- Rehabilitating flow regimes through the provision of environmental releases is an activity that can be done within the scope of a demonstration reach program.
- The sites for planned environmental releases could be used to develop demonstration reaches.
Regulation of natural flow regimes and the extraction of water for consumptive use has significantly impacted on riverine fishes in the Murray-Darling Basin and throughout Australia. Regulation alters the hydraulic nature of flows, often resulting in a reduction in flow and habitat diversity. In the Basin, high volume, high velocity irrigation flows in summer are the opposite to what would have been natural periods of low flows. This has resulted in a decline in the abundance, distribution and recruitment of many native fishes.
The decline in regular natural floodplain inundations has impacted on a wide variety of native fishes, including floodplain wetland specialists. It has also reduced the nutrient exchange between the floodplains and the river. In the lower Murray, weir pools have changed a flowing environment into a non-flowing one, disadvantaging some species. Changes in flow timing have also reduced spawning and movement cues for native fishes.
Changes to legislation and policies in the Basin have led to more water being made available for the environment through the provision of environmental water allocations. Determining flow requirements (quantity and timing) for a demonstration reach requires expert input and coordination with jurisdictional and Commonwealth natural resource management agencies. Such negotiations can now work within the scope of a demonstration reach project, and where environmental flow releases are planned it could be advantageous to enhance the impact of these releases by undertaking habitat rehabilitation through the establishment of a demonstration reach (see example below).
Katfish Reach – Katarapko South Australia
The Katfish demonstration reach was established in 2007 to provide a holistic approach to the management of the health of the Katarapko anabranch system and its associated floodplain. Constructions of locks and weir structures along the Murray River have created predominately lentic habitats (standing water and pools) where there were once hydrodynamically diverse lotic systems (moving water). The Katarapko anabranch and floodplain system bypasses Weir 4, and has retained hydraulically diverse aquatic habitats. However there are barriers to fish movement and a lack of environmental flows has caused widespread ecological decline of the floodplain.
Significant funding has been secured through the Murray Futures Riverine Recovery Project and an integrated hydrological operating plan is being developed. There are six flow related management interventions being implemented:
- Improve spring/summer inundation of Eckert Island at low river flows.
- Temporarily partial dry and vary pool level of Eckert Creek anabranch system.
- Achieve fish passage and increased in-stream flow for Eckert Creek anabranch system.
- Achieve fish passage and increased in-stream flow for Katarapko Creek.
- Improve flows, Carp control and fish passage at Ngak Indau Wetland.
- Improve opportunities for wetland inundation frequency at a number of temporary wetlands and Katarapko Island Saline Water Disposal Basin.
You can read more about these works by downloading this fact sheet.
Baumgartner, L.J., Conallin, J., Wooden, I., Campbell, B., Gee, R., Robinson, W.A. and Mallen-Cooper, M. 2013. Using flow guilds of freshwater fish in an adaptive management framework to simplify environmental flow delivery for semi-arid riverine systems. Fish and Fisheries, Blackwell Publishing.
Koehn, J.D., King, A.J., Beesley, L., Copeland, C., Zampatti, B.P. and Mallen-Cooper, M. 2014. Flows for native fish in the Murray-Darling Basin: lessons and considerations for future management. Ecological Management and Restoration, 15 (Supplement S1), 40-50.