South America's Orinoco River

Sun shining through trees on river, Orinoco River, Orinoco Delta, Venezuela

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The Orinoco river system is one of the largest in South America, originating along the southern borders of Venezuela and Brazil, in the state of Amazonas. The exact length of the river is still undetermined, with estimates between 1,500 to 1,700 mi (2,410–2,735 km) long, making it among the world's largest river systems.

The Orinoco river basin is huge, estimated between 880,000 and 1,200,000 square km. The name Orinoco is derived from Guarauno words meaning “a place to paddle”—i.e., a navigable place. 

It flows west, next north, creating the border with Colombia, and then turns east and bisects Venezuela on its way to the Atlantic. North of the Orinoco is the vast, grassy plains called llanos. To the south of the river is almost half of Venezuela's territory. Huge tropical forest areas cover the southwestern portion part, and large portions are still virtually inaccessible. The Guiana Highlands, also known as the Guyana Shield, covers the remainder. The Guyana Shield is composed of pre-Cambrian rock, up to 2.5 billion years old, and some of the oldest on the continent. Here are the tepuis, stone plateaux rearing out of the jungle floor. The most famous tepuis are Roraima and Auyantepui, from which Angel Falls descend.

Over 200 rivers are tributaries to the mighty Orinoco which extends 1290 mi (2150 km) from source to delta. During the rainy season, the river reaches a width of 13 mi (22 km) at San Rafael de Barrancas and a depth of 330 ft (100 m). 1000 mi (1670 km) of the Orinoco are navigable, and about 341 of those can be used for sailing large ships.

The Orinoco River is composed of four geographical zones:

Alto Orinoco

The Orinoco begins on Delgado Chalbaud mountain, a high, narrow river with waterfalls and difficult, forested terrain. The most notable fall in this area, at 56 ft (17 m) is Salto Libertador. Navigation, where possible on this part of the river, is by shallow dugout, or canoe. 60 miles (100 km) from the source, the first tributary, the Ugueto, joins the Orinoco. Farther on, the descent slows and waterfalls become rapids, fast and difficult to navigate. 144 miles (240 km) downstream, the High Orinoco ends with the Guaharibos rapids.

Amazonas is Venezuela's largest state, and contains two very large national parks, Parima Tapirapecó and Serranía de la Neblina, plus smaller parks and natural monuments, such as Cerro Autana, a tepuy south of Puerto Ayacucho, which is the sacred mountain of the Piaroa tribe who believe it to be the birthplace of the universe.

This is also the homeland of many native tribes, most famous are the Yanomani, Piaroa, and Guajibo. Puerto Ayacucho, which has an airport with flights in and out of Caracas and other smaller cities, is the main gateway to the state. There are tourist and commercial facilities. Lodgings, known as camps, offer various degrees of comfort. The most well-known camp is Yutajé Camp, in the Manapiare Valley east of Puerto Ayacucho. It has its own airstrip and can accommodate up to thirty people.

Traffic in and out is by the river and by air, but roads are being built up and maintained, most notably the one to Samariapo, upriver past the rapids. 

Orinoco Medio

Over the next 450 miles (750 km), from the Guaharibos rapids to the Atures rapids, the Orinoco runs west until the Mavaca river joins it and the waters turn north. Other tributaries like the Ocamo join in and the river widens to 1320 ft (500 m) and sandy sediment forms little islands in the riverbed. The Casiquiare and Esmeralda rivers flow out of the Orinoco to join with another to form the Rio Negro which eventually reaches the Amazon.

The Cunucunuma river joins it, and the Orinoco veers to the northwest, bordering the Guyanese Shield. The Ventuari river brings with it enough sand to form the beaches at San Fernando de Atabapo. Where the Atabapo, Guaviare and Irínida rivers join the flow, the Orinoco widens to almost 5000 ft (1500 m).

Most of the Venezuelan aboriginal population lives within the Orinoco River basin. The most important indigenous groups include the Guaica (Waica), also known as the Guaharibo, and the Maquiritare (Makiritare) of the southern uplands, the Warrau (Warao) of the delta region, and the Guahibo and the Yaruro of the western Llanos. These peoples live in intimate relationship with the rivers of the basin, using them as a source of food as well as for purposes of communication. (Encyclopedia Britannica)

More tributaries flow in, increasing water flow and creating a new set of powerful rapids at Maipures and Atures across from Puerto Ayacucho. This is the only place where the Orinoco is not navigable. 

Bajo Orinoco

Extending from the Atures rapids to Piacoa, this 570 mi (950 km) accepts the bulk of the tributary rivers. Where the Meta joins in, the river turns northeast, and with the Cinacuro, Capanaparo and Apure rivers turn east. The Manzanares, Iguana, Suata, Pao, Caris, Caroní, Paragua, Carrao, Caura, Aro and Cuchivero rivers add to the Orinoco's bulk. The river here is wide and slow. 

This section of the Orinoco is the most developed and populated. Since the oil strikes in the mid 20th century, the industrialization, commercialization, and population have grown. Ciudad Bolívar and Ciudad Guayana have developed into important cities, built high enough away from the river banks to prevent flooding.

Among the islands in the river at Ciudad Bolívar is the one Alexander von Humboldt named Orinocómetro. It serves as a measurement tool for the rise and fall of the river. There are no actual seasons along the Orinoco, but the rainy season is referred to as winter. It begins in April and lasts until October or November. The rain-swollen torrents from the highlands carry dirt and rocks and other material from the highlands into the Orinoco. Unable to handle this excess, the river rises and floods the llanos and surrounding areas. The highest water period is normally in July when the water level at Ciudad Bolívar can go from 40 to 165 feet in depth. The waters begin to recede in August, and by November are again at a low point.

Founded in 1961, Ciudad Guayana, downstream from Ciudad Bolívar, produces steel, aluminum, and paper, thanks to power generated by the Macagua and Guri dams on the Caroní River. Growing into Venezuela's fastest growing city, it sprawls over the river and has incorporated the sixteenth-century village of San Félix on one side and the new city of Puerto Ordaz on the other. There is a major highway between Caracas and Ciudad Guayana, but much of the area's transportation needs are still served by the Orinoco.

Delta del Orinoco

The delta region covers Barrancas and Piacoa. The Atlantic coast forms its base, 165 mi (275 km) long between Pedernales and the Gulf of Pariah to the north, and Punta Barima and the Amacuro to the south, currently extending 12,000 sq mi (30,000 sq km), is still growing in size. Fluctuating in size and depth are the Macareo, Sacupana, Araguao, Tucupita, Pedernales, Cocuima channels as well as a branch of the Grande river.

The delta of the Orinoco constantly changes as the river brings sediment to create and enlarge islands, change channels and waterways called caños. It is pushing out into the Atlantic ocean, but as the sediment gathers and spreads outwards, the weight of it creates the sinking that also changes the topography of the delta. Dredging keeps the main channels open for navigation, but in the back channels, where mangroves and vegetation are lush,

Tortola, Isla de Tigre, and Mata-Mata are some of the better-known islands of the delta.

The Delta del Orinoco (Mariusa) in the delta covers 331000 hectares of forest, marshes, mangroves, varied flora and fauna. It is the home of the Warao tribe who continue their traditional lifestyle of hunter/fishers. The delta here is prone to extreme tidal action. Here too is the Cueva del Guácharo, the cave with prehistoric petroglyphs discovered by Humboldt as he explored the area. 

Camps and lodges located in the area give visitors the opportunity to explore the cañas by small boat, fish, enjoy the flora and fauna, and go birding.

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