Lagoons Creek wetland rehabilitation

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Queensland Wetlands Program

Herbert River Catchment Group

Landholders

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On-ground work, Monitoring

Queensland Wetlands Program (QWP) management case study

Australian Government

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Lagoon Creek lies on the Herbert River Floodplain of Hinchinbrook Shire and discharges into the Great Barrier Reef Marine Park. Lagoon Creek is surrounded by sugarcane. The lagoon has been subject to long-term, severe infestations of aquatic and floating weeds, especially water hyacinth, resulting in a deterioration of water quality in the lagoon as a result of nutrient loading and loss of dissolved oxygen. Focus of the on-ground works included an aquatic weed removal trial using natural flushing and mechanical weed removal.

To facilitate natural flushing, various pre-treatments were trialled, including breaking the binding of the weed mat to the bank by spraying with conventional herbicide and loosening the binding of the mat itself by aerial application of a brine solution.

Excavators were used to clear weed from bottleneck areas. An aquatic weed harvester was also used. The harvester worked in conjunction with the excavator, which lifted the weed from the water and stockpiled it on the bank. Edge spraying with herbicide increased the efficiency of the weed harvester as less time was spent dragging the weed mat from the banks. Immediately after harvesting, boat-based spraying was required to treat weed clumps that the harvester had not been able to shift, mainly because the weed was snagged on submerged logs.

The project:

• removed floating aquatic weeds on the Herbert River floodplain, which resulted in rapid improvement in water quality and fish diversity.

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Assisted flushing of aquatic weed mats through flood events can be a cost- effective way of improving water health. However, there are limitations such as chokes in the system, which can block flushing. In addition, consideration must be given to downstre

Lagoon Creek wetland rehabilitation