The Largest Man-Made Lakes In The World

If someone asks you to name the largest human-made lake in the world, the honest answer is another question: largest how? Reservoirs, the giant lakes that pool behind dams, can be measured two very different ways, and the two measures crown two different champions. By the sheer volume of water held, the winner is Lake Kariba on the border of Zambia and Zimbabwe. By the area of land covered, it is Lake Volta in Ghana. Both answers are right; they are just answering different questions. What every lake on this list has in common is a river, a dam, and a decision to trade a valley for water, power, or both. Here are the giants, starting with the deepest reserves of stored water and ending with a table that ranks them all.

Lake Kariba

Lake Kariba is the largest reservoir on Earth by volume, holding roughly 180 cubic kilometers of water, about four times as much as China's Three Gorges. It fills the Kariba Gorge on the Zambezi River, held back by a 420-foot concrete arch dam designed by the French engineer Andre Coyne and completed in 1959. The lake that rose behind it between 1958 and 1963 runs about 170 miles long and reaches depths near 320 feet. Creating it meant relocating around 57,000 Tonga people out of the valley, and as the water climbed it stranded wildlife on shrinking islands, prompting a famous rescue effort called Operation Noah that carried roughly 6,000 large animals to safety. Today the dam's two power stations, one on the Zambian bank and one on the Zimbabwean, have a combined capacity of about 2,130 megawatts after expansions on both sides, which makes the lake a backbone of the regional grid. It is owned jointly by the two countries through the Zambezi River Authority, which recently completed a major rehabilitation of the dam's flood-eroded plunge pool.

Bratsk Reservoir

Second by volume, and far less famous, is the Bratsk Reservoir in Siberia, which holds about 169 cubic kilometers behind a dam on the Angara River. The Angara is the only river that flows out of Lake Baikal, so Bratsk is essentially catching some of the world's deepest lake on its way north. The dam was finished in the mid-1960s under punishing conditions, in a place gripped by hard frost most of the year, and its crest is so long, close to 2.7 miles, that both a highway and the Baikal-Amur Mainline railway run across the top of it. Its power station is one of the largest in Russia at around 4,500 megawatts. The reservoir loomed large enough in the Soviet imagination that the poet Yevgeny Yevtushenko built an entire book-length poem around its construction.

Lake Volta

Lake Volta is where the two definitions of largest part ways. By surface area it is the biggest reservoir on the planet, spreading across 3,283 square miles, roughly 3.6 percent of Ghana's entire land area, which is more than enough to be obvious from orbit. By volume, though, it holds about 150 cubic kilometers, placing it third behind Kariba and Bratsk. The lake formed behind the Akosombo Dam, built on the Volta River between 1961 and 1965 largely to power Ghana's aluminum industry. Filling it displaced roughly 80,000 people across hundreds of villages. The dam's original output of 912 megawatts was raised to about 1,020 megawatts in a 2006 upgrade, and it still supplies a large share of Ghana's electricity, with some exported to neighboring Togo and Benin.

Manicouagan Reservoir

Canada's Manicouagan Reservoir is the strangest-looking entry on the list, a near-perfect ring of water about 40 miles across. The shape is not the dam's doing; it traces the scar of a meteorite some three miles wide that struck about 214 million years ago, and the reservoir fills the eroded moat circling the crater's center. Seen from above it is distinct enough that people call it the Eye of Quebec, with the central Rene-Levasseur Island sitting like a pupil. The water is held by the Daniel-Johnson Dam, the largest multiple-arch buttress dam in the world, with 14 buttresses and 13 arches, and, as it happens, another Andre Coyne design. The reservoir holds about 140 cubic kilometers, fourth by volume, and feeds the Manic-5 generating stations run by Hydro-Quebec, with a capacity of roughly 2,600 megawatts.

Lake Nasser

Lake Nasser, on the Nile in southern Egypt, is one of the most consequential reservoirs ever built. It was created by the Aswan High Dam, completed around 1970, which finally gave Egypt control over the Nile's annual flood. The reservoir holds about 132 cubic kilometers and reaches south across the border into Sudan, where it is known as Lake Nubia. Filling it drowned a long stretch of the Nile valley and forced more than 100,000 Nubian people from their homes. It also threatened some of antiquity's greatest monuments, which set off one of the most ambitious salvage projects in history: an international UNESCO campaign that cut the temples of Abu Simbel into blocks and reassembled them on higher ground, safely above the rising water.

How The Largest Reservoirs Rank

The lakes above are only the largest handful. Here is how the world's biggest reservoirs line up by nominal volume, the standard measure of storage capacity. Keep in mind that this orders them by the water they hold, not the area they cover, which is exactly why Lake Volta sits third rather than first.

Why The World Builds Them

None of these lakes exist for their own sake. Reservoirs are built to do work: generating hydroelectric power, supplying drinking and irrigation water, holding back floods, cooling industry, and feeding fisheries and recreation. The idea is ancient. Some of the earliest known reservoirs were built about 4,000 years ago in Egypt, China, and Mesopotamia, mostly to bank water for crops and drinking through the dry months. What has changed is the scale. A single modern dam can turn a river valley into an inland sea, light up two countries, and rearrange the lives of tens of thousands of people all at once, which is why the question we opened with matters so much. When a lake gets this big, largest is never just a number. It is a decision about what a river is for.