Great rivers in the world

The Amazon River in South America is the largest river by discharge volume of water in the world, and the disputed longest river system in the world in comparison to the Nile.The headwaters of the Apurímac River on Nevado Mismi had been considered for nearly a century the Amazon basin's most distant source until a 2014 study found it to be the headwaters of the Mantaro River on the Cordillera Rumi Cruz in Peru.The Mantaro and Apurímac rivers join, and with other tributaries form the Ucayali River, which in turn meets the Marañón River upstream of Iquitos, Peru, forming what countries other than Brazil consider to be the main stem of the Amazon.

The Mississippi River is the primary river, and second-longest river, of the largest drainage basin in the United States.From its traditional source of Lake Itasca in northern Minnesota, it flows generally south for 2,340 miles (3,766 km)to the Mississippi River Delta in the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains all or parts of 32 U.S. states and two Canadian provinces between the Rocky and Appalachian mountains. The main stem is entirely within the United States; the total drainage basin is 1,151,000 sq mi (2,980,000 km2), of which only about one percent is in Canada. The Mississippi ranks as the thirteenth-largest river by discharge in the world.

The Mekong or Mekong River is a trans-boundary river in East Asia and Southeast Asia. It is the world's twelfth-longest river and the third-longest in Asia with an estimated length of 4,909 km (3,050 mi) and a drainage area of 795,000 km2 (307,000 sq mi), discharging 475 km3 (114 cu mi) of water annually.From its headwaters in the Tibetan Plateau, the river runs through (where it is officially called the Lancang River), Myanmar, Laos, Thailand, Cambodia, and southern Vietnam. The extreme seasonal variations in flow and the presence of rapids and waterfalls in the Mekong make navigation difficult. Even so, the river is a major trade route between Tibet and Southeast Asia. The construction of hydroelectric dams along the Mekong in recent decades causes serious problems for the river's ecosystem, including the exacerbation of drought.

The Yenisei River is the largest river that flows into the Arctic Ocean. Also known as the Enisei, Yenisey, Evenk Ioanesi, or Jenisej, the river is among the three major river systems that drain into the Arctic Ocean, the two other rivers being the Lena and the Ob. Draining a huge region of Central Siberia, the Yenisei has a maximum depth of about 80 feet and an average depth of around 45 feet. The river's outflow has a depth of about 106 feet, while its inflow has a depth of around 101 feet. With a length of about 2,136 miles, the Yenisei River is the longest river within the Yenisei-Angara-Selenga-Ider river system.The Yenisei River flows through two countries: Mongolia and Russia. The source of the river is Mungaragiyn-Gol, which is located at the ridge of Dod-Taygasyn-Noor, Mongolia, and has an elevation of about 10,994 feet.

The Irrawaddy River is a river that flows from north to south through Myanmar (Burma). It is the country's largest river and most important commercial waterway. Originating from the confluence of the N'mai and Mali rivers,it flows relatively straight North-South before emptying through the Irrawaddy Delta in the Ayeyarwady Region into the Andaman Sea. Its drainage basin of about 404,200 square kilometres (156,100 sq mi) covers a large part of Burma. After Rudyard Kipling's poem, it is sometimes referred to as 'The Road to Mandalay'.As early as the sixth century, the river was used for trade and transport. Having developed an extensive network of irrigation canals, the river became important to the British Empire after it had colonized Burma. The river is still important today because it is used for a significant amount of traffic and (export) goods. In the Irrawaddy Delta, rice is grown using river water as an irrigation source.

The Amur is the world's tenth longest river, forming the border between the Russian Far East and Manchuria/Northeastern China. The Amur proper is 2,824 kilometres (1,755 mi) long, and has a drainage basin of 1,855,000 km2 (716,000 sq mi).Including its source river Argun, it is 4,444 km (2,761 mi) long.The largest fish species in the Amur is the kaluga, attaining a length as great as 5.6 metres (18 ft).The river basin is home to a variety of large predatory fish such as northern snakehead, Amur pike, taimen, Amur catfish, predatory carp and yellowcheek, as well as the northernmost populations of the Amur softshell turtle and Indian lotus.

The Rio Grande is one of the principal rivers (along with the Colorado River) in the southwestern United States and in northern Mexico.The length of the Rio Grande is 1,896 miles (3,051 km), making it the 4th longest river in North America by main stem. It originates in south-central Colorado, in the United States, and flows to the Gulf of Mexico.The Rio Grande drainage basin (watershed) has an area of 182,200 square miles (472,000 km2);however, the endorheic basins that are adjacent to and within the greater drainage basin of the Rio Grande increase the total drainage-basin area to 336,000 square miles (870,000 km2).The Rio Grande with its fertile valley, along with its tributaries, is a vital watersource for seven US and Mexican states, and flows primarily through arid and semi-arid lands.

The Purus River is a tributary of the Amazon River in South America. Its drainage basin is 371,042 km2 (143,260 sq mi), and the mean annual discharge is 11,207 m3/s (395,800 cu ft/s). The river shares its name with the Alto Purús National Park and the Purús Province (and its conformed Purús District), one of the four provinces of Peru in the Ucayali Region.The Purus River rises in defines the boundary between Peru and Brazil in the centre of the state of Acre, then runs for a short distance along the boundary of the 231,555 hectares (572,180 acres) Santa Rosa do Purus National Forest, a sustainable use conservation unit created in 2001 after it is joined by the Santa Rosa River. It then flows north east through Manoel Urbano