Abstract
Since 2010 there have been several large unregulated flow events occurred in the Mid-Murray that have resulted in inundation of large areas of floodplain. Carbon and nutrient release following the inundation of agricultural and forested floodplain, can result in water with high organic loads (usually dark/black in colour) entering waterways from the floodplain. Water can become hypoxic (low dissolved oxygen concentration) when large amounts of organic material in rivers are broken down by bacteria, consuming dissolved oxygen in the water. Prolonged low oxygen concentrations can result in the interruption of flood-response movements, stress or death of native fish.
In the Edward/Kolety-Wakool River system large unregulated flow events occurred in 2010-11, 2012 and 2016-17. On each of these occasions hypoxic water has developed and Commonwealth environmental watering actions from irrigation escapes were delivered to create small refuges of higher dissolved oxygen for fish and other aquatic biota. For example, in 2010-2011 the delivery of environmental water from the Wakool Escape into the Wakool River increased dissolved oxygen (DO) increased 1-2 mg/L for at least 40 km downstream of the escape, and there were fewer days when DO was below the sub-lethal threshold of 4 mg/L at which fish are known to become stressed. Furthermore, there were no fish deaths in reaches nearby to the Wakool and Edward escapes where environmental water was delivered, whereas fish deaths were reported elsewhere throughout the system.
In the Edward/Kolety-Wakool River system large unregulated flow events occurred in 2010-11, 2012 and 2016-17. On each of these occasions hypoxic water has developed and Commonwealth environmental watering actions from irrigation escapes were delivered to create small refuges of higher dissolved oxygen for fish and other aquatic biota. For example, in 2010-2011 the delivery of environmental water from the Wakool Escape into the Wakool River increased dissolved oxygen (DO) increased 1-2 mg/L for at least 40 km downstream of the escape, and there were fewer days when DO was below the sub-lethal threshold of 4 mg/L at which fish are known to become stressed. Furthermore, there were no fish deaths in reaches nearby to the Wakool and Edward escapes where environmental water was delivered, whereas fish deaths were reported elsewhere throughout the system.
Original language | English |
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Place of Publication | Australia |
Publisher | Commonwealth Environmental Water Holder |
Commissioning body | Commonwealth Environmental Water holder, Department of Climate Change, Energy, the Environment and Water |
Number of pages | 105 |
Publication status | Published - 06 Nov 2023 |