Orinoco

Geography

Delta Amacuro – 200 km (120 mi) long that empties into the Gulf of Paría and the Atlantic Ocean, a very large delta, some 22,500 km2 (8,700 sq mi) and 370 km (230 mi) at its widest.

At its mouth, the Orinoco River forms a wide delta that branches off into hundreds of rivers and waterways that flow through 41,000 km2 (16,000 sq mi) of swampy forests. In the rainy season, the Orinoco River can swell to a breadth of 22 km (14 mi) and a depth of 100 m (330 ft). The stream gradient of the entire river is 0.05% (1,047 m [3,435 ft] over 2,250 km [1,400 mi]). Downstream of Raudales de Guaharibos the gradient is 0.01% (183 m [600 ft] over 1,964 km [1,220 mi]), which is also the gradient from Ciudad Bolivar to the ocean (54 m [177 ft] over 435 km [270 mi]).

History

The mouth of the Orinoco River at the Atlantic Ocean was documented by Christopher Columbus on 1 August 1498, during his third voyage. The Orinoco as well as its tributaries in the eastern Llanos, such as the Apure and Meta, were explored in the 16th century by German expeditions under Ambrosius Ehinger and his successors. In 1531, starting at the principal outlet in the delta, the Boca de Navios, Diego de Ordaz sailed up the river to the Meta. Antonio de Berrio sailed down the Casanare to the Meta, and then down the Orinoco and back to Coro. In 1595, after capturing de Berrio to obtain information while conducting an expedition to find the fabled city of El Dorado, the Englishman Sir Walter Raleigh sailed down the river, reaching the savanna country.

Ecology

The environment and wildlife in the Orinoco's basin are extremely diverse. The boto and the giant otter inhabit the river system. The Orinoco crocodile is one of the rarest reptiles in the world; its range in the wild is restricted to the middle and lower Orinoco River basin.

More than 1,000 fish species have been recorded in the river basin, and about 15% are endemic. By far the largest orders are Characiformes and Siluriformes, which together account for more than 80% of the fresh water species. Some of the more famous are the black spot piranha and the cardinal tetra. Because the Casiquiare canal includes both blackwater and clear- to whitewater sections, only relatively adaptable species are able to pass through it between the two river systems, such as the cardinal tetra.