Adaptive Management of Environmental Flows: Using Irrigation Infrastructure to Deliver Environmental Benefits During a Large Hypoxic Blackwater Event in the Southern Murray–Darling Basin, Australia
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Widespread flooding in south-eastern Australia in 2010 resulted in a hypoxic (low dissolved oxygen, DO) blackwater (high dissolved carbon) event affecting 1800 kilometres of the Murray–Darling Basin. There was concern that prolonged low DO would result in death of aquatic biota. Australian federal and state governments and local stakeholders collaborated to create refuge areas by releasing water with higher DO from irrigation canals via regulating structures (known as ‘irrigation canal escapes’) into rivers in the Edward–Wakool system. To determine if these environmental flows resulted in good environmental outcomes in rivers affected by hypoxic blackwater, we evaluated (1) water chemistry data collected before, during and after the intervention, from river reaches upstream and downstream of the three irrigation canal escapes used to deliver the environmental flows, (2) fish assemblage surveys undertaken before and after the blackwater event, and (3) reports of fish kills from fisheries officers and local citizens. The environmental flows had positive outcomes; mean DO increased by 1–2 mg L−1 for at least 40 km downstream of two escapes, and there were fewer days when DO was below the sub-lethal threshold of 4 mg L−1 and the lethal threshold of 2 mg L−1 at which fish are known to become stressed or die, respectively. There were no fish deaths in reaches receiving environmental flows, whereas fish deaths were reported elsewhere throughout the system. This study demonstrates that adaptive management of environmental flows can occur through collaboration and the timely provision of monitoring results and local knowledge.
KeywordsEnvironmental flows Blackwater Dissolved oxygen Fish kills Refugia Adaptive management
The authors thank Edward–Wakool landholders, the Wakool River Association and the Edward–Wakool Anglers Association for their interest in the project and providing access to monitoring sites on their properties. Thank you to James Dyer and Elena Griffiths for field assistance. Figure one was prepared by Deanna Duffy (Charles Sturt University Spatial Analysis Unit). Fish collections were carried out under New South Wales Animal Care and Ethics Authority 10/01 and Scientific Collection Permit P01/0059(A). Funding for the water quality monitoring was provided by Charles Sturt University and also funding to the (then) Murray Catchment Management Authority (MCMA) by the Australian Government under the Caring for our Country Programme. Funding for the fish surveys was provided by the MCMA, New South Wales Department of Primary Industries (Fisheries) and the (then) Department of the Environment, Heritage, Water and the Arts. Thanks to the editor and several reviewers for their constructive comments on drafts of this manuscript.
Compliance with Ethical Standards
Conflict of Interest
The authors declare that they have no competing interests.
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