Casiquiare Canal, a remarkable stream in southern Venezuela that provides a permanent, natural link between the Orinoco River and the Río Negro (a major tributary of the Amazon River). Originating at the bifurcation of the Orinoco into separate rivers, the Casiquiare is about 222 miles long. It flows across a relatively smooth plain, picking up velocity as its volume increases. Most of this water is supplied by three large tributaries, rather than by the Orinoco itself.
By the mid-seventeenth century some Europeans, probably Spaniards traveling the upper Orinoco, knew of the Casiquiare's existence and must have been surprised to encounter Portuguese-speaking people who had come entirely by water from the Brazilian Amazon in search of slaves. Native Americans had long been using this route. By the 1740s information on the Casiquiare had reached Europe, arousing the interest of scholars there. Among Alexander von Humboldt's goals when he came to America in 1799 were to see and measure the Casiquiare. Even though Humboldt mapped it correctly nearly two centuries ago, some cartographers still cannot bring themselves to draw the Casiquiare as a natural, navigable link between the Orinoco and the Amazon rivers. That is because at a fork in a stream, cartographers assume one is joining the other, not leaving it. So some depict the Casiquiare as disconnected from either the Orinoco or the Río Negro.
The Casiquiare is generally believed to represent an example of stream capture, in which the Amazon Basin is growing at the expense of the Orinoco Basin. Because the capture has been so slow, the Casiquiare is an important route for the dispersal of numerous types of plants and animals, including freshwater dolphins.
U.S. Army Corps of Engineers, Report on Orinoco-Casiquiare-Negro Waterway Venezuela-Colombia-Brazil (1943).
Douglas Botting, Humboldt and the Cosmos (1973).
Tellería, Ma. Teresa. La comisión naturalista de Löfling en la expedición de Límites al Orinoco. Madrid, Spain: Real Jardín Botánico, Consejo Superior de Investigaciones Científicas, Caja Madrid, 1998.
Whitehead, Neil L. Histories and Historicities in Amazonia. Lincoln: University of Nebraska Press, 2003.
William J. Smole