Impacts and implications of farm dams on catchment hydrology: Methods and Application to Chaffey Catchment.

In the last twenty five years, numbers of farm dams have increased significantly in response to changing land use and land management strategies. However, teh construction of large numbers of dams ina catchment impacts on water resources in a number of ways, in particular, by reducing streamflow. Consequently, other uses of water downstream of dams, including environmental, may be compromised. Because the impact of farm dams on the hydrologic regime have widespread environmental and socio-economic ramifications, future development needs to be assessed in legislation and policies supported by sound scientific monitoring and analysis. Examinationof the legal/policy context indicates that it does not specifically address the environmental impacts of farm development, nor are there measures in place to establish, monitor and control relevant water allocations. A project funded principally by the Murray Darling Basin Commission aims to study 25 catchments within the Murray Darling Basin which have experienced significant dam development. Modelling the water balance in the catchments involves a 'before and after' approach to dam development to assess the downstream impacts of farm dams, especially on low flows across a range of climatologies and landscapes. The description and analysis of results from an initial catchment defines part of hte methodology for this project and provides some indicative results.

Figure 3: Model changes in discharge between adjacent period