A recent study published in Nature Ecology and Evolution journal provides support for better control over flood flows such as would be captured by the New Bradfield Scheme and redirected to storage dams inland. Flood flows carry debris, sediments, nutrients, and other pollutants into the coastal regions – and add further stress to the Great Barrier Reef. Improving local water quality may help some reefs better withstand the bleaching impacts of climate change.
Using a composite water quality index, we find that while reefs exposed to poor water quality are more resistant to coral bleaching, they recover from disturbance more slowly and are more susceptible to outbreaks of crown-of-thorns starfish and coral disease—with a net negative impact on recovery and long-term hard coral cover.
See Dirty water biggest risk to reef recovery in the Australian.
Water quality mediates resilience on the Great Barrier Reef
Estimates of river pollutant loads to the Great Barrier Reef lagoon indicate the Fitzroy and Burdekin catchments contribute at least 70 per cent of the anthropogenic total suspended solids load to the Great Barrier Reef lagoon, with grazing lands (gully and hillslope erosion) (45 per cent) and streambank erosion (39 per cent) the main sources.
The same report states that compared to pre-European conditions, mean-annual river loads to the Great Barrier Reef lagoon have increased; 3.2 to 5.5-fold for total suspended solids; two to 5.7-fold for total nitrogen; and 2.5 to 8.9-fold for total phosphorus. The total pesticide load to the Great Barrier Reef lagoon is likely to be considerably larger, given that a total of 34 pesticides have already been detected in the Great Barrier Reef catchments.
Flood water in rivers contains much higher ‘total suspended solids,’ or volume of other debris materials (like soil, plant material, dust, and other particulate material) than normal flow conditions. For example, the transitory TSS for an Adani infringement notice due to a controlled release in high rains at a monitoring point was 58 mg/L when the maximum limit of total suspended solids allowed in a flood water release under the Port’s Environmental Authority is 30 mg/L. But this is a fraction of the levels usually found in natural flood events.
The research shows that the dominant sediment supply to many rivers in the Great Barrier Reef catchment is from a combination of gully and streambank erosion, and subsoil erosion from hillslope rilling.
The cumulative effects of flooding of Queensland Rives may have reduced coral growth by 50%. A Bradfield Scheme would reduce total flows by capturing some of the flood water and redirecting inland to provide irrigation, town and mine water supplies. The capture and redirection of flood water would reduce the overall sediment discharge and potentially help to maintain the health of the Great Barrier Reef.
The approval of the massive Adani (Carmichael Coal) Mine has been delayed by ongoing concerns with the groundwater plan. What if the mine did not have to use groundwater at all, but drew water from massive storages created nearby at Lake Buchanan and Lake Galilee? The unused salt lakes perched on the Great Dividing Range could be filled with flood water from an aqueduct to Hells Gate Dam on the headwaters of the Burdekin River.
Low-cost gravitational flow is viable, as it is downhill from all the way from the headwaters of the Burdekin, providing Hells Gate Dam is built to a sufficient height.
Not only Adani, but 5 mines have been approved for the Galilee Coal Basin (see image). Are they going to run into the same water sourcing problems too? A Galilee pipeline should be constructed to pipe water east from the two storages and so mitigate the environmental impact of these mines on ground and surface waters.
The mines in the Bowen Basin draw water from the Burdekin Falls Dam via a pipeline – why not build the same river saving infrastructure for the Galilee Basin?
In addition, the storages could also be used for town water supply and irrigation of the fertile Mitchell Grass Downs to the west of the Great Dividing Range. Use a renewable supply of flood waters and leave the limited groundwater source alone.
Renewable hydropower generation is also possible at and between Lake Buchanan and Lake Galilee, as well as locations along the aqueduct route. The power generated could be sold to the mines, generating carbon-free revenue.