Multicentury tree ring reconstruction of annual streamflow for the Maule River watershed in south central Chile

Because of the reported decreasing trends in precipitation in south central Chile and the high priority of the Valdivian rain forest ecoregion conservation, it is essential to understand long-term changes in water availability in this area. Thus, this study presents a 410 year annual streamflow reconstruction for the Maule River watershed located in a Mediterranean-type climate in the northern part of the ecoregion (35 degrees S-36 degrees 30'S). The annual streamflow reconstruction used Austrocedrus chilensis tree ring chronologies, and the adjusted R-2 was 0.42. The reconstruction was characterized by interannual, interdecadal, and multidecadal oscillation modes, some of which might be explained by solar and lunar cycles and by ocean-atmospheric forcings. Temporal correlations between the reconstruction and climatic indices, such as the El Nino-Southern Oscillation and the Antarctic Oscillation, demonstrate that water availability is influenced by tropical and high-latitude forcings in this area. Extreme low and high streamflows are particularly related to ocean-atmospheric conditions in the tropical Pacific. The Maule River watershed streamflow reconstruction reveals a higher proportion of streamflows below the mean in the last century compared to the previous three centuries.