Office for Environmental Programs - Theses

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End date: 2012 × Subject: Water management × Subject: Environmental flows ×

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    Modelling the effect of environmental flows on riparian vegetation
    Wand, Joanna Elizabeth Marion ( 2012)
    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 support
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    An assessment of environmental risks of using recycled water to create environmental flows in the Werribee River, Victoria
    Ewert, Jamie M. ( 2004)
    Recycled water created from highly treated sewerage is now considered a viable water source for selected, appropriate uses. One potential use is to create environmental flows in stressed rivers if this is a low risk and low cost option. To evaluate these risks, a case study is investigated using the degraded Werribee River, Victoria. Environmental flows could be supplied to the river from the nearby Western Treatment Plant. Risks are identified using the judgement of river and water management experts and are evaluated using conceptual models and a Bayes network. Key risks investigated include risks to human health (gastroenteritis and arbovirsus infection) and risks to environmental health (blue-green algae blooms). Results show that these risks already exist to some degree but are unlikely to increase if recycled water is used to create environmental flows. While the creation of environmental flows with recycled water creates opportunities for health risks to increase, the risk is limited by low numbers of infected hosts. Blue-green algae risks are already high as the river currently exceeds nutrient guidelines. Adding more nutrients will not increase this risk and interestingly improving stream flows using saline recycled water will prevent blue-green algae accumulation, actually decreasing the risk.