The Casiquiare Canal
High resolution satellite images of canal beteen rio Orinocco and rio Amazon
This page follows on from examples of canals and ponds in the Paraguay river which also included an explanation about levees, examples of canals and ponds in the Parana river and examples of canals and ponds along the Amazon river.
This page looks at the canal between the rio Orinocco and the rio Amazon known as the Casiquiare and follows it into the rio Negro.
"In 1744 a Jesuit priest named Father Roman, while ascending the Orinoco River, met some Portuguese slave-traders from the settlements on the Rio Negro. He accompanied them on their return, by way of the Casiquiare canal, and afterwards retraced his route to the Orinoco. La Condamine, seven months later, was able to give to the Académie française an account of Father Roman's voyage, and thus confirm the existence of this waterway, first reported by Father Acuña in 1639. But little credence was given to Father Roman's statement until it was verified, in 1756, by the Spanish Boundary-line Commission of Yturriaga and Solano. In 1800 German scientist Alexander von Humboldt and French botanist Aimé Bonpland explored the river."
the rio Orinocco to Amazon
The rio Casiquiare according to Humboldt, if you find the longitude a bit out, note it is reckoned from the Paris meridian!
the canal Casiquiare begins as a branch off the upper reaches of the rio Orinocco
close up of entry point from rio Orinocco
On the way to the river Negro, part of the route looks like it has been straightened or canalised,
this section measures about 1100 ft or 1000 Sumerian feet wide.
It wanders along for a distance of 200 miles then exits into the upper waters of the rio Negro which itself discharges into the Amazon. There is nothing remarkable about the exit point, but before that it is joined by a tributary river, the rio Baria which makes a curious semi-circular turn at the point of junction, then the last section is named "brazo" meaning "arm" as shown above and on the following map.
the rio Orinocco to Amazon
The curious semi-circular turns at the junction point of a tributary river, the rio Baria.
The two arms of the Casiquiara canal appear to have been man-made and the bend artificially engineered at this point. The width on the bend is about 1650ft or 1000 Sumerian cubits. Was the rio Baria diverted to flow west to the rio Negro instead of north-east to the rio Orinocco at some time?
We can try and reconstruct the method used for the bend construction. The circular channel is about 1,000 Sumerian cubits of 19.8" wide. For the outer bend, I have used part of a circle whose radius is 1000 Sumerian double yards of 66". Then I moved the centre north-east by 1,000 Sumerian double yards and constructed another circle with radius 1000 Sumerian double yards  The diagonal line passing through the centre of both circles is noticably parallel to the section of canal on the right.
This section of canal also seems to measure about 1650ft or 1000 Sumerian cubits, consistent with other "Sumerian" measurments found in Beni region of Bolivia and along the Paraguay and Parana waterways.
J.M. Allen, January 2011