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A modern fish screen is a physical barrier designed to prevent fish from swimming or being drawn into a diversion on a waterway when water is extracted for human use. Fish screens are a device installed on water pumps and diversion channels to keep fish and debris where they belong – in the river and out of water infrastructure. Fish screens protect native fish and keep a reliable supply of clean water flowing to water users. A modern fish screen needs to meet several important design specifications.
Modern fish screens work by lowering the velocity of water entering a pump or channel, without affecting the volume of water that is diverted. This is achieved by using a large surface area of fine mesh that spreads the intake flow over a greater area. The velocity of water near a modern screen is less than 0.1 metres per second, which means native fish can swim near the screen safely.
Fish Screens Australia (FSA) is a collaboration between fisheries managers, water users, manufacturers, scientists, engineers and fishers. Our goal is to share knowledge and work together to bring a best-practices guidelines to Australian water users. The group manages this website, showcasing the latest screen technology, sharing experiences and learning what works best for businesses and other water users. This is done in partnership with OzFish Unlimited, the voice of Australia’s recreational anglers, partnered with manufacturers, water users, farming groups and fisheries experts from the NSW Department of Primary Industries and Charles Sturt University to create fishscreens.org.au.
Farmers and other water users need a reliable supply of water, but waterways are full of sticks, leaves, animals and debris. These get sucked into pumps and diverted down channels. The problem is, most gravity-fed channels are not screened, and most pumps currently use traditional ’trash racks’. This outdated technology often fails to prevent fish and debris being sucked out of waterways, impacting water infrastructure, costing many water users time and money. Modern fish screens are low maintenance and engineered for performance. They reduce the need to back-flush lines, replace filters and clear sprinklers. The best screens are also self-cleaning, either by design, or with the addition of automatic brushes or jets water or burst of air that keep the screen clear of debris.
They In life you get what you pay for. A screen needs to operate underwater under testing conditions. A poorly designed and installed screen, built from inferior quality components, will not perform or last as long as one of a higher quality. However, if the modern screen is fit-for-purpose and well maintained it should provide many years of operation. Advice around how to design and install screens for maximum life is provided in the practical guide to screening. This advice is general in nature and if you intend on buying a screen, it always pays to do your homework and ensure you are familiar with a manufacturer’s maintenance schedule and service or warrantee arrangements.
Modern fish screens cost approximately $1,000 per megalitre of pump or channel capacity. Generally, a smaller variety of fish screens that can support 10 megalitre per day output will cost roughly $18, 000 depending on the style that is used. This works out to less than a thousand dollars a year for the screen’s lifetime. As the screens become larger and are used to cope with volumes as large 800 megalitres per day, they can increase to a million dollars per screen. The maintenance costs for a typical 10 megalitre fish screen will be very low for at least the first seven years. Thereafter, the typical unit may need the odd brush replaced but this works out to be less than $500 per part. These costs are more than offset by the cost benefits the screen provides to the farmer.
No. The volume and rate at which water can be diverted remains the same. Modern fish screens simply spread that same volume over a larger surface area of mesh, lowering the velocity of that water as it passes the screen. By the time the water has passed the screen and is in the pipe or diversion channel it will have maintained the same volume as it would if the screen wasn’t present.
No. A screen doesn’t affect the volume or rate at which water is diverted, and it does not create any additional turbulence that may affect the meter.
No. Newspaper articles from as early as the 1920s reported cod, perch and blackfish being diverted into irrigation canals along the Murray River. A string of articles in 1946 and 1947 discussed the need to address the significant numbers of Murray cod and other native fish being lost to Murrumbidgee Irrigation canals. Technologies have just advanced to such a level that now there is a perfect solution to this century-long problem.
Native Australian fish species have limited swimming abilities compared to many overseas species, like salmon. This means they can very easily get sucked into a pipe or channel that is diverting water from a natural waterway. NSW DPI Fisheries research has found that water velocities of less than 0.1 metres per second at diversions are needed to protect native fish.
Modern screens can reduce losses of native fish by up to 90%. This amplifies the benefits of other conservation actions, like fish stocking. More fish in the river means better fishing, which has flow-on benefits for regional towns through tourism.
Australia has some of the world’s best data on fish losses at water diversions, which gives a good insight into the scale of the problem. Once fish are entrained at a diversion, they are removed from breeding populations forever and the impact therefore accumulates over successive generations. Total annual losses of fish are likely in the millions. Modern fish screens can protect, on average, 3 native fish per megalitre of water diverted.
A range of modern fish screens are available to suit different types of water diversions. This means that any type of diversion can be effectively screened to protect both fish and water users. However, it is critical that the right technology be used in the right place because every water diversion presents its own challenges. Using the wrong technology will create problems like clogging of the screen. For example, just because a screen stops debris does not mean it protects native fish. The Practical Guide for Fish-Protection Screens in Australian Fish screening guidelines provides more detail on finding the right type of screen for a diversion.
Visit the supplier’s section of this website to find a fish screen supplier that suits your needs. For the best results, complete the Pump Screening Information Questionnaire [insert link].