The Magdalena River (, ; less commonly ) is the main river of Colombia, flowing northward about through the western half of the country. It takes its name from the biblical figure Mary Magdalene. It is navigable through much of its lower reaches, in spite of the shifting sand bars at the mouth of its delta, as far as Honda, at the downstream base of its rapids. It flows through the Magdalena River Valley. Its drainage basin covers a surface of , which is 24% of the country's area and where 66% of its population lives. Course The Magdalena River is the largest river system of the northern Andes, with a length of 1,612 km. Its headwaters are in the south of Colombia, where the Andean subranges Cordillera Central and Cordillera Oriental separate, in Huila Department. The river runs east then north in a great valley between the two cordilleras. It reaches the coastal plain at about nine degrees north, then runs west for about , then north again, reaching the Caribbean Sea at the city of Barranquilla in the zone known as Bocas de Ceniza. Flora and fauna Fish The Magdalena River basin, which includes the Cauca River and other tributaries, are very rich in fish. , 213 fish species were known from the basin. Since then several new species have been described from the basin such as five Hemibrycon in 2013, two Ancistrus in 2013 and a Farlowella in 2014. Among the more famous species in the basin are Kronoheros umbriferus, Ctenolucius hujeta, Geophagus steindachneri, Ichthyoelephas longirostris, Panaque cochliodon, Pimelodus blochii, Potamotrygon magdalenae, Prochilodus magdalenae, Pseudoplatystoma magdaleniatum and Salminus affinis. About 55% of the fish species in the basin are endemic, including four endemic genera: The catfish Centrochir and Eremophilus, and the characids Carlastyanax (often included in Astyanax) and Genycharax. In general, the fish fauna shows connections with surrounding basins, notably Atrato and Maracaibo, but to a lesser extent also Amazon–Orinoco. The most productive fishing areas in Colombia are in the basin, but there has been a drastic decrease in the annual harvest with a fall of about 90% between 1975 and 2008. The primary threats are pollution (such as human waste, mining, farming and deforestation causing siltation) and habitat loss (such a dams). Additional dams are being constructed, including El Quimbo (opened in 2015) and Ituango (expected operational in 2018), which has caused some controversy. As a