Magdalena (mägħälāˈnä) [key], river, c.1,000 mi (1,600 km) long, rising in the Cordillera Central, SW Colombia and flowing N to the Caribbean Sea near Barranquilla. It flows in a fault-block valley (c.50 mi/80 km wide) through the Andes to a broad, swampy, alluvial plain where the Cauca River, the chief tributary, joins its lower course. The Magdalena is a natural and important avenue of communication, linking the interior highlands with the coastal lowlands. Its navigability is hampered by sandbars, rapids, and fluctuating water levels. La Dorada, c.600 mi (970 km) upstream, is the head of navigation. Railways connect navigable sections. The tropical valley of the Magdalena is thinly populated. Economic development has been retarded except for the oil industry. Coffee is the chief crop along the river's upper course. Rodrigo de Bastidas, the Spanish explorer, discovered (1501) the Magdalena, and since the time of exploration (1536) by Gonzalo Jiménez de Quesada, the Spanish conquistador, the river has profoundly influenced the economic and political life of Colombia.