2CSalt requires the following spatial data.

1. A digital elevation model (DEM) with a resolution of 250m or smaller (100m recommended). 2. Groundwater Flow Systems (GFS) map containing aquifer depth (m), groundwater salinity (uS or mg/l), specific yield, positive water level (m) and hydraulic conductivity (m/day) 3. A soils map of the catchment 4. A map of climate zones in the catchment 5. A land use map of the catchment For each combination of climate, soil and land use, 2CSalt requires the input of monthly timeseries of surface runoff, subsurface lateral flow, recharge and evapotranspiration. These are sourced from the CRCCH Industry Partners unsaturated zone modelling and will become available for download as 2CSalt is progressively rolled out across the upland areas of the Murray-Darling Basin. Numerous unsaturated zone models are being used in eastern Australia to explore the impacts of land use change at a paddock or landscape unit scale. Rather than forcing a user to use a single unsaturated zone model embedded within 2CSalt, a user has the flexibility of importing output from their preferred model (will require simple reformatting of model output into 2CSalt input format). 2CSalt can then be applied to extrapolate from a paddock scale to whole of catchment impacts using output from any unsaturated zone model. To apply 2CSalt in areas outside the Murray Darling Basin requires extensive data preparation. This would require the input of data and knowledge from a team of hydrogeologists, soil scientists, hydrologists and water balance modellers.

At the catchment outlet the model outputs a monthly timeseries of stream flow (m^3) and stream salt (kg).

For each spatial unit in a catchment, 2CSalt outputs monthly timeseries of:
- total runoff, subsurface lateral flow, evapotranspiration and recharge from hillslope and alluvial areas
- current storage volume, discharge and surface overtopping from the hillslope and alluvial aquifers
- salt export to stream from surface wash-off, subsurface lateral flow, aquifer discharge and aquifer overtopping from the hillslope and alluvial aquifers
- stream flow and stream salt loads at the catchment outlet

Extreme caution is advised in using output from individual spatial units as 2CSalt was designed to provide catchment scale predictions. Output can be viewed as summary files, time series graphs, maps, videos of time sequences of maps and exported comma separated files

2CSalt has a restricted geographical focus. It was designed for predicting salt movement from upland catchments in the Murray-Darling Basin. It models salt export at the catchment outlet only. It is not applicable for use in catchments where hydrology is dominated by regional groundwater flow processes. The model only simulates pathways of water or salt movement within a catchment in a semi-distributed way. It will not simulate explicit pathways of water and salt through landscape elements.

2CSalt predicts the impacts of land use on stream flow and salt load at the catchment outlet. Land use changes can be spatially explicit within a catchment to capture the spatial variability of topography, climate, soil type and aquifer properties. However, 2CSalt does not simulate the impacts of land use change on adjacent areas to the land use change.

Another assumption of 2CSalt is that it uses surface terrain modelling to define groundwater response units. That is, it assumes that all groundwater hydrology processes are reflected in surface topographical features.

2CSalt is dependent on the input of some data layers that are limited to the Murray-Darling Basin, such as the Groundwater Flow Systems mapping of the basin at a scale of 1: 250 000. Since 2CSalt was specifically designed for use by CRCCH Industry Partners within the Murray-Darling Basin, its dependence on specific data, may make the model difficult to set up in other geographical areas.

The major limitation in setting up a 2CSalt model for a catchment is the dependency on unsaturated zone modelling obtained from the CRCCH Industry Partner modelling frameworks (e.g. Beverly et al. 2003, Littleboy et al. 2003, and Owens et al. 2003). The unsaturated zone models partition rainfall into surface runoff, subsurface lateral flow, recharge and actual evapotranspiration.

As such, 2CSalt is not a traditional stand-alone model but is rather an integrative tool that analyses existing paddock-scale unsaturated zone modelling to a whole-of-catchment prediction. For each combination of climate, soil and land use attributes in the climate, soil and land use maps, 2CSalt requires the input of monthly time series of surface runoff, subsurface lateral flow, recharge and actual evapotranspiration. These are imported as ASCII files referred to as data cubes.