CONICET | Buscador de Institutos y Recursos Humanos

The rising demand on surface water resources calls for a better prediction of the characteristics of hydrological drought. One of the parameters of interest for the analysis of streamflow deficiencies is the annual number of days with low streamflow, and their associated temporal variability. A threshold level method was considered on a daily basis in order to define a day with low streamflow. These days were considered as those with streamflow values less than the flow exceeded the 70% of the time. The annual number of days with low streamflow was calculated for 11 sites with at least 50 years of daily streamflow data. These sites were located over the Argentinean Andes, between 30°S and 50°S. During the period 1943-2008, significant trends towards a decrease in the days with low streamflow were observed in San Juan and Atuel basins, which belong to Cuyo region, in the northern portion of the domain. This decrease was in order of 20 days per decade in San Juan basin and 30 days per decade in Atuel basin. In the Northern Patagonia region, the trends were non-significant, with a decrease of 2 days per decade in Neuquén basin and an increase of 3 days per decade in Chubut basin. In order to analyze the interdecadal variability, an 11 year weighted running mean was used. By means of spectral analysis, we identified significant periodicities between 11 and 34 years for the Cuyo region, while the Patagonia region showed periodicities between 11 and 48 years. The low streamflow variabilities in the basins of the Cuyo region showed a phase shift during the 1970 decade, in agreement with the behavior of precipitation in that region. Decadal predictions on a regional scale are crucial in order to depict if these trends will continue during the next decades.

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