Without the Nile, there is no Egypt. Egyptians have been the masters of the river for thousands of years. But the Nile has never been under such strain. Pollution, climate change and Egypt’s soaring population are taking an immense toll. Now Egypt is sparring with Ethiopia over a giant dam being built 2,000 miles upriver. Time is running out. Can they find a solution to avoid a wider conflict?

For Thousands of Years, Egypt Controlled the Nile. A New Dam Threatens That. Ethiopia is staking its hopes on its $4.5 billion hydroelectric dam. Egypt fears it will cut into its water supplies. President Trump is mediating.

MINYA, Egypt — The Egyptian farmer stood in his dust-blown field, lamenting his fortune. A few years ago, wheat and tomato-filled greenhouses carpeted the land. Now the desert was creeping in.

“Look,” he said, gesturing at the sandy soil and abandoned greenhouses. “Barren.”

The farmer, Hamed Jarallah, attributed his woes to dwindling irrigation from the overtaxed Nile, the fabled river at the heart of Egypt’s very identity. Already, the Nile is under assault from pollution, climate change and Egypt’s growing population, which officially hits 100 million people this month.

And now, Mr. Jarallah added, a fresh calamity loomed.

A colossal hydroelectric dam being built on the Nile 2,000 miles upriver, in the lowlands of Ethiopia, threatens to further constrict Egypt’s water supply — and is scheduled to start filling this summer.

“We’re worried,” he said. “Egypt wouldn’t exist without the Nile. Our livelihood is being destroyed, God help us.”

The dispute between Egypt and Ethiopia over the $4.5 billion Grand Ethiopian Renaissance Dam — Africa’s largest, with a reservoir about the size of London — has become a national preoccupation in both countries, stoking patriotism, deep-seated fears and even murmurs of war.

To Ethiopians, the dam is a cherished symbol of their ambitions — a megaproject with the potential to light up millions of homes, earn billions from electricity sales to neighboring countries and confirm Ethiopia’s place as a rising African power.

After years of bumpy progress, including corruption scandals and the mysterious death of its chief engineer, the first two turbines are being installed. Officials say the dam will start filling in July.

That prospect induces dread in Egypt, where the dam is seen as the most fundamental of threats.

“The Nile is a question of life, a matter of existence to Egypt,” President Abdel Fattah el-Sisi said at the United Nations last September.

For eight years, officials from Egypt, Ethiopia and Sudan — which lies between the two countries — squabbled fruitlessly over the dam. Ninety-five percent of Egyptians live along the Nile or in its teeming delta, and the river provides nearly all of their water. They worry that, if the dam in Ethiopia is filled too quickly, it could drastically curtail their water supply. In November, in a last-ditch effort, the talks moved to Washington, where the White House has been mediating.

Mr. Trump, playing on his self-image as a deal maker, has suggested that his efforts might merit a Nobel Prize. The White House is pushing for an agreement by the end of February, but Egyptian and Ethiopian officials warn it will not be easy.

In an interview last month, Seleshi Bekele, Ethiopia’s water minister, called Egypt’s claims to the Nile “the most absurd thing you ever heard.”

Preparing For the Largest Dam in Africa Mediterranean Sea IRAQ Cairo LIBYA EGYPT SAUDI ARABIA Aswan Nile River Red Sea CHAD Khartoum YEMEN SUDAN Grand Ethiopian Renaissance Dam Blue Nile SOUTH SUDAN ETHIOPIA CENTRAL AFRICAN REPUBLIC White Nile SOMALIA DEM. REP. OF CONGO KENYA Lake Victoria Indian Ocean 250 Miles Mediterranean Sea IRAQ Cairo LIBYA EGYPT SAUDI ARABIA Aswan Nile River Red Sea CHAD Khartoum YEMEN Grand Ethiopian Renaissance Dam SUDAN Blue Nile SOUTH SUDAN ETHIOPIA White Nile SOMALIA DEM. REP. OF CONGO KENYA Lake Victoria Indian Ocean 250 Miles Mediterranean Sea IRAQ Cairo LIBYA EGYPT SAUDI ARABIA Aswan Nile River Red Sea CHAD Khartoum YEMEN Grand Ethiopian Renaissance Dam SUDAN Blue Nile SOUTH SUDAN ETHIOPIA White Nile SOMALIA DEM. REP. OF CONGO KENYA Lake Victoria Indian Ocean 500 Miles

For millenniums, Egyptians were the unchallenged masters of the Nile, drawing on the river to build ancient empires and modern republics.

The Pharaohs worshiped crocodiles and used the Nile to transport the giant granite blocks for the Great Pyramid of Giza. In 1970, Egypt’s towering post-independence leader, Gamal Abdel Nasser, oversaw the completion of the Aswan High Dam, taming the Nile’s seasonal flows and transforming Egyptian agriculture.

Egypt justified its dominance over the river by citing a colonial-era water treaty and a 1959 agreement with Sudan. But Ethiopia does not recognize them, and when its former leader, Mengistu Haile Mariam, proposed building a series of dams on the Nile in 1978, he met thinly veiled threats.

“We are not going to wait to die of thirst in Egypt,” said Egypt’s president at the time, Anwar Sadat. “We’ll go to Ethiopia and die there.”

The Renaissance Dam spans the Blue Nile, the river’s main tributary, which supplies most of Egypt’s water. Ethiopia’s young, modernizing leader, Abiy Ahmed, insists that Egyptian fears about its impact are overblown. After taking office as prime minister in 2018, Mr. Abiy flew to Cairo to offer his reassurances

“I swear, I swear, we will not hurt Egypt’s water supply,” he told reporters.

But by last fall, anxieties were rising again and Mr. Abiy offered an ominous warning.

“No force could prevent” Ethiopia from completing the dam, he told Ethiopian lawmakers in October, less than two weeks after winning the Nobel Peace Prize for resolving his country’s long conflict with Eritrea. If it came to it, Mr. Abiy added, he would get “millions readied” for war with Egypt.

While the two nations spar over the dam, hydrologists say the most pressing threat facing the Nile stems from population growth and climate change. Egypt’s population increases by one million people every six months — a soaring rate that the United Nations predicts will lead to water shortages by 2025.

Families swimming in the Nile in El Qanater El Khayreya city.

Women carrying their belongings after a day spent in El Qanater El Khayreya city.

Fishermen working on the Nile River in southern Egypt.

Rising sea levels threaten to nibble at Egypt’s low-lying coast and help push saltwater inland, spoiling fertile land. Increasingly volatile weather is another risk.

A study published last August by researchers at Dartmouth College found that while rainfall is likely to increase in the Upper Nile basin over the coming century, the incidence of hot and dry years could increase by a factor of two or three — even if global warming is limited to 2 degrees Celsius.

Ethiopia argues that storing the water upstream will help, because it is less prone to evaporation than in Egypt, which is drier.

“The dry years will be more severe, in that they will be hotter and more frequent,” said Ethan D. Coffel, the paper’s lead writer. “Life is going to get much harder for farmers on the Nile.”

Mr. el-Sisi’s Egypt has made modest efforts to prepare. Officials have imposed restrictions on water-intensive crops like rice and bananas. On Fridays, clerics deliver government-dictated sermons stressing the virtues of conservation.

On Judgment Day, warned one such sermon, “God will not look favorably” on water wastrels.

But criticism of Egypt’s own stewardship of the Nile is risky. A famous pop singer, Sherine, was prosecuted in 2017 for mocking the Nile’s notoriously dirty water, telling fans to “Drink Evian instead.”

She was eventually acquitted, perhaps partly because her jab hit home: Egyptians abuse the Nile as much as they revere it.

Sewage flows into its waters and garbage clogs irrigation canals. Successive Egyptian leaders have indulged in grandiose schemes that suckle from the river, including Mr. el-Sisi, who is building a sprawling new administrative capital in the desert outside Cairo that experts say will deplete the Nile further.

The dam has become the focus of Egypt’s water anxieties. The main sticking point with Ethiopia is how quickly it should be filled. Ethiopia says as few as four years, but Egypt, fearing a drought during the filling period, has argued for 12 or longer.

Grand Ethiopian Renaissance Dam ETHIOPIA Grand Ethiopian Renaissance Dam The completed dam will span the river with a 509-foot tall concrete structure. Guba Blue Nile River Potential reservoir after the dam has been completed. SUDAN A three-mile rock-fill dam will prevent water from flowing into Sudan. 3 Miles ETHIOPIA Grand Ethiopian Renaissance Dam The completed dam will span the river with a 509-foot tall concrete structure. Guba Blue Nile River Potential reservoir after the dam has been completed. SUDAN A three-mile rock-fill dam will prevent water from flowing into Sudan. 3 Miles Grand Ethiopian Renaissance Dam The completed dam will span the river with a 509-foot tall concrete structure. Blue Nile River SUDAN Potential reservoir after the dam has been completed. ETHIOPIA 3 Miles Grand Ethiopian Renaissance Dam The completed dam will span the river with a 509-foot tall concrete structure. Blue Nile River Potential reservoir after the dam has been completed. SUDAN ETHIOPIA 3 Miles By The New York Times

Beyond the technical arguments, the dispute is driven by politics. Mr. el-Sisi, a military strongman, is acutely sensitive to suggestions that he is soft on Egypt’s security.

Mr. Abiy, who faces elections this year, is under pressure from ordinary Ethiopians, who helped finance the dam by buying government-issued bonds. More broadly, he needs to deliver on a prestigious project in a country that considers itself an emerging power.

Ethiopia has one of the world’s fastest growing economies. The dam offers it a chance to become Africa’s biggest power exporter. And, just as in Egypt, the Nile is central to the country’s sense of itself.

“For how long will the river flow down taking everything with it, even the branch of a tree?” goes one song taught to Ethiopian schoolchildren.

The Blue Nile falls, a few miles downstream from Lake Tana, the source of the Blue Nile.

The Grand Ethiopian Renaissance Dam will be the largest in Africa — a $4 billion hydro-electricity colossus, capable of generating enough power to satisfy Ethiopia’s growing economic ambitions.

Meskel Square in Addis Ababa, Ethiopia. The dam project is central to the country’s ambitions.

During an interview with The New York Times at the dam in 2018, Semegnew Bekele, the project manager, said the undertaking would “eradicate our common enemy — poverty.”

He cited the Hoover Dam in the United States as inspiration.

“It makes America America,” he said, adding that he hoped Ethiopia’s dam would do the same for his country.

Soon after, he was found slumped behind the wheel of his Toyota Land Cruiser, a gunshot wound to the head. The police ruled it a suicide. A few weeks later, Mr. Abiy fired the dam’s main contractor over accusations of widespread corruption.

Despite the setbacks, the Ethiopians say they are close to finishing the dam. They started building it in 2011 at the height of the Arab Spring, when Cairo was still in turmoil, and hostilities have dogged the project from the start.

Simegnew Bekele, the project manager, at the dam site in 2018, shortly before his death.

In 2013, a television broadcast showed Egypt’s leaders — including the president at the time, Mohamed Morsi — discussing covert tactics to scupper the dam, including a bomb attack. The tough talk came to nothing, but soon Egyptians were accusing their rivals of slow-rolling the technical talks while they continued to build.

The Ethiopians, in turn, say the Egyptians treat them with a highhandedness that stretches back to a failed Egyptian invasion of Ethiopia in the 1870s. In October, one Ethiopian negotiator accused Egypt of seeking to turn his country into a “hydrological colony.”

Mr. el-Sisi insists he wants a peaceful resolution, embarking on a diplomatic offensive to win support from Ethiopia’s neighbors. The Nile Museum, which opened in Aswan in 2016 emphasizes Egypt’s ties with its “African brothers.” Inside, a three-story waterfall symbolizes the Nile wending through 10 African countries before arriving in Egypt.

Yet Mr. el-Sisi has also sent a message that he is ready to resist in other ways. Egypt has fostered ties with Ethiopia’s adversaries, shipping weapons to the government of South Sudan, according to United Nations investigators. Inside Ethiopia, officials have accused Egypt of sponsoring anti-government protests and armed rebellions, accusations Cairo denies.

In the talks, Mr. el-Sisi is at a marked disadvantage — the longer negotiations take, the closer Ethiopia moves toward finishing the dam.

Mr. Abiy’s hand is also strengthened by Ethiopia’s growing geostrategic muscle. In recent years, many countries — including the United Arab Emirates, China and the United States — have vied for influence in the Horn of Africa, where many analysts have proclaimed a new “Great Game.” Ethiopia, the region’s most populous country with more than 100 million people, is central to those calculations.

It scored a major diplomatic victory in the negotiations over the dam when it persuaded Sudan, which had traditionally sided with Egypt, to take its side in the dispute.

Salt covering land as a result of rising sea levels along Egypt's north coast.

Fishermen on the Nile in Aswan, southern Egypt.

A donkey grazing in a field owned by Ahmed Gouda, who grows mangoes, peaches, dates, corn and rice — all squeezed into just two acres.

The White House and World Bank-brokered negotiations haven’t gone as Egypt had hoped, Western diplomats say. Despite the close ties between Mr. Trump and Mr. el-Sisi — who Mr. Trump once called “my favorite dictator” — Egypt has had to concede key demands over the Nile.

On Feb. 1, a day after the latest talks ended, Mr. Abiy sounded an upbeat note on Twitter, boasting that Ethiopia was drawing ever closer to “our continental power generation victory day.”

But Ethiopian ministers acknowledge that Mr. Trump is pressing them to do a deal, too.

“Of course, pressure is everywhere,” Mr. Bekele, the water minister, told reporters.

An Egyptian government spokesman did not respond to questions. The two sides are scheduled to reconvene in Washington on Feb. 13.

The Nile ends its winding 4,000-mile journey through Africa in Ras el-Bar, a seaside town on Egypt’s north coast, where the river slips quietly into the Mediterranean. One morning, Ahmed el-Alfi, 16, stood on the rocks on its bank, fishing for shrimp.

The young fisherman didn’t know much about the talks with Ethiopia, but he could see the river’s problems himself.

“The sea is clear but the Nile is dirty,” he said Mr. el-Alfi. “It’s full of rubbish.”

And yet, he added, Egypt had no option but to fight for it.

“Without the Nile,” he said, “there is no Egypt.”

A hotel cafe overlooking the Nile in Cairo.

A statue of a woman from ancient Egypt referring to the sacrifices that were presented to “Hapi,” the god of the annual flooding of the Nile in ancient Egyptian religion. The little mermaid Disney character “Ariel” in the background mural brings a modern twist to ancient Egyptian cultures of mythology.

A wedding celebration aboard a boat on the Nile in Cairo.

Declan Walsh reported from Minya, Egypt, and Somini Sengupta from the Grand Renaissance Dam, Ethiopia. Simon Marks contributed reporting in Addis Ababa, Ethiopia and Nada Rashwan in Cairo.