Spatio-temporal assessment of streamflow droughts over Southern South America: 1961–2006

Abstract

This paper performed a streamflow drought climatology considering some of the most important rivers of Southern South America, a region highly vulnerable to climatic variations, based on the analysis of monthly streamflow records. The standardized hydrological drought index (SHDI) was used in order to depict the main characteristics of droughts—number of drought events, mean duration, and mean severity—over the period 1961–2006. Firstly, the suitability of this index based on the two-parameter gamma distribution was evaluated, considering that the use of the SHDI has been limited over the region. The regional aspects of streamflow droughts were identified through a clear relationship between drought frequency and its duration, indicating different temporal variations in streamflow records over the study area. Spatial patterns exhibit heterogeneous features in terms of streamflow drought severity and can be associated to the geographical characteristics of the basins. Observed trends in the SSI are in line with the increases in precipitation totals over the second half of the twentieth century over much of the study area. Nevertheless, drought conditions are observed more often in the basins south of 40°S, in line with recent trends in large-scale climatic oscillations. The streamflow drought characteristics can provide critical values for different water-based activities, as also information to develop strategic plans that are needed for adequate water resource management considering the different climatic features over Southern South America.