An overview of Monitoring and Evaluation for the LDC project

Work in progress at the Strathbogie Station gully remediation site.

First results at Strathbogie are encouraging

Treatment

Treatment on the gully system at Strathbogie Station included five hillslope flow diversion banks and a small rock revetment near a headcut designed to prevent subsidence.

Exclusion fencing was also installed. 

Results

While only one season of post treatment data has been collected from this site, monitoring at Strathbogie for several wet seasons prior to the treatment taking place has provided higher levels of confidence in monitored changes that are detected. 

Remediation carried out in 2019 has generated statistical reductions in the total suspended sediment concentrations and total nitrogen levels leaving the system and entering the Great Barrier Reef lagoon. 

The site did receive lower than average rainfall in 2019-2020, where it has been monitored that the mechanical treatment applied has successfully prevented runoff from entering the active gully. 

The monitoring also shows that the vegetation and landscape are still fragile so ongoing management and monitoring will be important to assess how the treatment site responds to variable rainfall over additional years. 

The images show that the treatment applied to the gully system at Strathbogie is preventing the gully from receiving the runoff and sediment that it has in prior years. 

Data collected on the adoption and effectiveness of landscape remediation techniques and farm management practices is used in the annual Reef Water quality Protection Plan report card as well as to enhance the catchment models. 

This is facilitated through the Paddock to Reef integrated monitoring, modelling and reporting program.

Many of the samples are collected by helicopter in collaboration with Fruition Environmental.

Water quality monitoring samples ready to be transported to the Townsville laboratory. 

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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.

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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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