Reform to the Australian water industry has received considerable attention in recent years. This can be partly attributed to growing community concerns about environmental degradation, increasing competition from extractive water users and greater focus by governments on micro-economic reform. One of the key reforms shared across a number of States is the implementation of the Murray-Darling Basin Commission’s Cap on irrigation diversions. In recent years, the Cap for the Barwon-Darling River has been exceeded and there is pressure on the NSW Government to address the situation. The purpose of this paper is to review some of the issues associated with Cap implementation in the Barwon-Darling River and to discuss the methodology being used to assess the farm level economic impacts of alternative options proposed to achieve Cap. The paper provides an overview of alternative approaches to achieve Cap, the development of representative farm models to assess agricultural effects and a description of some preliminary results of our analysis.