Research Spotlights

Understanding how decreasing rainfall is impacting river regions in South-Western Australia.

By Georgia Barrington-Smith & Dr Rebecca Duncan

Global rainfall patterns are changing, leading to dryer conditions in numerous biodiversity hotspots. Rivers in the Southern Hemisphere are particularly sensitive to these climate-induced changes.

To mitigate biodiversity loss and manage our precious water resources, we need to better understand the impacts of changing rainfall patterns on river systems. Specifically, we need to understand whether rivers can buffer or modulate changes in streamflow under a drying climate. The key to unlocking this puzzle lies in determining how surface water and groundwater interact to govern streamflow patterns in river systems.

Rose-Anne’s river investigations

Previous studies in how rainfall affects streamflow patterns in the South-West Australian region have not yet addressed variability in streamflow, arising from storage and release of water, or other hydrological processes.

With this gap in mind, Rose-Anne Bell, AINSE PGRA scholar and University of Western Australia student, has collaborated with ANSTO to investigate the streamflow response in the Donnelly Catchment in the south-western tip of Australia, approximately 250 km south of Perth. This catchment has been drying for several decades, with local rainfall reducing by 15-20% since the 1970s.

Rose-Anne and her collaborators investigated the streamflow response of three adjacent sub-catchments in the Donnelly Catchment: Donnelly River, Barlee Brook and Carey Brook.  By analysing long-term trends in streamflow, they identified periods when the streams had undergone a hydrological change including changes in flow patterns.

Within these periods Rose-Anne and her collaborators discovered that declining rainfall had caused two of the streams to lose year-round-flow (with statistical changepoints in 1975 and 2001), while the third stream (Carey Brook) had continued to flow all year round. This non-uniform response was attributed to depleted catchment water stores in the streams that had lost year-round flow (Donnelly River and Barlee Brook). This suggests that underlying geology and soil profiles with greater water storage capacity may be enabling the still-flowing stream to buffer changes in rainfall.

Combining chemistry and hydrology to understand the effects of climate change.

The team also conducted a series of field campaigns to install streamflow loggers and collect surface and groundwater samples to assess streamflow. The samples were then analysed for ion chemistry, radon, stable water isotopes, and radiocarbon in surface water and groundwater, with some of this analysis taking place at ANSTO’s Centre for Accelerator Science (CAS) facility.

Based on this analysis, Rose-Anne was able to demonstrate how and where groundwater was contributing to streamflow.  For example, radon concentrations and radiocarbon trends along the Carey Brook showed the potential for higher levels of groundwater to inflow across the transition zone between hard rock and coastal geological plains.

These results pose an interesting question for future research: what potential impact could hydrogeological features in the landscape, such as the presence of a fault or impermeable geological layer, play in streamflow generation processes and a stream’s ability to buffer climatic stressors?

Investigations such as these are important for understanding surface and groundwater interactions, which will play a crucial role in protecting biodiversity and better preparing these important and diverse ecosystems to resist the worsening effects of climate change.

AINSE are proud to spotlight Rose-Anne Bell for her insightful research.

Read more research spotlights at ainse.edu.au/research-spotlight and keep connected for next month’s Spotlight Series as we dial up the fun for Fungi February!
First up is Carl McCombe, whose research aims to understand how pathogenic fungi attack our important plant crops and how they can be stopped.

Stay up to date with AINSE by following us on all our social media platforms @ainse_ltd on Instagram, Facebook, Threads, LinkedIn and X.

By Georgia Barrington-Smith & Dr Rebecca Duncan

The Antarctic ice sheet holds 61% of all the fresh water on Earth. How this ice sheet is responding to climate warming remains the biggest source of uncertainty in determining future global sea levels. Interpreting clues from the past ice margins is critical to understanding the future, and that’s where Lottie Stevenson comes in.

Lottie is an AINSE Pathway scholar and University of Wellington Honours student. In collaboration with ANSTO, she has investigated the deglacial (ice melting) history of Byrd Glacier, a critical East Antarctic outlet glacier. Byrd Glacier is the largest of the outlet glaciers draining ice from the East Antarctic ice sheet (EAIS), responsible for approximately 10% of the EAIS draining overall.

Lottie used cosmogenic nuclide surface exposure dating at ANSTO’s Centre for Accelerator Science (CAS) to determine the rate, timing, and magnitude of thinning ice at Byrd Glacier. She did this by extracting rare cosmogenic nuclides from glacial erratic cobbles, which are rocks deposited by the glacier as it thinned since the Last Glacial Maximum (LGM).  By pairing the two cosmogenic nuclides (long-lived ¹⁰Be and short-lived in-situ ¹⁴C), Lottie was able to determine the extent of post-LGM glacial thinning in the Ross Embayment. By understanding the Byrd Glacier’s past response to natural climatic changes, she is helping forecast future ice sheet change.

Ka mua, ka muri – ‘Walking backwards into the future’
(Māori proverb)

Lottie’s journey to the south pole

Lottie’s research took her to Antarctica, where she collected the erratic cobbles from the mountains adjacent to the Byrd Glacier fjord. These rocks were transported to Australia and crushed, allowing the quartz to be extracted, purified and eventually analysed by Lottie using accelerator mass spectrometry (AMS) at ANSTO’s Centre for Accelerator Science.

Her results revealed that the ice surface had thinned >600m since 7000 – 8000 years ago. This aligns with other studies that suggest the mid-Holocene was a time of rapid deglaciation across the Ross Embayment, whilst providing new knowledge that Byrd Glacier thinning was a more rapid and significant event than previously thought. These results are extremely useful for informing ice sheet modellers as they can strengthen numerical models used to predict future ice sheet and sea level response to climate change. This research is ongoing, and Lottie hopes to continue interpreting her results by performing a data-model comparison on them, and to derive a new inland paleo-thinning rate for Byrd Glacier.

Lottie’s experience with AINSE and ANSTO

Lottie was honoured to receive the AINSE Pathway Scholarship, as it allowed her to “…visit and experience state-of-the-art science at ANSTO”. Her Honours project exceeded her expectations, and she “…appreciated the site-wide tour, hands-on learning in the labs and AMS control room, and the friendly atmosphere of the CAS and AINSE teams”.

Lottie hopes to become an influential voice in Antarctic science, conservation, and decision-making – for she believes “…the icy continent is a unique place”.

We look forward to watching Lottie’s research journey as she looks to pursue a future PhD in polar science.