Droughts and floods in northern Argentinean Patagonia

ROMERO, PAULA ELISA; GONZÁLEZ, MARCELA HEBE; GARBARINI EUGENIA MARIA

The Andes: Geography, Diversity and Sociocultural Impacts

NOVA PUBLISHER

Lugar: nueva york; Año: 2017; p. 5 - 28

The northern Argentine Patagonia region covers a continental Argentina between 38° and 43°S, comprising the basins of the Limay, Neuquén, Negro, Colorado rivers and in a closed basin located towards the south of the Negro river. The Andes Mountain extends west from north to south and eastward the landscape is a quite dry plateau. The first two basins are relevant for hydropower generation and are located in an area called ?Comahue? where rainfall prevails in winter and over the western high mountain. The other basins are arid but with valleys where growing fruit thrives. In particular, the closed basin is the driest. Monthly and annual precipitation and mean annual flow data over the period 1985-2012 were used to perform this study. For each station, the 25th and 75th percentiles of precipitation and flow were used to classify each one of the years as dry (precipitation or flow less than 25th percentile), wet (greater than 75th percentile) or normal. Finally the years were classified as dry, wet or normal if the greater number of stations within each basin belongs to that category.Some parameters were defined and calculated in order to assess the intensity and the spatial coverage of all the extreme (wet and dry) events. Thus, all extreme events are revealed in the different basins and their severity and area affected in each case was documented.Finally, the presence of significant climate forcing associated with extreme precipitation detected above, was investigated. As the maximum signal was in Spring, climate forcing in this season were analyzed in detail. Results indicate that positive phase (negative) of the Indian Ocean Dipole, El Niño Modoki and the El Niño-Southern Oscillation are associated with the highest positive (negative) precipitation anomalies in spring in the Comahue region. Positive (negative) precipitation anomalies are also associated with the negative (positive) phases of the Antarctic Oscillation, the South Atlantic Ocean Dipole and Multidecadal Atlantic Oscillation and with the weakening and eastward shift of the Pacific High and the intensification and shift to the south of the Atlantic High.