The arrival of the Far North Queensland summer rains brought much-needed relief to a region being scorched by a month-long heatwave, and also provided vital data to the Tropical Water Quality Hub’s flagship project.

Accurately determining the source of dissolved inorganic nitrogen, sediment and other pollutants is key to implementing management actions to reduce them and meet water quality targets set under the Reef 2050 plan.

‘First flush’ flood runoff from sugarcane fields in the Russell-Mulgrave catchment, Queensland. Photo: Aaron Davis JCU

‘Project 25’ is a first-of-its-kind, real-time, fine-scale water quality monitoring and behavioural change project in the Russell-Mulgrave catchment just south of Cairns.

The practices of sugarcane farmers in are a major influence on water quality in the catchment, and providing ground-truthed data is vital to farmers’ decisions to alter those practices.

Sensors and sampling at multiple points along the catchment provide the most comprehensive picture of the quality of the water flowing out toward the Great Barrier Reef lagoon to date, built on close engagement between project lead Dr Aaron Davis at JCU and participating farmers with sugar industry peak body CANEGROWERS.

Babinda cane farmer Stephen Calcagno said the project is generating valuable information for growers as well as researchers.

“Project 25 is great information for the whole industry, not just the farmers but the mills as well, because they’re also dependent on our social licence to operate,” he said.

“It’s going to be very interesting to compare data from 2017 to this year, particularly because last year we had a wet crush, which means it’s longer before fertilization happens and the plants have less time to take up the nitrogen. I would be expecting the Project 25 data to show there would be less nitrogen movement off-site this year.”

Mr Calcagno, who is also working with TWQ researcher Tony Webster from CSIRO on a project trialling enhanced efficiency fertilizers, said knowledge and appreciation of Project 25 was steadily spreading throughout the industry.

“In farming, things take a while, but the interest is definitely out there amongst the growers and it’s getting bigger,” he said.

“Aaron Davis presents at the CANEGROWERS AGM at the end of each year and he’s got fifty or sixty farmers hanging on every word.”

The torrential rains at the beginning of December cause a ‘first flush’ effect where the highest concentration of possible contaminants will be washed into the waterways, meaning that collecting data during this period is especially vital.

“For the sampling during the dry season, streamflow rates are really low so I’m collecting samples for laboratory analysis on a monthly basis most of the time, but when the rains hit and you get the minor to moderate flood events starting to come through, I’m out there sampling sometimes several times a day,” Dr Davis said.

“These first flush events are important because they give us the best indications of what’s going on – instream concentrations can vary in a major way over a few hours so that’s why it’s really important to get out there and sample. These first few flood events really seem to dictate the final scale of nutrient and sediment movement from a catchment over the course of the Wet season. We also have three remote sensors installed that are providing continuous, real-time data on apps like 1622 under CSIRO’s Digiscape program that can get the information into the palm of the farmer’s hand right as it’s happening.”

Dr Davis said the usefulness of the data contributed to the high level of engagement from farmers.

“One of the best things about the rainy season and I guess the project as a whole is that it’s really helping paint a picture of where exactly the water quality issues in the catchment are originating – it’s not just the cane farms,” he said.

“For example, phosphorous loss is often attributed to canefarmers, but our data highlights it’s largely originating from other sources in the Russell-Mulgrave catchment. Catchment water quality is everyone’s responsibility, the cane industry definitely has its part to play but there are lots of factors at work in this system.”

Mr Calcagno said sugar growers were eager to contribute to reducing impact on the Great Barrier Reef and would be enabled to do so with ground-truthed data like that provided by Project 25.

“What growers are really looking for is the data,” he said.

“Data is king in the end.”


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