Source: Carl Walters, Goulburn-Murray Water
Casey's Weir
When Casey's weir was built downstream of Benalla in the late 19th century, our forefathers would have had little regard for the movement of Murray Cod, Golden Perch and other native fish up and down the Broken River system. After all, it’s estimated there were ten times as many native fish in the Murray Darling Basin, and it would have required some extraordinary foresight to predict the environmental issues we face today.
But, according to, Wayne Tennant, Manager of Riverine Strategies with the Goulburn Broken Catchment Management Authority, with the benefit of greater research into the health of our freshwater rivers and streams, it’s now a lot easier to understand exactly how these ecosystems work, why we need to protect them, and what we can do to help. “The evolution of science and technology has helped us more accurately assess how our waterways have responded to over 100 years of modification,” said Mr Tennant. “This also allows to develop some effective solutions to help repair the damage.”
According to Mr Tennant, research has helped us recognise that native fish need access throughout rivers and streams as part of their natural migration patterns - a key component of a fish’s lifecyle. The Golden Perch, for example, has been known to travel upstream more than 1,000 kilometres to spawn. Man-made barriers such as dams, weirs and roadways can block fish routes up and down the river, and can disturb breeding patterns and affect the distribution of the fish throughout a river.
Fortunately, a 1998 agreement between the state government and the Goulburn Broken Catchment Management Authority (GBCMA) provided funds for fish movement works within the Broken River system, and Caseys Weir has been identified as a priority site. The GBCMA engaged environmental consultants Sinclair Knight Merz to undertake design of a fishway (a concrete construction that provides adequate passage for native fish), while Goulburn-Murray Water have provided construction services and will own and operate the new fishway into the future
The fishway is an open concrete chute structure with a number of vertical slots placed at regular intervals. The effect is a flow that resembles a number of broken pools that resemble the flow in the river. These pools provide resting areas for fish using the passage, who can then swim onwards and upwards into another pool or into the weir.
Now 70% complete, the fishway is expected to help rebuild native fish species populations in the river, and while it will be impossible to help numbers reach the estimated pre-European settlement levels, Mr Tennant is confident the passage will at least assist the natural migration of some threatened species.
