AWMA have partnered with the North Central Catchment Management Authority (NCCMA) to design, construct and install Australia’s first conical Fish Exclusion Screen through the Cohuna Irrigation Diversion Screen Project. Funding for the project has been provided by the Victorian Environmental Water Holder (VEWH).
Approximately two years ago AWMA was approached by renowned fish ecologist Martin Mallen-Cooper along with the NCCMA to provide feedback on the viability of screening irrigation off-takes to protect native fish. From this time, AWMA have been involved in the project steering committee and assisted in developing the concept design for the screens.
AWMA has built strong relationships across the sector and gained in-depth knowledge of how (and how not) infrastructure should be specified, designed, operated and serviced to facilitate sustainable fish passage. AWMA have travelled to the US on a number of occasions to meet with screen operators, owners, fish scientists, universities and screen manufacturers. The technology review has resulted in an in-depth understanding of the application, the engineering and the operation of fish screens. Considerable time was also spent with the NSW fisheries scientists, understanding the differences between the US Salmon and our native fish to allow engineering and specification changes to the screen design to suit our native fish species. The Cohuna Irrigation Diversion Screen project will demonstrate to the industry that screening can be successfully implemented in Australia, delivering sustainable results that will benefit all parties.
The aim of this project is to boost native fish populations by preventing fish movement out of the natural waterway into irrigation channels. Uninterrupted irrigation flows are also critical, with minimal headloss through the fish screen structure being a key design criteria.
A sheet pile wall, manifolds and four Cone Fish Screens will be installed in front of the Number 3 Offtake in the Cohuna Weir Pool. AWMA will design, manufacture, install, commission and monitor the fish exclusion screens. The structure will also utilise AWMA Segmented Stopboards to provide water control and maintenance access. Safety during construction is paramount to ensure all operators and public are protected at all times with minimal disruption to the natural habitat (waterway, flora and fauna).
Conical (cone) Fish Screens have been chosen for this site due to their suitability in shallow water, they have been well proven in diversion pools, rivers and channels, to protect fish from entrainment and impingement. The screens will be submerged below the water level to ensure the area remains aesthetically pleasing. The screens are self-cleaning with a positive brushing action preventing debris build-up, sedimentation, and bio-fouling. An internal flow baffle distributes flow evenly across the screen surface. A marine-duty hydraulic drive motor rotates cleaning brushes with a control panel allowing user defined cleaning cycles. The cone shaped design is very strong and hydraulically efficient.
The screens weigh 28 tonnes in total and will pass 600ML/d through 3mm wedge wire screens with a head loss of less than 20mm.
All native fish species are crucial in sustaining a balanced aquatic ecosystem. Once fish enter irrigation systems they are lost to their natural environment. AWMA are dedicated to assisting fundamental projects aimed to increase environmental sustainability.
The environmental sector is a major part of AWMA’s business. AWMA have partnered the MDBA and their construction contractors on the majority of the water control infrastructure installed to facilitate forest watering events such as the Perricoota and Hattah projects and many wetland control structures to assist in viable management practices. AWMA has been involved with the supply of gates to the majority of the fish ladders, locks and lifts within the Murray Darling Basin.
AWMA’s significant contribution to this project will enable the introduction of new and innovative screen technology to Australia and specifically to manufacturing in regional Victoria.