The ridge forming the water-parting between the basins of the Cauca and Patia rivers crosses between the Central and Western Cordilleras at this point and culminates a few miles to the south.
It is worthy of note that the principal rivers of these three classes - the Patia, Cauca, Magdalena, Caqueta and Putumayo - all have their sources on the high plateaus of southern Colombia and within a comparatively limited area.
The principal rivers of this group, starting from the southern frontier, are the Mira, Patia, Iscuande, Micai, Buenaventura or Dagua, San Juan and Baudo.
The Patia is the longest river of the Pacific group, and is the only one having its sources on the eastern side of the Western Cordillera.
The canyon of the Patia through the Western Cordillera is known as the "Minima gorge," and has been cut to a depth of 1676 ft., above which the perpendicular mountain sides rise like a wall some thousands of feet more.