The role of hydrological modelling has not been more critical than in the current, but evolving, climate of water planning, in which water dependent eco-systems, in addition to human consumptive needs, are considered a key stakeholder. This is reflected in the policy and legislative frameworks at both national and state levels and is at different stages of implementation ex. the River Murray Basin Plan preparation at a national level and regional and catchment water allocation and management plans at the state levels. Establishing environmental water requirements and attempting to provide for them explicitly has since become a necessity to meet hose legislative requirements. Hydrological modelling has been adapting to this change, from its traditional and more quantitative and definitive areas of water engineering, to addressing these recent needs of reflecting the flow regime aspects of environmental water requirements. There has been a large number of innovative and high quality scientific work and modelling work undertaken internationally and nationally. South Australian organisations, like the Commonwealth and other States, has, in the recent past, undertaken extensive scientific investigation and modelling exercises that have played a critical role in framing policies that have implications to water planning and management at a state and national level.