Streamflow droughts over the central Andes of Argentina: current crisis (2010-2014) in historical perspective

JUAN ANTONIO RIVERA; DIEGO ARANEO; OLGA PENALBA

Santiago de Chile

Conferencia; 11th International Conference on Southern Hemisphere; 2015

Universidad de Chile

In the central Andes of Argentina, permanent and semi-permanent rivers originate mainly from snow melt and glacier ablation. These rivers have enabled the development of large agricultural oasis and the construction of numerous dams and reservoirs for irrigation and power generation. In the case of the Cuyo region, most of the population and economic activities are located in a small irrigated fraction of the territory, where the variations in available water resources largely determine the socio-economic vulnerability of the region. In this context, it is extremely important to assess the periods of streamflow droughts, taking into account that during the last 4 years the scarce snowfalls over the Andes resulted in a period of water crisis.In this study, we performed a comparison of the streamflow deficiencies during the period 2010-2014 over the central Andes of Argentina with other historical dry periods, considering its duration, severity and magnitude. Streamflow drought events were defined by applying a threshold level approach on the daily streamflow time series, using several daily varying thresholds. The truncation level were defined by the percentiles Q70, Q80 and Q90; which caracterize moderate, severe and extreme drought conditions, respectively. Periods in which the streamflow values are below the thresholds were analyzed through the use of two yearly indices: the annual cumulated duration of all the drought events and the annual cumulated deficit volume standardized by seasonal mean flow. Based on 12 gauging stations located between 30° and 36°S, in some of the major river basins of the region -San Juan, Mendoza, Diamante, Atuel and Tupungato, among others- it was found that the recent dry period is the most important of the last 40 years in all the basins analyzed. In some of these basins was obtained that the deficit during the years 2010-2014 exceeds the deficit conditions recorded in the late 1960s and early 1970s. This dry period could reach extraordinary conditions in all basins of the region taking into account the streamflow forecasts for the hydrological year 2014/15.