The ecological outcomes of the Murray-Darling Basin (MDB) Plan (the Basin Plan) will depend upon the effective provision of environmental water (e-water), which is also likely to enhance the indigenous values of the MDB. As part of the Basin Plan, South Australia’s Department of Environment, Water and Natural Resources (DEWNR) is required to develop a Long-Term Watering Plan and annual priorities for e-water, to be considered during e-water allocation planning by e-water holders. However, because climatic and hydrological conditions continuously change, real-time management decisions are also required. To be effective, all three levels of decision making (long-term and annual planning, and delivery) must be underpinned by the best available science, with a capacity to incorporate new knowledge.