The Zambezi River is one of Africa’s best-known waterways, but a new scientific report has created a stir by showing that its source is in Angola, not Zambia, and that it is more than 10% longer than previously recorded.
The research also shows that clean water from the Angolan highlands contributes as much as 70% of the volume over the Victoria Falls, more than 500km downstream, far more than suspected. This influx of pure water has important environmental implications for the health of the river, surrounding wetlands, Lake Kariba and the Zambezi Delta, where the river enters the sea in Mozambique.
Researchers from The Wilderness Project, which was founded in 2018 to study African freshwater systems including the Okavango and the Zambezi, paddled from the traditionally accepted source in Zambia and along Angola’s Lungwebungu River to ascertain which rose furthest from the sea. They calculated that using the Angolan source, the Zambezi is 342km longer than previously thought.
In 2022 and 2023, in conjunction with the National Geographic Okavango Wilderness Project and the Wild Bird Trust, researchers paddled the entire length of the Zambezi, including the Lungwebungu’s 1,032km.
The Zambezi is now considered to be 3,421km long, still the fourth-longest river in Africa, behind the Nile, Congo and Niger.
This discovery redefines our understanding of the Zambezi system: without the Angolan Highlands Water Tower, the mighty Zambezi would be significantly reduced in flow
— Research from The Wilderness Project
“By surveying both headwater sources and combining high-resolution satellite imagery with our expedition findings, this study reveals that Angola’s Lungwebungu River extends 342km farther from the ocean than the Zambian source,” the researchers state in Assessment of Source Regions of the Zambezi River: Implications for regional water security, published in the journal Hydrology & Earth System Sciences in September 2025.
The river originates in the Angolan Highlands Water Tower (AHWT), a region of high rainfall that gives rise to a number of other major rivers, including the Cubango and Cuito, which join to form the Okavango River that flows into the Okavango Delta in Botswana.
“In addition, the AHWT contributes almost three-quarters (roughly 70%) of the total flow of the upper Zambezi River,” the researchers write. “This discovery redefines our understanding of the Zambezi system: without the AHWT, the mighty Zambezi would be significantly reduced in flow.
“Victoria Falls, a Unesco world heritage site that gets roughly 70% of its water from Angola, would also be vastly diminished, and hydroelectric dams across the region would struggle to produce electricity,” they add.
Much of the region through which the Lungwebungu flows was the scene of intense fighting during Angola’s war for independence (1961-1974), which was followed by civil war (1975-2002). For decades minefields have made research in the area dangerous and difficult. Research efforts have also been hampered by the remoteness of the region.
The Lungwebungu flows through deep Kalahari sands that filter its waters, a cleaning process aided by the huge Kameia wetlands and Luena flats. These wetlands also play an ecologically important role in the ecosystem of the upper Zambezi, but until recently this was poorly recorded.
“While our results are exploratory, they represent the first combined assessment using multiple lines of evidence: greater river length, higher discharge, water quality, and wetland coverage; collectively, these attributes position the Angolan rivers as the more significant source of the Zambezi,” say the researchers. “This effort marks the first time the Angolan portion of the Zambezi basin headwaters has been scientifically surveyed.”
The Zambezi basin covers about 1,370,000km2 spread across eight countries — Angola, Botswana, Malawi, Mozambique, Namibia, Tanzania, Zambia and Zimbabwe — and is home to about 50-million people.
It is the largest river basin in Southern Africa and a significant biodiversity hotspot, with more than 200 species of mammals, 700 species of birds, 290 species of reptiles and amphibians and 190 species of fish having been recorded.
The wildlife areas bordering Zimbabwe and Zambia along the middle Zambezi and the upper Zambezi upstream from the Victoria Falls are important for conservation and are major international tourism attractions.
The Zambezi basin plays a key role in the livelihoods of millions of people but faces increasing environmental challenges due to climate change, development and human water use.
Rainer von Brandis, research director for the project, says: “Our teams have spent years exploring and scientifically documenting the AHWT, uncovering its hidden role as the lifeblood of the Zambezi and [while doing so] showing why protecting it is vital for the future of this mighty river and its people.”
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