Ecological Responses to Flooding in the Lower River Murray Following an Extended Drought
Dr Quifeng Ye, SARDI
SARDI, CSIRO, Flinders University, University of Adelaide
The overall project objective of Murray Flood Ecology (MFE) was to investigate the ecological response to flooding in the lower River Murray following an extended drought. The project had 11 research tasks with specific objectives to investigate:
The influence of flow on abiotic and biotic conditions in the River Murray channel.
Flow induced alterations in total river metabolism and changes in component contributions.
Annual variation in larval fish assemblages in a heavily regulated lowland river.
Effects of flooding on recruitment and abundance of golden perch in the lower River Murray.
Movement and mortality of Murray cod during overbank flows in the lower River Murray.
Flow induced alterations to aquatic macrophyte communities and fish assemblages in the River Murray channel.
What is the response of wetland fish assemblages following flooding?
Resilience and resistance of aquatic plant communities downstream of Lock 1 in the River Murray.
Investigate the response of river red gums to the current flow/flooding event.
Floodplain response and recovery: comparison between natural and artificial floods.
Conceptual river–ecosystem model.
All these objectives were achieved through field-based research or desktop study (modelling). Workshops were also run engaging stakeholders and independent experts from interstate to ensure the quality of the research outputs from this project and to maximise the outcomes.
Progress Update and Key Findings
The project captured an unique opportunity to investigate ecological response to a natural flood (>90,000 ML/day) in the lower River Murray following about ten years drought. The project took a holistic approach, undertaking research on flow/flood related ecological processes and the response of key biota across the main channel, wetlands and floodplain. The research demonstrated that natural flooding in 2010-11 facilitated important ecological processes including increased primary production, improved lateral and longitudinal connectivity, lateral bank recharge, re-structuring of aquatic plant communities, plant recruitment and fish spawning, recruitment and movement, leading to increased abundances, improved condition and recovery of key communities after drought.
The research outcomes highlight that flooding, as an integral part of the natural flow regime, is important in maintaining the ecological integrity of floodplain rivers. The knowledge developed will inform environmental water planning and flow management to maximise ecological outcomes in the lower River Murray.
Adoption and Impact
The initiation of this project was driven by the need of flow related ecology to inform the policy and management of environmental water in the South Australian River Murray, and the unique opportunity of the 2010-11 flood event (soon after the establishment of the Goyder Institute) to investigate how the ecosystem response/recovery in the lower River Murray after a long period of drought. There were numerous discussion and consultations with DEWNR staff and other state agencies (e.g. SAMDB NRMB, PIRSA) at the establishment of this project and a project Stakeholders Committee was also established to ensure their ongoing engagement throughout the project to assist with the information exchange, communication and knowledge adoption in policy making, management and river operations to maximise the ecological outcomes for the lower Murray. A broader stakeholder workshop was held at the completion of the MFE research tasks to disseminate research outcomes and discuss about how the knowledge developed could be used to underpin river management and environmental water use. The project results have been taken up by State agencies particularly DEWNR in environmental water planning and management; riverine restoration/rehabilitation under the Riverine Recovery Project. Some of the knowledge developed through the MFE has informed the ecological evaluation of the Basin Plan.
In addition to the targeted stakeholder workshop, the project outcomes have been presented in numerous conference/forum and public seminars. Further, the key scientists from the MFE team have continued to work closely with state agencies (DEWNR, SAMDB NRMB, EPA, SA Water and PIRSA) and commonwealth agencies (MDBA, CEWO) to support them with best science to underpin environmental watering strategy and river management.