The world's biggest man-made lake that's 139 miles wide and took 5 years to fill

Spanning the border between Zambia and Zimbabwe, Lake Kariba is the world's largest man-made lake by volume - a colossal body of water that has shaped the region's environment, economy and energy production since its creation over six decades ago. Built in the late 1950s, it remains a vital source of hydroelectric power and water in southern Africa, however, its future is increasingly at risk.

Created after the construction of the Kariba Dam on the Zambezi River, the lake stretches more than 139 miles in length and reaches up to 25 miles wide. At full capacity, it holds around 44 cubic miles of water - equivalent to about 73.5 million Olympic-sized swimming pools - and covers nearly 2,150 square miles. With such a vast size, it's no wonder that it took an incredible five years to fill, between 1958 and 1963. It is the world's largest man-made reservoir by volume - four times larger than China's Three Gorges Dam.

The enormous mass of water is believed to have caused induced seismicity in the seismically active region, with more than 20 earthquakes of a magnitude of five or above on the Richter scale being recorded.

Kariba Dam, completed in 1959, is one of the most significant engineering projects in Africa's history. It supplies electricity to millions through two major power stations, Kariba North in Zambia and Kariba South in Zimbabwe, with a combined capacity of more than 2,000 megawatts. This is enough to power about 1.6 million average homes in developed countries, and as many as three million in countries in Africa with lower average usage.

While the lake brought electricity and development, it came at a cost. During the valley's flooding, an estimated 57,000 people, mostly from the Tonga ethnic group, were displaced. Homes and ancestral lands were lost, and many communities were resettled with little support.

At the same time, the rising waters trapped thousands of animals. In response, a rescue mission known as Operation Noah was launched between 1958 and 1964. More than 6,000 animals, including elephants, antelope and big cats, were relocated to nearby game reserves and national parks.

Over time, Lake Kariba developed a thriving ecosystem. The waters are now home to various fish species, including kapenta and tigerfish, while crocodiles and hippos are common in shallow areas. The surrounding areas attract elephants, buffalo and predators such as lions and leopards. The lake also supports a busy fishing industry and attracts tourists for boat safaris, fishing trips and wildlife watching, particularly near Zimbabwe's Matusadona National Park.

Despite its impressive size, Lake Kariba has struggled in recent years due to prolonged droughts. In 2024, water levels dropped to critical lows, forcing major reductions in electricity generation. Some towns and cities in Zambia and Zimbabwe faced blackouts lasting up to 21 hours a day. Authorities blamed the situation on El Niño - the warming of sea surfaces temperatures every few years - and changing climate patterns, warning that the region's overreliance on hydropower has become unsustainable.

To reduce dependence on the dam, Zimbabwe has begun work on a floating solar farm on Lake Kariba. The first phase will generate 250 megawatts, with plans to scale up to 1,000 megawatts. Officials say the project should help to stabilize the national grid.