Living in the Barron River catchment is a great lifestyle for many – but come the first rains of the wet season the water turns different shades of muddy brown, and often resembles chocolate milk. Over the wet it stays a constant brown, sometimes dark, clay or tan. The reason is sediment – soil and debris washed off the land and into the river during rain. Big storms will often see the water go brown very quickly, full of sediment washing out of the river mouth and into the sea. It then drifts onto coral reefs and destroys them.
Why is it so muddy brown, every year? The main problem is agricultural land, cleared of trees and often ploughed it means the runoff is much higher, and topsoil just flushes into creeks and rivers. Take a drive out to the Atherton Tablelands in the wet season and you will still see fields here and there freshly ploughed, rich red soils eroding and creeks running a muddy brown. Clearly some farms are not managing soil runoff.
Water quality is a big problem for the reef. The Queensland and Commonwealth Governments have spent billions of dollars trying to improve runoff and pollution from farms. There are multiple programs – best management practices (BMPS) for farmers, extension services, restoration projects, science and research and behavior change. The Queensland Government has also introduced regulations designed to increase compliance for managing soils and nutrients. So far these programs have met with mixed success, and in the Wet Tropics region the uptake of BMPs has been very low – below 10% across farming properties.
The Government publishes regular report cards on the state of the rivers. The Barron River recorded a score of ‘good’ in 2018 – 2019. [1] But the sediment score was only moderate, decreasing from good the previous year. Concentrations of total suspended solids frequently exceeded guideline values during the wet season, with the very high rainfall events and floods leading to increased erosion.
So something is not going well in the Barron catchment if the sediment score is getting worse, and millions more tonnes of soil is eroding off the land. The Great Barrier Reef is in dire straits, and could be gone in the next decade or so. Reducing runoff is critical to any hope of its survival – and rapid change is clelary needed.
It’s clearly time to consider other ways to stop runoff, and turn the Barron into a clean, healthy river again - all year. Reforesting large areas of the catchment is probably the best way to protect the soils, and has the benefit of storing carbon to generate credits and providing sustainable timber. Perhaps governments should start large scale native reforestation now and make it a viable, short and long term investment for landowners.
[1] https://wettropicswaterways.org.au/wet-tropics-report-card/freshwater/barron-basin/