Water Journal : Water Journal April 2012
catchment management water APRIL 2012 115 concentrations in the mid-Goulburn catchment measured by AshWatch were: Sunday Creek at Seymour Road Bridge, 297 NTU; King Parrot Creek before Goulburn River, 253 NTU; and Dry Creek at Broadford, 254 NTU. Goulburn Valley Water also reported high turbidity at their Seymour town offtake (Goulburn River); in the first week of January raw water turbidity was around 300 NTU (previous maximum was around 50 NTU). Elevated turbidity levels were also observed in the Goulburn River. Due to a lightning strike no turbidity data is available at Trawool from 2 to 5 January; therefore, the full impact is not able to be determined at this site. The site came back online on 5 January and the turbidity was elevated at 160 NTU and was decreasing; however, concentrations remained above 20 NTU until 16 January. Ashwatch monitoring measured turbidity just before Seymour (the closest site to Trawool) at 633 NTU on 5 January. By 30 January 2010, Ashwatch monitoring showed that throughout the mid-Goulburn catchment water quality had reverted to previous levels with all sites below 25 NTU. The maximum daily inflow into the Goulburn Weir was recorded on 4 January. Increases in electrical conductivity (EC) , turbidity and a decrease in dissolved oxygen (DO) levels began late on 3 January at Tabilk (just upstream of Goulburn Weir). EC and turbidity continued to increase until 9 January. The maximum EC recorded was 115 μS/cm, turbidity concentrations were in excess of the detection limit (400 NTU) for 5 days, and the lowest DO recorded was around 4ppm. There was a significant delay in the turbidity slug reaching the Goulburn Weir structure (see Figure 5). Increases in turbidity did not occur until 10 January with the maximum turbidity occurring on 13 January at 283 NTU (high spike readings not included). DO concentrations significantly reduced at the same time to below 1ppm for a number of days. By 13 January DO levels had increased above 5ppm and turbidity gradually improved, with most readings below 50 NTU by 24 January 2010. No fish kills or other impacts on aquatic life were reported. Response Action -- Translocation of Threatened Species Noting the potential impact on a number of threatened species from receiving waters carrying sediments, ash and the like, the Department of Sustainability and Environment, together with the community, commenced the translocation of key threatened species: • Barred Galaxias (Galaxias fuscus); and • Macquarie perch (Macquaria australasica) Barred Galaxias case study The Barred Galaxias is a rich-orange fish with one to 10 distinct, dark oval bars on its side and clear to reddish-brown fins (Allen, 1989). The Barred Galaxias has suffered a serious decline over most of its range and has become fragmented within this reduced range (Raadik, 1993). It is currently restricted to just 11 populations in 22 known sites. The known remaining populations of Barred Galaxias (DSE, 2003) all occur in the upper reaches of tributaries of the Goulburn River system. Bushfires in December 2006 and February 2009 have burnt over all but three known Barred Galaxias sub-populations. According to Raadik et al. (2010) remnant populations of Barred Galaxias are all geographically isolated, small, and restricted to headwater streams in the forested upland portion of the Goulburn River system. Because of this, and their poor recolonising ability, the immediate and post impacts of bushfire can devastate populations (Raadik et al., 2010). During a bushfire, the temperature of the water in the small headwater tributaries can become elevated, leading to fish mortailty. Post-bushfire, sudden pulses of ash and sediment carried into the stream with runoff from storm events can drastically alter water quality conditions, causing high or complete fish mortality (Raadik, 2007). High sediment loads can smother the substrate (or completely infill streams), reducing or eliminating aquatic food supplies and smothering spawning and resting habitat for fish. Risk assessment and decision The majority of known sites for Barred Galaxias aligned with high soil-burn severity (from February 2009 fire), which increased the risk of impact and loss of individual communities and polulations. The key impact on the galaxias that were assessed included: stream inputs such as sedimentation and ash, changes/ destruction of barriers to predatory species allowing shared access to zone with galaxias, management of stream debris and salvage logging. Translocation action Eleven sites were assessed post-fire. One site was dry and two sites were only lightly burnt. From eight sites, a total of 394 fish were collected and translocated to the Arthur Rylah Institute for Environmental Research to prevent direct and indirect impact to the species post-fire Return and captive breeding The translocated Barred Galaxias were returned over a 16-month period, following regular surveys by ARI to assess habitat rehabilitation at each site. These reintroductions occurred between December 2009 and March 2011. Fish from Little Rubicon River, Luke Creek and Torbreck Creek were returned in December 2009. Fish from Upper Taggerty River, Rubicon River and Keppel Hut Creek were returned in June 2010. Fish from S Creek were returned in February 2011 and those from Robertson's Gully returned in March 2011. Although attempts had been made to breed Barred Galaxias at ARI, these Figure 5. Goulburn Weir inflow and turbidity post-January 2010 rainfall event.
Water Journal May 2012
Water Journal December 2011