Discovering Where the Nile Really Starts

There it was, high in the cloud forest of Rwanda’s Nyungwe National Park, a shimmering spring emerging from the spongy soil.

It was the first day of their expedition in early February, and conservation biologist Steve Boyes and his team had found what they were looking for: the first hard evidence of the mountain peatlands—absorbent beds of ancient plant matter—feeding the Nile River. “We predicted there were peatlands up there,” Boyes says. “And there were.”

Having achieved formal recognition for the Angolan Highlands Water Tower that sustains the biodiverse Okavango Delta in southern Africa, Boyes, who is a Rolex National Geographic Perpetual Planet Explorer, has been on a mission to replicate that work along the spine of the African continent.

On other continents, vast amounts of water accumulate each winter as snow and ice—dubbed water towers by hydrologists—which then melt and feed rivers through the spring and summer.  In Africa, by contrast, Boyes and his colleagues have theorized that many high-elevation peatlands exist in the mountains and serve this role.

These peatlands soak up water in the wet months and gradually release it, so that the rivers keep flowing long after the rains stop. Because these peatlands have never been fully documented or mapped, Boyes argues, we cannot properly protect the water supplies that more than a half billion people and some of the last remaining populations of large mammals on the planet depend on.

Four years ago, Boyes and the organization he founded, the Wilderness Project, launched a program to survey and monitor four of Africa’s great river basins—the Okavango, Zambezi, Congo, and Nile—and the water towers that feed them.

The $3 million-a-year program now runs dozens of expeditions annually with local partners. Expedition-goers travel on foot and by canoe to capture standardized data on water quality and biodiversity along with 360-degree images and drone photos of the landscape.

“We’re the largest non-military expeditionary mobilization in modern African history,” Boyes says.

Boyes’s work on peatland water towers began as a response to a 2020 publication in the journal Nature, which included a global map of the most important—and most vulnerable—water towers on the planet. As a South African, he was stunned to see that all of Africa was left blank. (The lead author of that report, Walter Immerzeel, a hydrologist at Utrecht University, says that his team had decided to focus only on glaciers and snow cover because they were most readily accessible from publicly available datasets. “We fully acknowledge the African water towers, and Steve Boyes’ work exactly shows their critical importance,” Immerzeel says.)

Last year, for example, the Wilderness Project and collaborators published their discovery that the most distant source of the Zambezi—like that of the Okavango—was located in the Angolan Highlands Water Tower, which provides more than 70 percent of the Zambezi’s flow during the wet season. That finding extended the length of the river that feeds Victoria Falls by more than 200 miles and has significant implications for its protection.

This is the kind of work that can’t be done simply by squinting at satellite maps. “You have to physically walk those systems,” says Fenton Cotterill, a senior scientific advisor for the Wilderness Project. “You have to ground truth it.”

In the first eight months of this year, the Wilderness Project had completed 20 expeditions, and it plans to wrap up 200 by 2030. Boyes says that the reason they are moving so fast is that Africa’s population is growing at a tremendous rate.

The continent is projected to reach 2.5 billion people by 2050, and Boyes believes that more than 150,000 square miles of Africa’s water-producing peatlands need to be better explored, mapped, and protected.

Rwanda, which is among the most densely populated countries in Africa, lost more than 65 percent of its forest cover over a 40-year period, and many of its permanent wetlands have been drained for rice and sugarcane cultivation.

In 2025 and 2026, the team’s goal in the Nile Basin has been to descend the three major tributaries flowing into Lake Victoria and then follow the river north to Uganda’s border with South Sudan. 

The team has already identified a new population of red colobus monkeys—one of Africa’s most endangered groups of monkeys—in Burundi’s Ruvubu National Park. “We found no written record of them in any of the literature,” says Sabine Henry, a senior researcher with the Wilderness Project.

The 25-day expedition in the Nile’s Rwandan headwaters in February, with 16 team members, included a film crew from the BBC. The team covered more than 400 miles and took measurements at 103 survey sites.

As with any expedition to Africa’s most storied of rivers, an exploration of the Nile would not be complete without puncturing a few misconceptions.

The first waited for team members at one of the supposed sources: “This is the furthest source of the Nile River,” declared a green signboard inside Nyungwe National Park. It had been installed there 20 years ago, after three explorers from Britain and New Zealand claimed to have discovered the source during their Ascend the Nile Expedition in 2006.

The only problem? The water bubbling up from the ground flows south and west into Lake Kivu and the Congo River, not into the Nile. “It was great for us because we took a Congo water sample,” Boyes says.

But the team also traveled to the real source of the Nile several miles away. This is a spring-fed stream first documented by German explorer Richard Kandt in 1898 and is generally believed to be the farthest source of the river.

It was here that Boyes was delighted to confirm the presence of peat, which the team had expected based on the altitude, rainfall, and forests in the region. These peatlands weren’t as extensive as those his team has documented in Angola, but the Nile Basin is complex and has many sources in neighboring countries as well.

That small mountain stream joins countless others to form the Nyabarongo River, which crashes down the mountainside and merges with the Ruvubu River to become the Kagera, the largest of the rivers feeding Lake Victoria, where the Nile proper begins.

During the journey, the group found the densest wildlife populations in the papyrus swamps, which were home to monkeys and hippos, along with some of the largest crocodiles they’ve seen, including one individual estimated at 18 feet.

“Most crocs just want to leave you alone,” Henry says. “You do find the odd, curious one who will follow your boat, and that’s sometimes a bit nerve-racking.”

The team members have many more crocodiles to face as they follow the river across Uganda and—with luck—begin exploring the Sudd swamp in South Sudan next year, one of the team’s critical priorities.

The Sudd is the largest wetland in Africa. At its peak during the wet season, it spreads over an area nearly the size of Maine. When the Roman emperor Nero sent the Praetorian Guard up the Nile to find its source in A.D. 61, the soldiers got mired in its mud and reeds and abandoned their expedition.

An estimated six million antelope move between the swamp and the vast grasslands to the east in what conservationists have described as the largest land mammal migration in the world. Since the 1980s, however, the Sudd has also seen significant declines in populations of large mammals, including elephants, buffalo, and hippos.

In 2022, members of the government of South Sudan began talking about reviving an abandoned mega project known as the Jonglei Canal, which would divert the Nile’s flow around the swamp and further jeopardize the ecosystem and the small communities that depend on it.

“That would have just catastrophic environmental consequences,” Henry says. Although a resurrection of the canal project is not imminent, Henry notes that gathering baseline data on the region will be crucial for the inevitable debates about water resources in the region.

As vast as it may be, the Sudd is still just one small stretch of the Nile’s estimated 4,400-mile course from the mountains of Rwanda to the Mediterranean Sea.

Naturally, no expedition to the Nile would be complete without an updated assessment of its true length. Boyes says that the mapping work the team members did in advance of their research indicates that the Nile is at least 25 miles longer than the Amazon.

He is careful to call the finding provisional—the margin is small—and he hopes his work will spur groups in South America to take a closer look at their own rivers.

“I am African, so I am going to lean in that direction,” Boyes says. “But as far as we can tell ... the Nile is the longest river in the world.”