In line with CRDC’s goal to improve sustainability, research is underway to better understand and minimise the impact of irrigation infrastructure on fish populations in rivers.

Specialists from QLD DAF, with support from CRDC, will evaluate how various fish species interact with different types of irrigation infrastructure. This information will enable measures to be developed to avoid fish being entrained - or caught up - in irrigation systems.

Evaluating the relative impact of different irrigation infrastructure types will identify which are lower impact and which types should be prioritised for mitigation measures in the future. Available mitigation measures and the potential costs and benefits will also be examined.

This work is an important step in developing and prioritising best management practices to reduce the direct impacts of water extraction on fish without sacrificing irrigation efficiency. The results of this work could be applied to new irrigation developments and upgrades to existing systems.

There are many variations in irrigation infrastructure systems, design and function. Pumps vary in size, and the locations and style of the inlets also vary. For example, some inlets are close to the river bank, others extend further out into the river and some are positioned in short side channels  perpendicular to the river. Other irrigations systems rely on gravity fed diversion channels. Fish may also behave differently in natural flow events, compared to irrigation flow releases from dams and weirs, says QLD DAF Principal Fisheries Biologist Michael Hutchison, who is leading the research.

“All this variation means some systems are likely to have a lower impact than others when it comes to entrainment of fish,” Michael said. 

“The intent of this work is to build on existing international and national research and make best practice recommendations to CRDC for irrigators to minimise impacts on fish. These measures may also be beneficial to the irrigation infrastructure operating efficiency and maintenance.”

Some of Michael’s previous research evaluated movements of small and medium sized fish in the Northern Murray-Darling Basin. Michael and fellow researcher Dr Andrew Norris also have a background in restoring fish stocks through habitat restoration and enhancement.

Their award-winning work in the Condamine River near Dalby led to substantial increases in the abundance of fish at rehabilitated sites. Much of this work involved collaboration and cooperation with landholders. All observed increases in fish numbers occurred without irrigators reducing their use of water.

“Based on our past experience some fish species or sizes are more likely to be entrained than others,” Michael said.

“Some species, even though abundant in the river, may rarely pass through an irrigation system, whereas other less-common, poorer swimming species may be over-represented. For example juvenile catfish seem particularly susceptible to entrainment.”

Work begins in the north

Fyke nets and electrofishing are used to sample the river reach near irrigation offtakes.The experimental work will be undertaken in the Fitzroy River Basin, which has a mix of typical southern and northern catchment fish species. The results from this catchment will therefore be applicable to both tropical and temperate systems where cotton irrigation already occurs or is planned. Some of the well-known angling species that occur in the proposed study region include barramundi, Murray cod, golden perch and saratoga.

Michael said his team are currently preparing a review of existing mitigation technologies, including what is known about the effectiveness of the different systems for eliminating entrainment and impingement of fish, as well as other functional and economic aspects such as cost, ease of maintenance, self-cleaning capacity and impacts on pumping efficiency. Functional self-cleaning systems are important to maintain pumping capacity. Most of the newer designs appear to be very effective.

Priority research

CottonInfo's Natural Resource Management technical lead, and CRDC R&D Manager, Stacey Vogel said this project represents the commitment by the cotton industry to identifying key management strategies to protect and improve riverine areas including the condition and resilience of fish populations within cotton landscapes.

“CRDC has prioritised research relating to fish entrainment as an outcome from the industry’s 2019 fish stewardship R&D priority workshop,” Stacey said.

“Representatives from industry, universities, state and Australian Government organisations attending the forum rated fish entrainment as the highest R&D priority due to its potential impact on the resilience of native fish populations and the subsequent threat it poses to the industry’s social license to irrigate.”

Irrigators are proactively investigating methods of avoiding entrainment in the Macquarie Valley. A trial is underway by growers at the Trangie Nevertire Irrigation Scheme and NSW DPI Fisheries.

“We wanted to see for ourselves if it is at all possible or feasible to screen fish, fish eggs, larvae, and other debris at the pump site, while not effecting or reducing flow or extraction rates,” said scheme member Jim Winter.

“If this is doable it would be a win for the environment in healthier rivers and ecosystems.

“It’s a win for our irrigation members, through cleaner water extraction, meaning better pumping conditions with less debris in water and possibly less blockages in both sprinkler and flood irrigation.”

Taking a proactive approach at Trangie

Fish screens installed this year as part of a trial in the Macquarie Valley to assess the impacts on fish and pumping efficiency.After attending an information seminar at Trangie in August 2019 on the benefits of fish screens, a group of local irrigators decided to take a proactive approach.

After the meeting, the Trangie Nevertire Irrigation Scheme expressed interest in working with NSW DPI Fisheries and a commercial screen company to conduct a screen trial. A screening solution was designed and fish exclusion screens were fitted to one of the scheme’s pump stations in July this year. The installation was funded via the sale of environmental water in 2018 which is now being reinvested into fish-friendly infrastructure through the NSW Drought Initiative.

Scheme manager Shane Smith said the set-up involves using cone screens, which are designed for shallow water and partially submerged, silty conditions. They meet NSW Fisheries’ guidelines to protect fish from entrainment or impingement, along with protecting pumps from clogging with debris and “hopefully reducing running costs via reducing power demand charges and increase pump efficiency”.

“The screens have low maintenance requirements and costs. 

“Being constructed from 304 stainless steel wedge wire they are strong and hopefully have a long asset life,” Shane said.

“There are three cleaning brush arms on each cone which are automated to clean in the event of head loss through the screens, or once a day minimum for a total of four minutes a day.”

Shane explained that the advantages in selecting cone screens is they have a positive brushing action to prevent debris building up, sedimentation and bio-fouling and they can be used even if not fully submerged, having large surface area with a smaller footprint. The primary way the screens do this is by reducing approach through-slot velocities. For example a normal pump inlet could have an inlet velocity up to and possibly over 3m/second, meaning the area of influence around the pump inlet is significant which can drag a lot of debris to the pump from a long way away.

A cone screen has an approach velocity of only 0.12m/second at a flow capacity of 600ML/day and much less at lower pumping volumes. By pumping less debris at the pump station, the scheme hopes its members will be see less debris being delivered on-farm, which hopefully will also reduce running costs.

“Most of the scheme members now use lateral move or pivot irrigation systems with nozzles prone to blocking with debris,” Shane said.

“Another advantage is hopefully for the environment, by not pumping debris, eggs, larvae and even adult fish, we hope it is a win-win for our members and the fish along with other users of the river.”

NSW DPI researchers will conduct controlled tests through the 2020-21 season, including monitoring fish and egg larvae and determining the screens’ effectiveness.

“Hopefully if we can see a good outcome for fish, this can open the door for more support for growers installing these type of systems,” Shane said.

The screening project is a partnership with NSW DPI Fisheries and the NSW Department of Planning, Industry and Environment.

CRDC supporting the Australian Screen Advisory Panel

CRDC is co-investing with OzFish Unlimited to assist with administration of the Australian Screen Advisory Panel (ASAP).

ASAP facilitates the planning and implementation of fish screening R&D with representation from international and national fish ecologists and engineers as well as anglers and irrigators, including National Irrigators’ Council CEO Steve Whan.

“Getting a healthy river environment is about more than the amount of water,” Steve said.

“National Irrigators’ Council has been a strong advocate of measures to improve conditions in our rivers for native fish, that includes getting water temperatures and river management right, connectivity, reducing feral pests and things like re-snagging.

“Modern fish screening has the potential to offer effective protection for native fish and facilitating safe and efficient pump operation.

“On that basis we are keen to support efforts to further develop and inform irrigators about the screens.”  

Key activities of the group are to recommend R&D needs, and review and promote the latest R&D around biological and engineering performance of screens. It will ensure best practice design criteria and guidelines are supported nationwide and adopted by management agencies, screen manufacturers and industry.

ASAP also complements the recently launched website Fish Screens Australia which is an information hub featuring the latest information on screening from fisheries, university and industry experts.

“By investing in ASAP, CRDC are supporting the transfer of R&D knowledge between researchers, manufacturers, anglers and irrigators ensuring the best outcome for both fish and irrigators,” CRDC’s Executive Director Dr Ian Taylor said.

“This is not a new space for CRDC as we have supported earlier industry research to improve fish management.

“During the years of the Cotton Cooperative Research Centres, CRDC supported a scoping study of international fish screening programs and field experiments in the Namoi River to develop initial design criteria for fish screens at water diversions in the Murray-Darling Basin.”

This article originally appeared in the summer 2020-21 edition of CRDC's Spotlight magazine. For more information, contact CottonInfo's Stacey Vogel: