Abstract
The rivers originating in the southern Andes (18°–55°S) support numerous ecosystems and a large number of human populations and socio-economic activities in the adjacent lowlands of Chile, Argentina and Bolivia. Here we show that ca. 75% of the total variance in the streamflow records from this extensive region can be explained by only eight spatially coherent patterns of variability. Five (three) of these Andean patterns exhibit extreme dry (wet) conditions in recent years, with strong interannual variations in northern Chile; long-term drying trends between 31° and 41°S; a transitional pattern in the central Patagonian Andes; and increasing trends in northwestern Argentina and southern Bolivia, the Fueguian Andes, and the eastern portion of the South Patagonian Icefield. Multivariate regression analyses show that large-scale indices of ENSO variability can predict 20% to 45% of annual runoff variability between 28° and 46°S. The influence of Antarctic and North Pacific indices becomes more relevant south of 43°S and in northwestern Argentina and southern Bolivia, respectively, but their overall skill as predictors of Andean streamflows is weak. The analyses provide relevant new information to improve understanding of the spatial coherence, the main temporal features, and the ocean-atmospheric forcings of surface runoff across the southern Andes.
Highlights
The rivers originating in the southern Andes (18°–55°S) support numerous ecosystems and a large number of human populations and socio-economic activities in the adjacent lowlands of Chile, Argentina and Bolivia
By no means definitive, these analyses provide an original overview of the most important hydrological patterns of the southern Andes, and can help improve the current understanding and management of the water resources that originate in this mountain range
As discussed in the Data and Methods section, the processing of the original mean monthly streamflow records included their statistical aggregation into one reference series per river basin, and the subsequent application of Principal Component Analysis (PCA) to identify their main modes of variability over the 1986–2015 period
Summary
The rivers originating in the southern Andes (18°–55°S) support numerous ecosystems and a large number of human populations and socio-economic activities in the adjacent lowlands of Chile, Argentina and Bolivia. The PC1 record in the central Andes of Chile and Argentina covers the July 1909 – June 2016 period (1284 months with ≥ 2 series over the entire interval) and shows a strong intra- and inter-annual variability embedded in a marked multi-decadal pattern (Fig. 4A).
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