Witness the Power of Pure Water Quiz

Answer: Congo

In terms of discharge volume (41,200 m³/s /1,450,000 cu ft/s), only the mighty Amazon tops the Congo River, which is also Africa's second-largest; its depth has been recorded at over 220 m (720 ft). The Congo river system also comprises the Lualaba (name given to the Congo upstream of the cataracts of Boyoma Falls) and its tributary, the Chambeshi.

The Congo, named after an indigenous population, rises in the highlands of the East African rift, and flows northward through the two countries named after it - the Republic of the Congo and Democratic Republic of the Congo - emptying in the Atlantic Ocean near the town of Muanda.

The Congo rainforest is the world's second-largest rainforest area, home to a wide range of plant and animal species, such as the forest elephant, the bonobo and both the lowland and mountain gorilla.

Answer: Yenisei

The Yenisei river system (which also includes the Angara and the Selenga) flows through Central Siberia, passing through the city of Krasnoyarsk - known for the beauty of its natural landscape. The Yenisei is one of the three great rivers that flow into the Arctic Ocean (the other two being the Ob and the Lena).

It has an enormous drainage area (2,580,000 km2/1,000,000 sq mi) and an average discharge of 9,600 m3/s (690,000 cu ft/s). Though navigable, at present the Yenisei is only used for local transport, as the railway is a much quicker and more reliable option.

The Angara River, the main headwater tributary of the Yenisei, drains Lake Baikal, the world's oldest and deepest lake.

Answer: Rio Negro

The world's seventh-largest river by average discharge (28,400 m³/s /1,000,000 cu ft/s), the Rio Negro rises in Colombia, and is the Amazon's largest left tributary. As its name of "Black River" implies, its waters are a dark brown colour, similar to strong tea, which looks black at a distance; this colour is due to the presence of tannins derived from decayed vegetation. Near the Brazilian city of Manaus (the capital of the state of Amazonas), the Rio Negro meets the pale-coloured Solimões River, and together they form the Amazon River, the world's largest by discharge, and the second-longest after the Nile.

The Meeting of Waters, a phenomenon in which the two rivers run side by side for 6 km (3.7 mi) without mixing because of differences in temperature, speed and water density, is one of Manaus' main tourist attractions.

Answer: Mekong

With an average discharge of 16,000 m³/s (570,000 cu ft/s) and a length of 4,350 km (2,700 mi), the Mekong is one of the world's 20 largest rivers. Its headwaters are found in a protected area of the Tibetan Plateau known as Sanjiangyuan, or "Source of the Three Rivers", as it also contains the headwaters of the Huang He (Yellow River) and the Yangtze. From Tibet, the Mekong flows through the Chinese province of Yunnan, Myanmar, Laos, Thailand, Cambodia (whose capital Phnom Penh lies on its banks), and finally Vietnam, where it empties in the South China Sea through a vast delta (the world's second-largest). Human activity along the course of the river has caused the loss of much of the forest cover and depleted the soil of nutrients.

In spite of that, the Mekong basin is still an area of rich biodiversity; in particular, the river boasts many species of very large fish, such as the Mekong giant catfish and the giant freshwater stingray.

The Mekong basin is also one of the world's most important areas in terms of hydropower potential, with a large number of dams already in use and others under construction.

Answer: Saint Lawrence

The Saint Lawrence River (Saint-Laurent in French) flows northeast from the outflow of Lake Ontario, and empties in the Atlantic Ocean, forming a huge estuary - the world's largest - that begins not far from Quebec City. Though the river itself is about 1,190 km (744 mi), it is part of a much larger system that begins in the Great Lakes region, in the US state of Minnesota.

The St Lawrence's average discharge is 16,800 m3/s (590,000 cu ft/s); it passes through several towns and cities in the Canadian provinces of Quebec and Ontario, and forms part of the border between Ontario and the US state of New York.

The river forms the basis of the Saint Lawrence Seaway, a remarkable engineering feat consisting of a system of locks, canals and channels that allow seafaring ships to travel from the Atlantic Ocean to the western end of Lake Superior.

Answer: Brahmaputra

The deity in Brahmaputra's name is, of course, Brahma, the Hindu creator god: the river's name means "son of Brahma". Its headwaters are found in the Angsi Glacier in the Himalayas; the river's upper course, known as Tsangpo ("Purifier"), flows eastward through Tibet, then turns sharply south.

The course of the Tsangpo is characterized by deep gorges and canyons. When it enters the Indian state of Assam, it takes the name of Brahmaputra and becomes very wide, especially during the rain season. In Bangladesh, the Brahmaputra (Jamuna) merges with the Padma River, or lower Ganges, and the two great rivers flow into the Bay of Bengal.

The delta formed by these two rivers is the world's largest; the area known as Sunderbans is also the world's largest mangrove forest. With an average discharge of 19,800 m3/s (700,000 cu ft/s), the Brahmaputra is subjected to frequent, destructive floods, but also creates favourable conditions for agriculture by depositing fertile alluvial soil along its lower course.

Answer: Orinoco

Rising in the highlands on the border between Venezuela and Brazil, the Orinoco is the world's fourth-largest river by discharge, with an average of 37,000 m3/s (1,300,000 cu ft/s). Its middle course flows along the Venezuelan-Colombian border for about 270 km (170 mi), then it runs through a large alluvial plain in Venezuela, emptying in the Atlantic Ocean and forming a wide delta that was documented by Christopher Columbus on his third voyage, and explored by various expeditions in the 16th century.

The Orinoco basin is also an area of rich biodiversity, which includes over 1,000 fish species, as well as unique animals such as the giant river otter, the pink river dolphin and the critically endangered Orinoco crocodile. However, though the Orinoco's environment is in a much better condition than many other major river systems, it is threatened by pollution and mining activities.

Answer: Madeira

The Rio Madeira (Portuguese for "Wood River"; named Cuyari by indigenous peoples) is one of South America's largest waterways. Receiving a huge quantity of rainfall in its upper basin, the Madeira is one of the world's largest rivers by discharge, with an average of 37,000 m3/s (1,300,000 cu ft/s).

The river has a rather distinctive conformation, as it is formed by the confluence of a number of smaller rivers originating in the Andes between Peru and Bolivia; it flows northward through northwestern Brazil, finally merging with the Amazon. Though navigable for only part of its course, the Madeira is a very active waterway, and the capital of the Brazilian state of Rondônia, Porto Velho, located on the river's eastern shore, is a major trading and transportation centre.

The thriving biodiversity of the Madeira River's basin - especially in terms of fish species - is sadly threatened by human activity, such as the construction of two huge hydroelectric dams.

Answer: Yangtze

Also known as Chang Jiang ("Long River"), Asia's longest river, the world's third-longest, is also the sixth-largest by discharge (30,166 m3/s /1,065,300 cu ft/s). The country the question refers to is, of course, China; one-third of the country's huge population lives in the river's basin.

The Yangtze originates from several tributaries in the Tibetan Plateau, not far from where the Mekong (see Question 4) and the Yellow River also have their headwaters. From there, it flows eastward and then south, flowing through a number of major Chinese cities (such as Yangzhou, Chongqing, Wuhan and Nanjing) on its way to its mouth on the East China Sea; Shanghai, one of the world's most populous cities and busiest container ports, is located in the Yangtze delta.

This great river, whose course is steeped in history, holds another world record: as of 2019, the massive (and controversial) Three Gorges Dam, completed in 2012, is the world's largest power station in terms of installed capacity. Unfortunately, human activity has taken its toll on this mighty waterway, causing - among other things - the functional extinction of the baji, or Yangtze river dolphin.

Answer: Rio de la Plata

The "River of Silver" is really an estuary, formed by the confluence of the Uruguay and Paraná rivers, which empties into the Atlantic Ocean on the southeastern coast of South America. Both of these rivers (especially the Paraná, which is the world's eighth-longest river) are considerably longer than the Rio de la Plata, which is only 290 km (180 mi) long, and is considered by some geographers to be a gulf or a marginal sea. If considered a river, the Rio de la Plata has the distinction of being the widest in the world, reaching a maximum width of 220 km (140 mi).

Not surprisingly, its average discharge of 22,000 m3/s (780,000 cu ft/s) is also quite remarkable. The Rio de La Plata forms part of the border between Uruguay and Argentina, and these countries' capital cities - Montevideo and Buenos Aires - are located respectively on its northern and western shores. Though its coasts are densely populated, the river is still home to various species of fish, as well as providing a favourable habitat for sea turtles.

The Rio de la Plata was so named by Venetian explorer Sebastian Cabot in the early 16th century because of the silver trinkets he acquired by trading with the local populations.