Challenges with irrigation in the lower Burdekin
The lower Burdekin holds Queensland’s largest reservoir to support its farms. It is the only region that offers an irrigation scheme at this scale for sugarcane cultivation, providing an abundant, consistent, and reliable water supply for growers. Yet, despite its advantages, this reliance on irrigation sets a unique challenge in managing water use for the farm and the environment.
Growers in this region rely on fertilisers, pesticides, and irrigation for productive crops. But these chemicals can be lost to waterways through paddock runoff and deep drainage if irrigation is not carefully managed. Typically, about 20% of applied furrow irrigation water runs off the paddock. On top of this, water also seeps down and is lost as deep drainage, causing rising groundwater levels.
Encouragingly, monitoring results show that introducing improved irrigation practices can halve water loss, significantly mitigating nutrient and pesticide runoff, and improving farm productivity.
What are the environmental problems with excess irrigation?
The Lower Burdekin region is northern Australia's largest and most extensively cultivated agricultural floodplain. Despite its agricultural significance, streams that run through the landscape are intricately connected to valuable freshwater, estuarine, and marine waterbodies. These environments have high ecological values and are used frequently by communities and recreational fisheries – making water quality management important.
Nutrients and pesticides in waterways
Freshwater and estuarine creeks are knitted into the Burdekin’s agriculture landscape, directly exposed to runoff from paddocks. These waterways are often close to paddocks, amplifying concentration levels and heightening the risk of poor water quality. This can lead to problems like excessive algae and weed growth in waterways, and low levels of dissolved oxygen in the water.
The Lower Burdekin’s Haughton River and Barratta Creek are the primary systems to receive the majority of irrigation runoff, with water quality monitoring results showing elevated and concerning levels of nutrients and pesticides in these waterways. These major streams feed directly into the internationally recognised Ramsar Bowling Green Bay wetland, covering more than 35,000 hectares of freshwater and marine ecosystems.
Rising groundwater tables
Intensive irrigation has caused increased deep drainage, where excess water seeps down beyond the root zone of crops into deeper soil layers and subsurface pathways. This is leading to a substantial rise in groundwater tables in certain districts, including parts of the Mulgrave, Woodhouse, Haughton, Selkirk and Horseshoe lagoon sub areas.
Rising water tables can lead to paddock waterlogging, hindering crop nutrient uptake and growth. Water from these elevated tables can also seep through stream banks into nearby streams, elevating nutrient concentrations.
What are the benefits to the farm when irrigation is reduced?
Growers can irrigate more efficiently while supplying sufficient water for the sugarcane crop. By reducing water usage, farmers will lower the risk of losses via surface runoff and deep drainage, while saving money on water charges and pumping costs. Benefits to the farm include:
By reducing water usage, growers save on water and electricity costs
Energy savings from reduced pump run times and number of irrigations required over the growing season
Savings in labour and improvements (i.e. reduced after-hours labour required)
Reduced fluctuations in channel levels
Less volume of runoff in tailwater drains
Managing rising groundwater tables ensures viable farming. Reducing excessive irrigation stops waterlogging, aiding cane growth and maintaining soil health.
How can growers respond to these challenges?
Reducing excess water use and minimising nutrient and pesticide losses are significant challenges for growers in the Lower Burdekin. Frequent irrigation means soil moisture levels remain high, increasing the risk of runoff throughout the crop life. On top of this, the complex and variable soil composition in the Burdekin region affects how well the crop and soil absorb water, nutrients, and other substances. This, in turn, influences the extent of nutrient and pesticide losses and crop production.
To tackle these issues, local growers are adopting innovative irrigation practices. With automated technologies and advanced scheduling tools, they’re not only gaining deeper insights into water flows across their paddocks but also improving manual intervention and fine-tuning water inflow rates. Automated technologies are also gaining traction, offering growers a powerful way to optimise water use while providing the flexibility growers need to manage their time effectively.
The Burdekin Irrigation Project supports lower Burdekin growers to adopt improved irrigation practices, through tailored expert advice and appropriate enabling technology. Extesntion staff conduct water quality monitoring on multiple Burdekin farms, where landholders are refining irrigation strategies to enhance efficiency:
Understanding irrigation and product loss: Extension providers establish water quality monitoring programs to help growers understand how much irrigation, along with pesticides and fertilisers, is being lost off their farms.
Recommend intervention strategies: The team evaluates data to recommend irrigation interventions tailored to each farm's unique conditions, considering soil type, block layout, water inflow rates, and soil moisture levels.
Fine-tune irrigation practices: Growers fine-tune irrigation methods to reduce losses by increasing water flow and using midstream shutoffs. They also use modern technologies like automated pumps, valves, sensors, and advanced scheduling programs.
Pesticide and fertiliser management: Growers carefully manage application methods and product choices. For fertilisers, this includes timing, rates, placement, and product selection. For pesticides, it involves timing, product choice, and strategic application. Machinery can allow for precise application.
