Monitoring group mobilises for ex-Cyclone Penny deluge

JCU TropWATER scientist Zoe Bainbridge demonstrates the correct way to collect a water sample

MERI Officer Barb Colls

A community-based water quality monitoring group established in September is already proving its worth to scientists trying to get hard data on how much sediment and nutrient run-off is flowing into the Great Barrier Reef from the Bowen, Broken, Bogie (BBB) catchment, around Bowen and Collinsville.

The water quality monitoring effort is part of the Landholders Driving Change (LDC) project, which focuses on catchment-scale solutions to improving land management, pasture cover and the quality of water running off to the reef.

Monitoring and evaluation is an integral part of the LDC project – one of two Queensland Government-funded Major Integrated Projects (MIPs).

Monitoring, Evaluation, Reporting and Improvement Officer at NQ Dry Tropics, Barb Colls, said water samples needed to be collected from flowing streams during, and immediately following, rain events.

“They’re tributaries to the main watercourses, so they only flow when it rains,” Ms Colls said.

Since September last year, local landholders have been trained and have successfully collected water samples on five of nine properties selected in the BBB.

When ex-Cyclone Penny made its way across part of the BBB in early January, four properties captured water samples at monitoring sites as the flow started, again at its peak and as water levels fell.

Between members of the monitoring group and the material collected from automated sampling sites, a total of 106 water samples were taken.

“That was a big rain event, but it was patchy, with very intense rain in some areas, through to almost no rain in other areas,” Ms Colls said.

She said the local knowledge among landholders in the water monitoring group was crucial to the success of the program, which would run until the end of the 2020 wet season.

“The people who live and work there, know their land,” she said.

“They know for instance if they can see rain to the west, the creek near their homestead will soon begin to flow.”

She said the monitoring sites were close to each homestead, and samples could be collected without too much interruption to the normal workday routine on the property.

Samples are collected using a modified pool-cleaning scoop to easily get the sterilised sample bottles out into the current for filling.

Details of the date, time and water level in the stream are recorded on field sheets and the samples stored in fridges and freezers until they are collected and analysed in the lab.

Ms Colls said the water monitoring group made a direct and active connection between farmers and scientists.

Scientists will share what they learn from the data with landholders, ensuring everybody benefits as graziers and technical experts strive together to improve water quality.

Visit the NQ Dry Tropics website at www.nqdrytropics.com.au for more details.

Some of the 106 samples collected

An automatic monitoring station at Mt Wickham

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Figure 1. Total fine sediment reduction by project type and erosion source. Inset shows the proportion of the total project area for each project type.

These estimates have been calculated using two methods: 

1) The pollutant reduction component of the Alluvium/Great Barrier Reef Foundation (GBRF) investment tool for hillslope and streambank erosion management projects; 

2) The Reef Trust Gully Toolbox method for gully erosion management projects. The LDC Water Quality Report 2020 (Waterhouse et al., 2020) highlights that a number of assumptions underlay these calculations, therefore these figures should be treated as the best available estimate of sediment reductions to date.

Preventing sediment from reaching the Great Barrier Reef

Each wet season sediment is washed into local waterways and out to the Great Barrier Reef (GBR). 

Most sediment is very fine, and can stay suspended for a long time and can travel great distances. Valuable topsoil is lost from production, and increased concentrations on the reef can be harmful to seagrasses and corals. 

Landholders in the BBB have completed 69 on-ground water quality practice changes, and it is estimated that these have contributed a fine sediment reduction of 6,154 tonnes per year from reaching the GBR. 

Of this, approximately half of the sediment savings are attributable to grazing land management changes on hillslopes and streambanks, and the other half as a result of gully remediation treatments across a broad range of scales, as shown in the graphs above. 

The table below also highlights the relatively small area of intervention in the gully management projects compared to the large sediment savings that these can achieve - 60 per cent of the sediment savings over only 4 per cent of the project area.

Table 1. Estimated sediment reductions (tonnes) from projects completed in the LDC Project to date.

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*GLMWW = Grazing Land Management Wire and Water

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*The Exploring New Incentives activity area has provided an opportunity for graziers to adopt improved land management practices through a range of activities. For some of these properties, it was the first time they signed contracts for on-ground works.

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The LDC project monitors four gully sites (represented in this table) with gold standard equipment and analysis, carried out by CSIRO.

Results have been compiled in a preliminary report from Bartley et al (2020), with the final report expected to be released by the end of 2020. The preliminary report shows all four sites have indicators of improvements, notably the Strathbogie and Mt Wickham sites.

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Reef regulations - grazing, standard conditions

  1. For land in good or fair condition (more than 50 per cent ground cover at 30 September), continue using measures to maintain land condition.
  2. For land in poor condition (less than 50 per cent ground cover at 30 September), steps must be taken to improve land condition.
  3. For land in degraded condition (less than 20 per cent ground cover at 30 September), steps must be taken to improve land condition OR prevent areas from further degrading or expanding.
  4. Keep records of measures taken and also of agricultural chemicals, fertiliser and mill mud or mill ash applied to land.
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