Oral Presentation Australian Society for Limnology Congress 2013

Around the world governments are making huge investments in environmental flows. However, much of the rationale for these releases is based on expert opinion, which is non transparent and can be challenged. Radically different approaches are required to inform the development of general predictive models of ecological response to flow alteration. Here, we describe such an approach, which attempts to make best use of all the information available from the literature, experts, and monitoring data to inform the development of general quantitative response models. We illustrate the process using the example of terrestrial vegetation encroachment into regulated river channels. Environmental flow assessments frequently propose that flow releases can be used to remove this vegetation. However, the evidence for these predictions has not been rigorously tested. Our analysis of literature, experts, and a purpose-designed monitoring data set of nearly 10,000 points, found strong evidence that increased inundation duration reduces terrestrial vegetation within river channels. Predicted cover dropped rapidly towards 0% with relatively short inundation period (e.g. 50 days) for most sites. However, dividing the same total inundation period into several separate inundation events reduces its effectiveness. More importantly, the model allows us to make quantitative predictions of vegetation cover under different inundation scenarios. While our project is focused on demonstrating that the Victorian environmental flows program has been a sound investment of public funds, our results also have the potential to be incorporated into planning and decision-making processes, helping to drive a transformation in evidence-based practice for environmental flow management.