Casiquiare

The Casiquiare is a natural waterway in western Venezuela that forms a hydrological link between the Orinoco River basin and the Amazon River basin. It originates from the Orinoco system and flows southwest to become the headwaters of the Rio Negro, a major tributary of the Amazon. In this way, the Casiquiare links two of the world’s largest river basins through a single, continuous watercourse.

Hydrology and dynamics of the canal are influenced by seasonal rainfall and river stages. Because it is a natural channel rather than a man-made canal, its flow direction and volume can vary, allowing limited interbasin water exchange under differing hydrological conditions. The canal is notable for enabling the transfer of water—and, to some extent, aquatic organisms—between the Orinoco and Amazon systems.

Ecologically the Casiquiare supports biodiversity and provides a corridor for migratory fish and other aquatic species between basins. The region surrounding the canal is sparsely populated, and local Indigenous communities have long relied on its waters for transportation, fishing, and seasonal resource use.

Historically, the Casiquiare has drawn the interest of naturalists and explorers as a rare natural example of interbasin connectivity. It has appeared in colonial-era and later writings as evidence of the dynamic and interconnected nature of South American river systems. The name Casiquiare is derived from local Indigenous language sources, reflecting its long-standing presence in the region.