On-farm sites have catchment repair potential

Monica Haynes
April 30, 2018

On-farm sites in the Johnstone and Tully River catchments have been assessed as possible catchment repair locations for the Wet Tropics Major Integrated Project More than 40 on-farm sites in the Johnstone and Tully River catchments have been assessed as possible catchment repair locations for the Wet Tropics Major Integrated Project (MIP) – a reef water quality initiative that is the first of its kind in the Wet Tropics.

Catchment Repair Project Officer Suzette Argent said 15 sites had been assessed in April alone.

“We’ve racked up a lot of hours in the field and have covered a lot of ground.”

“This month we’ve focused on wetland sites because they take longer to design and construct so we need more lead time. We’re hoping to have two constructed by end of 2018, to get as much monitoring time as possible.”

Catchment repair and treatment systems have the potential to reduce nutrient and sediment loads entering the Great Barrier Reef, and their effectiveness in the Wet Tropics will be trialled and monitored over the life of the project.

The MIP is funded by the Queensland Government and designed by the local community. A consortium of more than 40 organisations, and hundreds of community members pooled their knowledge of Tully and Johnstone catchment to design a program tailor-made to the environment.

‘Walking the Landscape’ workshops – where scientific information from maps and reports is combined with decades of local knowledge – has helped with the selection of possible catchment repair sites.

Suzette is working closely with Mark Bayley from Australian Wetlands Consulting, who has more than 15 years’ expertise in catchment repair. The pair worked together on Australia’s first bioreactor, on a Sunshine Coast pineapple farm.

“There are different criteria we need to consider. Most importantly, landholders have to be open to the idea of us working on their land’’ Suzette said.  “We’re really encouraged by the level of willingness so far. Growers are keen to drive water quality improvements”.

“We also need to know if the right technology is going in the right spot in the landscape. During a preliminary site assessment, we’ll check to see if the site is in a low point in the landscape and if it has the ability to intercept the base flow, or the constant and steady flow of water, as well as storm flows”.

“The MIP is all about local knowledge informing action. The success of catchment repair technologies are reliant on knowing how the water moves and who better to know this than the landholders who live here”.

Suzette and Mark also take the wetland-to-catchment size ratio into account when making their recommendations.

Wetland size, treatment area size and the amount of land that would need to be taken out of use (if any) all help to give a theoretical dissolved inorganic nitrogen (DIN) reduction rate in kilograms per year, which is compared to the cost of construction. In short, this gives a cost per kilo of DIN removed, and provides a good value-for-money check.

First stage sites are expected to be finalised in May. The team will make recommendations based on an assessment matrix, before putting them before the MIP Project Panel for consideration. Once the panel has reviewed and endorsed selections, more detailed site investigations will take place to inform the engineering designs of the wetlands and bioreactors.

“This is the rigorous stuff – drilling holes for soil and hydraulic studies; risk assessments; flora and fauna surveys; and cultural heritage assessments” Suzette said.

Information sessions will be held in early June, followed by expressions of interest for construction work. Construction is expected to begin in July.