National Wetlands Update September 2012
Issue No. 21, September 2012
Commonwealth environmental water helps to maintain river health in the Murray River
Commonwealth Environmental Water
Flooding in the summer of 2011-12 exceeded the floods recorded in 2010-11 in a number of areas of the southern Murray-Darling Basin. This was particularly the case with the Murrumbidgee River which experienced massive flooding after the March 2012 rainfall with areas of the floodplains inundated for the first time in over a decade.
The accumulations of organic matter that were washed into wetlands and waterways as a result of the floods decayed and darkened the water, turning it black. As the organic matter decays, oxygen in the water is consumed, sometimes at faster rates than it can be replenished. The low levels of dissolved oxygen can cause stress and sometimes death to fish and other aquatic species.
Significant levels of blackwater started to occur in the Murrumbidgee River and flow into the Murray River in April 2012 with the potential to impact adversely on fish and other aquatic species.
Benefits of environmental watering
As the lower Murrumbidgee River was already in a state of natural flooding, environmental water could not be used at that time to help dilute the areas of blackwater occurring in the Murrumbidgee River.
Commonwealth environmental water was provided to maintain flows in the Murray River at levels that would be able to provide a suitable ratio for dilution of water coming out of the Murrumbidgee River. From 16 April to 17 May 2012, 92 gigalitres of Commonwealth environmental water were released from Hume Dam, adding to flows already in the Murray River. A further approximately 45 gigalitres were delivered to the Edward-Wakool River system to provide important refuge habitat for fish from blackwater in this region. The flows from the Edward-Wakool system flowed through to the Murray River, contributing to maintaining higher Murray River flows at the Murrumbidgee River junction.
The additional flows of environmental water were not able to fully counteract the negative impacts of blackwater. However they did maintain river flows at levels that assisted in maintaining or improving aquatic habitat and providing important refuges for fish and other aquatic species.
The quality of water in the Murray River has been maintained, and the impacts of the blackwater were negated within a very short distance from the confluence of the two rivers.
For further information on the monitoring results of this environmental watering visit Commonwealth Environmental Water helps to Maintain River health in the Murray River. To keep up to date with Commonwealth Environmental Water news and events please subscribe to our mail list by visiting Commonwealth environmental water email updates.
A snapshot of Commonwealth Environmental Water monitoring in the Murray River. (Commonwealth Environmental Water)