Impact of land-use change on water and salt export from upland areas: using the BC2C model as a prioritisation tool.

Changes in land-use in Australia associated with clearing of native vegetation and its replacement with agricultural development over large areas have altered land and water salinities in rivers. For salinity management purposes, the impact of possible land-use actions on catchment water and salt export need to be estimated. This is in terms of the trade-offs between salt load and water yield impacts, estimating any time delays between making a change to land-use, and realising an impact in water and salt export to streams. The Biophysical Capacity to Change model (BC2C) was developed in recognition that the application of a simplified tool to assess the prioritisation of catchments was a necessary early step in catchment planning exercises. BC2C uses topography to disaggregate the study area into groundwater response units. A simple and robust mean-annual water balance is used, with groundwater flow systems information (GFS) used to provide parameters needed to estimate the spatial variability of inherent groundwater time delays. BC2C is intended as a catchment scale prioritisation tool for predicting likely impacts of land-use changes, and to help identify locations for more detailed modelling or on-ground monitoring.