Characterization of meteorological droughts across South Australia

Abstract

An understanding of drought characteristics is vital for sustainable management of water resources. This is particularly important for dry regions such as Australia where large‐scale water supply infrastructure has to be designed to withstand multiyear variability in rainfall anomalies. This study considers the Standardized Precipitation Index (SPI) at time scales of 3, 6, 12 and 24 months to assess both short‐term and long‐term droughts. Trends in the SPI at 46 selected rainfall stations across South Australia (SA) are investigated. Furthermore, various drought parameters such as frequency, severity and duration are estimated, and their spatial distributions are presented. Drought risks are estimated in terms of copula based bivariate joint return periods and compared with traditional univariate return periods. Finally, the dominant climatic modes of sustained drought and wet anomalies are identified using correlation analysis. Results show that 23 out of the 46 selected stations had a significantly negative trend for the 24 month SPI whereas the count is four for the 3 month SPI. This reveals that droughts have intensified over 1960–2010 and this intensification is more prominent for long‐term drought. Strong spatial variability is evident in drought parameters across SA. The results also highlight the suitability of a bivariate joint return period over a univariate return period for drought risk assessment because drought is a multi‐faceted phenomenon. Thus, drought risk estimated for the univariate return period was found to be different from the drought risk estimated by the bivariate return period. The dominant climatic modes identified in this study are Niño3.4 and the dipole mode index (DMI), which are able to represent the SPI across SA at the selected time scales. The outcomes of this study are useful for water managers and policy makers involved in sustainable water resource management.