Produced through the Ecological Responses to Altered Flow Regimes Flagship Research Cluster
Kingsford, R.T., Watts, R.J., Koehn, J.D., Thompson, R.M. & Sims, N.C. (eds)
Flow regimes define the character of a river and its dependent ecosystems and their characteristic biota and driving processes. The size, frequency, timing and duration of flows and their associated floods provide the template for understanding the responses of different organisms and dependent processes at all the different spatial and temporal scales associated with a river. Periods of low flow are also important restructuring phases in the organization of freshwater ecosystems (Lake, 2000b, Lake, 2003). Freshwater ecosystems are highly dependent on the full range of flows from large structuring floods (booms) to the periods of low to no flow (bust) as well as flows in between which trigger a subset of process and responses from dependent organisms (Kingsford et al. 1999; Bunn et al. 2006).
High flows and floods can trigger the germination of aquatic plants and emergence of invertebrate biota (Brock et al. 2006; Boulton et al. 2006). These form the food web for higher order organisms such as frogs, fish species and waterbirds which can occur in large abundances, particularly in wetlands, following large flooding. Floods which move across the floodplain connect different parts of the river, allowing for the movement of invertebrates and fish which colonise highly productive aquatic habitats on the floodplain. These integrated processes are critical to the entire food web, linking the many different dependent organisms and processes operating at longitudinal and lateral dimension on the river. Humans have disrupted all of these processes, particularly through the building of dams, extraction of water and development of structures on floodplains that alter flow connectivity across floodplains (Kingsford 2000; Bunn and Arthington 2002; Arthington and Pusey 2003; Steinfeld and Kingsford 2012). Flow regulation changes the flow regime across a range of temporal and spatial scales
Specifically, this relates to effects on the size, timing, frequency and duration of specific flow events. The effects of flow regulation vary among systems and may include reductions in average or event-specific discharges. River regulation may also change in the frequency, duration and timing of specific flow events such as floods, cease-to-flow periods or in-channel flow pulses. Such changes are widespread across rivers of the Murray-Darling Basin, which has a long history of river regulation. In recent years, governments have invested in the buyback of water to provide environmental flows across the Murray-Darling Basin with the aim of restoration of ecosystems as well improving planning and management frameworks. Such restorative actions will be effected through mechanisms such as the Murray-Darling Basin Plan, its watering strategies and water sharing plans. There is increasing need to focus on effective ways of measuring the impacts of different management approaches on ecosystem responses in freshwater ecosystems.
To maximize the value of this research we chose to focus our efforts on systems where there was already substantial scientific knowledge amongst the project team, which capitalised on available long-term data on existing knowledge of the organisms and processes operating at each site. This provided more explanatory power over the high variability experienced by rivers and wetlands, thereby increasing our ability to quantify relationships among the considerable spatial and temporal variability always encountered in freshwater ecosystems. Consequently, the research focus was on four major research areas in the Murray-Darling Basin including one in-channel system, the Edward-Wakool river systems and three floodplain systems; the Macquarie Marshes, the Lowbidgee wetland and the Barmah-Millewa Forest, each respectively supplied by the Macquarie River, the Murrumbidgee River and the River Murray.
The project derived specific conceptual models for each of the organisms and processes investigated in these regions. While these organisms and processes are inextricably linked to one another through river flows and flooding conditions, they can be conveniently defined spatially in terms of (i) in-channel, and (2) floodplain and wetlands.
For the full report Kingsford-et-al-2014-Flow-dependent-ecological-responses-lo-res (October 2014)
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