Abstract
Widespread flooding in south-eastern Australia in 2016 resulted in a hypoxic (low dissolved oxygen, DO) blackwater (high dissolved organic carbon) event affecting a large area of the southern Murray-Darling Basin. There was concern that prolonged low DO would result in death of aquatic fauna, as a similar event in 2010 resulted in widespread fish deaths. Australian federal and state governments and local stakeholders collaborated to create refuge areas by releasing environmental flows with higher DO and lower DOC from irrigation
canals via regulating structures (known as ‘irrigation canal escapes’) into rivers in the Edward-Wakool system. In addition, a group of local citizens installed borrowed and homemade aerators in an attempt to create small fish refuges by temporarily raising the DO.
We evaluated 1) water chemistry results from river reaches upstream and downstream of the escapes through which the environmental flows were delivered, 2) fish assemblage and movement data collected before and after the event, and 3) observations from fisheries officers and local citizens of fish deaths during the event, and reports of fish caught after the event. Although many fish deaths were reported during the hypoxic blackwater event, the environmental flows had some positive outcomes. The mean DO increased by 1 to 2 mgL
-1 downstream of the environmental flow delivery sites. Fish monitoring results and catch records of recreational fishers showed that live Murray cod were present in the reach of the Edward River that received an environmental flow, but were absent further downstream where there was no environmental flow. The effectiveness of the aerators in raising DO levels was not definitively established, however fish, turtles and crustaceans were observed in close proximity to the aerators. This study demonstrates that environmental flows in conjunction with local landholder ingenuity can create local refuges to help mitigate adverse
outcomes during extreme events.
canals via regulating structures (known as ‘irrigation canal escapes’) into rivers in the Edward-Wakool system. In addition, a group of local citizens installed borrowed and homemade aerators in an attempt to create small fish refuges by temporarily raising the DO.
We evaluated 1) water chemistry results from river reaches upstream and downstream of the escapes through which the environmental flows were delivered, 2) fish assemblage and movement data collected before and after the event, and 3) observations from fisheries officers and local citizens of fish deaths during the event, and reports of fish caught after the event. Although many fish deaths were reported during the hypoxic blackwater event, the environmental flows had some positive outcomes. The mean DO increased by 1 to 2 mgL
-1 downstream of the environmental flow delivery sites. Fish monitoring results and catch records of recreational fishers showed that live Murray cod were present in the reach of the Edward River that received an environmental flow, but were absent further downstream where there was no environmental flow. The effectiveness of the aerators in raising DO levels was not definitively established, however fish, turtles and crustaceans were observed in close proximity to the aerators. This study demonstrates that environmental flows in conjunction with local landholder ingenuity can create local refuges to help mitigate adverse
outcomes during extreme events.
| Original language | English |
|---|---|
| Publication status | Published - 2017 |
| Event | 20th International River Symposium - Brisbane Convention and Exhibition Centre, Brisbane, Australia Duration: 18 Sept 2017 → 20 Sept 2017 Conference number: 20 http://riversymposium.com/wp-content/uploads/2019/09/RS17-Program.pdf (Program) |
Conference
| Conference | 20th International River Symposium |
|---|---|
| Country/Territory | Australia |
| City | Brisbane |
| Period | 18/09/17 → 20/09/17 |
| Internet address |