Islands in the Orinoco

To the east of Trinidad and Tobago is the Atlantic, on the west the Caribbean Sea. However, the most powerful influence of water on these islands might be the fresh waters coming off the South American mainland. This week, Anjani Ganase, marine biologist, looks at the mighty Orinoco river whose delta comprises islands many times the size of Trinidad. This feature was first published in the Tobago Newsday on Thursday, December 1, 2016
Follow Anjani Ganase on twitter: @AnjGanase

“When Columbus sailed into the Gulf of Paria he had to make sense of two anomalies. His navigational readings were picking up the earth’s equatorial bulge, and the Orinoco being in spate meant that the water was fresh. Captivated by the apparently friendly natives, the exuberant vegetation, the benign climate and the extraordinary landscape, he called the area Tierra de Gracia (Graceland).”
-John Stollmeyer, Place of Beginnings, the World Views of the Amerindians of Cairi and of Medieval Europe, 2003

Columbus sailed through the Gulf of Paria on 1st August 1498, during his third voyage. It was this occasion that Trinidad and Tobago also marked as our “discovery day” commemorated in Moruga by mock landings of Columbus’ caravels, even though it is commonly thought that Columbus never came ashore.

In August, at the height of the rainy season, the Gulf of Paria would have seemed to the explorer a land-locked lake of fresh (sweet) water. Columbus didn’t stay in the Gulf of Paria but sailed south to the Orinoco delta, the region now called Amacuro, some 40,000 sq km of swampy forested islands.

Almost a hundred years later, Sir Walter Raleigh wrote of his 1595 voyage: “…the great river of Orenoque or Baraquan hath nine branches which fall out on the north side of his main mouth; on the south side it hath seven other fallings into the sea … but the islands are very great, many of them as big as the Isle of Wight… “ He also noted, “between May and September the river of Orenoque riseth 30 foot upright, and then are those islands overflowen 20 foot high above the level of the ground.”

Travel at any time of the year in the delta was necessarily by boat, and Raleigh wrote, “… these people that dwell upon the branches of the Orenoque, called Capuri and Macureo, are for the most part carpenters of canoes, for they make the most and fairest canoes and sell them in Guiana for gold, and into Trinidad for tabacco.”
 
Warao children paddle in the Orinoco delta. Photo courtesy Marc de Verteuil who leads tours up the Orinoco from Trinidad.

Raleigh persevered upriver and “beheld that wonderful breach of waters … more than 20 miles away, and there appeared some ten or twelve overfals in sight, everyone as high over the other as a church-tower, which fell with that fury, that the rebound of water made it seem as if it had been all covered over with a great shower of rain.” One of these mighty waterfalls would have been Angel Falls, the highest in the world. (Angel Falls tumbles off Rio Kerepacupai Meru which flows into a tributary of the Carrao River, itself a tributary of the Orinoco.)

Trinidad and Tobago sits on the continental shelf of South America. Trinidad is 12 kilometres from Venezuela, and Tobago 30 kilometres from Trinidad. Both islands are geological extensions of the mainland. Trinidad’s Northern Range and Tobago’s Main Ridge may be the easternmost extensions of a cordillera of the Andes. It is thought that Trinidad was separated about 11-15,000 years ago. The flora and fauna of our islands are identical to South American populations. A couple species that remain specific to the Orinoco are the pink river dolphin and the endangered Orinoco crocodile (the largartos of Raleigh’s description) which can grow to twenty feet.

The name Orinoco came from Guarauno words meaning “a place to paddle,” a place for transportation or navigation by canoes. It is also uniquely connected to the Amazon by the Casiquiare canal, a hydrographic divide between the Orinoco Basin and the Amazon Basin. The Orinoco flows west–north–northeast into the Caribbean; the Amazon flows east into the western Atlantic in the northeast of Brazil. The Casiquaire is a west-flowing section of Venezuela's Orinoco River with an outflow into the Amazon Basin.

Boat building in the Orinoco delta. 
Photo courtesy Marc de Verteuil who takes tours up the Orinoco from Trinidad.

The Orinoco basin covers an area of approximately 950,000 km2. It is bordered by the Andes to the west and north, the Guyana Highlands to the east, and the Amazon watershed to the south. The river, approximately 2,200 km in length, runs in an arc and its basin occupies an area that is most of Venezuela and part of Colombia.

The Orinoco delta, a region called Amarcuro, is a wide triangle extending about 400 km along the Atlantic coast of Venezuela from Pedernales on the Gulf of Paria to Punta Barima on the Boca Grande. The river flows into the southern Caribbean Sea, its waters bathing Trinidad and Tobago.

The outflow of the Orinoco delta brings a tremendous torrent of freshwater during the rainy season (usually April to November). These outflows bring many terrestrial and freshwater species from South America to Trinidad. It is rich in nutrients, and because it is less dense than seawater, the fresh water remains at the surface. This plume of waters can be observed, in satellite images, emanating from the Orinoco delta enveloping Trinidad and Tobago, and swirling into the Caribbean Sea, as far north as Puerto Rico.
 
Obtained by remote sensing from space, images like this illustrate biological and physical oceanic phenomena. In this view, warm colours are high chlorophyll. (From the Goddard Earth Sciences Data and Information Services Centre NASA)
Orinoco waters are carried around Trinidad and Tobago by what is called the Guiana Current. Tobago is subjected to the full force of this current which divides at the southeast coast; one part flowing in a northeasterly direction, and the other passing between Trinidad and Tobago in a northwesterly direction.

How do we know the Orinoco is flowing past our islands? When you dive in Tobago waters and observe the ocean’s green tint, you are seeing increased chlorophyll concentrations in the fresh water coming off the South American mainland. As much as we might like to identify as Caribbean islands, our South American connection is unmistakable.

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