The effects of river run-off on water clarity across the central Great Barrier Reef

Reductions in river run-off can significantly improve water clarity on the central Great Barrier Reef, with measurable benefits for ecosystem health. The study analyzed ten years of data, including daily river load, oceanographic measurements, and satellite imagery (MODIS-Aqua), to assess changes in photic depth—defined as the depth at which 10% of surface irradiance reaches. After accounting for wave and tidal effects, researchers found strong correlations between water clarity and river freshwater (R²=0.65) and phosphorus loads (R²=0.51). During wetter years, photic depth was reduced by nearly 20%, falling below water quality guidelines for an average of 156 days compared to just 9 days in drier periods. The impacts were most pronounced inshore and midshelf (12–80 km from the coast), with weaker effects near chronically turbid coastal areas. These findings highlight the potential for targeted river load management to enhance water clarity and support reef health.

Fabricius, K. E., Logan, M., Weeks, S., & Brodie, J. (2014). The effects of river run-off on water clarity across the central Great Barrier Reef. Marine Pollution Bulletin, 84(1-2), 191–200. https://doi.org/10.1016/j.marpolbul.2014.05.012