute Database (2013). A joint body on paper is not evidence that it meets.

Shared aquifers

• Aghdarband AquiferTurkmenistan · data limited
• Janatabad AquiferAfghanistan, Turkmenistan · data limited
• Karat AquiferAfghanistan · data limited
• Lenkoran/AstaraAzerbaijan · data limited
• Nakhichevan / Larijan and Djebrail AquiferAzerbaijan · data limited
• Sarakhas AquiferTurkmenistan · data limited
• Taurus-Zagros Mountain rangeIraq, Turkey · data moderate
• Taybad AquiferAfghanistan · data limited
• Torbat-e-jam AquiferAfghanistan · data limited

Source: IGRAC and UNESCO, Transboundary Aquifers of the World. Data reliability is IGRAC’s own assessment of the information behind each outline.

Three bodies share the water file. The Ministry of Energy manages water resources and large works such as dams and main canals.²⁴ The Ministry of Agriculture handles tertiary canals, on-farm works and crops, and the Department of the Environment sets environmental policy.²⁴ The ministry that supplies bulk water is therefore separate from the one whose sector uses most of it. Irrigation operation and maintenance runs through 19 companies, 49% owned by the Ministry of Energy and 51% private.²⁴ The Iran Water Resources Management Company publishes national reservoir data.⁹

In the cities, water and sewerage companies set up in the early 1990s have some administrative and financial autonomy.⁵ Regional water boards handle bulk works such as reservoirs, transmission and treatment. The National Water and Wastewater Engineering Company coordinates the urban utilities.⁵

Law and water rights

All water bodies are public property, and the government is responsible for managing them.²⁴ The first water law after the revolution, approved in 1982, gives the Ministry of Energy power to allocate water and permit its use.²⁴ Rights differ by source. Surface water rights pass with the land, groundwater is mainly private and traded, and qanats are held in shared ownership.²⁴ Food policy adds pressure. Iranian law requires 85% of domestic food to be produced at home, a Kharazmi University expert notes.²⁵

Pricing and reform

Cheap water and energy sit at the core of the problem. The Targeted Subsidies Law, enacted in 2009, has been implemented since December 2010.¹ Before it, indirect subsidies reached about US$77 billion in 2007, or 27% of GDP.¹ Officials now describe water as an economic commodity.¹⁰ In November 2025 the energy minister said high-consuming urban users would be penalised.²⁵ The ministry has also invited local and foreign investors to co-finance water and energy projects through public-private partnerships.²⁰

Volumetric delivery to farms is the long-promised fix. The Ministry of Agriculture says at least 15 annual laws and medium-term programmes have required it of the Ministry of Energy, with poor results for surface water.¹⁸ A guideline under Article 40 of the Seventh Development Plan Law, drafted in August 2026, would pass water management to farmers’ organisations.¹⁸ The energy ministry’s SAMAB water database is being linked to the farm zoning system, to set water volumes per farmer.¹⁹ In October 2025 the government adopted a National Climate Change Management Plan to build resilience in water and farming.⁴

Iran’s water future is the region’s biggest single variable. The strain is now visible from space. About 56,000 km² of the country is subsiding, mainly because of irrigation pumping, and 3,000 km² sinks faster than 10 cm a year.³⁰ Agriculture is the lever. In the Lake Urmia basin, farm water use explains about two-thirds of the fall in river inflows since 1985.³⁶ Shrinking irrigated farming would ease both problems. It would also cut rural incomes in the provinces least able to absorb the loss.

The cities are already testing the limits. In November 2025, 19 major dams were effectively dry.²⁶²⁵ The president warned that Tehran might have to be rationed or even evacuated.²⁵ Water has also become a trigger for unrest and a target in war. Isfahan farmers set fire to a transfer station in 2025,²⁸ and strikes hit water reservoirs in 2026.⁶⁰ The open question is whether adjustment comes by plan, through pricing, farmland retirement and reuse. The alternative is adjustment by force, through subsidence, salt and migration.