Casiquiare Canal - Hydrographic Divide

Hydrographic Divide

The Casiquiare canal–Orinoco River hydrographic divide is a representation of the hydrographic water divide that delineates the separation between the Orinoco Basin and the Amazon Basin. (The Orinoco Basin flows west–north–northeast into the Caribbean; the Amazon Basin flows east into the western Atlantic in the extreme northeast of Brazil.)

Essentially the river divide is a west-flowing, upriver section of Venezuela's Orinoco River with an outflow to the south into the Amazon Basin. This named outflow is the Casiquiare canal, which, as it heads downstream (southerly), picks up speed and also accumulates water volume.

The greatest manifestation of the divide is during floods. During flood stage, the Casiquiare's main outflow point into the Rio Negro is supplemented by an overflow that is a second, and more minor, entry river bifurcation into the Rio Negro and upstream from its major, common low-water entry confluence with the Rio Negro. At flood, the river becomes an area flow source, far more than a narrow confined river.

The Casiquiare canal connects the upper Orinoco, 9 miles below the mission of Esmeraldas, with the Rio Negro affluent of the Amazon River near the town of San Carlos.

The simplest description (besides the entire area-floodplain) of the water divide is a "south-bank Orinoco River strip" at the exit point of the Orinoco, also the origin of the Casiquiare canal. However during the Orinoco's flood stage, that single, simply defined "origin of the canal" is turned into a region, and an entire strip along the southern bank of the Orinoco River.