Integrating environmental flows into regulated river systems

The global decline in freshwater ecosystem health has prompted governments to return water to rivers to restore natural flow regimes. Adequate volume, temporal variability and spatial connectivity of flows are essential requirements for maintaining freshwater ecosystem integrity. However, a major challenge is integrating environmental flow requirements into regulated river systems historically managed for water supply and flood mitigation. In my thesis, I aimed to: (1) evaluate operational opportunities and challenges for the allocation, release and delivery of environmental flow in regulated rivers; and (2) support environmental flow management capacity building through decision support tools and techniques. I focused on two inland river systems in Australia's Murray-Darling Basin, the Gwydir River and the Macquarie River, where unprecedented environmental water investment aims to rehabilitate degraded semi-arid floodplain wetlands of international significance: the Gwydir wetlands and the Macquarie Marshes. Chapter 1 provides an overview of the global importance, progress and challenges of integrating environmental flows into regulated rivers. Chapter 2 outlines the development and application of a long term daily decision support tool for explicit simulation of environmental water allocation and flexible specification of water management rules. Chapter 3 demonstrates the importance of management and biophysical factors in influencing long term availability of environmental water. Chapter 4 examines operational implications of different environmental water release strategies, illustrating the need to include operational opportunities and risks together with ecological outcomes in a strategic environmental watering planning framework. Chapter 5 examines techniques for efficiently and effectively identifying floodplain earthworks built for irrigation and flood mitigation which often fragment spatial flow connectivity and interrupt delivery of environmental flows to target floodplain assets. Results demonstrated that semi-automated Geographic Information Systems techniques were an effective and efficient alternative for large scale earthwork detection compared to traditional visual interpretation. Chapter 6 synthesizes the research presented in my thesis and suggests directions for future research towards a transparent, systematic and adaptive approach to decision making in river systems progressing towards sustainable integrated water resource management