The Zambezi is one of Africa's great rivers. Its basin, covering approximately 1,370,000 km2, is home to approximately 50 million people and spreads across eight countries: Angola, Botswana, Malawi, Mozambique, Namibia, Tanzania, Zambia, and Zimbabwe. The river cascades over Victoria Falls, Mosi-oa-Tunya, "the smoke that thunders," a name used by the Indigenous Batonga and Lozi people, and one of the natural wonders of the world, while also powering major hydroelectric dams such as Kariba and Cahora Bassa. It sustains vast floodplains and productive fisheries, supporting rural economies and local livelihoods across southern Africa. Yet a crucial part of the Zambezi River has been missing from public and policy discussions: Angola's contribution to its waters.
A recent study published in Hydrology and Earth System Sciences demonstrates that Angola's headwaters are not just one of many sources of the Zambezi, they are the dominant ones. Using a combination of field expeditions and satellite data, the research provides the first quantitative estimate of how much Angola contributes to the Zambezi's overall flow and water quality.
Rethinking the "Source" of the Zambezi
Follow us on WhatsApp | LinkedIn for the latest headlines
Traditionally, the source of the Zambezi is recognised as a small, marshy spring near Kalene Hill in the Mwinilunga District, a remote location in northwestern Zambia near the borders of Angola and the Democratic Republic of the Congo. However, new data reveals a broader picture and is expanding our understanding beyond this conventional view, especially since the Angolan headwaters have remained largely understudied. Rivers can be defined by several criteria, including the length of the main stem, the volume of water contributed, the origin of flow, and its importance to people and ecosystems. Other factors such as water quality, historical and cultural significance, and political or administrative importance also shape how a river's source is recognised.
The Angolan headwaters, particularly in the southeastern provinces of Cuando, Cubango and Moxico (Leste and Oeste), were areas of intense conflict during Angola's war for independence (1961-1975) and the subsequent civil war (1975-2002). These regions served as battlegrounds and zones of strategic importance, and they remain among the most heavily landmine-contaminated areas in the country. The widespread presence of residual landmines has continued to restrict access, keeping both local communities and researchers out for decades. As a result, scientific work in these provinces was virtually non-existent throughout the latter half of the twentieth century. However, in the last decade, the National Geographic Okavango Wilderness Project (NGOWP) has undertaken extensive field surveys of the region's biodiversity, rivers, forests, and peatlands. Through this work, the Angolan Highlands have been identified as a critical "water tower" for southern Africa, a source region providing freshwater to millions of people across several of the continent's crucial river systems, including the Congo, Zambezi, and Okavango.
Due to this long-term gap in scientific research, the NGOWP research team sought to extend investigations beyond the Okavango system to other major river networks originating in Angola. This led to the establishment of a sister initiative, The Wilderness Project (TWP), whose first expedition focused on the Zambezi River. From this starting point, both the most distant source of the Zambezi in Angola (the Lungwebungu River) and the traditionally recognised source in Zambia were surveyed, allowing for a comparative assessment of their hydrological characteristics and contributions to the river's overall flow.
The Lungwebungu River, which represents the westernmost source of the Zambezi, was found to be approximately 342 kilometres longer to its confluence with the Zambezi River at Lukulu, Zambia, than the course beginning from Zambia's traditional source near Mwinilunga. This makes the Lungwebungu of Angola the longest tributary and therefore the source of the Zambezi River by definition of river length criteria. TWP subsequently conducted a series of scientific expeditions between 2022 and 2024, covering the entire length of the Zambezi River, from its headwaters to its mouth in the Indian Ocean, quantifying a total river length of 3,421 kilometres, through direct travel in traditional mekoro paddle boats. This was the first series of expeditions of its kind along this great river system.
The research teams directly measured river discharge within the Upper Zambezi, yielding a major finding: during the late wet season, between March and May 2023, the Angolan portion of the Upper Zambezi and Lungwebungu sub-basins contributed approximately 70% of the flow measured upstream of the Barotse Floodplain. While the traditionally recognized source of the Zambezi is still essential to recognise for its cultural and ecological significance, these findings indicate that the Angola's headwaters contribute a larger portion and provides further evidence that the source of the Zambezi, by both river distance and flow contribution, lies in Angola.
The study also highlights the critical ecological role of the Angolan headwaters. The Lungwebungu and Upper Zambezi sub-basins of Angola buffer and reduce elevated conductivity, salinity, and total dissolved solids, likely introduced by mining activities in the Kabompo sub-basin of Zambia. Furthermore, the Upper Zambezi sub-basin contains the highest proportion of wetland coverage in the entire basin, with approximately 19,200 km2 of wetlands located in Angola. This coverage is particularly concentrated in the Kameia and Luena wetlands, which play a crucial role in maintaining overall river health, including moderating water quality, supporting biodiversity, and regulating flows.
The study emphasises the role of the Angolan Highlands Water Tower (AHWT) as the shared headwater region for both the Okavango and Zambezi rivers. Precipitation and hydrological conditions in this highland region have direct and significant impacts on the flow regimes, flood dynamics, and water availability throughout both river systems. This highlights the critical importance of the AHWT not only for sustaining riverine ecosystems and biodiversity, but also for supporting downstream human communities, tourism initiatives and water management across multiple southern African countries.
What Next?
Dialogue on the Zambezi River Basin must explicitly include Angola and its critical water tower. Scientific research and publications should account for the Angolan headwater portions, which are often overlooked or excluded due to the historical context of the region. These headwaters are free-flowing, supporting vital ecological processes and biodiversity, while other downstream sections of the basin have been heavily modified by dams and mining, displacing communities and reducing ecological integrity. Climate change further threatens this water-dependent region, amplifying risks for both human and ecological communities across the basin.
Sign up for free AllAfrica Newsletters
Get the latest in African news delivered straight to your inbox
An appreciation for the entire river system, from head to mouth, is essential. Our results warn against seeing African rivers purely through a downstream lens. Just as we are learning to value wetlands and forests for their role in sustaining broader ecosystems, we must also value the "water towers" of Africa's great basins. These zones are not peripheries; they are foundational to the hydrological health of entire regions. Put simply, if the Zambezi is a lifeline for southern Africa, then Angola's highlands are an underappreciated but vital artery.
Conservation of these headwaters is essential to maintaining the ecosystem services they provide. However, with growing demands for economic development in the region, it is unlikely that Angola alone can bear the full cost of protecting the basin. Greater recognition of these source waters is critical because they underpin regional water security. Governments across the Zambezi Basin must collaborate across departments and sectors to holistically manage the basin's waters and safeguard the long-term future of one southern Africa's most iconic river systems.
Mauro Lourenço is a geospatial ecologist and data analyst for the National Geographic Okavango Wilderness Project. He works on research topics related to freshwater ecosystems, wetlands, forests, fire, carbon, and environmental monitoring. He uses Remotely Sensed datasets and Geographical Information Systems towards high-impact scientific outputs and research. He has worked throughout southern Africa including Lesotho, Angola, South Africa and Botswana.
