In our modern era, it might be reasonable to presume that science has definitively resolved some of the more significant inquiries regarding the natural world, particularly those reliant on precise physical measurements.
However, one apparently straightforward question has remained perplexing: What, exactly, constitutes the world’s longest river?
Indeed, in 2023, the scientific community continues to grapple with this question.
The title of the “world’s longest river” has been officially attributed to Africa’s Nile by reputable sources such as Encyclopedia Britannica and Guinness World Records. Nevertheless, an imminent Amazon River expedition involving a group of international explorers and researchers, embarking on rafts, horseback journeys, and solar-powered boats, is preparing to challenge this designation.
“The Nile is like a worm and the Amazon is an anaconda,” explains 55-year-old Brazilian expedition leader Yuri Sanada, who is both an experienced explorer and film producer. This metaphor highlights the Amazon’s tremendous volume, which carries four times more water than any other river.
“So there’s no comparison – we have the biggest river. But the longest, we will see.”
The expedition, scheduled to commence in April 2024 and spanning five months, intends to navigate the entire length of the Amazon River. Employing state-of-the-art river-mapping satellite technology, the expedition aims to provide conclusive scientific evidence that the Amazon is not only the world’s most voluminous river but also the longest.
It’s important to note that the Amazon is not a single continuous watercourse; instead, it’s part of an extensive “river system” that extends across a significant portion of northern South America. Comparable to the branches of a tree, this network comprises various origins and tributaries.
The dispute over the Amazon’s length primarily revolves around the question of its starting point.
Traditional measurements, as recognized by Britannica and others, consider the river’s origins to be at the headwaters of the Apurimac River in southern Peru. However, American neuroscientist turned river expeditionist, 51-year-old James “Rocky” Contos, asserts that he has identified a more distant source for the river – the Mantaro River in northern Peru – during his research on whitewater rafting routes in the country.
“I was aware that the most distant source of the Amazon was considered to be the Apurimac, but when I was gathering all information – maps, hydrographs, etc. – in preparation for my trip to Peru, I realized that another river appeared to be longer,” Contos says.
To corroborate this finding, he conducted extensive research using topographic maps, satellite imagery, and GPS measurements while kayaking in the region.
This research was subsequently published in 2014.
“The discovery of the new source adds 77 kilometers (48 miles) to the length of the Amazon compared to the previously considered source,” he says.
Sanada contends that Contos’s discoveries provide the expedition team with a valid reason for being there. While mapping the river serves as the expedition’s primary objective, it has a broader mission of extensively documenting and drawing global attention to the remarkable biodiversity of the Amazon rainforest region.
The proposed spring expedition, covering a distance of 7,000 kilometers (4,350 miles), will follow the course of the Amazon River through Peru, Colombia, and Brazil. It will commence at the newly identified source of the Mantaro River, nestled deep in the Peruvian Andes.
The expedition will commence with Contos leading a rafting adventure through the turbulent waters of the Mantaro River. Once the Mantaro merges with the Ene River, the journey’s more extensive portion will get underway. It will be carried out on a trio of specially designed solar- and pedal-powered boats, tracing the Amazon’s course until it reaches the Atlantic Ocean along the Brazilian coast.
Sanada indicates that a secondary expedition is planned for early 2025, commencing at the Apurimac River in Peru, the traditionally recognized source of the Amazon. This phase will enable a second series of measurements. Notably, French explorer Celine Cousteau, the granddaughter of the renowned oceanographer Jacques Cousteau, will reportedly participate in this segment, traveling on horseback along the riverbanks.
Sanada currently leads a team of approximately 50 collaborators for the project, hailing from various regions across the Americas and Europe. The expedition has already established significant partnerships, including backing from the Explorers Club, a collaboration for a related IMAX film production, and the responsibility of creating a new Amazon river map for Harvard University.
Sanada added that the expedition will also welcome a diverse group of international scientific researchers, including those from partner universities in Brazil, Peru, Colombia, the United States, and other nations. They will participate at various stages with the goal of introducing sustainable technology to the traditional communities of the Amazon.
“These projects will teach them how to treat the water, techniques on how to build better houses with natural materials, bring electric energy from renewable sources, waste treatment, electromobility transportation, and more,” he explains. “It’s going to really change the life of people there.”
The expedition’s hybrid solar- and pedal-powered boats are intended to showcase an economical, efficient, and environmentally friendly alternative to the gas-powered motorboats currently utilised by local communities.
In collaboration with a Brazilian university, these vessels are being fabricated using locally sourced bioresin and natural fibers, along with motors produced through 3D printing technology. Post-expedition, the boat motors will be contributed to the local community, which Sanada regards as a crucial part of the expedition’s lasting impact.
Armed guards, bullet-proof cabins
However, despite these optimistic goals, this is not a journey without peril.
“In this kind of expedition, a lot of things can go wrong,” Sanada acknowledges, highlighting the risks such as boat failures and the hazards of the wilderness, which includes threats like jaguars, anacondas, poisonous frogs, and more.
“The most dangerous part,” though, Sanada says, is “the human interaction.” He notes every time the team comes across somebody in the wilderness, they’ll have to wonder, “Are they drug lords? Are they enemies? Or just a friendly tribe trying to invite you to have dinner with them?”
As a precaution, the expedition team is collaborating with local authorities to arrange for armed escorts while traversing regions notorious for illegal mining and drug trafficking. Additionally, the boat cabins are being equipped with materials that provide protection against bullets and arrows.
And Sanada is placing deep trust in his team. “I have local guides from the Amazon, from Peru – people who really know about the land and know about how to survive there,” he says.
Sanada feels the risks are well worth it.
“You cannot stop (because of risk). We are doing this for science. We are bringing this legacy for the Amazon,” he says.
He considers it a privilege to be one of approximately 10 explorers, and the first South American, to ever undertake the historic endeavor of traveling the river’s entire length.
Nevertheless, Sanada acknowledges that the expedition might not ultimately provide a definitive answer regarding the river’s length or conclusively establish it as the world’s largest.
Dr. Suzanne Walther, an associate professor specializing in environmental and ocean sciences at the University of San Diego, sheds light on the difficulties associated with measuring rivers. She underscores the dynamic and intricate nature of waterways and the potential for differing human interpretations concerning recognized river origins and terminations as significant challenges.
She notes that rivers can “change over time in a variety of ways,” citing variations in movement, the water volume they contain, and in their seasonal patterns. “You can imagine then that if you’re measuring something and it is moving, that will actually change the outcome even if you measure it the exact same way,” she adds.
“Whether it’s because of the tools and atmospheric interference, or whether it’s the human component, there’s always a little bit of uncertainty with every measure we take.”
She emphasises that there’s often a human-driven incentive in asserting a remarkable geographical feature such as the world’s longest river. This can bolster national pride and present opportunities for tourism revenue.
“It gives prestige to a place,” she says. “We place value on those things as humans, even if the rivers don’t care if they’re longer or not.”
Searching for knowledge
Regardless of the expedition’s outcome, Sanada expresses his desire to undertake a similar exploration of the Nile in the future, employing the same techniques and measurement methods.
The Nile, which courses through northeastern Africa before culminating in the Mediterranean Sea through Egypt, is also embroiled in a source dispute, as multiple African nations lay claim to harboring the river’s headwaters.
“So let’s see if we survive this first, and then we plan the next one,” Sanada says.
Following the conclusion of the expedition, a comprehensive documentary and an IMAX film related to the journey are anticipated to premiere in 2026.
Sanada is confident that these initiatives can contribute to bolstering regional pride and promoting international tourism. Consequently, he believes they can also further conservation endeavors in the Amazon by illustrating its immense value and emphasizing the imperative need for preservation.
Ultimately, Sanada says that record or no record, “it’s all about a search for knowledge. We’re going to be showing the world what the Amazon is all about.”
