Abstract
The Snowy River in southern Australia has been impacted by flow diversion since the construction of a dam in the upper catchment, constructed between 1955 and 1967. As part of a monitoring program the effects of two flow releases were studied in 2010 and 2011. The estuarine component of the monitoring and the estuarine modelling phase of the Snowy River Increased Flows Program has been presented. The impact on the estuarine salinity distribution for the selected flow releases is reported and a subsequent modelling exercise outlined. A simple numerical model has been used to simulate about 100 events in a mature barrier estuary, from which a sequence of response types has been identified. The occurrence of each response type has been related to the duration, inflow volume and peak flow rate of the inflow event and to relevant parameters of the estuary. It has been found that the salinity changes may be classified in terms of a dimensionless "estuary flushing parameter" E, which represents the ratio of the direct flushing by the river inflow to the tidal exchange.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/76fefltUCro
Highlights
The recognition that water flowing from catchments to the sea should not be regarded as a “loss”, but rather, an integral component of ecosystem function in rivers and estuaries has been a relatively recent development
Recent advances in the development of environmental flow regimes have incorporated the idea that flow releases should attempt to mimic the natural pattern of stream discharge before regulation, but with reduced flows
Determining the impact of these reduced flows on the receiving waters is an important component in the development of any Environmental Flow Releases (EFRs) method
Summary
The recognition that water flowing from catchments to the sea should not be regarded as a “loss”, but rather, an integral component of ecosystem function in rivers and estuaries has been a relatively recent development. While environmental flows were initially viewed simplistically as a low river flow, below which significant changes in the environment would occur, it has been lately extended to include a range of critical flows which could be crudely summarized as habitat flows and channel maintenance or geomorphic flows As their names imply, these are flow levels and durations which exceed threshold levels regarded as critical to ecosystem or geomorphic function. Perhaps recognizing the difficulties of determining these thresholds, attempts to mimic the pattem of flows in a natural stream have formed the basis of water sharing and catchment storage release programs for regulated streams (reported in Williams, et al, 2019). Because of a paucity of data for many streams these techniques often form the basis of “best practice” applications to setting environmental flows for rivers in S.E Australia
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