BC2C is a conceptual mass balance model designed to simulate the long-term average salt and water yield of whole catchments. The catchments should be unregulated, that is man-made structures and flow manipulation should not greatly impact on the actual stream flow, and they should be large enough that all rain falling within the boundary is discharged to the surface or stream within the same boundaries. BC2C is aimed at a catchment or sub-catchment scale, not at an enterprise/farm scale.

BC2C is a rapid assessment tool designed for state extension officers, catchment management groups and planners, policy staff and managers in consultancies and state, regional and local government agencies.

BC2C is fast to run, and designed to be simple to use by a range of people. It does however require knowledge of the processes affecting the flow of water through catchments, along with some supporting data to assist in fitting the model. BC2C can be run with a user-friendly interface that allows changes to surface vegetation to be reflected in water and salt yield over time. A GIS version is also available when greater control of parameters is required, or a more detailed description of the spatial patterns is required.

BC2C has wide applicability within Australia, but has been used mainly within the Murray-Darling Basin. The areas of application have included:

• Prioritising catchments for salinity benefits in the Goulburn-Broken, Victoria
• Searching for areas with a potential downstream salinity benefit if converted to commercial tree plantations, ACT
• Determining the scale of impact of tree planting in the Little River, NSW
• Assessing the salinity impact at Morgan of tree planting across the uplands of the Murray-Darling Basin

BC2C is a rapid assessment tool, and therefore it has certain features and associated limitations. It readily allows a user to get a feel for the current situation in terms of water and salt yield, and the relative differences that can be made by changing the percentage of tree cover within individual sub-catchments of the catchment. Far from being an end point, this quickly allows the user to decide where further investigation is warranted, and those areas for which vegetation manipulation will not produce the desired results.