ANSTO's research capabilities, led by the OPAL nuclear research reactor and associated instruments provide access to users investigating areas as diverse as materials, life sciences, climate change and mining/engineering.
Isotopes in the hydrological cycle
| Surface water sampling Gregory River, North West Queensland. |
ANSTO's ability to trace the movement of water using isotopic and nuclear techniques can help water resource managers make more informed decisions.
Shortcuts:
The water cycle, also known as the hydrological cycle, describes the movement of water above and below the surface of the Earth. As water changes its state (liquid, vapour, solid) and travels throughout the hydrosphere, isotopes can be used to record the chemical or physical changes.
Nuclear science offers a number of analytical tools and techniques that use changes in water isotopes to characterise water masses and trace their interactions and movement through the water cycle.
For example, water originating from monsoonal fronts feeding rivers and aquifers in the Gulf of Carpentaria will have different water isotopic signatures to rainfall in southern Australia (Climate Variability and Water Systems).
Similarly, groundwater contained in a limestone aquifer such as the Barkly Tablelands in the Northern Territory will be chemically and isotopically different to that found in a sandstone landscape, such as the Sydney Basin.
| Changes in bulk isotopic signatures through water. |
Nuclear and isotope methods are useful in regions where more traditional hydrologic tools give ambiguous results, or insufficient information.
This makes them valuable tools for water resources management. The understanding of water sources, is in many studies, only the first step. In areas, such as the Perth Basin, researchers within the group are studying how long the water typically takes to travel from surface to underground aquifers. This is called the water residence time or groundwater age.
In other environments, such as the Darling River Basin, researchers are interested in the reverse process where the groundwater is discharging into rivers and creeks, impacting water quality.
Knowing the groundwater flow path and groundwater recharge rates for a catchment is important in understanding water quality issues. This research helps resource managers make informed decisions about the effective management of water resources in Australia.
Research locations
| Main river catchments and study areas. |
From the Top End of Australia across to the arid interiors and around major catchments and cities, team members are working on several sites around Australia. Currently, the team is working on a project commissioned by the Western Australia Department of Water (DoW) to investigate groundwater resources in northern Perth and in the Pilbara region.
Another project involves a collaboration with the Department of Water and Energy (DWE) to investigate water residence times in the Sydney Basin and in areas of the Darling River Basin.
The group is also working with university and research institutions to investigate surface-groundwater connectivity in various locations across Australia, including Riversleigh (north-west Queensland), the floodplains of Cooper Creek (between South Australia and Queensland), the Wimmera region (Victoria) and the Namoi River catchment (NSW).
Research to better understand the relative importance of groundwater, catchment runoff and evaporation in surface water (rivers, creeks and reservoirs) is being carried out at a number of sites across New South Wales.
| Groundwater sampling near Lawn Hill NW-Queensland. |
Along the entire length of the Darling River, stable water isotopes are being use to identify evaporative losses and groundwater inputs to this stressed dryland river.
In collaboration with the NSW DWE and CSIRO, monthly stable isotope data has been collected and is being used to develop an isotope-enabled model of the river.
ANSTO's research in the Macquarie Marshes is using isotope tracers to investigate the degree of hydraulic connection between the ground and the surface waters, and to look at sources of water for riparian vegetation in a changing hydrological environment.
All these projects are important for integrated management of either surface or groundwater and in some cases for the linked management of surface and groundwater.
Instruments and processes
Researchers in this group rely on field-based information such as groundwater and surface water samples collected
from specific study areas.
| Collection of drill chip samples in the Sydney Basin. |
Correct collection, handling and preservation of samples are vital in ensuring appropriate results.
Team members use a range of specialised sampling equipment from submersible groundwater pumps to a truck mounted reel with dual inflatable packers for isolating a section of the borehole for discrete interval groundwater sampling. Pressure sensors built into the discrete interval sampler allow measurement of hydraulic conductivity for the selected interval.
Once samples are collected and submitted to ANSTO's laboratories, the team uses Isotope Ratio Mass Spectrometry (IRMS) to determine the ratio between a heavy and a light isotope of the same element in a number of molecules and elements (i.e. hydrogen, oxygen, carbon and nitrogen).
Naturally-occurring radioactive isotopes are vital, particularly the measurement of tritium (3H) by liquid scintillation and 14C by Accelerator Mass Spectrometry (AMS). These isotopes allow the researchers to determine ages based on the decay they undergo.
The results are generally complemented by detailed chemical analysis using more conventional methods, such as ion chromatography (IC), Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) and Induced Couple Plasma Mass Spectroscopy (ICP-MS).
ANSTO has developed a patented capability to measure the continuous variation in hydraulic conductivity and porosity in rock surrounding an open borehole. This method uses Prompt Gamma Neutron Activation Analysis (PGNAA) equipment to activate the surrounding rock with neutrons and analyse the gamma spectral emissions for different elements (i.e. H, Si, Cl, Fe and Al). A sensitive relative porosity is approximated by a ratio (H/H + Si), while measuring hydraulic conductivity requires the injection of a salt tracer, normally NaCl.
| Isotope Ratio Mass Spectrometry instrument. |
Other research areas
ANSTO is in a privileged position to contribute to improved definition and monitoring of sustainable groundwater extraction.
Radiocarbon and tritium age dating of groundwater carried out at ANSTO provides water managers with an independent tool to assess sustainable use of groundwater resources.
Crucial to effective management is knowing how quickly an aquifer is replenished, or recharged and a clue to this is the groundwaters age. Young groundwater indicates the recharge is rapid and derives primarily from rainfall.
Old groundwater indicates the recharge is slow, so usage has to be managed with particular care. ANSTO is using its specialist radiocarbon and tritium dating facilities to provide water managers with detailed water-age maps of aquifers throughout Australia.
Key contact
Dioni I. Cendon
Task Leader, Isotopes in the hydrological cycle
ANSTO Institute for Environmental Research
Locked Bag 2001 Kirrawee DC NSW 2232, Australia
Phone: +61 2 9717 3937
Email: Dioni.CendonSevilla@ansto.gov.au
Team members
- Chris Dimovski (Laboratory Technician/Biologist),
- Stuart Hankin (Geoscientist),
- Suzanne Hollins (Isotope Hydrology/Ecohydrology),
- Cath Hughes (Stable and Radiosotope Tracing/Hydrology),
- Karina Meredith (Hydrogeochemistry/Isotope Hydrology),
- Mark Peterson (Geoscientist), Chris Waring (Geoscientist).
Publications
A list of current publications can be found here