 A longer sediment core from the same site was used to reconstruct the evolution of the lake and its drainage basin during the last 18,000 years.At the time the glacier occupying the Puyhue basin had retreated during deglaciation as to calv at a proglacial Puyehue Lake the glacier at Rupanco basin (40°49' S) was at its maximum extent.For a time meltwater from the Rupanco glacier flowed north into Puyehue Lake.