Abstract

Northern Patagonian River systems located between the Araucanía and the Los Lagos Regions of Chile are characterized by lake regulation and seasonal predictable flow regime. As these systems originate in large glacial lakes, their flow velocities are lower compared to other Andean River systems in Chile. The San Pedro River (Valdivia River basin) is an iconic largely pristine northern Patagonian River system characterized by rich hydrogeomorphology and biodiversity as well as unique paleontological and human histories. It originates from a chain of eight lakes that generate lacustrine influence in upper zone, followed by a middle section with high slope and flow velocities, lower reaches with developed floodplains, to discharge to the Pacific Ocean in Valdivia Estuary. Consequently, this river system in a stretch of just 100 km accommodates the highest diversity of freshwater fish species in Chile. The paleontological record along the San Pedro River system is also highly relevant with fossil deposits found in sedimentary rocks originating between Triassic and Quaternary periods that have allowed historical climate and vegetation reconstructions. Besides, the strongest earthquake registered worldwide in 1960 in this region directly affects the river and human population which has generated respect for nature. In this way, geological history, fossils, and present biodiversity are input to protect the territory from potential threats.