Nytimes.com | Vivian Yee, Leily Nikounazar

Lawmakers are warning that one province will run out within three months, and the shortage is inflaming tensions with the country’s neighbors.

Summer has come to Sistan and Baluchistan province, an impoverished fragment of chapped earth and shimmering heat in Iran’s southeast corner, and all people there can talk about is how to get water.

For weeks now, taps in cities like Zahedan have yielded nothing but a salty, weakening trickle. In the villages that water pipes have never reached, the few residents who remain say people can barely find enough water to do the laundry or bathe themselves, let alone fish, farm or sustain livestock.

“Sometimes, just to wash the dishes, we have to wait for so long,” said Setareh, 27, a university student in Zahedan, the provincial capital. “Everything from cooking to other chores is an ordeal for us.”

Drought has stalked Iran for centuries, but the threat intensified in recent years as political priorities trumped sound water management, experts say. Climate change has only made things worse in an area that typically gets no rainfall for seven months out of the year, and where temperatures can soar to 124 degrees in July.

Sistan and Baluchistan, where Iranian lawmakers warn the water will run out altogether within three months, might sound like an extreme case. But other regions are not far behind. Drought is forcing water cuts in the capital, Tehran, shrinking Lake Urmia, the largest saltwater lake in the Middle East, and the livelihoods that came with it, and stoking mass migration from Iran’s countryside to its cities.

Now, the hazards have spread to Iran’s borders, where water disputes are inflaming tensions with neighboring countries like Turkey and Afghanistan. A long-running disagreement between Iran and Afghanistan over rights to the Helmand River, which supplies Sistan and Baluchistan but has provided less water over time, peaked in late May when two Iranian border guards and an Afghan soldier were killed in clashes along the border near the river’s mouth.

Iranian groundwater and wetlands are irreversibly depleted, water experts say. Because of climate change, Iran can expect hotter temperatures and longer dry spells, as well as a greater risk of destructive floods.

Yet the country continues to spend precious water on agriculture, which does little to expand the economy but keeps people working in rural Iran, where many government supporters live. It is also developing already-thirsty areas that will only demand more water.

“Iran is in a water bankruptcy trap and it cannot get out. Unless you cut off consumption, the situation is not going to get better,” said Kaveh Madani, a water expert at the United Nations and the City University of New York who was once a deputy vice president of Iran. “Neighboring countries are suffering from the same issue. Water is becoming more scarce in the region, and competition over water will increase.”

Mismanagement of Iran’s water goes back at least to Shah Mohammed Reza Pahlavi, who ruled Iran before being deposed in its 1979 Islamic Revolution. He dedicated scarce water to building up agriculture, helping to desiccate the ancient Persian system of underground aqueduct-like canals known as qanats.

After the revolution thrust Iran into global isolation, its authoritarian clerical leadership doubled down on agriculture, aiming to produce all the food the country needed at home instead of having to import it. Subsidies for agriculture kept farmers in rural areas employed, satisfying a key political constituency of the government, experts say.

But this emptied aquifers faster than they could be replenished and encouraged farmers to drill illegal wells when they ran out, which only worsened the problem.

So many illegal wells were drilled to irrigate rice and wheat crops around the UNESCO world heritage site of Persepolis, in south-central Iran, that the ground is sinking, threatening the ancient ruin, local media reported last year.

The focus on agriculture also diverted water from industrial uses, which could have strengthened Iran’s economy as it contended with Western sanctions designed to force it to limit its nuclear activities, Mr. Madani said.

Sistan and Baluchistan province depends on the Helmand River, which runs from the Hindu Kush mountains in Afghanistan to the Hamoun wetlands in southeastern Iran, providing critical water for drinking, fishing and farming to people in both countries. But as the river’s flow has shrunk, the wetlands have gone dry.

Experts said it was not clear what was causing the water shortage, but they predicted the situation would worsen as agriculture and other development increased along Afghanistan’s share of the river.

Members of Iran’s parliament said in an open letter last week that Sistan and Baluchistan’s water reserves would be exhausted by mid-September, leaving the provincial population of about two million with little choice but to leave.

“We will see a humanitarian disaster,” warned the letter, signed by 200 lawmakers.

Like other Iranian officials, they accused Afghanistan’s Taliban administration of restricting the river’s flow in violation of a 1973 treaty that divided the rights to its waters, and they demanded that the Taliban reopen the spigot. Afghanistan, however, says there is simply less water to send.

For the moment, at least, tensions appear to have eased.

Iran’s ambassador to Kabul announced on Saturday that the Taliban had agreed to allow Iranian hydrologists to inspect the level of water behind an Afghan dam.

That will not bring any immediate relief to the residents of Sistan and Baluchistan. They said that before, people were concerned mostly about the rising prices of water and the anemic flow. But now, they are worried the water will be totally cut off.

Long neglected by the government, the inhabitants of Sistan and Baluchistan were quick to join the antigovernment protests that erupted across Iran last September after the death in police custody of a young woman. Though demonstrations in the province were violently suppressed, they outlasted protests in other regions.

The protests in the province were about grievances far broader than water scarcity, reflecting what residents say is longstanding discrimination against Baluchs, an ethnic minority in Iran.

Unrest over water rights has gripped far more prosperous and influential areas of Iran, including the central city of Isfahan, where the government’s diversion of the Zayanderud River led to protests on its dry, cracked bed in 2021.

Under the Islamic Republic, dams were built to divert water to politically powerful areas, drying up lakes, experts say. Now, faced with declining water levels, Iran has turned to new technical solutions, like transferring water from one area to another and desalinating seawater, an energy-intensive and polluting practice.

The government is constructing a 620-mile pipeline to bring desalinated water from the Sea of Oman to Sistan and Baluchistan province and other parts of Iran. But even with such measures, it will be a struggle to reverse Iran’s rapid descent into water bankruptcy, experts said.

To address the root of the problem, the government should “quickly create job opportunities other than agriculture in the region, so that farmers’ lives don’t have to be tied to water-based jobs,” said Mohsen Moosavi, a hydraulic structures specialist in the Iranian capital, Tehran.

Socializing at the Khaju bridge in Isfahan. Faced with declining water levels, Iran has turned to new technical solutions like desalinating seawater, an energy-intensive and polluting practice.Credit...The New York Times

But for many in Sistan and Baluchistan, it is too late.

Seven years ago, Mohammad Ehsani, a filmmaker, interviewed farmers, herders and others who lived around the once-fertile Hamoun wetlands for a documentary, “Once Hamoun.” It shows a landscape full of ancient history and modern decay: hut-like homes sitting in the dust where a lake used to be; camels and sheep drinking from dribbles of rainwater, all the moisture their owners could find; men marooned at home for lack of fish or other employment.

When Mr. Ehsani returned for a visit four months ago, it was much worse, he said. In 2016, residents wanted to stay on their land despite the challenges. Now “you look at their eyes and you see agony,” he said. “Villages are emptying out, one after the other.”

“The region,” he added, “is destroyed.”

Vivian Yee is the Cairo bureau chief, covering politics, society and culture in the Middle East and North Africa. She was previously based in Beirut, Lebanon, and in New York, where she wrote about New York City, New York politics and immigration. @VivianHYee