Orinoco River, Basin, and Delta (South America)

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Orinoco River, Basin, and Delta (South America)

Mon, 08/19/2019 - 16:59
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Beginning high in the Sierra Parima Mountains of Venezuela and Brazil, the Orinoco River flows in a giant arc before discharging into the Atlantic Ocean in Venezuela. Its tributaries are the primary transportation system for eastern and interior Venezuela and the Llanos of Colombia.

Orinoco River

The Orinoco River is one of the longest rivers in South America. It is the third largest river in the world by discharge volume of water. Throughout most of its course, it flows through Venezuela, except for a section that forms part of the frontier between Venezuela and Colombia.

The river and its tributaries are the primary transportation system for eastern and interior Venezuela and the Llanos of Colombia. The environment in the Orinoco Basin is highly diverse; it hosts various flora and fauna.

Beginning high in the Sierra Parima Mountains of Venezuela and Brazil, the river flows in a giant arc for more than 2,736 km (1,700 mi), originating in the Guiana Highlands of northern Brazil and discharging in the Atlantic Ocean in Venezuela.

For most of its length, the Orinoco flows through the impenetrable rainforest or through the vast grassland (savanna) region of the Llanos, which occupies three-fifths of the Orinoco Basin north of the Guaviare River and west of the lower Orinoco River and the Guiana Highlands.

These waters are home to the critically endangered Orinoco crocodile, river dolphins, giant river otters, the giant anaconda and more than 1,000 fish species. It is also a hub for rich bird life, including flamingos, colorful parrots and the scarlet ibis.

Map of the Orinoco Basin

Map depicting the Orinoco Basin

Orinoco Basin

    This vast drainage basin, bordered by the Andes Mountains to the west and the north, the Guiana Highlands to the east and the Amazon watershed to the south, the Orinoco Basin covers an area of about 948,000 sq km (366,000 sq mi). It encompasses approximately 80% of Venezuela and 25% of Colombia.

    A vast savanna or grassland region known as the Llanos is the primary biome of the Orinoco River basin.

    Major tributaries in the Orinoco Basin:

    • 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

    • Casiquiare Canal: in SE Venezuela, a distributary from the Orinoco flowing west to the Negro River, a major affluent to the Amazon

    • 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, the border with Venezuela east into the Orinoco

    • Ventuari: from eastern Venezuela (the Guiana Highlands) southwest into the Orinoco

    • Vichada: from Colombia east into the Orinoco

    Orinoco Delta

    The Orinoco Delta is a vast river delta of the Orinoco River, located in eastern Venezuela and is one of the eight natural regions of Venezuela. The delta is fan-shaped, formed by the river as it splits into numerous distributaries, called caños, which meander through the delta on their way to the sea.

      The predominant vegetation is in the Orinoco Delta swamp forests ecoregion. Along the coast and river margins are stretches of Amazon-Orinoco-Southern Caribbean mangroves, specifically the Guianan mangroves ecoregion. To the west and closer to the coast are patches of the Orinoco wetlands ecoregion.

      The delta includes large areas of permanent wetlands and seasonally-flooded freshwater swamp forests. The river margins of the delta are fringed with mangroves.