Modelling the effect of environmental flows on riparian vegetation

The anthropogenic alteration of flow regimes through river regulation is having profound negative effects on riparian ecosystems worldwide (Webb et al. 2010b). Maintaining the integrity of river ecosystems is essential for the continual provision of ecological services to benefit the natural environmental and human uses. In South-East Australia, alterations to flow frequency for irrigation and water supply have disrupted native biota and resulted in a decline in ecosystem health. Riparian vegetation, in particular, supplies key ecosystem services and is sensitive to alterations in the natural hydrological regime. Managers are attempting to balance ecological needs through 'environmental flows'. However, there is little evidence supporting the effectiveness of this river restoration method (Lake 2001). Sound decision making for allocating flows is dependent on strong scientific evidence describing the causal relationships in the ecological system (de Little et al. 2012). This project used a rigourous process to promote the use of evidence-based synthesis and build evidence for causality between 'environmental flows' and native riparian vegetation abundance. This project aimed to build a Bayesian belief Network (BBN) to assist in the management of riparian systems in South-East Australia. Initially, causal linkages in a conceptual model, which described the relationships between flow and vegetation response, were defined through a causal criteria analysis in the form of a systematic literature review. The review found support for causal links between the frequency of high flow and an increase in condition. In addition, the review found an increase in over bank flows and an increase in germination, a decrease in woody adult mortality and an increase in herbaceous vegetation and woody seedling mortality. Some linkages showed suppor