Vegetated farm drains improving water quality

Vegetated farm drains – they’re the mini wetlands of our region with trials showing they can improve the quality of water flowing into creeks, rivers and the ocean.

15 per cent reduction in nitrate 

We visited a Tully farm recently where we’ve seen a 15% reduction in nitrate (dissolved inorganic nitrogen or DIN) as water moves along the farm’s 570m central drain during steady flows.

This drain was monitored by us for 18 months back in 2021-2023. It wasn’t specifically designed for water treatment and hasn’t had any modifications. A lot of the bank has trees along it, shading in-stream plants, but this drain also has a couple of very well-vegetated sections that are probably working to strip out nitrates through the denitrification process. It seems like the combination of some open water and vegetation patches is working well.

Other drains, on cane and horticulture farms a little further south, have been monitored by researchers from the Queensland Department of Primary Industries. They’ve also shown that vegetated drains can effectively remove nitrate from farm runoff. (Results will be coming out soon.)

What factors make a farm drain suitable?

Not every drain is suitable – it depends on things like depth, water flows, organic carbon levels and the vegetation cover. But there is so much potential in a region with this many drains…

Thanks to the crew from Herbert Cane Productivity Limited and to Carla from DPI for organising the recent trip to Tully, to the Ingham cane farmers who came along, to Alicia from Terrain NRM for taking everyone through the Tully results and to Tully landholders for having us all on site.

This trip was part of the Herbert Integrated Project and the Queensland Department of Primary Industries’ Treatment Train Solutions Project. The Herbert Integrated Project is funded through the Queensland Government’s $330.5 million Queensland Reef Water Quality Program and delivered by Terrain NRM in partnership with Hinchinbrook Shire Council, Herbert Cane Productivity Services Ltd, Canegrowers Herbert River, JCU TropWater, QCAR, Agforce, and DPI.

Cane drain monitoring in Tully was part of the Wet Tropics Major Integrated Project and our Local Scale Monitoring, funded by the Queensland Government’s Queensland Reef Water Quality Program.