Streamflow variations across the Andes (18°-55°S) during the instrumental era

Authors: MASIOKAS, MARIANOS, - University Of Western Ontario; CARA, LEANDRO - University Of Western Ontario; VILLABA,, RICARDO. - University Of Western Ontario; PITTE,, PIERRE - University Of Western Ontario; LUCKMAN, BRIAN - University Of Western Ontario; TOUM, EZEQUILE - University Of Western Ontario; CHRISTIE, DUNCAN - University Of Western Ontario; LE QUESNE, CARLOS - University Of Western Ontario; Mauget, Steven

Submitted to: Hydrology and Earth System Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/29/2019
Publication Date: 11/29/2019
Citation: Masiokas, M.H., Cara, L., Villaba,, R., Pitte,, P., Luckman, B.H., Toum, E., Christie, D.A., Le Quesne, C., Mauget, S.A. 2019. Streamflow variations across the Andes (18°-55°S) during the instrumental era. Hydrology and Earth System Sciences. 9:17879. https://doi.org/10.1038/s41598-019-53981-x.
DOI: https://doi.org/10.1038/s41598-019-53981-x

Interpretive Summary: The rivers originating in the Andes mountains are important agricultural water sources throughout Chile, western Argentina and south-western Bolivia. To detect recent changes in Andean streamflow a database of monthly streamflow records was tested for trends and periods of high and low flow during 1986-2015. In the central Andes of Chile and Argentina dry conditions since 2010 and longer-term drying trends were found. By contrast, increasing streamflow trends were found in northwestern Argentina and southern Bolivia. As the drying trends in the central Andes are consistent with regional warming trends and reduced runoff from glaciers, these results emphasize the need for better agricultural and municipal water management in the coming years.

Technical Abstract: The rivers originating in the Andes (18°-55°S) constitute a crucial natural resource and support numerous ecosystems, human populations and a large number of socio-economic activities throughout Chile, western Argentina and south-western Bolivia. However, the variations in surface runoff in this extensive mountainous region have not yet been assessed comprehensively to identify areas with common hydroclimatic patterns of variability during the instrumental era (early 20th century – present). Here we use an extensive database of mean monthly streamflow records from Chile, Bolivia and Argentina to identify their main modes of variability across the Andes. About 75% of the total variance in the dataset can be explained by only eight spatially coherent patterns of variations over the 1986-2015 period. Regionally averaged time series that reflect these eight modes of variability show quite different temporal patterns. The extreme dry conditions reported since 2010 in the central Andes of Chile and Argentina are clearly evident in three sub-regions, which also show long-term drying trends over their period of record. In contrast, the rivers in northwestern Argentina and southern Bolivia, and in the southernmost Patagonian-Fueguian Andes, show positive trends that reflect wetter hydroclimatic conditions in recent years/decades. The other modes of variability show transitional patterns in the north Patagonian Andes, strong interannual variations in northernmost Chile, and the dominating influence of glacier melt on surface runoff in the eastern portion of the South Patagonian Icefield. The analyses provide relevant new results to improve understanding of the spatial coherence and the main temporal features of recent hydroclimatic changes in the southern Andes. The assessment of the relative magnitude of current hydrological conditions using a longer term regional context can also help improve the management of mountain water resources across this extensive area.