Project 4.1 'Tracking coastal turbidity over time and demonstrating the effects of river discharge events on regional turbidity in the Great Barrier Reef'

For each of the four Natural Resource Management (NRM) regions between Gladstone and Port Douglas, this project aims to deliver an improved understanding of the quantitative relationships between changing deliveries of suspended solids from their main river ways to the Great Barrier Reef (GBR), and changes in the coastal water clarity within their region.

Turbidity is a fundamental environmental property of coastal marine ecosystems, because suspended particles reduce irradiance for primary producers, alter trophic structures, and can be vectors for nutrients, pollutants and diseases. On the GBR, increasing turbidity has been related to a five-fold increase in macroalgal cover and a 30% reduction in coral biodiversity. Due to its relevance, both levels of turbidity and changes in turbidity are used as indicators for environmental reporting of the condition of estuarine and coastal waters.

A recent study investigated the spatial and temporal variation in turbidity at 14 inshore reefs in four regions of the GBR over three years. It documented that inshore turbidity is strongly related to river runoff and rainfall, and that it improves in the dry season if wave height and tidal currents are being accounted for. The study showed that distance of a reef to the nearest major river mouth was a strong predictor of turbidity, and so are wave height, wave period and tidal ranges (leading to sediment resuspension). The data show that significant intra-annual changes in turbidity on the inshore GBR are related to variation in terrestrial runoff. The study suggested that a reduction in the river loads of fine sediments and nutrients through improved land management should lead to measurably improved inshore water clarity.

The objective of this study will be to determine for each NRM region specific quantitative relationships between changed terrestrial runoff to the GBR and intra- and inter-annual variation in coastal water clarity

Specific objectives and intended outputs of this Project are detailed in the NERP TE Hub Multi-Year Research Plan.

Final Report

Tracking GBR water clarity over time and demonstrating the effects of river discharge events Progress Report: Southern and Northern NRM Regions

Project Factsheet

Technical Reports

The relationship between Burdekin River discharges and photic depth in the central Great Barrier Reef

Link to the Project 4.1 homepage on e-Atlas