Río Negro (Black River)

The Río Negro has its headwaters in Venezuela, in the flat western lands of the Amazon State. In its long road southward, this river defines part of the frontier between Venezuela and Colombia. From there on, it enters in Brazil and little by little takes course to the East, toward the city of Manaos, where it joins the Amazon River in its long journey to the Atlantic Ocean.

The dark color of its water is notorious, especially when contrasts with the light brown color of the Orinoco or the Amazon rivers. Its dark color is due to the presence humic acids or tannins. These are complex organic compounds, manufactured by the plants of the region and used to repel or warn off herbivores.

The long distance covered by the Negro River to Manaos shows a course characterized by very dark water. Upon observing the Amazon River after both rivers join, you can witness how, for quite a distance, the waters of both rivers maintain their original color and do not mix. This phenomenon is similar to the one observed in the meeting place of the black waters of the Caroní and the light brown Orinoco river water at Puerto Ordaz, in eastern Venezuela.

Actual communication between the Rio Orinoco and the Negro, through the natural channel called Casiquiare, has produced the thought of building the necessary hydraulic works that may permit navigation as far down as Rio de La Plata. Building it would be costly and unnecessary now a days, since the maritimee communication permits moving greater loads without the high cost of building and maintaining navigation channels and destroying the natural life of the rivers.