research program 4
salinity mapping and hazard assessment
Salinity Dynamics
The dynamics of salinity in Australia: origins, mobilisation and transport of salt in the Australian regolith and reponse times relating to salinity
Project Leader : Richard Cresswell, CSIRO Land and Water
Start date and duration: 1 July 2005 to end December 2007
Participants : CSIRO Land & Water, Geoscience Australia , Australian National University
Brief project description :
- This project investigates the physical, chemical and environmental factors influencing salt mobilisation in an Australian regolith context.
- Integration of salt mobilisation understanding into a broad landscape and climatic context.
This project aims to determine quantitative parameters that address system response times in salinity-prone environments. The following specific questions will be addressed by the project:
1. What is the origin of the salt?
This question will be addressed on 3 fronts: isotopic studies ; rainfall chemistry studies and through chemical modelling in the unsaturated zone.
2. How does saline water and salt interact with regolith materials?
This will be addressed through geochemical modelling; lysimeter experiments and chemical equilibrium, determined through CEC and XRD analysis
3. How and how fast is it mobilized?
Basic hydraulic properties of regolith materials will be determined through field pump tests and laboratory analysis (porosimetry, x-ray tomography, permeability test, etc) on samples collected from drill cores. Isotopic studies will help elucidate timeframes for mobilisation and components of the mass balance equations.
4. Where and at what rate is it transported?
Landscape analysis, hydrology and hydrogeology models will be used to characterise different terrains and model the 3D spatial variability in salinity mobilisation using the parameters determined in 3. Climate as a driver will be examined in well-characterised catchments and the effects of land-use change evaluated.
To date, salinity parameters have been largely semi-quantitative. Working constructs, such as groundwater flow systems provide a targeting approach for more detailed studies, but generally involve poor integration of sub-surface regolith constraints. The continuing MDBC-funded project is attempting to redress this issue, but requires quantification of parameters such as hydraulic conductivity, transmissivity, permeability, specific yield and porosity that are specific to regolith materials, particularly where these materials act as groundwater hosts. This information is required at micro- macro- and regional scales.
Water transport properties for the regolith are vital components of transport models, and require detailed quantification. The interaction and ionic exchange of salts, particularly at high salinities, is also critical when deducing potential end-of-valley salt loads and correlating standard electrical conductivity measurements to actual salt impact. Hydrochemical studies aimed at elucidating the transport of salts within, and through, the regolith, are also fundamental to this project. This also links to projects under Programs 1, 2 and 3.
Climate trend analysis will be integral to the development of salinity risk maps (e.g. through 2Csalt) and will, therefore, come under the scope of this project.
Deliverables (outputs) and expected impacts of research (outcomes):
Scientific Deliverables
- Rainfall chemistry evaluated and assessed for salt accession (Oct-06)
- Geochemical modelling incorporated into a groundwater flow systems framework (Dec-06).
- Integrated look-up tables of hydrogeological parameters pertinent to groundwater modelling in regolith dominated environments (Dec-07).
- Salinisation response times determined through a combination of geochemical and isotopic tracers and modelling (Auf-07).
- Report documenting salinity mitigation products in Qld catchments (eg Hodgsons Creek) (Dec 07)
- An assessment of salinity dynamics and processes in MDBC project areas (Jul 07)
Deliverables to Client (Adoption mechanisms)
- 3D hydrogeological and hydrogeochemical frameworks for modelling of key NRM areas (Jun-07).
- Rainfall/hydrograph analysis tool (Dec-07).
- Integrated look-up tables of hydrogeological parameters pertinent to groundwater modelling in regolith dominated environments (Dec-07).
- Journal papers, Technical Reports and Open File Reports
- Communication of results through conferences, workshops and literature
Outputs
- Journal papaers, Technical reports and Open File Reports
- Papers presented at National and International Conferences
- Coordinate special session on Salinity Processes and Dynamics at International Salinity Forum
- Salinity Dynamics Thematic Volume (Journal Volume or Monograph)- ISF08 link.
- Communication of results through conferences, workshops and literature
Outcomes
- Improved understanding and assessment of salinity risks and response.
- Consolidation of research on the age, origins, distribution and mobilisation of salts in the Australian regolith.
- Integration of chemical processes into salinity delivery mechanisms.
- Adoption of novel techniques (e.g. airborne geophysics, regolith characterisation) into salinity management procedures and modelling exercises
- Establishment of hydrogeological dynamics (response times of a system) to changes in land-use and/or climate change
- Demonstration of the relevance of regolith and geophysical information to decision support systems for land management of salinity
- Incorporation of regolith-specific M&E for salinity miti ga tion and amelioration
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