Using Hydrology to Target Salinity

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Groundwater Flow Systems

Background

The overarching objective of this work is: “To produce a framework and suitable outputs to ensure that funding and resources for salinity management is targeted towards appropriate management activities ”.

The Groundwater Flow Systems (GFS) component needs to be considered as part of a continuum of projects:

• National Classification of Catchments for Land and River Salinity Control (Coram 1998)
• Australian Groundwater Flow Systems Contributing to Dryland Salinity (Coram et al. 2000)
• Case studies from NLWRA and this project
• Monitoring through NLWRA and “National Dryland Salinity Data Infrastructure Project”
• MDBC “Tools for Dryland Salinity Management” project.

By the mid-1990s, it became necessary to consider the impact of dryland salinity in the MDB. A framework was required that included the variability of landscape response to land use, and recommended options for different parts of the landscape, with an assessment of salinity risk. Such a framework would have to include groundwater explicitly and a number of elements had already been developed by then. These included:

• Methods of breaking-up the landscape into approximately homogeneous units
• Regionally relevant catalogues of conceptual models
• Automated mapping techniques based on digital terrain models
• Case studies on some key catchment types.

The National Classification Project developed a nationally relevant catalogue of catchment types at risk of dryland salinity and suggested appropriate management options. The National GFS Project mapped broadly the distribution of these catchment types. It illustrated that the main groundwater flow systems amenable to dryland salinity impacts were limited in their range of remediation options. This was reinforced by the case studies especially for the deeply weathered pre-Cambrian.

Monitoring suggested that the current network needs to be better distributed according to groundwater flow systems and the landscape elements within these systems.

Objectives

• Produce a groundwater flow systems map specifically for the Murray-Darling Basin using higher resolution data than for the National classification
• For each region within Victoria, NSW and Queensland, hold workshops to facilitate the development of finer-scale GFS maps that encompass local knowledge
• For the widest possible range of mapped GFS, perform or summarise case studies of the historical spread and control of salinity and high water tables by land-use change
• Develop the theory of time responses of idealised groundwater systems, and test against numerical modelling.

Findings

• The MDB map shows relevant groundwater flow systems for the MDB consistent with the national groundwater flow systems map. This provides a framework for regional maps, reporting (Groundwater Status Report) and monitoring.
• The regional workshops have provided groundwater flow systems map at 1:250,000 scale. More importantly, the groundwater flow systems at the regional scale have filled a void for regional groups in providing a planning framework. There has been high adoption of groundwater flow systems by both regional and state groups.
• A number of case studies were added to those in the National Land and Water Resources Audit (NLWRA). The selected case studies appeared to be more responsive to land use change than those in the Audit, provided closer connection to streams and more prone to episodic events. Together with the NLWRA case studies, a wide range of groundwater flow systems have been represented. In looking for further examples, the project team found few examples where there was sufficient data to test the conceptual model.
• A dimensional analysis allowed groundwater time responses to be estimated that related to a wide range of catchments from small sloping upland catchments to flatter intermediate and regional groundwater systems.
• The FLOWTUBE model, previously been developed as part of the Liverpool Plains Project, was found to be suitable for most of the case studies. For the deep leads system, the model needed to be modified. Also, a sub-grids representation method was developed that enabled area of saline land to be estimated in some circumstances rather than area with water tables within 2 m. Under an NDSP project with the Agriculture WA, a more friendly user interface is being added and a series of workshops are being held on the model.
• Together with the associate projects, the groundwater flow systems framework provides an approach to deal with landscape variability.

Modelled salt generation rates in the Goulburn-Broken Catchments using finer detail GFS related data

Modelled salt generation change for the 100% tree scenario after 50 years

It is generally known that tree planting leads to a reduction in salt loads. These maps show that the reduction in salt load within a given time can vary considerably and not correlate well with total salt loads. Taken together with similar maps showing reduction in water yield, these maps can highlight the areas best suited for the cost-effective use of trees in salinity mitigation. The greatest risk is that the reduction in water is much greater than the reduction in salt load – a risk more likely to occur in the higher rainfall areas of the catchments.

Publications

Cresswell R, Dawes W, Summerell GK, Walker GR (2003) Assessment of salinity management options for Kyeamba Creek, New South Wales: Data analysis and groundwater modelling. CSIRO Land and Water Technical Report 26/03, CRC for Catchment Hydrology Technical Report 03/9, MDBC Publication 12/03, Murray-Darling Basin Commission, Canberra. (PDF, 3.3 MB)

Dawes W, Gilfedder M, Stauffacher M and Walker G. (2001) Salinity Case Studies of Australian Groundwater Flow Systems. in proceedings of Murray-Darling Basin Groundwater Workshop 2001, Victor Harbor.

Dawes W, Gilfedder M, Walker GR, Evans WR. (2001) Biophysical modelling of catchment scale surface and groundwater response to land-use change, in Proceedings of MODSIM 2001, Ghassemi F, Whetton P, Little R, and Littleboy M (eds.). Modelling and Simulation Society of Australia and New Zealand: Canberra; 535-540.

Dawes W, Gilfedder M, Walker GR, Evans WR. (2004) Biophysical modelling of catchment scale surface and groundwater response to land-use change. Mathematics and Computers in Simulation 64(1): 3-12.

Dawes WR, Zhang L, Smitt C (2004) Flow regime, salt load and salinity changes in unregulated catchments. CSIRO Land and Water Technical Report 14/04. CSIRO Land & Water: Canberra. (PDF, 1.2 MB)

Gilfedder M, Smitt C, Zhang L, Walker GR. (2001) Impact of increased in recharge on groundwater discharge: development and application of a simplified function using catchment parameters. in proceedings of Murray-Darling Basin Groundwater Workshop 2001, Victor Harbor.

Gilfedder M, Stauffacher M, Walker GR, Coram J (2002) Characterising Groundwater Flow Systems Using a Dimensionless Similarity Parameter, Proceedings of International Association of Hydrogeologists, International Groundwater Conference, 12-17 May 2002, Darwin NT; [published as CD ROM].

Gilfedder M, Smitt C, Dawes, WR, Petheram C, Stauffacher M, Walker GR. (2003) Impact of increased recharge on groundwater discharge: development of a simplified function using catchment parameters. CSIRO Land and Water Technical Report 19/03, CRC for Catchment Hydrology Technical Report 03/6, MDBC Publication 05/03, Murray-Darling Basin Commission: Canberra. (PDF, 1.2 MB)

Hekmeijer P, Dawes W (2003) Assessment of salinity management options for South Loddon Plains, Victoria: Data analysis and groundwater modeling. CSIRO Land and Water Technical Report 24/03, MDBC Publication 10/03, Murray-Darling Basin Commission, Canberra. (PDF, 2 MB)

Hekmeijer P, Dawes W (2003) Assessment of salinity management options for Axe Creek, Victoria: Data analysis and groundwater modelling. CSIRO Land and Water Technical Report 22/03, MDBC Publication 09/03, Murray-Darling Basin Commission, Canberra. (PDF, 3.7 MB)

Knight JH, Gilfedder M, Walker GR. (2002) Impacts of irrigation and dryland development on groundwater discharge to rivers: A unit response approach to cumulative impacts analysis. CSIRO Land and Water Technical Report 3/02. CSIRO Land & Water: Canberra; 23. (PDF, 352 kB)

Knight JH, Gilfedder M, Walker GR. (2002) Effect of a change in recharge on baseflow and salt loads to rivers - A unit response approach, Proceedings of International Association of Hydrogeologists, International Groundwater Conference, 12-17 May 2002, Darwin NT; [published as CD ROM].

Petheram C, Smitt C, Walker G, Gilfedder M. (2003) Testing in-class variability of groundwater systems: Local upland systems. CSIRO Land and Water Technical Report 21/03, CRC for Catchment Hydrology Technical Report 03/8, MDBC Publication 07/03, Murray-Darling Basin Commission: Canberra. (PDF, 883 kB)

Smitt C, Doherty J, Dawes W, Walker G (2003) Assessment of salinity management options for the Brymaroo catchment, South-eastern Queensland. CSIRO Land and Water Technical Report 23/03, MDBC Publication 08/03, Murray-Darling Basin Commission, Canberra. (PDF, 3.7 MB)

Stauffacher M, Walker G, Dawes W, Zhang L, Dyce P (2003) Dryland salinity management: Can simple catchment-scale models provide reliable answers? An Australian case study. CSIRO Land and Water Technical Report 27/03, MDBC Publication 13/03, Murray-Darling Basin Commission, Canberra. (PDF, 1 MB)

Smitt C, Gilfedder M, Dawes, WR, Petheram C, Walker GR. (2003) Modelling the effectiveness of recharge reduction for salinity management. CSIRO Land and Water Technical Report 20/03, CRC for Catchment Hydrology Technical Report 03/7, MDBC Publication 06/03, Murray-Darling Basin Commission: Canberra. (PDF, 1.1 MB)

Walker GR, Gilfedder M, Evans WR, Dyson P, and Stauffacher M (2003) Groundwater flow systems framework – essential tools for planning salinity management. MDBC Publication 14/03, Murray-Darling Basin Commission: Canberra, 40.

Walker GR, Gilfedder M, Evans WR, Dyson P, and Stauffacher M (2003) Groundwater flow systems framework – essential tools for planning salinity management – Summary Report. MDBC Publication 15/03, Murray-Darling Basin Commission: Canberra, 6.

Smitt C, Gilfedder M, Dawes W, Petheram C, Stauffacher M, and Walker G. (2001) Modelling the Effectiveness of Recharge Reduction for Salinity Management: Preliminary Results for Sensitivity to Catchment Characteristics. in Proceedings of Murray-Darling Basin Groundwater Workshop 2001, Victor Harbor.

Permission to publish CRC-CH Technical Reports granted by David Perry for the CRC-CH