Submitted to: Journal of Hydrometeorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2010
Publication Date: 6/1/2010
Citation: Masiokas, M., Villalba, R., Luckman, B., Mauget, S.A. 2010. Intra-to multidecadel variations of snowpack and streamflow records in the Andes of Chile and Argentina between 30 degrees and 37 degrees S. Journal of Hydrometeorology. 11:822-831. Interpretive Summary: Streamflow from melting snowpack in the Andes provides fresh water to cities and agriculture in Chile and Argentina. Significant connections between long-term (> 10 year) high and low flow periods in historical records of Andean streamflow and similar variation in Pacific Ocean sea-surface temperatures (SST) suggests that these flow regimes might be predicted, if SST could be predicted. Using a sophisticated time-series analysis method, research here shows that a low flow period of Andean streamflow during 1945-1977 coincided a period of cool Pacific SSTs that occurred during that same time. Those cool sea-surface temperatures, which are associated with a slowly varying see-saw of Pacific SSTs known as the Pacific-Decadal Oscillation (PDO), may one day be predictable as the behavior of the atmosphere and ocean over the Pacific become better understood. Thus this work suggests that forecasts of the long-term state of the PDO may also lead to similar long term forecasts of water supply in parts of Chile and Argentina.
Technical Abstract: Regional composites of winter snowpack (1951-2008) and mean annual river discharges (1906-2007) are used to evaluate the main intra- to multi-decadal hydrologic variations in the Andes of Chile and Argentina between 30° and 37°S. The streamflow record shows a non-significant negative trend but two significant regime shifts in 1945, when levels dropped 31%, and in 1977 when they increased 28%. These events coincide almost exactly with shifts observed in a PDO series which suggests an influence of this feature in modulating the low frequency modes of hydroclimatic variability in the study area. Analyses of the magnitude of 5-20-year moving windows indicate that the most significant concentration of high (low) discharges occurred between 1977 and 1987 (1954 and 1971). All post-1987 moving windows analyzed have remained within non-significant levels despite the occurrence of some extreme dry years. The regional snowpack series shares remarkable similarities with the streamflow record but shows stronger year-to-year variability, a slight, positive trend and no significant regime shifts.