A long-term analysis of rainfall and temperature trends across two of South Australia’s most important agricultural regions has found a significant long-term decline in rainfall – particularly across Upper Eyre Peninsula – alongside rising temperatures.
The peer-reviewed study – ‘Trends in Rainfall and Temperature in the Murray Mallee and Upper Eyre Peninsula Region of South Australia – Connections to Climate and Land Use Change’, published in Environmetrics – analysed annual rainfall and temperature data from 1950 to 2023 across 26 Bureau of Meteorology stations in the Murray Mallee (MM) and Upper Eyre Peninsula (UEP).
Lead author Sachinda Ekanayake, a PhD candidate from Adelaide University’s Industrial AI Research Centre, said the findings highlighted increasing climate pressures on rainfall-dependent farming systems.
“Our results show that annual rainfall has decreased considerably in the Upper Eyre Peninsula over the past seven decades, with every station in that region recording a decline,” he said.
“In the Murray Mallee, most stations also show decreasing rainfall trends. However, we observed a cluster of locations – including Murray Bridge, Mannum and Callington – where rainfall has increased since the 1970s.”
Across upper EP, rainfall declines ranged from around 11 per cent to more than 33 per cent over the study period, with the largest reductions recorded at Yeelanna, Lock and Tumby Bay.
In contrast, parts of the Murray Mallee experienced increases of up to 11 per cent.
The researchers applied robust statistical techniques – including linear regression, exponential smoothing and three independent change-point detection methods – to identify long-term trends and abrupt shifts in rainfall and temperature patterns.
Co-author Professor John Boland said the statistical evidence suggested the rainfall reductions were unlikely to be due to natural variability alone.
“In the Murray Mallee, 11 out of 15 stations showed declining rainfall trends, and in the Upper Eyre Peninsula the decline was consistent across all stations,” he said.
“When we tested whether this pattern could be due to chance, the statistical evidence indicated it is highly unlikely. This points to broader climatic drivers affecting the region.”
The study also identified significant change points – years when rainfall or temperature patterns shifted abruptly – potentially linked to industrial expansion, urbanisation, land-use change and broader climate change influences.
One notable finding was a localised increase in rainfall near the Monarto Plateau in the Murray Mallee.
Researchers noted that large-scale revegetation programs in the 1970s may have contributed to enhanced rainfall in surrounding areas, although further investigation was needed.
“This spatial clustering of increasing rainfall near Monarto is intriguing,” Prof Boland said.
“It suggests that land-use change, particularly vegetation cover, may play a role in modifying local rainfall patterns.
“However, climate systems are complex, and multiple interacting factors are likely involved.”
Temperature data from selected stations in both regions showed consistent warming trends, reinforcing concerns about compounding climate pressures on agriculture and water resources.
The Murray Mallee and Upper Eyre Peninsula are highly dependent on seasonal rainfall for cropping and livestock production.
Declining rainfall combined with rising temperatures increased evaporation rates, reduced soil moisture and heightened drought risk.
“Our findings are particularly important for farmers, water managers and policymakers,” Mr Ekanayake said.
“Understanding long-term regional trends allows for better planning around water allocation, crop selection and climate adaptation strategies.”
The researchers said the study provided a detailed, region-specific analysis that complemented broader southeastern Australia climate studies, offering new insight into how global climate change and local land-use practices may be interacting at a regional scale.
The team plans further research to examine the spatial relationships between land cover, climate drivers such as the Southern Annular Mode and ENSO, and observed rainfall shifts.
