Denil fishway

Denil fishway – Key considerations

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• Overview
• Key considerations
• Planning and design
• Construction and operation
• Links and references

In addition to the general information for all fishway types, the following applies to Denil fishways.

Requirements for effective passage

In Australia, passage of small fish (<120 mm long) through Denil fishways has been poor unless the fishway is at a relatively low slope (1:12 vertical:horizontal or flatter) compared with the usual steep slopes of 1:4 to 1:7 used in other countries[1][2]. For this reason, Denil fishways tend to be used in combination with a vertical slot or fish lock fishway where there is a clear need to service a separate ecological and hydraulic function. For example, at Wentworth Weir on the Murray River, a vertical slot fishway services small- to large-bodied fish at low and medium flows, and a Denil fishway with a high discharge and a wide channel width services large Murray cod migrating at high flows[4].

Suitability and limitations

Denil fishways discharge relatively high volumes of water. The large flow associated with the Denil design reduces the deposition of sediment within the fishway and provides good attraction capability, assisting the fish in finding the fishway however, water supply and usage can be a constraint for choosing Denil fishways in Queensland.

There are presently no successful or functional Denil fishways in Queensland. An example of a poorly-designed and non-functional Denil fishway is located on the Luscombe Weir on the Albert River, which has head losses between pools, velocities and turbulences much greater than local fish communities are capable of passing through on a regular basis[3].

Examples of Denil fishways in Australia are on the Tweed (Bray Park Weir) and Richmond (Jabour Weir) rivers in northern New South Wales, and on the Murray River and in southern New South Wales (e.g. Euston Weir, Wentworth Weir, Mildura Weir, Gulpa Creek, Edward River, Koondrook-Pericoota floodplain, and the Torrumbarry weir pool)[5][4].

References

1. ^ Baumgartner, LJ & NSW Department of Primary Industries (2006), 'A preliminary assessment of fish passage through a Denil fishway on the Edward River, Australia', Fisheries Research Report Series. [online], vol. 86, p. 24. Available at: https://www.dpi.nsw.gov.au/content/research/areas/aquatic-ecosystems/outputs/2006/779.
2. ^ Mallen-Cooper, M & Stuart, IG (5 January 2007), 'Optimising Denil fishways for passage of small and large fishes: Small and Large Fishes in Denil Fishways', Fisheries Management and Ecology. [online], vol. 14, no. 1, pp. 61-71. Available at: http://doi.wiley.com/10.1111/j.1365-2400.2006.00524.x [Accessed 10 November 2020].
3. ^ Moore, M, McCann, J & Power, T (2018), Greater-Brisbane-Fish-Barrier-Prioritisation-Report.pdf. [online] Available at: http://catchmentsolutions.com.au/files/2018/05/Greater-Brisbane-Fish-Barrier-Prioritisation-Report.pdf [Accessed 11 November 2020].
4. ^ a b O’Connor, J, Stuart, I & Mallen-Cooper, M (2015), 'Performance, operation and maintenance guidelines for fishways and fish passage works', Trove. [online] Available at: https://nla.gov.au/nla.obj-480267623 [Accessed 10 November 2020].
5. ^ Thorncraft, G & Harris, JH (2000), Fish passage and fishways in New South Wales - a status report, Cooperative Research Centre for Freshwater Ecology, Albury, N.S.W..

Last updated: 10 May 2021