The Plutonic Waters of the Great Artesian Basin

Synopsis

In two previous papers in Focus on the Great Artesian Basin (see references) I put forward my view that the present official concept of recharging of the Basin from surface waters was incorrect. At the time I was not certain as to the actual origin of the waters, only that recharging from surface waters was a physical impossibility. My continuing studies set me on a quest for the source of the waters.

It was evident (to me anyway) that the sedimentary rocks of the artesian basin should have been dry before there was any drilling of boreholes. Examination of records from 1888 showed that the sediments were mostly dry when the first bores were drilled. Water was found in the bedrock below the strata, and often at high pressures. I concluded that the water had subsequently entered the shallower strata from these deeper boreholes, by the simple process of hydraulic jacking from the high-pressure waters of the deeper bores.

The deeper underground source meant that the waters were of plutonic origin. The water is of similar origin to the waters that explode as steam from volcanoes, and gush from the deep ocean vents. The eastern boundary of the Basin merges with a wide zone of recent vulcanism extending from Cape York to Tasmania, and which has been active in the last 40 million years, most recently at Mt. Gambier only 5000 years ago. The chemical composition of the waters, the temperatures and the association with natural gas all confirm a plutonic source. The huge volume of water already taken from the Basin, say 100 times Sydney Harbour, is also consistent with a volcanic source and certainly not slow seepage through the strata. The waters probably accumulated during this period of vulcanism, and may represent an accumulation over tens of millions of years. I believe that the present usage of the water from the Basin greatly exceeds any potential recharge from these deep sources.

I have also concluded that these deep plutonic waters also form a water drive for all of the resources of oil and natural gas in this same area, and the nearby resources in the Otway and Gippsland Basins.

As the sustainability of both the water resources and the petroleum resources depends on the drive of the plutonic waters, I think it is critically important to ensure that all these resources be understood and managed as parts of an integrated system of natural resources. Thus the continuing waste of artesian waters is highly damaging to the potential recovery of oil and gas as well as limiting any future recovery of water. I think this is a matter of critical national importance.

A wonderful aspect of my studies has been the discovery of the writings of J. W. Gregory, FRS, who was Professor of Geology at the University of Melbourne from 1899 to 1904. In 1901-02 he took a party of students into the area around Lake Eyre, and studied the flowing bores of Central Australia. Gregory, who was an outstanding scientist with wide experience in geology, and who had studied the geothermal waters and volcanic features of the Great Rift Valley in Kenya, stated quite firmly that the waters were plutonic. He was quite right, and that was 100 years ago.

Here we are 100 years later, and Australian scientists, the several governments involved, and the oil and gas industry operating in this region, have not yet comprehended the simple truth that was stated so clearly and positively by Gregory so long ago. The paper discusses how the present sad situation came to pass.

The Great Artesian Basin

The Great Artesian Basin spans four states and covers one fifth of Australia. The rocks are a normally consolidated sedimentary series of Jurassic and Cretaceous age. Down-warping of the crust of the earth has created a saucer shaped basin, with a maximum thickness of sediments of about 2000 metres.

Figure 1: Under the Constitution, water is a responsibility of state governments. The management of the Basin is the responsibility of three states , ie Queensland, NSW and SA, and the Northern Territory. It is my view that this division of responsibilities for the management of this important national resource is one of the causes of the serious problem now facing the nation.

Drilling of bores into the Basin began in 1886. By the end of the century, in 1899, there were 524 wells, of which 505 were productive. The yield at the end of 1899 was 1000 megalitres per day, a remarkably large flow of water. But by 1899 there was already concern about the declining flow from most bores.

The total discharge from the Basin reached a maximum in 1917 and has been declining ever since, despite an increasing number of bores.

Management of the Basin

The state representatives, together with an Australian Government representative, meet as a Technical Committee. There is also a users group called The Great Artesian Basin Consultative Council. Mr. John Seccombe, who has a property near Longreach, is Chairman.

There are several aspects of the Queensland Government diagram which convey a false impression. It has a greatly exaggerated vertical scale, which is not stated. If the diagram were drawn to a natural scale it would appear as a single line across the page. The diagram takes no account of the difference in relative density of the water (1.0) and the rocks (2.6). It carries the implied assumption that the pressure head of the seepage water from the intake beds, less friction losses all the way, would be sufficient to overcome the stresses in the rock at the base of the borehole, which is a physical impossibility.

The sediments are normally consolidated. The water that was in these sediments at the time of deposition has been slowly squeezed out over geological time. Some of the sediments were derived from clays, and these consolidate to form strata that are highly impervious, and quite plastic. Such mudstone rocks can create impervious blankets over vast distances, and this is obviously the case in the Great Artesian Basin.

Sediments derived from sands consolidate into sandstones. Even though a bed of sand may originally have an open structure, the processes of consolidation reduce the porosity. Waters derived from the consolidation of other sediments may enter the free spaces and precipitate other minerals, and the sand structure deforms under the increasing stresses.

It has been claimed that there are water-bearing porous sandstones at the base of the sedimentary rocks. Such porous rocks could only exist if the water pressure was quite high, certainly much higher than any possible pressure from seepage water from the so-called intake beds. The water pressure would have to comparable to the stresses in the rock, which indicates a plutonic source of the water from the bedrock below the strata.

The intake beds

The rocks in the so-called recharge areas are sound and impervious. The concept of surface waters entering these rocks and then percolating underground for hundreds of kilometres is a fallacy.

The Queensland diagram above shows the intake beds as strata lying in an almost vertical direction with the beds exposed to the rainfall. That is quite misleading. In fact the beds are virtually horizontal in these areas. The diagram simply reflects the greatly exaggerated vertical scale and some artistic licence.

As part of my studies of the Great Artesian Basin, I have looked at possible alternative sources of surface water for town supplies, and even irrigation, in central and Western Queensland. I have visited some of these so-called recharge areas.

There are sound prospects for inland water diversion from some of the rivers flowing into the Gulf of Carpentaria. Over one fifth of the runoff of mainland Australia flows into the Gulf. There are several potential dam and reservoir sites at high level in the upper catchment of the Gulf Rivers. Storages at high level could command a wide range of potential irrigation areas in the Gulf country and further south in Queensland, possibly extending to the Queensland parts of the Murray-Darling Basin. With improved transport, irrigation developments in this area could be quite feasible.

The dam and reservoir sites that I have looked at on the ground are part of the area classified as recharge areas for surface water to enter the Great Artesian Basin. When I inspected these prospective damsites recently I observed that the reservoirs would be quite watertight. I could not understand how people ever imagined that these areas of sound rock would act like a sponge in soaking up surface water for the Great Artesian Basin.

Flow through porous media

One of the obstacles to the conceptual understanding of the behaviour of the Great Artesian Basin is the prevailing view that the flow regime in deep underground rocks can be described and simulated by mathematical models based on the Darcy formula for flow through porous media.

Henri Darcy (1803-1858) was a highly capable French engineer who built roads, railways and water supply systems. As new problems arose in his many projects, he tried to improve his understanding through research. He was a great hydraulic researcher, and his work became part of the standard curriculum for teaching hydraulics at the time, and remains so to this day.

The studies by Darcy, in 1856, of the flow of water through sands were initially directed to the design of sand filters for the Dijon water supply. The Darcy apparatus was quite simple. He used a vertical iron pipe to contain the sand, and measured the headloss for various discharges and various sizes of sand.

Darcy found that the velocity of flow was directly proportional to the hydraulic gradient, and that the constant of proportionality was different for each type of sand that was used.

In the case of flow of water in underground rocks at depth, the size of the flow path is not fixed like in an iron pipe. There is a balance of forces between the pressures in the water and the stresses in the rock, and this determines the dimensions of the flow path. The water passages can only remain open where the water pressure is so great that it is, effectively, holding the rock apart.

It should be noted that this balance of forces of water pressure and rock stress can be quite independent of the actual volume of water that is present. It is similar in a way to sitting on a rubber hot water bottle: release some of the water and the pressure remains the same with the smaller volume of water. This is what has been happening in the Great Artesian Basin: a truly huge volume of water has been extracted and some borehole pressures remain high. That should never be regarded as recharging from intake beds hundreds of kilometres away. It simply reflects the great weight of the super-incumbent rocks acting on the remaining water.

In my paper on Reservoirs in Naturally Fractured Rock it was explained that the conventional assumption that deep aquifers occur as porous rock was mostly incorrect, and that the ground-water flow is properly described as flow through joints and fissures in the rock. My views have obviously cut across the conventional views of people involved in geohydrology. These conventional views have been anchored for generations in an implicit faith in the validity of the Darcy law, which is for flow in porous media, as being applicable for flow in underground rocks. In almost all cases it is just not applicable.

It is a case of a mathematical model, which was adopted for its simplicity, becoming accepted as reality. As time has gone by, each generation has forgotten about the assumptions, and built up a vast range of ground-water studies and reports which often have little relation to reality. This has happened in the case of the Great Artesian Basin.

These days the mathematical analyses are aided by computer, and computer programmes are available that show the groundwater flow in three dimensions, and in colour, which adds to the self-delusion of the users. An internet search of the topic 'groundwater software' reveals the great range of computer programmes which are now available. These programmes seem to me to be potential traps for the unwary.

I gather that there are one or two dissenting scholars in the ground-water game who are concerned about the Darcification of their profession. They should be concerned, and I hope their colleagues listen.

Review of early drilling

On purely theoretical grounds, it would be expected that the Basin sediments would have been originally dry over the entire depth to bedrock. In similar sediments worldwide, and at similar depths, it is not normal to find rocks with open joints or any significant porosity. Consolidation and plastic flow over time has closed all openings.

But there is water in the strata. When the first bores were drilled, there were gushing bores throwing fountains of water into the air. What was the source of these waters, and the reasons for the very high pressures?

In order to resolve these questions, it was necessary for me to go back and review the records of the early drilling in the Basin. Summary records of all the early bores had been kept by the state governments, and reproduced in a series of national conferences of the riparian states.

The records for Queensland up to June 1911 showed:

• There were 453 bores.

• Maximum depth was 5045 feet. Eleven bores were over 4000 ft deep.

• About half the number of bores were taken down through the entire sedimentary sequence and into the bedrock below.

• Waters under sufficient pressure to rise to the surface were mostly found in the bedrock, or in strata adjacent to the bedrock boundary.

• Drilling continued until useful water was found. Sediments were mostly dry over the entire depth to water.

The data for NSW in records up to June 1914 reveal a similar pattern. The records indicated that the strata were dry, and that the water was in the bedrock below.

Song of the Artesian water

I discovered an early poem by A. B. (Banjo) Paterson, the Song of the Artesian Water. It had been published in The Bulletin, 12 December, 1896. The poem has not been included in some of the compilations of selected poems by Paterson, and it is not well known. But it sang a song I was pleased to hear.

It is a time of drought, and the stock have started dying. The drillers have been called in to drill for water. The driller is a Canadian, and he is driving the engine hard:

But the shaft has started caving,
And the sinking's very slow,............

But there is no artesian water
Though we've passed three thousand feet.

And it's down we've got to go,
Though she's bumping on the bedrock four thousand feet below,

And then,

The whistle's blowing with a wild exultant blast,....
...for they've struck the flow at last,
and it's rushing up the tubing from four thousand feet below.

Although Banjo Paterson had a propensity to tell a good yarn, I suspect there was sufficient natural drama in these events for Paterson to tell it as it was happening at the time. The poem confirmed my view that the artesian water originally came from the bedrock and not from within the strata.

Injection effects of the first bores

Having identified that the normal condition of the strata in the Basin was dry prior to the drilling of bores, the question arose as to how the strata came to be water bearing afterwards. It is evidently due to the injection into the strata of high-pressure waters from the earlier bores.

This was possible because of the differences in density of the water and the rocks. Water in the bedrock that was trapped below the impervious blanket of the Basin sediments must have been held at water pressures approaching the overburden stress of the rock. The early boreholes punctured the impervious blanket, enabling these high pressure waters to escape to the surface. It would be readily possible for these high-pressure waters in these deep bores to get behind the staged casing and into the shallower strata.

Thus there may have been two categories of boreholes:

• Primary Bores, which tapped the water in the bedrock,

• Secondary Bores, which found water in shallower strata, and depended on water injected into these beds from the primary bores.

In these circumstances, it would be expected that the primary boreholes would flow for a longer period and the secondary boreholes would have a short life.

Now, over 100 years later, there is a very large number of non-flowing bores.

Later drilling

In the last few decades there has been extensive studies of the region of the Great Artesian Basin for the purposes of petroleum exploration and production. There seems to have been little mutuality of interest of the water and petroleum scientists. It was intriguing to note that in a study of petroleum prospectivity in NSW, reported in 1996, Alder,et al, noted in a section on water bore data, "A surprisingly large number of water bores in the Surat and Eromanga Basins were drilled to basement." My comment on that is that the bores were drilled to basement because that was the source of the artesian water.

Berry and Armstrong (1996) show drilling to basement in their paper on water supply for Olympic Dam operations.

The boreholes are shown in the accompanying profile, taken from a paper by Berry and Armstrong in 1996. It is noted that all of the boreholes were taken down to basement. Presumably that was the source of water.

Reservoirs in naturally fractured rocks

If the water was not originally in the sediments, it meant that the source must be in the much older fractured rocks below the sedimentary series.

I prepared a paper for FOCUS on Reservoirs in Naturally Fractured Rock, suggesting that the oil and gas found in the region and the artesian water may originate from the same source of fractured rocks below the Basin. That was obviously too much for some people, even friends.

But the evidence was accumulating. The release of methane in large quantities was associated with many of the early boreholes. In the early days, the methane released from boreholes was captured in small pressure vessels. The methane was sometimes flared at night and used as a light and a beacon for stock mustering. Great quantities of natural gas must have been wasted over the past century. Nobody was interested.

In 1914, the Government Geologist in Queensland noted that people were not interested in looking for intake beds for the methane and petroleum. He seems to have been quietly ignored as a cynic.

As natural gas and oil are lighter than water, the association of water and petroleum in the Great Artesian Basin means that the water is below the petroleum. The petroleum is being driven upwards by these deeper plutonic waters. This is called a water-drive, a phenomenon often observed in petroleum reservoirs around the world.

It is of interest to note that in the petroleum industry one of the conventional ways of enhancing the flow of oil and gas from a petroleum reservoir is to inject water at high pressure into the rocks at the base of the well. This has the effect of opening fractures in the rock by hydraulic jacking, thereby enabling the oil and gas to migrate more readily.

In the case of the Great Artesian Basin, exactly the opposite has been done over the past 120 years. An enormous volume of water and gas has been extracted and mostly wasted, inevitably leading to the closure of previously open fractures in the rock.

The volume of water taken from the Basin to date is in the magnitude of 100 times the volume of Sydney Harbour. That volume of water must have been held in open fractures in the rock. As water is removed the joints inevitably close. Thus the fractures in the rock that once held water have now been reduced in volume by that amount. This must have had a most damaging effect on the potential recovery of oil and gas from this region, as well as water.

Regional tectonics

The sediments of the Great Artesian Basin constitute a vast impervious and thermal blanket over the basement rocks over one fifth of Australia. This impervious blanket has acted as a cap to the upward migration of plutonic waters, and of oil and gas.

The sediments of the Basin have less thermal conductivity than the basement rocks. This means that these strata are an insulating blanket over the hot rocks below. It is of interest that the hot spots in Australia are observed in the area of the Great Artesian Basin.

In the paper on Reservoirs in Naturally Fractured Rocks I referred to the work of Emeritus Professor S. W. Carey on the Expanding Earth. Carey was head of Geology at the University of Tasmania for many years.

About 40 years ago I was working on designs for an underground power station in Tasmania. As part of the design process, we measured the residual stresses in the rock. The horizontal rock stress in one direction was surprisingly high. I had the opportunity to discuss our findings with Professor Carey, head of geology at the University of Tasmania. Carey quickly assured us that our measurements were consistent with his understanding of the tectonic behaviour in the region.

Carey outlined his views on Continental Drift, demonstrating on spherical models that the continents fitted together extra-ordinarily well if they were matched at the edge of the continental shelf, and if the earth was much smaller in size such that continents occupied the entire crust. Carey had concluded that the earth was expanding.

It was quite convincing to me, as the evidence was so clear. The trouble was that Prof. Carey, and everybody else, had no idea of the physical mechanism which could cause the earth to expand. This led to the world geological community rejecting the Carey concept of an expanding earth, even though it is much more consistent with the growing knowledge and measurements of the actual structural behaviour of the crust of the earth.

Carey believes that the earth has been expanding for the past 200 million years or so. Measurements of the age of the rocks on the ocean floor show that the oceans are expanding laterally by means of sea-floor spreading, and to a great extent.

The region of the Great Artesian Basin can be regarded as one such zone where there has been a lateral extension in the earth's crust. The sagging basin shape of the Basin is an indication of lateral extension. The extension is generally in the east-west direction.

The consolidating sediments would have tended to follow the down-warp into the Basin shape without fracture, remaining as an impervious blanket over the basement rocks.

The hard crustal rocks below the sediment would adjust to the lateral extension by the opening of pre-existing fractures, thereby providing paths for rising plutonic water, oil and gas.

Volcanism and the Great Artesian Basin

The Great Artesian Basin adjoins a wide north-south zone of volcanism in Australia, extending from Cape York to Tasmania. It is little recognised that this belt of volcanism extending over the entire length of eastern Australia is one of the world's most extensive volcanic zones.

The most recently active centres were Mt. Gambier, 4600 years ago, and north Queensland, 13,000 years ago. A north-south line joining these two recently active volcanic centres passes through the middle of the Great Artesian Basin, and through the hot spots shown in Figure 9. It is reasonable to think that the great thickness of impervious sediments in the Basin, (2000 metres), would have tended to inhibit volcanism directly within the Basin. Thus the volcanism adjoins the Basin, but does not penetrate the sediments.

The north-south zone of volcanism can also be regarded as a zone of crustal extension. It follows the same linear trend as the Tasman Fracture Zone in the southern ocean between Tasmania and Antarctica.

The more easterly volcanic provinces vary in age from 6 to 42 million years. The extensive and more recent lava fields in northern Queensland and Western Victoria are up to 6 million years old.

There is much evidence concerning the waters of the Great Artesian Basin that confirms that the waters are of plutonic origin. These include the combination of natural gas and water, helium concentrations, fluoride, and hydrogen sulphide, and the high temperature gradients.

Finding a friend

I was starting to feel rather alone. I seemed to be the only person in Australia who was saying that the Great Artesian Basin was definitely not being recharged from surface rainfall. My friends and colleagues were apprehensive.

I was surprised at the intensity of the opposition, especially at state government levels. Apparently the Australian Geological Survey Organisation was told to keep out of ground-water studies, as that was a state responsibility.

And then I found a friend. Although I could only read what he had written, I was greatly impressed and encouraged.

John Walter Gregory, FRS. DSc. (1864-1932)

Gregory began his career as a geological assistant in the British Museum in London in 1887 and began his academic studies in the evening at the Mechanics Institute. He then went on to the University of London, where he gained B.Sc. (First class honours) (1891) and D.Sc. (1893).

Working with British Museum, he obtained a very wide range of geological experience in a few years. In 1891 he visited the Rocky Mountains and the Great Basin in America. In 1896 he went as a naturalist on an expedition to Kenya. The expedition disintegrated and Gregory organised his own expedition and with 40 Africans covered 1650 miles in 5 months. He explored the Rift Valley, the nearby volcanoes ,lava fields, and geothermal springs, and the glaciers of Mount Kenya. At the same time he was recording the flora and fauna of the area and the native peoples whom he met.

His book, "The Great Rift Valley" was published in 1896. The book reveals a fascinatingly erudite and highly observant explorer. He then went on an expedition to make the first crossing of Spitzbergen and also travelled to the West Indies. Meanwhile he completed a 3 volume catalogue of the fossil bryozoa held by the Museum. He became a Fellow of the Royal Society.

In 1899 Gregory was appointed Professor of Geology at the University of Melbourne. His qualifications for the appointment were so outstanding that the London committee did not interview any of the other candidates.

The geology of Australia became his new field of exploration, and he travelled widely. In 1901-02 he took a group of students on a field trip to Lake Eyre and studied the artesian bores. He wrote a book about this trip, "The Dead Heart of Australia", which was published in 1906.

Chapter 17 of the book is entitled "The Flowing Wells of Central Australia". It is a most scholarly analysis of the origins of the water. In my studies of the Great Artesian Basin I have looked at many papers on the subject, but in my opinion the Gregory analysis has an outstanding breadth and intellectual quality that has not been equalled, in 100 years!

The following are some direct quotations from the book. It reads as if it was written yesterday.

Extracts from book by J.W Gregory, "The Dead Heart of Australia" 1906

"Subterranean water may be derived from one of two sources. Cool water, which occurs at comparatively slight depths, is no doubt, generally, rain-water ....As this water comes originally from the sky it is called 'meteoric' water..

The second source of subterranean water is the interior of the earth. The rocks of the deeper layers of the earth's crust contain water. The quartz in granite owes its milky whiteness to abundant minute cavities, filled with water. The vast steam cloud, which hangs over volcanoes,...has no doubt been brought.. from the interior of the earth.

Plutonic waters are especially important in mining countries, because most of the chief ore-deposits are due to them. And as the deep, water-bearing basin of Central Australia is surrounded on all sides by rocks containing rich mineral veins - from the Queensland gold-fields on the east, the Cobar copper-field and Broken Hill in the south, and the Cloncurry god-field in the west -, there is likely to be a considerable amount of plutonic water under Central Australia.

Where these ascending waters are cut off from the surface by an overlying sheet of clay, they accumulate in any porous beds they can enter, and remain in them subject to high pressure. Any plutonic water rising from the old rocks of Central Australia would collect in the permeable beds of sandstone beneath the clays. Thence it would rush to the surface, if a bore-hole were made through the water-tight cap above, just as oil and natural gas escape from the wells of the Caspian and Pennysylvania....

The tendency has always been to assign the origin of the flowing wells to distant localities. The ancient Egyptians supposed that the water which flowed from the artesian wells of Thebes came from the hills of Darfur, 700 miles to the south.

The source of the water of the famous well at Grenelle, near Paris, has been attributed to the Jura Mountains. Is, therefore, only in accordance with precedent, that the source of the deep-well waters of Lake Eyre should be sought in the mountains of New Guinea, the Andes, and the Himalaya...

The possible origin of Australian artesian water from the Himalayas or New Guinea was suggested, amongst others, by the Hon. J. T. Murray Prior, in a debate in the Queensland Legislative Council. "The great question must be", he said, "where does the artesian water come from? The nearest high mountains we have to Australia are in New Guinea; but still the water may actually come from as far as the Himalayas under the sea."

The explanation of the flowing wells of Central Australia as due to water-pressure in the distant Queensland hills is met by many difficulties. One of the chief is, that it under-rates the resistance to the flow of water through rocks due to friction. The analogy between the geological structure of eastern Australia and a U-tube fails, because Australia is not built up of tubes. The water has to percolate, not through open tubes, but through the pores of rocks; and as these rocks are under the pressure of sometimes as much as four or five thousand feet of overlying material the pores will be minute.

The average increase of temperature below the surface of the ground is generally taken as 1degree F for every fifty-three feet in depth...But many of the flowing wells in Australia show the rate of one degree F for every twenty-two feet. This high temperature indicates that the water has probably come from a much greater depth than that of the water-bearing layer. It is, therefore, more likely to be plutonic than meteoric water...

The association of compressed gas with the artesian waters has been denied or doubted, but it is admitted that many of the well-waters smell of sulphuretted hydrogen. Many of the Queensland waters are charged with carbonic acid.

I long hesitated before finally rejecting the ordinary artesian theory of the Central Australian wells, The question is not merely one of settling a theoretical explanation. It has an important practical bearing. Many of these wells now run to waste.

This waste is defended on the ground that the water is being renewed at a rate which so vastly exceeds the outflow from the wells, that they will last for ever without any diminished flow...

Legislation to stop this waste has twice been proposed. A Bill was carried through the Queensland Assembly in 1891; but the Legislative Council rejected it. In New South Wales a similar Bill was proposed in 1894, which would have authorised the Water-conservation Department to order the partial closing of the wells; but it also failed to pass.

Nature has stored up a vast - but probably a limited - supply in a safe, underground reservoir.. But to allow these deep-well waters - in obedience to a mistaken analogy as to their origin - to run heedlessly to waste, is a policy of which a later generation of Australians may have bitter cause for complaint."

Of course, Gregory was quite right. Here we are 100 years later, and we have not yet learned the simple truths that Gregory explained so clearly.

It is understandable that other people at that time, including geologists, had difficulty in comprehending such clear statements by Gregory. After all, he was probably the only person in Australia with such a scientific background in the subject.

In 1904 he left the University of Melbourne for an appointment at the University of Glasgow. His later books reveal a scholarly range that may not have been achieved had he stayed in Australia. The debate on the origin of the waters lapsed.

In 1911 there was talk of a five thousand pound prize for the best essay on the origin of the waters, but it seems that any essay along the lines of thought of Gregory was not likely to win the prize.

Concluding remarks from Fellows

I have concluded that the water in the Great Artesian Basin is of plutonic origin, and probably accumulated under the impervious blanket of strata of the Basin during 40 million years of recent volcanic activity in eastern Australia. The pressure of the plutonic waters provides a water drive to the artesian wells, and also to the oil and gas wells within the Basin.

It is a large but limited resource of residual underground water. The water is stored in fractures in the bedrock below the strata of the Great Artesian Basin. As a result of the extraction of water to date, the earlier fractures in the rock have closed by an amount equal to the volume of water removed, which is a total volume comparable to 100 times the volume of Sydney Harbour. This must have caused an extensive closure of fractures in the rock, thereby closing flow paths and harming the future yield of water, and the future yield of oil and gas.

It is probable that the extraction to date has already removed a large part of the stored waters, and an uncountable volume of natural gas. It remains to be seen whether a smaller sustainable flow of water is possible.

It is a national economic calamity that such a huge amount of water and natural gas has been wasted over the past 110 years.

It is a national scientific scandal that so many people who carried responsibilities for the management of the Great Artesian Basin did not understand the physical characteristics of the Basin. They contemplated the disturbing evidence of declining flows and closure of bores without comprehension or action.

When I prepared my first paper on the Basin over a year ago there was an attempt to persuade ATSE not to publish the paper.

But the episode flashed some warning lights. It showed that scientific inquiry in Australia is not always free and open. In the case of the origin of the waters in the Great Artesian Basin and its management, it has taken 100 years to re-open the debate started by Gregory and then only because of my own studies at my own expense. There is no way my studies would have been acceptable under peer review and external funding. (I am not putting myself in the same category as Gregory. After all, he understood the matter 100 years earlier).

Gregory was a true intellectual, comfortable in several disciplines, looking at the whole picture. Our system these days is not kind to such scholars. The struggle for funds has led to an increasingly narrower concentration of effort. Yet most of the problems we face are inter-disciplinary in some way. The activities of our learned societies are becoming increasingly specialised.

There is little learned debate any more. The presentation of any paper, no matter how comprehensive or substantial, is limited to a 20 minute (or less) time slot in a crowded symposium, competing with many other papers sometimes extending in number to over 100 papers. Our whole intellectual effort is thereby directed to performing under a brief spotlight at some conference somewhere. Mostly there is no discussion, only questions and certainly no speculation. The attendees do not bother to read one another's papers. All of this breeds triviality

But it is a general phenomenon. We are now having difficulty in rational discussion of any complex issue, especially if politics are also involved. The Great Artesian Basin is one example, but there are many others.

References

• L. A. Endersbee, " The Great Artesian Basin of Australia"

• J. W. Gregory, "The Great Rift Valley", John Murray, London, 1896.

• J. W. Gregory, "The Dead Heart of Australia", John Murray, London, 1906.

• J. W. Gregory, "The Making of the Earth', Williams and Norgate, London,1921.

• J. W. Gregory, "The Elements of Economic Geology", Methuen, London, 1928

• J.W. Gregory, "Earthquakes and Volcanoes", Benn, London,1929.

• L. Sutherland, "The Volcanic Earth", UNSW Press, 1995.

• P. A. Evans, "Fluoride Anomalies in Aquifers of Queensland Section of the Great Artesian Basin and Their Significance" in Mesozoic Geology of Eastern Australian Plate, Geological Society of Australia, 1996.

• Bryan, Constantine, et al. "The Whitsunday Volcanic Province (Cental Queensland) and the Gippsland/Otway Basins (Victoria): A Comparison of Early Cretaceous Rift-Related Volcano-Sedimentary Successions", ibid.

• Alder, Bamberry, Pratt, Foss, '"Recent Investigations of the Great Australian Basin in New South Wales." ibid.

• Berry, Armstrong, "Eromanga Basin Water Supply Development for Olympic Dam Operations" ibid.