The effects of water resource development and changes to flow regime are not uniform across the Murray-Darling Basin. The Cluster has produced a basin-scale classification and mapping of freshwater ecosystems and assessed how these ecosystems have been affected by water resource development and land use change. • Impacts to freshwater systems are not only due to flow regulation and the impact of large dams – bores, farm dams and levees are a significant issue in many parts of the Murray-Darling Basin. The Cluster has mapped these threats at the basin-scale and quantified the proportion of each freshwater ecosystem that may be affected. • While multiple stressors impact freshwater ecosystems, flow alteration is a major driver of observed changes and these changes can be addressed through provision of environmental flows. The Cluster has refined optimization modelling to give greater confidence in the delivery of environmental water to achieve the best outcomes and address important aspects of the flow regimes (seasonal flow reversal, low flows, high flows and floodplain inundation and flow pulses). • Environmental flows from held environmental water will not address all of the flow-related threats to freshwater ecosystems in the Murray-Darling Basin. The Cluster has estimated the proportion of each type of aquatic habitat that can be watered from regulated river flows and the impact this is likely to have on key aquatic species. • Monitoring the success of environmental flow interventions has proven to be a major challenge. Work within the Cluster has identified robust indicators that are responsive to flow alteration. These will prove useful in measuring success of environmental watering in the future.