| Abstract: |
The objective of the current study was to monitor the vegetation of the Pike Floodplain, Riverland region, South Australia, in 2015, to provide baseline/reference data against which to evaluate vegetation response to future regulator operation. Secondly, we aimed to compare data collected in 2015, with similar data collected in 2010 and 2011, to provide insight on recent natural floodplain vegetation dynamics.
Floodplain ecosystem degradation, as a result of river regulation and water abstraction, is widespread throughout the lower River Murray in South Australia. Environmental regulators that enable inundation under flows that would not normally inundate floodplain habitats have been constructed (e.g. Chowilla) or are proposed for several sites on the lower River Murray. These regulators may reinstate aspects of the inundation regime and provide conditions suitable for the recruitment of native floodplain species.
PIKE FLOODPLAIN:
Such an environmental regulator has been proposed for the Pike Anabranch system under the South Australian Riverland Floodplain Integrated Infrastructure Project (SARFIIP). The Pike Anabranch system bypasses Lock and Weir Number 5, resulting in a 3 m head differential between its upstream inlets and the downstream confluence of the Pike River and River Murray. This head differential provides the opportunity to undertake engineered floodplain inundation events through the use of environmental regulator. Information regarding the plant community prior to construction of the proposed regulator is required to evaluate vegetation response to engineered floodplain inundation.
METHODOLOGY:
The monitoring program established in 2010 and continued in 2015, will provide a baseline to evaluate temporal variability in vegetation communities and responses to both natural flooding, and management interventions. The dispersion of sites among areas that will be inundated by the proposed regulator and areas that will not be inundated, will enable causative relationships to be determined because of the provision of reference sites. Collection of several years of pre-regulator data will enable assessment of changes in the plant community through time (or in response to natural flooding) to be investigated to gain a multi-year baseline. Floodplain plant communities are naturally dynamic and an understanding of this natural dynamism is fundamental to elucidate potential responses to regulator operation. Furthermore, the recent removal of grazing from the Pike Floodplain appears to have benefited the plant community, which could confound the response to engineered inundation and a multi-year baseline will provide information to quantify the response to the removal of grazing. Katarapko Such an environmental regulator has been proposed for the Katarapko system under the SARFIIP. The Katarapko Anabranch system bypasses Lock and Weir Number 4 resulting in a 3 m head differential between its upstream inlets (e.g. Bank J) and the confluence of Katarapko Creek and the River Murray. This head differential provides the opportunity to undertake engineered floodplain inundation events through the use of an environmental regulator. Information regarding the plant community prior to construction of the proposed regulator is required to evaluate the benefits (or dis-benefits) of engineered floodplain inundation. The current vegetation survey for the Katarapko Floodplain will provide a baseline that can be used to detect the change in vegetation through time, in response to natural flooding events, drying phases and management actions including managed inundations via the operation of the proposed environmental regulator. The collection of several years of pre-construction data will enable the changes in vegetation through time to be investigated and gain information regarding decline or recovery depending on natural conditions prior to regulator construction.
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