First commissioned in 1923 and later rebuilt in 1997, Torrumbarry Weir is an important feature of the heavily managed Murray-Darling system and a significant barrier to migrating fish.
A classic vertical-slot fishway sits on the left bank of the Murray here. When it was built in 1990 it was the first of its kind in the country. The original fishway was later rebuilt to address the inability of smaller fish to ascend (Mallen-Cooper, 1999). With 39 pools spanning a total length of 131 m and a 1:18 gradient, it is still a considerable obstacle for weaker swimmers.
The fishway is now fitted with PIT antennae to monitor the passage of tagged fish. Daily counts are also kept of fish collected in a trap at the exit. However, neither technique is adequate for monitoring the passage of juveniles and small-bodied species, such at the Australian smelt.
Crossing the river takes you into New South Wales, where ‘Torrumbarry Cutting’ was recently constructed to periodically flood the Koondrook-Perricoota Forest as part of plans to reallocate unprecedented amounts of water back to the environment. The flood gates are a barrier to fish movement when the cutting is in operation, so a dual vertical-slot/Denil fishway was installed alongside.
Such dual fishways are now popular in Australia. The very narrow vertical slot is for smaller fish, whereas the Denil is suitable for larger species like the Murray cod.
Monitoring is ongoing.
Martin // Melbourne