Cauca (kouˈkä) [key], river, c.800 mi (1,290 km) long, rising in the Cordillera Central, near Popayán, W Colombia. It flows north in a rift valley between the Cordillera Central and Cordillera Occidental to the Magdalena River. It is navigable in its lower course and drains a fertile valley; coffee is the chief crop. The valley has many minerals including gold. There is a river-control and utilization scheme on the upper Cauca.