A golden perch caught by electrofishing in river pools to assess populations and species

Impacts and solutions: Evaluating interactions between irrigation infrastructure and fish


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

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

CRDC Natural Resource Management 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.”

For more, see the Summer 2020-21 edition of the CRDC Spotlight magazine.