Culenco River
Culenco a river of moderate volume that runs from the southern part of the commune of Santa Juana, through the northwestern part of the commune of Nacimiento to its confluence with the Nicodahue River. It has origins in streams from the eastern slopes of the Nahuelbuta Range in the Catirai region to the south of the town of Santa Juana, where it unites several streams from that side of that forested mountain range, and goes towards the southeast to join with the Nicodahue River after a course of more than 35 kilometers, to form the Tavolevo River about  seven kilometers from the confluence of the Tavolevo with the Bio Bio River. In its lower part it is more open and fertile. Among the valleys and gorges of its upper part existed some indigenous populations in the early period of the Arauco War, and the fort of San Jerónimo de Millapoa was built there to control them in 1585.