April 25, 2015
Hope springs eternal
And so we learned that although two-thirds of the Great Artesian Basin lies beneath Queensland, little was known about the springs around the Basin's eastern edge before his relatively recent research. Many springs are now extinct, and with them will have disappeared plant and animal species that have never even been identified. Today, springs are still under threat of drawdown as a result of development of various kinds.
Springs were an important driver of pastoral settlement: they were a signpost to what might lie beneath the ground. From the late decades of the 19th century onwards more and more wells were sunk to water arid regions, and the subsequent reduction in water pressure meant the demise of many springs.
Springs have been historically significant the world over: think North African oases in an otherwise barren landscape. There are four types: those that supply waterholes such as billabongs; those issuing out of a hole in rock (important refreshment sources for Aborigines); discharge springs, which flow under pressure; and gravity springs, formed by rainwater percolating through rock from higher elevations.
Described as cradles of evolution, springs have made an important contribution to the diversity of life. They have permitted unique species to develop. Queensland has springs that are the only ones of their type on the planet. Yet some critical questions about springs are not ecological but hydrogeological. It is important to know how they function, specifically their source aquifers. The springs in the Doongmabulla complex are both discharge and gravity, but not all have been characterised conclusively. It is even arguable precisely how many springs there are in the group. They are at least 1,000 years old but probably much older still.
The Doongmabulla Springs are a few kilometres west of the Carmichael site, but are a key feature of the mine's potential environmental impact assessment as a result of disagreement among expert hydrogeologists identifying the source aquifer. If it is the same rock strata as the one in which the coal seams are located then that will be dewatered and the Springs will cease to exist (see also Leaky aquitards, April 2015).
This permanent artesian fresh-water spring complex is listed in the Directory of Important Wetlands. There are four groups – Joshua, Moses, Little Moses and Surprise – that extend over about 10 hectares. Both expert witnesses agreed that the Springs have 'exceptional ecological value', reflecting the endemic species found in the complex, which is classed as a Threatened Ecological Community (TEC). Six species are only found here. What were described as 'exotic aquatic animals and plants' – and I believe the meaning of exotic here to be strikingly different or unusual rather than foreign – are found in the Springs and their associated wetlands. Among the plants there is Salt Pipewort and Blue Devil, the rarest, and others that are so uncommon they don't have common names; and there are molluscs, unique water mites and even small fish.
Spring sources have been substantially transformed by human use. Cattle and feral pigs trample plant species, although it is now believed that plants recover from this quicker than was first thought. There is a world of difference, however, between the impacts of trampling and dewatering.
The first mention of offsetting in the Carmichael case was made in connection with the threat to springs and their ecology. It would involve 'enhancing' existing springs or the reversal of extinct springs in the area. Even Adani's spring ecologist had to admit that there are no examples of translocated endemic species doing well in artificially created springs. For one thing, the chemistry of spring water is critical for land species.
A key problem with offsetting revealed during this case was the fact that detailed monitoring and mitigation will only be done once approval is finalised and the mine is up and running, which may well be too late for impacted springs and endemic species. Also, there is the 'additionality' condition. The offset has to be bigger than the existing feature. I find it hard to imagine how exceptional ecological value could be replicated, let alone improved. And, another question for the proponents of offsetting: do offsets end with the termination of the Environmental Authority? So much uncertainty; so many questions yet to be answered adequately.
I have mentioned the chemical composition of springs. Chemical signatures could be used to compare Doongmabulla Spring water with groundwater samples from the coal-seam-bearing Colinlea and the Clematis/Dunda Beds above the less permeable Rewan formation. This might be useful in identifying the Springs' source. There are samples available from the Colinlea, and there is some similarity with the springwater. There are few bores in the Clematis/Dundas, however, and the best belong to Adani. Unfortunately, a request by
Dr Fensham for a sample for his ongoing Lake Eyre Basin Springs Assessment project was politely declined.
The photograph at the top of the page is of Moses 3 Lagoon, part of the Doongmabulla Spring complex, and fed by a spring from beneath the Lagoon. Courtesy of Land Services of Coast and Country, 2014