Mapping and modelling

Mapping

A range of data sets and mapping products have been produced that are relevant to salinity management, including maps of:

These maps are derived using direct field observations and data modelling techniques.

Modelling

Modelling is used to fill information gaps where data is limited or to add value to data by combining it in ways that represent processes that are otherwise not directly mappable. For example, it is not possible to directly map the extent of salinisation in 2050, but by using a model that represents the processes of dryland salinisation, it is possible to extrapolate from existing spatial data to make predictions about future condition.

To manage salinity in a catchment we need to know:

  1. Where and how much salt is stored in the landscape
  2. How salt and water moves in the landscape
  3. How the geology and structure of the landscape contributes to the problem
  4. What affects the rate of movement of salt
  5. How changing something in one location affects the rest of the catchment or basin.

Computer-based modelling tools also support natural resource management by enabling different management options to be explored and evaluated, or to allow data to be extrapolated in time and space when limited data is available. A suite of models make it possible to:

  • evaluate where salinity is currently occurring in the landscape and where it might occur in the future
  • predict the impacts of land use changes on run-off, salt loads and salinities from catchments to streams
  • evaluate the contributions of these changes to meeting within valley and end-of-valley targets.

The models provide information needed by regional bodies to develop target-based management strategies. They provide practical scientific and technical support on biophysical aspects of salinity management for property and catchment planning. This includes the setting, reviewing and auditing of end-of-valley and within valley targets, and the development and accreditation of Catchment Action Plans, and  salinity interventions at a landscape scale.

Models will collectively provide information at the three scales relevant to implementing salinity management in NSW, which are:

  1. The property or farm scale
  2. The scale of catchments up to about 2,000 km2 in area
  3. The river basin scale.

At the property scale the main modelling tool being adopted is PERFECT, which is a well-established tool for modelling recharge and the impacts of vegetation changes on recharge, at a given location.

Catchment scale-modelling tools can predict the effects of land-use change on streamflows, in-stream salinities and salt loads at catchment scale. A range of different catchment scale models have been either developed or applied in NSW.

  • CATSALT has been developed and applied across upland catchments of the Murray-Darling Basin to predict the effects of land-use changes on streamflows, in-stream salinities and salt loads at catchment scale. It is an 'umbrella' model in that it uses outputs from other models such as FLAG and SMAR to produce its results.
  • 2Csalt was developed in collaboration with CSIRO and the Victorian and Queensland state governments as a modelling tool to provide a consistent methodology for salt mobilisation modelling for State reporting under Murray-Darling Basin reporting arrangements. In NSW, it has been applied in the 2008 Salinity Audit update (PDF 3.13MB). It has also been used  for coastal catchments as part of the CERAT risk assessment tool to help identify and prioritise land use planning decisions to protect and preserve the health of coastal estuaries.
  • CLASS is a distributed eco-hydrological modelling framework. CLASS predicts land-use impacts at paddock, hillslope and catchment scales. It can be used for modelling water balance, solute balance, vegetation growth, recharge-discharge dynamics, lateral flow and streamflow.
  • CATPLUS is an extension of the Catchment Analysis Tool (CAT) developed by the Department of Primary Industries Victoria and the former Cooperative Research Centre for Plant-based Management of Dryland Salinity. The model predicts the impacts of various land-use scenarios on dryland salinity and enables enhanced prediction of catchment water yield and salinities to stream. It uses a range of farming system and forest growth models to determine catchment water use, recharge and quick flow. In NSW, CATPLUS has been applied in NSW in the Tarcutta Creek Catchment in the Murrumbidgee Valley (PDF 2.36MB).

Results from catchment scale models can then be used as input to other models, such as IQQM, to evaluate cumulative impacts from multiple catchments and contributions to meeting within-valley and end-of-valley targets. IQQM was developed to manage water access and water sharing arrangements within catchments, but is currently being further developed to estimate the impacts of land use changes on end-of-valley targets.

Page last updated: 15 June 2015