Press Release

New Study Defines Boundaries of Angolan Highlands Water Tower, a Critical Step Toward Its Conservation

A new academic article by a team of National Geographic Okavango Wilderness Project researchers is the first to scientifically define the boundary of the Angola Highlands Water Tower within Angola’s Central Bié Plateau- a critical step in its conservation and for ensuring water security for millions of people.

An unnamed waterfall at dusk

Photograph by Cory Richards

ANGOLA (July 10, 2023) - Due to the lack of permanent snow and ice, global maps typically portray Africa as having no water towers - but a team of National Geographic Okavango Wilderness Project (NGOWP) researchers challenges that notion, in a new article published in the July issue of Springer’s Environmental Monitoring and Assessment.

Angola is a source of many major rivers in southern Africa and is referred to as the “water tower” of the region; its highlands store large quantities of freshwater, which flow hundreds of kilometers downstream, eventually feeding people, farms, and nature in some of southern Africa’s most arid regions.

However, despite its ecological and hydrological importance, within academic science, a lack of defined boundaries around the Angolan Highlands Water Tower (AHWT) has hindered global efforts to protect and preserve it.

The article found that an average of 423 cubic kilometers of rainfall falls over the AHWT each year - which amounts to nearly 170 million Olympic-size swimming pools. The AHWT, as defined by the report, occupies an area of 380,382 square kilometers, providing freshwater resources to seven countries: Angola, Zambia, Zimbabwe, Mozambique, Democratic Republic of the Congo (DRC), Namibia, and Botswana. Further, the AHWT provides water to some of the most important biodiversity areas in the world, including the Okavango Delta, which provides a vital habitat for iconic species, including the largest remaining population of endangered African elephants.

This is the first academic article to define the boundary of the AHWT as an area of Angola’s Central Bié Plateau above an elevation of 1,274 meters. NGOWP defined the boundary of the AHWT using 40 years of regional precipitation data. Like most of Africa’s water towers, the Angolan Highlands Water Tower lacks snow or ice - its steady supply of water is made possible by gradual groundwater flow, highland source lakes, and extensive peatlands.

Defining the AHWT’s boundary is a critical step in its conservation and for ensuring water security for millions of people amid Africa’s rapid population growth, says the article.

The AHWT is the southern source of the Congo Basin, the western source of the Zambezi Basin, and the sole water source of the Okavango Basin and Okavango Delta. Approximately 95% of the water that flows into the Okavango Delta in Botswana originates from precipitation in the Angolan highlands. The Okavango Delta is formally protected by Botswana and is recognized as a UNESCO World Heritage site and Ramsar Wetland of International Importance. However, the newly defined Angolan Highlands Water Tower lacks any such protections - despite being the source of the Delta.

“Defining the Angolan Highlands Water Tower and quantifying its contributions to rivers downstream, is an important step toward conservation for this critical freshwater resource,” said Dr. Mauro Lourenco, lead author of the article and geospatial ecologist and data analyst for the Wild Bird Trust, which co-founded the NGOWP with National Geographic Society and locally implements science and conservation. “Africa’s water towers have been overlooked by science due to water towers typically requiring permanent snow or ice cover. This article shows us the importance of alternative water towers - characterized by forests and extensive peatlands - and their implications for water supply, food security, and biodiversity throughout southern Africa.”

Dr. Lourenco added, “Angola, like many African countries, is an emerging economy with a rapidly growing population and increasing demand on freshwater resources. We need to continue to study and understand the functioning of the AHWT, and many other African water towers, and their role in providing freshwater to people and wildlife.”

Between 2000 and 2022, the population of Angola more than doubled to 35.59 million people. Population projections for 2050 and 2100 indicate that Angola’s population is likely to double again, potentially reaching 72.33 and 132.90 million by 2050 and 2100, respectively. It is critical to ensure that developments to accommodate population growth are sustainable, and do not disrupt the environmental integrity and hydrological functioning of the AHWT, says the article. This requires a continued understanding of the AHWT’s functioning and role in providing water to surrounding basins.

“The Angolan Highlands Water Tower is not only keystone to the future of southern Africa and its long-term resilience to climate change, but it has profound cultural and spiritual importance. It’s called ‘Lisima Lya Mwono’ (source of life) in the local Luchaze language, and the people who live here have sustained this landscape through their traditions and knowledge,” said Dr. Steve Boyes, National Geographic Explorer and founder of the National Geographic Okavango Wilderness Project. “Now that we’ve defined the boundaries of Angolan Highlands Water Tower within academic science, we need to protect it, in partnership with communities. An important first step is recognition of the water tower as a Ramsar Wetland of International Importance, and we look forward to securing that designation.”

Open access funding for this article was provided by University of the Witwatersrand.



Since 2015, National Geographic Okavango Wilderness Project has been working with communities and governments to secure permanent, sustainable protection for the greater Okavango Basin - which spans Angola, Namibia, and Botswana. A team of National Geographic Explorers, local and regional experts, and partners at the Wild Bird Trust are working to accomplish this through rigorous scientific research, impactful conservation education projects, establishment of community-driven systems of protection, and storytelling about the ecosystem and people who live there. Learn more at


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