A framework for integrated hydrologic, sediment and nutrient export modelling for catchment-scale management

Many catchments in Australia have experienced increased sediment and nutrient loadings and concomitant declines in water quality and increases in problematic blue–green algal blooms over the past several decades. This paper describes an integrated hydrologic, sediment and nutrient export modelling framework known as catchment-scale management of diffuse sources (Catch- MODS). The modelling framework is designed to simulate and assess catchment-scale land and water management activities designed to reduce nutrient and sediment delivery to receiving waters. The Ben Chifley Dam Catchment in New South Wales, Australia is used as a case study for describing the development of the framework. Improving water quality through reduction of sediment and nutrient loads will reduce the probability of algal bloom occurrence in the dam. The innovation of the system is the integration of otherwise separate modelling approaches to enable biophysical and economic assessment of different management options. The outputs from the research are used to improve and focus on-ground remediation, targeted to specific stream reaches or subcatchment areas, as well as to encourage sustainable management practices more broadly in the catchment. With minimal modification, the methods developed are applicable elsewhere to address water quality decline.