CONICET | Buscador de Institutos y Recursos Humanos

The Río Malargüe and other smaller streams feed Laguna Llancanelo, a permanent shallow lagoon located close to the Andes, in Malargüe, Mendoza. Being an endorheic basin, spatial variations in the size of the Laguna Llancanelo can be used as a regional index of water availability in the southern sector of the Mendoza province. In this presentation, we update the development of a regional water stress index derived from variations in the size of Laguna Llancanelo determined from satellite images and the study of the relationships between variations in lake size and remote (snowpack) and local (rainfall) water inputs. Based on Landsat satellite images since the mid-1980s, a monthly series of variations in size of this lagoon has been developed for the last 30 years. This record, based on 289 satellite images has many missing data during the 1980s and 1990s, but it is almost complete since the beginning of the 21th century. The comparison between monthly variations in Llancanelo size and in Río Malargüe streamflow at the Pincheiras gauge station, suggest a close relationship between monthly snow-fed streamflow and lake size variations (r = 0.6, n = 242). Local rainfall events may also play an important role in lake fluctuations and therefore lake size variations were also compared with regional precipitation records. We noted that some rapid lake fluctuations are linked to intense precipitation events recorded from the plains adjacent to the Andes. Regression analyses indicate that the variability in Llancanelo size fluctuations are primary modulated by snowpack melt and rainfall in the upper Cordillera (as inferred from Rio Malargüe streamflows) and secondarily by local rainfall events. The integration of winter (snowpack and rainfall) and summer (rainfall) water sources from the Pacific and Atlantic Oceans respectively, makes Laguna Llancanelo size variations a good index of regional water balance east of the Andes.