A dispute over the Nile, the world’s longest river, is coming to a head. At stake are the lives and livelihoods of millions of people who depend on its water.

Egypt is objecting to efforts by Ethiopia to start operating a $4.8 billion dam on a major tributary of the Nile, a hydroelectric project that it hopes will power a social and economic transformation of the country, without a binding agreement that preserves Cairo’s rights to the waters.

The project is regarded by Egypt as a threat that could cut off nearly all of a key source of water for the country’s rapidly growing population. The country has exerted outsize control over access to the Nile since colonial times.

Water scarcity has become a geopolitical, economic and business concern around the globe, with populations competing with farming and industry.

The dispute over the Nile is one of the world’s major flashpoints over water rights. Disagreements have intensified in recent years over how much water each country along the Nile and its tributaries can tap, with the U.S. and other African countries seeking to help mediate disagreements.

The Ethiopian government in Addis Ababa formally notified Cairo July 5 that it has started the second phase of filling a giant reservoir behind the dam without a binding agreement with Egypt and Sudan over how much water each country will be allotted once the dam is filled. Ethiopian officials have said they hope to conduct hydroelectric trials this year.

Egypt’s foreign ministry has said the move to resume filling the reservoir, after starting last year, threatens “security and peace” in the region.

Egypt and Sudan have lobbied the United Nations, the U.S. and other countries to stop Ethiopia from filling the dam before the three countries reach a legally binding agreement over its operation. U.N. Security Council members on Thursday backed the African Union’s efforts to mediate the dispute.

President Biden has underscored the U.S.’s interest in achieving a diplomatic resolution that meets the legitimate needs of all three countries.

Egypt, with more than 100 million people, consumes about 84 billion cubic meters of water and needs about 114 billion cubic meters, according to the Egyptian ministry of irrigation, each year, with about 55.5 billion cubic meters coming from the Nile.

The country depends on the Nile for more than 90% of its freshwater needs. To cover the rest of its needs, Egypt relies on recycling wastewater and desalination of seawater as well as virtual water import.

Meanwhile, Ethiopia, a country with about 115 million people and until recently one of the world’s fastest-growing economies, regards the dam as a catalyst to accelerating the country’s transformation from an agrarian to an industrial economy. It hopes that the project—called the Grand Ethiopian Renaissance Dam, or GERD—will go a long way in closing its energy deficit, one of the largest in the world, with many Ethiopians lacking access to electricity.

Water flows into the Nile from tributaries in 10 countries. According to a variety of longstanding agreements, a certain amount of water must be released from each country, essentially guaranteeing a steady flow for Egypt.

The country has enjoyed broad rights over the use of the Nile’s waters since colonial times. A 1929 agreement that included the U.K., which ruled much of the Nile region at the time, gave Egypt the right to veto construction projects, even in upstream countries, that might affect how much water it would receive.

Since the 1950s, Egypt has impeded Ethiopian dam-building with threats of military intervention.

According to a 1959 agreement, Egypt receives 55.5 billion cubic meters of water from the Nile each year, while Sudan can draw 18.5 billion cubic meters. Ethiopia receives no water from the Nile, but the new dam would have a storage capacity of 74 billion cubic meters of water.

Countries in the upstream Nile region have demanded more water rights and in the 1990s banded together to oppose Egypt’s control over the basin and its veto over construction projects along the river.

In 1999, an intergovernmental partnership of Nile basin countries, including Egypt, was established. By 2010, Egypt’s influence in Africa had significantly diminished, and there were more efforts to challenge Egyptian control and assert sovereign rights to the Nile.

Friction over access to the Nile has long been a concern in relations between Egypt and Ethiopia, which date to ancient times and are among the oldest on the African continent. Centuries ago, an Ethiopian emperor threatened to cut off the water flowing to Egypt.

In 1979, Egypt sought to prevent nascent plans by Ethiopia to build a dam along the Nile, while Ethiopia opposed an Egyptian plan to divert the river to irrigate the Sinai Peninsula, a move that would have lowered water levels in the Nile basin.

Relations further deteriorated after an assassination attempt against President Hosni Mubarak in Addis Ababa in 1995, when gunmen ambushed his motorcade during a visit for a summit of African leaders.

Then, in 2011, when Egypt was in the throes of the Arab Spring protests, Ethiopia began its giant dam project. Ethiopia struck a deal with Webuild, an Italian company that built other dams and hydroelectric plants in Ethiopia.

Work in 2019 on the Grand Ethiopian Renaissance Dam, which Ethiopia says it needs to address a shortage of electrical power.

Work in 2019 on the Grand Ethiopian Renaissance Dam, which Ethiopia says it needs to address a shortage of electrical power.

Photo: Eduardo Soteras/Agence France-Presse/Getty Images

In 2015, Ethiopia, Egypt and Sudan signed an agreement on cooperation, including a seven-year timeline for filling the dam. Talks on a full accord have been difficult, and disagreements remain on measures to address droughts and resolve disputes and on whether the deal will be legally binding.

Egypt and Sudan want a binding accord, while Ethiopia favors more flexibility. Sudan has sided with each party at various points of the standoff. The dam is near the border with Sudan, which lies between Egypt and Ethiopia and relies on the waters of the Nile for irrigation.

Construction is nearing completion, the U.N. said this month. Ethiopian media reported that about 80% of the dam has been finished. A manager for the project declined to comment.

When Ethiopia began filling the dam in July 2020, Egypt sought international mediation. It has lobbied the Arab League to pressure Ethiopia to stop filling until an agreement is reached. Egypt secured significant support—but not that of Sudan, which feared a pan-Arab conflict with Ethiopia.

In June 2020, Egypt unsuccessfully attempted to persuade the U.N. Security Council to intervene.

For Egypt, a major obstacle is that no studies have been agreed upon or completed on how the dam affects the Nile’s flow or on the material impact for the downstream countries, said Hafsa Halawa, an analyst and nonresident fellow at the Middle East Institute who has studied the dispute.

The Nile is a source of recreation as well as irrigation for Sudan, which has been seeking a binding agreement on Ethiopia’s dam.

The Nile is a source of recreation as well as irrigation for Sudan, which has been seeking a binding agreement on Ethiopia’s dam.

Photo: Ozan Kose/Agence France-Presse/Getty Images

Talks have faltered since Ethiopia first started filling the dam last year. The resumption of filling and the prospect that the dam will start generating energy soon has added pressure to the talks.

Egyptian and Ethiopian leaders have rallied support domestically for their positions by invoking national sentiment.

For Ethiopia, the dam, which will be the largest in Africa upon completion, has become a point of pride. Some 8,500 laborers are working long hours to finish it.

Ethiopia’s government has heralded the dam for the political leverage it will provide in addition to the economic and social benefits.

The Egyptian government has repeatedly promised its people that the country’s water share will be unaffected.

During a visit to Egypt in June 2018 by Ethiopian Prime Minister Abiy Ahmed, Egyptian President Abdel Fattah Al Sisi urged his guest to make a public pledge that his country wouldn’t harm the Egyptian people. “I swear to God, we will never harm you,” Mr. Ahmed said in Arabic after Mr. Sisi spoke in a joint press conference.

Egypt’s political leaders have suggested that the government in Cairo had the power to stop the project, if necessary by force. Mr. Sisi had previously ruled out the possibility of military action against Ethiopia, saying he preferred negotiations. But as talks with Ethiopia collapsed this year, Mr. Sisi said “all options were open.”

Meanwhile, Egypt has pushed to modernize the country’s irrigation systems, switching to the more efficient drip irrigation from old surface irrigation systems. Irrigation is the only option for large-scale agricultural production in Egypt. The Aswan High Dam reservoir helps the country to mitigate effects of drought.

Egypt has launched a public-awareness campaign aimed at encouraging the population to conserve water at home.

While the Nile is a key source of water for Egypt, other Nile basin countries including Ethiopia also receive water from rainfall, groundwater, lakes and rivers. Ethiopia has experienced several devastating droughts followed by food shortages and famines.

The shore of Lake Tana, the origin of the Blue Nile in Ethiopia’s highlands.

The shore of Lake Tana, the origin of the Blue Nile in Ethiopia’s highlands.

Photo: Eduardo Soteras/Agence France-Presse/Getty Images