The Orinoco is a main river in northern South America. It is one of the longest rivers in South America, at . Its drainage basin, sometimes called the Orinoquia, covers , with 76.3% of it in Venezuela and the rest in Colombia. The Orinoco and its tributaries are the main transport system for eastern and interior Venezuela and the llanos of Colombia. 

The Orinoco Basin is also ecologically important. It is the only habitat of the Orinoco crocodile. This is one of the rarest reptiles in the world, with fewer than 250 living in the wild. It is also home to Amazon river dolphins.

History 
The mouth of the Orinoco was recorded by Christopher Columbus on 1 August 1498. Its source, however, was first explored by non-native people in 1951, 453 years later. It was explored by a French and Venezuelan team. 

The delta, and tributaries in the eastern llanos such as the Apure and Meta, were explored in the 16th century. They were explored by German expeditions under Ambrosius Ehinger and his successors. Alexander von Humboldt explored the basin in 1800. He reported on the river dolphins, and wrote extensively about the plants and animals he found.

Geography 
The course of the Orinoco forms a wide arc that surrounds the Guiana Shield. The source of the river is at Cerro Delgado-Chalbaud, in the Parima Mountains. This is on the border between Venezuela and Brazil, at  high (). The river can be divided into four stretches:

 Upper Orinoco —  long, from its headwaters to the rapids Raudales de Guaharibos. This section flows through mountainous landscape in a northwesterly direction.
 Middle Orinoco —  long. The first part of this section has a general westward direction. It flows down to the confluence with the Atabapo and Guaviare rivers at San Fernando de Atabapo. The river then flows northward along the Venezuelan–Colombian border. On both sides of the river are the mountains of the Guiana Shield. The section ends at the Atures rapids, near the confluence with the Meta at Puerto Carreño.
Lower Orinoco —  long, with a wide alluvial plain. It flows in a northeast direction, from Atures rapids down to Piacoa in front of Barrancas.
 Delta Amacuro —  long. It forms a large delta that empties into the Gulf of Paría and the Atlantic Ocean.

At its mouth, the Orinoco forms a wide delta that branches off into hundreds of rivers and waterways. They flow through  of swampy forests. At its widest, this delta is about  large and  at its widest. In the rainy season, the Orinoco can swell to a breadth of  and a depth of .

Off the coast of the delta is Trinidad and Tobago, which is separated from the mainland by the Columbus Channel.

Major rivers in the Orinoco Basin 
Most of the important rivers in Venezuela are tributaries of the Orinoco. The largest are the Caroní, which joins it at Puerto Ordaz. The river is actually connected to the Amazon River through the Casiquiare canal. This is a distributary of the Orinoco, flowing into the Rio Negro and then the Amazon. This connection forms a natural canal between Orinoco and Amazon.

 Apure: from Venezuela through the east into the Orinoco.
 Arauca: from Colombia to Venezuela east into the Orinoco.
 Atabapo: from the Guiana Highlands of Venezuela north into the Orinoco.
 Caroní: from the Guiana Highlands of Venezuela north into the Orinoco.
 Caura: from eastern Venezuela (Guiana Highlands) north into the Orinoco.
 Guaviare: from Colombia east into the Orinoco.
 Inírida: from Colombia southeast into the Guaviare.
 Meta: from Colombia, border with Venezuela east into the Orinoco.
 Ventuari: from eastern Venezuela (Guiana Highlands) southwest into the Orinoco.
 Vichada: from Colombia east into the Orinoco.

Economics 

Boats can travel on the river for most of its length. Ocean ships can travel as far as Ciudad Bolívar,  upstream. River steamers carry cargo as far as Puerto Ayacucho.

There is a rich iron ore deposit in the Orinoco delta. It was found in 1926, south of the town of San Felix on a mountain named El Florero. Mining there began after World War II. At the start in the early 1950s, about 10,000 tons of soil with ore in it was being mined each day.

There are also tar sands in the Orinoco Belt, which may be a source of future oil production.

Notes

References

Other websites 

Map of Orinoco River that Includes Visible Islands and Tributaries at the Delta of the River, 1732
Image of the Orinoco River from Space

Rivers of Colombia
Rivers of Venezuela