Iran’s densely populated capital Tehran has popped up repeatedly in recent news headlines over the threat of “day zero”— the point at which a city runs out of water. While Tehran is indeed experiencing a water crisis, the rest of the country is in dire straits as well. Growing internal water demands, decades of poor water management, and transboundary water tensions on all sides have backed the Middle Eastern nation into a corner.

Urban Iranians have felt the strain for years with periodic water shutoffs, related power blackouts, and government mandated holidays tied to outages, all of which hurt livelihoods and the economy. In rural areas, water scarcity has contributed to outmigration to Iran’s growing cities, placing further pressure on already strained urban systems. This rapid urbanization is a human security issue: urban saturation drives the rise of informal settlements and weakens social cohesion—pressures that are further exacerbated by water insecurity.

Each of these stressors represents a possible pathway to instability in Iran. Water shortages have emerged as a particularly volatile lever in recent years as water-related protests have sometimes spread and merged with broader anti-regime movements. Together, these threats compound risk and raise questions about the Iranian regime’s ability to maintain its long-term hold over the country.

Revolutionary State-Building Sows Water Crisis

Understanding antecedent systemic conditions is vital to draw the connection from water stress to instability in a region. Water is only a crisis in the context of politics, governance, and social and economic structures.

In Iran, the 1979 Islamic Revolution and subsequent geopolitical isolation brought self-sufficient food security to the forefront of national security as a strategy to prevent foreign influence or reliance. The country’s family planning program also shifted, moving from small families to a pro-natalist stance; the Ayatollah encouraged families to have more children as the country was building the “twenty million army.” By 1986, the population was increasing by more than 3 percent per year, one of the highest rates in the world.

Now in 2025, agriculture consumes more than 90% of Iran’s water resources, and the population has grown more than 50% since 1990, reaching over 91 million today. While Iran continues to seek agriculture self-sufficiency, the intertwined drivers of a growing population and growing food needs have laid the foundation for a chronic mismatch of available water resources and ever-growing demand in an arid environment.

Water management—and mismanagement—matters, too. Dam construction became a central feature of Iran’s post-revolutionary state building. During this time, Iran was one of the top three dam builders in the world. Dams are generally a useful tool to regulate river flow and store water in times of drought or flood, but aggressive dam building in Iran has come with consequences like increased water loss from evaporation, reduced groundwater recharge, and low downstream flows. This has left some reservoirs low or empty for extended periods of time, calling their utility into question.

To offset surface water shortages, Iran has used considerable amounts of groundwater, including nonrenewable fossil groundwater. Inexpensive energy prices and improved pump technology helped the number of wells skyrocket with a concomitant decline in groundwater levels.

Afghanistan Pokes the Lion

Iran’s water woes are not all internal; transboundary tensions stemming from state-led hydro-development in both Afghanistan to the east and Turkey to the west are compounding water challenges and raising tensions across Iran.

Diplomatic relations between Iran and the Taliban have been deteriorating. The Helmand River, whose headwaters and roughly 80% of its basin area lie in Afghanistan, empties into the Hamoun Wetlands in eastern Iran in Sistan and Baluchestan and South Khorason provinces. These wetlands have sustained Iranians for millennia but are now drying as Afghanistan diverts upstream waters, leading to water conflict between the two states.

As Afghan diversions continue, Iranian farming and living conditions have become increasingly harsh, deepening poverty, food insecurity, and outmigration, and also fueling more frequent and intense dust storms. The restive region’s Sunni Baloch majority are deeply dissatisfied with Iran’s inability to improve conditions, staging protests that have been met with violence as the central government seeks to suppress instability. Afghanistan’s current trajectory in dam building could leave the region with little-to-no water from the Helmand River, which could push conditions over the brink. The basin’s 1973 water treaty has proven ill-equipped to resolve these bilateral disputes.

The Harirud River also originates in Afghanistan then flows into northeastern Iran, providing water to Mashhad, Iran’s second largest city, and to agricultural lands in southern Turkmenistan. Similar to the Helmand, dam building on the Harirud in Afghanistan has dramatically reduced downstream flows, causing diminished water levels in Iran’s and Turkmenistan’s Doosti reservoir. A Doosti water transfer project to Mashhad has now fallen short, providing a fraction of pipeline capacity.

The situation is only expected to worsen. The Pashdan dam has just come online, threatening the water supply for millions of Iranians. Iranian newspapers have described the Taliban’s behavior as hostile and have expressed discontent that the Iranian government would remain silent in the face of hostility. A basin agreement between the three countries in nowhere in sight.

Dams on the Tigris-Euphrates Strain Regional Relations

The Tigris-Euphrates River headwaters originate in Turkey, with eastern, smaller tributaries of the Tigris rising in western Iran. The vast majority of the river system flows through Iraq, where it serves as the country’s main source of surface water. Turkey’s Great Anatolian Dam Project (GAP) has led to the construction of 18 upstream dams, with four more on the way, reaching an overall capacity over 100 billion cubic meters (BCM).

Reduced flow into Iraq has prompted migration among Iraqi farmers and caused severe urban health problems—118,000 people hospitalized from water-related illness in 2018—as reduced river flows mix with pollution. Saltwater intrusion from the Gulf reaches as far north as Baghdad.

Iraq’s grave water scarcity situation has brought scrutiny of Iran’s dams on the eastern Tigris tributaries and shone a spotlight on their role in drying out Iraqi Kurdistan. Iran in turn has criticized Turkey’s GAP project, calling it dangerous for the region. These water issues are a source of growing geopolitical tensions between Iran and its neighbors. Dated bilateral agreements exist in this basin, but no multilateral agreement.

A Volatile Convergence: Climate Stressors and Political Grievance

Changing environmental conditions are commonly cited as driving water scarcity in Iran. And while biophysical conditions of the present and projected future are different than the past, these changes primarily exacerbate the impacts from current management choices and regional issues. Nationally, since 1990, annual rainfall has decreased significantly, about 1 mm per year or 30 mm over the past 35 years.

During that same period, temperatures have increased by 1.7 Celsius. This shift reflects more extreme heat in the summers and also warmer winters. In Iran, many of the rivers are snow-fed—earlier snowmelt is harder to manage and can leave less water in rivers and reservoirs in the summer dry season. Together, human and environmental stressors have reduced the amount of water available to Iran just as demand is at an all-time high.

Iran’s overuse of water, depletion of groundwater, transboundary water vulnerabilities, and changing environmental conditions are coalescing to create heightened and widespread impacts. Water shortages have hindered crop production and endangered rural livelihoods. With few other employment options, rural-to-urban outmigration has overpopulated Iran’s cities. In those cities, water demand continues to grow.

Low reservoir levels limit hydropower output, while natural gas shortages and aging thermal power plants constrain energy production and require large volumes of water for cooling, right when energy demand is increasing as extreme heat drives higher demand for cooling. Meanwhile, sanctions have hindered modernization in the energy sector. Estimates show that power outages cost Iran’s industrial sector billions of dollars a year and disrupt livelihoods of Iranians in a high-inflation environment. This leads to new grievances atop past grievances across the country.

The recent 12-day Iran-Israel war sparked a wave of nationalism that dampened protests nationwide. But that unity was short-lived. Worsening water and energy shortages have reignited demonstrations in Tehran and beyond, fueling growing public outrage that will only abate when the core drivers of the crisis are addressed.