Orinoco

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.
The first powerline crossing of the Orinoco River was completed in 1981 for an 800 kV TL single span of 1,200 metres (3,900 ft) using two towers 110 metres (360 ft) tall.
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:
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.
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.