Weetalaba Station — LDC’s third landscape rehydration site

The Mulloon Institute is designing a cost-effective way to address an erosion hotspot on Weetalaba Station to help hold and keep water on the property.

Weetalaba Station graziers Julie and Reid Muirhead.

Reid and Julie Muirhead, of Weetalaba Station, have made a strategic decision to focus on landscape function on the property. 

Landscape rehydration techniques are expected to improve productivity by slowing water movement across the landscape, and to promote infiltration rates to enhance pasture growth.

Slowing water movement reduces erosion, increases pasture yields and will generate economic and environmental rewards.

The erosion site that is being treated is an active alluvial fan that has incised and cut a shortened path to nearby Rosella Creek.

Large active black soil gullies from overland water flows are now dropping into the feature. The erosion is also threatening a nearby leucaena crop.

Mulloon Consulting, a subsidiary of The Mulloon Institute, has designed the project. Interventions will use natural materials to lift and spread water higher in the landscape and re-establish an older flow pattern where water used to run parallel to Rosella Creek for about six kilometres before re-entering the creek system.

The interventions will spread water across the landscape, increase inundation and infiltration across the plain, increase deposition of sediments, and slow subsurface moisture movements.

A grazing management plan will be implemented to combat erosion and to improve landscape function, specifically ground cover.

The long term benefits of the works will include increased water infiltration, healthier soils, more diverse pastures, increased grazing capacity, reduced erosion, and improved water quality.

Large gully on Weetalaba Station where the overland flow re-enters incised fan.

On top of fan feature looking in the direction of the old flow path.

Gully cutting up through a leucaena crop.

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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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