Abstract

The Puelo River is a watershed shared between Chile and Argentina with a mean annual streamflow of 644 m3 s-1. It has a high ecologic and economic importance, including introduced farmed salmon, tourism, sports fishing and projected hydroelectricity. Using Austrocedrus chilensis and Pilgerodendron uviferum tree-ring records we reconstructed summer-fall (December-May) Puelo River streamflow, which is the first of such reconstructions developed in the Pacific domain of South America. The reconstruction goes back to 1599 and has an adjusted r 2 of 0.42. Spectral analysis of the reconstructed streamflow shows a dominant 84-year cycle which explains 25.1% of the total temporal variability. The Puelo River summer-fall streamflow shows a significant correlation (P>0.95, 1943-2002) with hydrological records throughout a vast geographic range within the Valdivian eco-region (35 to 46°S). Seasonal Puelo River interannual streamflow variability is related to large-scale oceanic and atmospheric circulation features. Summer-fall streamflows showed a significant negative correlation with the Antarctic Oscillation (AAO), whereas winter-spring anomalies appear to be positively connected with sea surface temperature variations in the tropical Pacific. In general, above- and below-average discharges in winter-spring are related to El Niño and La Niña events, respectively. The temporal patterns of the observed and reconstructed records of the Puelo River streamflow show a general decreasing trend in the 1943-1999 period. Projected circulation changes for the next decades in the Southern Hemisphere would decrease summer-fall Puelo River streamflows with significant impacts on salmon production, tourism and hydropower generation. © 2007 Springer Science+Business Media B.V.