Using Hydrology to Target Salinity

Using Groundwater Flow Systems (GFS) and top-down hydrological approaches to target salinity mitigation measures in the Murray-Darling Basin

Understanding groundwater flow systems is critical to salinity management as the Australian landscape is highly variable - and what works in one area may not work for another.

Recognising this, the project team started developing maps of groundwater flow systems in the Murray-Darling Basin (MDB), highlighting differences and pinpointing where they occur in the landscape. A series of case studies followed, providing ‘real world examples’ of how to plan salinity management actions with an awareness of the underlying hydrology.

Models have now been developed to assist in this planning process, so that regional groups and catchment managers can look at maps and then ‘play’ with different management actions, with an appreciation of what the trade-offs might be.

The researchers were also keen to identify other (potentially unforeseen) impacts of salinity management actions and land use change such as revegetation or large-scale forestry plantation. Impacts can extend to water resources and catchment water yield. Tools such as BC2C allow both resource issues to be considered at the same time.

Most of the catchment groups in the Eastern MDB are already using the maps and models as part of the planning process.

• Objectives and Research Areas
• Key outputs
• Staff
• Collaborators

Objectives

D2013: To predict the regional scale impacts of afforestation and other land use changes on mean annual and seasonal catchment water yield, groundwater recharge, and stream salinity.

D9004: To produce a framework and suitable outputs to ensure that funding and resources for salinity management is targeted towards appropriate management activities.

The research effort that has gone towards meeting these objectives can be broken down into four distinct areas:

• Impacts of plantation forestry on mean annual water yield
• Impacts of plantation forestry on the flow regime
• Groundwater flow systems
• Impacts of land use change in non-irrigated upland catchments on stream salinity and salt loads

Key Outputs

• Zhang Curves: A robust and internationally recognised method of estimating mean annual water balance components from annual rainfall and percentage native cover, developed using data from over 300 catchments worldwide. Refer Impacts of plantation forestry on mean annual water yield and see specific publications Zhang L, et al. 2001, Zhang L et al. 2004.
• Best Method: A promising method of estimating the change in percentiles of the flow duration curve following land-use change. Capability has been demonstrated with integration into applications of river planning models such as REALM and IQQM. Refer Impacts of plantation forestry on the flow regime and see specific publication Best AE, et al. 2003.
• GFS Maps: Maps of the distribution of groundwater flow systems have been developed at a Basin scale, and also for upland areas within the Murray-Darling Basin. Refer Groundwater flow systems.
• GFS Case Studies: Including National Land and Water Resources Audit (NLWRA) case studies, we now have nine GFS case studies, which encompass conceptual models, quantitative modelling and management recommendations. Refer Groundwater flow systems
• Salinity planning framework: The GFS provides a framework for salinity planning, by defining relatively homogenous areas, their management options, associate concept models, a method for stratifying monitoring, and more importantly a common language across all levels of natural resource management (NRM). There have been high levels of adoption of this approach by Regions and States across the Murray-Darling Basin (MDB). Refer Groundwater flow systems and see specific publication Walker GR, et al. 2003
• Three store model: A preliminary model has been developed to better represent salt balance in the longer term. There will be further development of this approach in the CRC Catchment Hydrology 2C (salt mobilisation) project. See Impacts of land use change in non-irrigated upland catchments on stream salinity and salt loads
• Groundwater Response times: Theoretical development of the time response of groundwater systems to a charge in recharge regime. The methodology uses the GFS mapping, and the data derived from the GFS workshops. Refer Impacts of land use change in non-irrigated upland catchments on stream salinity and salt loads and see specific publication Gilfedder M, et al. 2003.
• BC2C: A robust broad-scale tool for prioritising upland catchments by quantifying the change in water and salt balance with current and proposed land use scenarios. This tool is based on the Zhang Curves, GFS data layers, and the G-parameter. There have been extensive applications of BC2C in Victoria, NSW and Queensland for both tree planting and tree clearing scenarios. Refer Impacts of land use change in non-irrigated upland catchments on stream salinity and salt loads and see specific publication Dawes W, et al. 2004.

Staff

Glen Walker, Lu Zhang, Mat Gilfedder, Warrick Dawes, Trevor Dowling, Jenet Austin, Alice Best, Klaus Hickel, Matthew Stenson

Collaborators

Ray Evans (Salient Solutions), Phil Dyson (Dyson and Associates), Peter Hekmeijer (DPI), Greg Summerell (DIPNR), Peter Baker (Bureau of Rural Sciences