Understanding South Australian rainfall trends and step changes

Rainfall is the key hydroclimatic variable that plays a vital role in the development of regional water management policies. Assessment of observed rainfall behaviour and its spatial and temporal variations are therefore important for climate change adaptation measures. This study assessed trends and step changes in observed annual and seasonal rainfalls across the South Australian region. More than 100 years of high-quality rainfall data from 53 rainfall stations were analyzed using robust statistical techniques. The results are presented according to the eight South Australian natural resource management regions. Increasing annual rainfall trends were observed for the Arid Lands, Alinytjara Wilinara and Adelaide and Mount Lofty Ranges regions whereas decreasing trends were found for the Murray Darling Basin, Eyre Peninsula and South East regions. Both upward and downward trends were identified in the Northern and Yorke region. Seasonally, austral spring and summer rainfalls exhibited increasing trends in most of the regions whereas autumn and winter rainfalls showed decreasing trends. Most of the rainfall step changes were observed to happen in the 1960s and 1970s. The study also includes a discussion on possible mechanisms of South Australian rainfall variability and changes that may have links to the observed trends and step changes.