Salinity problems have received increasing attention in recent years. This article addresses irrigation-related salinity in Australia's Murray River system. Analysis of these problems involves a number of issues which have so far received limited attention in discussions of salinity. These include farmers' incentives to adopt different land management practices and the structure of property rights. This article describes a model, based on concepts of common property, which has been developed to illustrate how different institutional structures can affect farm land use decisions and salinity-related problems. It is shown that open access solutions imply social welfare losses, and that procedures used in the past are likely to lead to underestimates of these losses.