Upper Catchment Impacts

June 2011

3Terrain before Plate40cThink of farming in the Wet Tropics and it conjures up visions of tropical fruits, lush sugar cane fields and cattle pastures. Agriculture in this region is possible because of water abundance and ironically Reef Rescue is helping farmers to improve their land management practices to reduce water runoff from their properties and flowing into reef waters.

But in the upper catchment beyond the Great Dividing Range it's a different story. Cattle grazing in the dry, inland country does present water quality issues, but generally only where land has been degraded. For graziers, Kate and Peter Waddell on Woodleigh station, soil degradation on their property was a major problem but not due to their grazing management. 

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Large tin dredges operated on the creek on Woodleigh station 30 years ago. The dredges were abandoned in 1980 and the tailings dams were breached, allowing the tailings to flow directly into the creeks. "The dams are an environmental disaster, as there was no legislation at the time to clean up the site once the mining company left our land," said Kate.

Through Reef Rescue funding the Waddell's were able to stop huge sediment loads entering the catchment, having an immediate and noticeable impact on water quality. Their project is an example of how Reef Rescue can have a huge impact on water quality by helping farmers to repair erosion hotspots, which they could not economically justify otherwise.

The tailings dams, covering 85ha were constructed above the floodplains to store the clay fines left over from washing the alluvial clays. Over the years water flowing out of the breached dams has eroded deep channels and carried massive amounts of sediment to the creek. "It is likely that the sediments are impacting far downstream on the Herbert River and entering coastal waters" said Ian Little, grazing extension officer.

With Reef Rescue funding the Waddells repaired the dam wall, constructed by-pass spillways with silt traps to catch the overflow of storm water. The erosion of the tailings has now ceased and flow-over sediment was trapped in silt traps preventing it entering the catchment.

There are numerous tailings dams on other tributaries of the Herbert River with the same problem and the Waddells are now encouraging neighbours to repair tailing dams on their properties to prevent further impact on the Herbert River.

Before and after
Images courtesy Terrain NRM