Assessing translucent environmental water releases in the Murrumbidgee River below Burrinjuck Dam, 1999-2002: Report 3. Effect of translucent releases on biofilms and periphyton in the Murrumbidgee River

Lorraine Hardwick, Benjamin Wolfenden, David Ryan, Bruce Chessman, Doug Westhorpe, Simon Mitrovic

Research output: Book/ReportOther report

16 Downloads (Pure)


Environmental flows in the Murrumbidgee River commenced in 1999. These were developed using river flow objectives to guide release rules. One of the river flow objectives was to increase small scale variability downstream of regulatory dams. The solution to this lack of variability was the development of the ‘translucency and transparency’ environmental flow rules. Ecological monitoring of these environmental flow rules was performed between 1999 and 2001. This report documents the outcome of monitoring the regulated Murrumbidgee and Tumut rivers impacted by translucency and transparency rules, and their unregulated tributaries, the Goodradigbee and Goobarragandra rivers.
Translucency both reduced constancy and increased variability of flows released from Burrinjuck Dam between April and October, although this study found limited evidence that translucent flows altered periphyton composition or biofilm biomass. The study was designed to test for a long term change in flow and corresponding changes to biofilms with the onset of translucent flows; the size of effect from translucency was unknown. Significant differences in biofilm composition were observed among rivers, but the observed differences were not consistent with the predicted impacts of regulation. Summer irrigation flows were found to be much greater than the relatively minor winter-spring translucent releases. With the overarching influence of irrigation releases on the flow regime of the Murrumbidgee River, environmental flows would need to create a substantial change to the rivers flow regime for this study to be able to detect a change in biofilms. Moreover, factors other than flow appeared to be strong drivers of biofilm dynamics in the Murrumbidgee catchment, governing patterns of biofilms observed among rivers. Returning natural flow variability to rehabilitate the Murrumbidgee River appears to be hindered by the effects of large summer irrigation flows and water-column nutrient dynamics.
Original languageEnglish
PublisherNSW Department of Primary Industries, Office of Water
Number of pages46
ISBN (Print)978174256
Publication statusPublished - 2014


Cite this