Landholders don gumboots to collect vital water samples

Mick and Natalie Comerford, of Exmoor Station being shown how to collect water samples by TropWATER scientists Steve Lewis (out of picture) and Zoe Bainbridge.

This year’s wet season provided limited sampling opportunities for the landholders who make up the LDC Community Water Quality Monitoring Group. 

All subcatchments had streamflows, however most of the flows were intermittent; quick to rise and fall, demonstrating the level of commitment by all landholders samplers who collected samples at all hours of the day and night.

More than 100 samples were collected from nine subcatchments across the BBB. This is a good effort and adds to the robustness of the dataset.

The samples are being analysed for phosphorous, nitrogen and sediment content.

When analysing the samples, The Centre for Tropical Water and Aquatic Ecosystem Research (TropWATER), James Cook University, use isotopic tracing to determine the source of sediment within subcatchments. Scientists are able to determine whether particles within the sample are from hillslope, gully or streambank sources. 

Results so far show the Bowen River sub catchment is an area highly susceptible to soil loss, most likely due to soil type and fine sediment particle size.

This year’s findings, and the combined results from all previous years monitoring, will be published later this year.

Monitoring group performs a vital role

Nine properties in the Bowen, Broken and Bogie (BBB) catchment make up the LDC Community Water Quality Monitoring Group. 

The group was established to better understand the water quality variations throughout the BBB catchment, with a focus on sediment and nutrient concentrations throughout a range of flow events. 

Scientists Zoe Bainbridge and Steve Lewis from The Centre for Tropical Water and Aquatic Ecosystem Research (TropWATER), James Cook University, trained landholders to collect and store water samples. 

The Community Water Quality Monitoring Group data is shared with the Queensland Government modelling team. The results are being used to enhance the Paddock to Reef Integrated Monitoring, Modelling and Reporting Program (Paddock to Reef Program) model and to improve confidence in load estimates and results for the BBB catchment. 

For more information about the Paddock to Reef Program:
https://bit.ly/PaddocktoReefprogram.

With monitoring, LDC is learning more about how, when and where sediment (and nutrients attached to sediment) moves. This means graziers can respond better to help reduce sediment flowing out into the Great Barrier Reef lagoon.

TropWATER Research Scientist Zoe Bainbridge talks about the results of the 2020-2021 wet season to members of the community monitoring group.

 

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.
KEQ #8

KEQ #7
KEQ #6

KEQ #5

KEQ #4

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.

KEQ #3

*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.

KEQ #1

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.

KEQ #2

*GLMWW = Grazing Land Management Wire and Water

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