Climate variability and water resources 
 

Groundwater sampling in the Murray-Darling Basin

Natural climate archives and isotope-enabled models are being utlised by ANSTO to assess the impacts of climate variability on catchment water resources.

Undertaking scientific research that underpins sustainable water management principles, under current and future climate scenarios, is a core objective of the climate variability and water resources group.

As Australia is a naturally dry continent, the impacts of climate change are likely to prove particularly challenging to those involved in water resource management. The Department of Climate Change reports that both rainfall deficits and droughts are projected to become more extreme in the future. Changes in the hydrological cycle play a central role in driving variability in the Earth's climate. By utilising isotopes in the water cycle ANSTO scientists can study these changes in a range of hydrological and climate processes at local, regional and global scales.

Isotopic techniques are used to reconstruct regional climate variation from records of isotopic composition of very old precipitation, preserved in high and low resolution environmental archives including speleothems (cave stalagmites) and groundwater. Accurately reconstructing regional climate variations from these environmental archives is challenging, and requires input data on the effect of climate variables such as rainfall or drought on isotopic signatures.

There are few long term records of these relationships, and observation sites are limited, so the researchers in this group use isotope-enabled climate models and satellite data to better understand the variations of isotopic inputs to groundwater or speleothems over time, and space.

Study locations and collaborations
 

Members of the climate variability and water resources group are working on a number of sites around Australia, including the southwest region of Western Australia (WA) and the Murray-Darling Basin, where they aim to improve knowledge of natural rainfall variability by extending rainfall records prior to the instrumental period.

This research is undertaken by reconstructing records of rainfall sensitive isotopes and trace elements preserved in cave stalagmites. Supported by Land and Water Australia, the WA Department of Environment and Conservation (DEC), the Water Corporation of WA and the NSW Office of Environment and Heritage (DEH), the research involves collaborations with scientists from the Australian National University, University of Newcastle, University of Melbourne and others.

Data on the isotopic values of rainfall and water vapour - from ground and space observations and from isotope-enabled global climate models (GCMs) - are important for interpreting isotopic archives.

Work to better define the isotopic source terms (rainfall and atmospheric water vapour) across Australia is being coordinated by ANSTO in collaboration with the Australian Bureau of Meteorology (BOM) and Commonwealth Scientific and Industrial Research Organisation (CSIRO).

This work forms:

ANSTO's contribution to the GEWEX Murray-Darling Basin Regional Hydrology Project and;
Australia's contribution to the Global Network of Isotopes in Precipitation (GNIP).
 

ANSTO is also undertaking detailed work in the Sydney Basin to establish a rainfall isotope dataset for use in regional hydrology studies and to investigate relationships between rainfall isotopes and past climate, as well as present day weather patterns.
 

This isotopic source term data is vital for use in present-day recharge and water balance studies (Isotopes in Hydrological Cycle) and in plant water use studies (Aquatic Ecosystems).

Deep groundwater systems have the potential to act as low resolution palaeo-environmental archives, containing palaeo-recharge information for the studied area.

ANSTO researchers are using geo-chemically corrected radiocarbon age dates for groundwaters of the western section of the Darling River Basin to provide insight into past climatic conditions in central Australia.

This information can then be correlated to the modern hydrological response of the Darling River to help water resource managers develop sound water management solutions under current and future climatic scenarios.

Instruments and processes
 

TES satellite tracks (points) over the Murray-Darling Basin plus a e scale of atmospheric 2H/1H observations from TES.

 The cave stalagmite (speleothem) research uses several isotopic and elemental concentration techniques, including O and C isotope measurements (single inlet mass spectrometry with carbonate and water equilibration devices), minor and trace elements (ICP-AES, laser ablation mass spectrometry) and U-series disequilibrium dating (multi-collector ICPMS).

Groundwater studies require the use of various hydro-chemical and isotopic tools that are applied to samples collected from suitable field sites. Groundwater mean residence times are evaluated by ANSTO researchers by using tritium (3H) which is analysed by liquid scintillation methods and most importantly, radiocarbon (14C) using Accelerator Mass Spectrometry (AMS).

Above: Cross-sections of cave stalagmites used to reconstruct records of climate-sensitive isotopes.

Radiocarbon age dating is the most accessible and widely used technique to age date groundwater for palaeo-environmental studies. However, to obtain reasonable estimations of the age of a groundwater sample, hydro-geochemically corrected ages are preferred.

To successfully interpret the hydro-chemical evolution of a groundwater, the chemical analysis of water samples are undertaken using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for cations and trace elements, respectively, and Ion Chromatography (IC) for anions.

The stable isotopes of ¹⁸O, ²H and ¹³C_TDIC are also useful for identifying the presence of palaeo-waters and the source of Dissolved Inorganic Carbon (DIC) for radiocarbon correction modelling. These isotopes are analysed using Isotope Mass Spectrometry (IRMS).

Publications

A list of current publications can be found here.