Water management options for urban and rural Australia

Groundwater Challenges and Opportunities for Australia in the 21st Century

Tuesday 2 November

Professor Craig T. Simmons
Professor of Hydrogeology, Flinders University
Director, National Centre for Groundwater Research and Training

Craig Simmons has been a significant contributor to global advances in the science of hydrogeology for many years and has published widely in areas including variable density groundwater flow, surface water to groundwater interaction, fractured rock hydrogeology, aquifer storage and recovery, and groundwater flow and solute transport modelling.

He is a member of the National Water Commission's Groundwater Technical Advisory Committee, which advises on high-level groundwater direction setting and investment strategies in Australia. His work has been recognised by numerous national and international research and teaching awards. Craig has served as an Editor and Associate Editor for numerous major international journals including Hydrogeology Journal (Editor), Water Resources Research, Journal of Hydrology and Ground Water.

Before I begin this talk, I would like to acknowledge that the land that we meet on this evening is the traditional land of the Ngunnawal people.

Groundwater really is a critical water resource for our nation. Different civilisations across the planet have used groundwater for thousands of years.

It has largely, in comparison to surface water, been a largely forgotten resource, at least in terms of properly managing it.

We are all familiar with one of the most popular visual icons of Australia, the tin-bladed windmill pumping water from below the dry land for stock, crops and people. Groundwater tends to be out of sight and, therefore, out of mind compared to surface water.

In this talk what I will do is give an overview of the field of groundwater hydrology, including how groundwater systems work, their role in the environment and some of the current technical developments relating to groundwater. I will also discuss some of the current challenges and opportunities relating to groundwater policy, and to groundwater management, research, education and training.

I hope in this talk I will be able to convince you that there has been never a greater opportunity for groundwater management, research and education to make a difference in Australia.

I want to start this presentation by discussing the importance of groundwater to us. Did you know that, excluding oceans and ice caps, 97 per cent of fresh water on Earth is hidden in the ground beneath our feet, and that only 3 per cent is visible in rivers, lakes and streams? Groundwater is, indeed, a massive and pervasive resource. Some estimates reveal that about one-third of the world's population is dependent on groundwater.

Australia has very large groundwater resources. In rough and ready terms, groundwater accounts for about 20 per cent of our total water use in this country. Groundwater is critical for a whole range of things: for agriculture, for industry, for mining, and in many parts of Australia for drinking and potable water supplies.

We also know that in terms of our future outlook that there has been a reduction in storminess across Australia, that Australia is getting warmer, that Australia is getting drier, that there have been declining inflows to our major surface water reservoirs and dams and, importantly, in my view, our population is increasing. When I looked up some of these statistics put out by the Australian Bureau of Statistics I was quite staggered by the fact that we expect our 30 June 2007 population of about 21 million to increase to anywhere between 31 million and 42.5 million by the year 2056, depending on the modelling. Invariably, either way, independent of the model, we are looking at a doubling of our population within the next 50 years.

We also currently estimate that most cities must find the equivalent of a 40 per cent reduction per person in water consumption in the next 25 years. Over the last few years 70 per cent of Australians have lived under some form of water restrictions. So why focus on groundwater?

We live in a dry and drying climate and it's absolutely clear that our reliance on groundwater will only increase into the future. Our understanding of groundwater hydrology or hydrogeology lags far behind that of surface water, both in terms of gauging and in terms of our ability to predict and understand the behaviour of these systems.

Groundwater monitoring and management lag far behind that of surface water, and one of the critical things that differentiates groundwater from surface water is that groundwater cannot be seen, and it is really difficult to measure.

Many of us are now turning to groundwater as an alternate water source. We know that new groundwater sources are relatively cheaply priced when compared to other water sources. For example, groundwater is priced at anywhere between 20 cents and $1.59 per kilolitre or per thousand litres of water, compared to sea water desalination, which ranges in price between about $1.15 and $3 per kilolitre, and long distance pipelines that vary anywhere between $1.30 and $9.30 per kilolitre.

I would like to talk about the importance of groundwater to the environment. Groundwater plays a critical role in the environment. It provides water to the environment, to trees, to wetlands, to lakes and rivers. We have seen time and time again throughout Australia examples of where groundwater is intimately affected and relates to environmental change in this country.

One popular example that we are all familiar with is dryland salinity. This occurs in areas where a change in the natural state of the groundwater system – for example, through changing the nature of the vegetation, or vegetation clearance – has caused a rise in the watertables, bringing those watertables up, concentrating salt in the groundwater near the surface zone and leading to salinity at the land surface and in shallow soils.

Salinity is a major issue throughout many parts of Australia, and in particular in the Murray-Darling Basin. It is intimately related to groundwater. We also know that surface water and groundwater communicate and exchange water. This will become one of the critical issues I'll talk about later, in terms of managing groundwater and understanding it.

The water that you see in a river or in a lake is not necessarily 100 per cent surface water, and in many cases it is actually largely groundwater. That is particularly the case in summer or if it hasn't rained for a period of time.

Groundwater can also be polluted by septic tanks, industrial waste discharge, leaky underground petrol tanks or by fertilisers and pesticides used in farming. Groundwater is also vital in many other parts of our ecological systems and there is a lot of good research being done on the way in which it sustains vital mountain springs and their ecological inhabitants in the Great Artesian Basin.

You may be aware that the Great Artesian Basin is arguably the largest groundwater aquifer in the world. It covers 1.75 million square kilometres. It plays a huge role in water supplies in Queensland and also in remote parts of South Australia.

Talking about artesian systems, I thought I would share with you one of my favourite pictures of the largest artesian system in the world. This is a picture of Catfish Farm Well in Texas, which National Geographic estimates as the largest free-flowing well in the world. It produces about 155 million litres of water per day. The little yellow people are hydrogeologists, drawn in for scale.

So what you can see here is that the water flowing out of Catfish Farm Well is gushing in excess of 15 metres into the air.

We know that over-pumping groundwater can lead to subsidence, where the land surface consolidates down. As we extract water from under the ground, the system depressurises, the land consolidates and, as shown on this slide, this is the sort of thing that can happen. We need to be aware of this because land subsidence is also a potential consequence of coal seam gas mining.

Here we see an example of where a really quite catastrophic outcome of land subsidence has occurred. A house which has collapsed completely into the ground as a result of land subsidence.

And it is probably not even as striking as the next picture, taken in 1977 in the San Joaquin Valley in California.

In this photo we see one of the US geological survey signs with Joe Poland showing us the land subsidence that has occurred in this valley over a period of about 50 years.

We can see right at the top the 1925 land surface level. We can see down at the bottom near Joe's feet the 1977 land surface level. The land surface had subsided by about 10 metres over this period of time. We know that this is one of the worst examples of land subsidence recorded in history.

We need to learn from these sorts of examples. We also know that over-pumping groundwater near the coast can lead to sea water being drawn into coastal aquifers. In worst case scenarios, directly into pumping bores themselves.

We also know that groundwater sustains and supplies critical freshwater discharges off the coast and interacts with vital marine and estuarine ecosystems. Some of you may have heard of wonky holes, submarine freshwater springs on the seabed in the Great Barrier Reef of Queensland. The sorts of wonky holes shown in the top left of the slide are quite common off the coast in the Great Barrier Reef. They bring lots of fresh water out to the coast and, with that fresh water, nutrients. Obviously with the nutrients you now have a feeding location for fish and, hence, fishermen. These are really quite interesting phenomena.

More recently there are increasing concerns regarding how changing land use, such as forestry, will impact groundwater systems, and how climate change or climate variability are likely to affect groundwater in the future. One thing is absolutely certain, a drying climate means less rainfall and therefore less water to recharge our aquifers.

I thought I would very briefly talk about aquifer types and how they work. Most of us know that aquifers are underground geologic materials that contain lots of water and are capable of transmitting water in sufficient quantities usually to a bore or spring. Typically these are sandy or gravelly layers, but they can also be what we call fractured rock aquifers. So you might have a dolomite rock or a shale or a granite that is fractured where the water flows through the cracks in that rock.

In Australia about half of our underground aquifers are sedimentary sandy systems and the other half are fractured rock aquifers. We know that our sedimentary or sandy systems are already over-allocated on average, and we are turning increasingly to the more complicated fractured rock environments.

Aquifers are recharged by rain. Rain on mountain tops feeds water into the top of the system at the mountain area or the highlands, it flows underground to low-lying areas, typically either lakes, rivers, or, in most cases, to the terminus, which is the ocean.

Many people ask me about underground rivers. Groundwater doesn't flow like an underground river. It flows very slowly – metres per year would be a fast groundwater flow rate – through the connected pore spaces between the grains of sand that make up the rock. It is flowing through those little pores.

What we often don't recognise, and this is critical from a management perspective, is that the water we extract today from our underground aquifers may be thousands or even hundreds of thousands of years old, such as in the Great Artesian Basin. Groundwater is a very old vintage indeed.

In 1856 French civil engineer, Henry Darcy, discovered Darcy's Law, the fundamental law which allows us to calculate how fast water moves in geologic material. This now famous law underpins every aspect of what we do in hydrogeology today. It marks the birth of quantitative hydrogeology.

So, as a hydrogeologist, what I am interested in studying is virtually everything about underground water in aquifers: the occurrence, the distribution, the movement and the quality of underground water. We are also interested in how much water is underground; how much can be safely extracted; and, very importantly, and increasingly so, what is the water quality of that aquifer system? Is it suitable and safe for its intended use, for example, drinking or irrigating crops?

Groundwater is managed much like we manage our own bank accounts. Indeed, aquifers, in my mind, are just like banks. Water levels in an aquifer reflect our bank balance. We earn money – recharged by rainfall – and we spend money – groundwater pumping from an extraction bore. We can see from our monthly bank statements, or water level records, whether we are on track to becoming multimillionaires or on track to becoming bankrupt. These water levels are absolutely critical. They form the basis for water allocation plans and our water budgets.

So what does the bank balance look like right now? Groundwater levels often reflect rainfall levels, as I have said. We know that in many parts of Australia there have been disturbingly low trends of below average rainfall since the early 1990s, and that some bore levels have been resilient but that many have also been showing a clear decline in groundwater levels in response to this lower recharge.

Earlier in this lecture series Peter Dillon gave a talk on aquifer storage and recovery or managed aquifer recharge. I thought I would say a few words on this, because it is a technology that we are going to see more and more of in Australia. Australia is in fact regarded as a world leader in ASR technology, where we use the underground aquifer to store water. It has the advantage that it reduces the land required for above-surface water storage. It reduces evaporative losses through evaporation and it provides natural filtration properties. There are many of these starting to emerge throughout Australia.

Groundwater has been linked with public health issues, human activism and the legal system. Not intensely so in Australia, but incredibly so in countries in Europe and in North America. I want to share two cases with you as examples of what can happen if we are not vigilant about the state of groundwater.

The first is from the movie Erin Brockovich, which is entirely based on a true story. This slide shows the real Erin Brockovich. She was played by Julia Roberts in the Hollywood blockbuster movie. The story is set in the town of Hinkley in California, which had its groundwater contaminated with a chemical substance called hexavalent chromium. This led to a legal case and a multimillion dollar settlement.

In the story, the company Pacific Gas and Electric operated a compressor station in the town for a natural gas transmission pipeline. It had large cooling towers which were used to cool the compressors. The water in those cooling towers contained hexavalent chromium to prevent rust in the machinery. When the water wasn't being used in the cooling towers it was stored in some unlined ponds next door to the cooling towers and ultimately leaked into the groundwater and, hence, the water supply for the town of Hinkley.

We know that hexavalent chromium is absolutely dangerous for human consumption. Many illnesses were allegedly linked to it, including cancers, birth defects and organ failures. The case was ultimately settled in 1996 for $333 million – the largest settlement ever paid in a direct action lawsuit in the United States history.

The second case is arguably the most notorious groundwater contamination example, and it is called the Love Canal Story. Love Canal is a neighbourhood in Niagara Falls, New York, which was discovered to have 21,000 tons of toxic waste buried beneath it by a company called Hooker Chemical. The case was surrounded by much controversy and it gained massive national and international attention. The United States Environmental Protection Agency in 1979 said:

residents exhibited a disturbingly high rate of miscarriages...Love Canal can now be added to a growing list of environmental disasters involving toxics, ranging from industrial workers stricken by nervous disorders and cancers to the discovery of toxic materials in the milk of nursing mothers.

We have not seen disasters of this magnitude in Australia, but in my view we need to be vigilant. It could happen if we are not careful. We need to learn from these international examples.

I want to talk now about a paper that I co-authored in 2006 called 'The national groundwater reforms paper'. I co-authored this with a group of six colleagues, other national water leaders in hydrogeology. The reason we wrote this paper was that we felt we needed to drastically and urgently encourage change in addressing natural groundwater issues. We highlighted major issues. We also provided major recommendations for how they could be addressed. I will summarise some of those points here.

The first question is: Why does Australian groundwater need reform? Groundwater is more important to Australia than our national usage figures suggest. I said it is about 20 per cent of total water use, but we know that it has many other important characters: broad-scale availability, interaction with surface waters, availability during drought and high security. And I've already said that we are absolutely sure that this is going to become an increasingly important resource. We also know, and I won't go into the details here, that the amount of funding put into groundwater research, monitoring and investigation over the last 20 or so years was less than probably half of what it was prior to 1987. That situation has changed more recently with the groundwater action plan, which has injected approximately $105 million into groundwater related activities.

There is a lot more that we need to do. There is a whole range of policy and management issues. We know that sustainable levels of extraction is a key issue. Many of our aquifers are already over-allocated and we are continuing to use those aquifers and to draw increasingly upon them. Licensing and metering are still problematic for our country. It is not just one state or two, or one territory or another, it is nationwide. This is a nationwide issue.

My argument has always been that you cannot manage what you do not measure. If we are not measuring and we are not licensing in a completely coherent and consistent way then we are going to continue to grapple with how to manage it.

Another management issue we are struggling with is environmental water requirements. Most states and territories across Australia have provision within their water legislation right now to allow water to be provided to water dependent ecosystems. But in most cases we actually do not know how much water those ecosystems need. We also know that illegal groundwater use across the country is probably rampant and, therefore, that we need to develop compliance programs.

Groundwater trading is probably something that we should be talking about, but if most of our aquifers, especially in the eastern states, are already over-allocated then we know that groundwater trading is only going to make that situation worse.

There are also important issues to consider with pricing. The value of groundwater, as with water generally, must reflect its true place in our society. We urgently need to come up with – and I know it is difficult – estimates on the value of groundwater. We need to do this because a major increase in groundwater fees and charges to reflect an increase in the required level of groundwater management is called for.

This is also important from the point of view that most of our groundwater monitoring infrastructure across Australia was built in the 1960s to 1980s, and given that most of our groundwater wells have a lifetime of about 20 to 30 years, we now know that much of our monitoring of the structure is collapsing across the country. This will only continue to get worse over the next decade or two if we don't continue to increase the future level of investment in groundwater monitoring.

We have got to spend more time and energy thinking about the groundwater resource. We are doing a lot more work now than we were about five or ten years ago, but it is clear that decisions concerning the availability of groundwater need to be underpinned by better technical understanding. This includes a whole range of processes and issues, recharge and discharge rates, groundwater dependent ecosystems, groundwater salinisation, climate influences, and connectivity in surface water.

The need for ongoing research and investigation is a vital requirement for good groundwater management. Yet, one thing that can be stated quite clearly is that there has been a serious de-skilling of some Commonwealth, state and territory agencies over the last decade or so, that has led to a decline in our intellectual capacity and capital to attack this issue.

The 'National groundwater reforms paper' also noted that there is a clear need for a strategic approach for safeguarding the ongoing collection of knowledge about the resource and that a focus on groundwater R&D and a nationally coordinated approach is desperately needed. The situation has largely been addressed through the creation of the new National Centre for Groundwater Research and Training, a $56-million initiative over five years, which is a co-funded centre of excellence of the Australian Research Council and the National Water Commission.

We have also got, as a national criteria, education and training reforms that are necessary in the area of groundwater hydrology. The 'National groundwater reforms paper' identified that there is currently a serious capacity shortage in hydrogeology across the nation, and that the current supply of trained professionals falls far short of industrial demand.

There are a few universities, a very small number of them, that have developed their capacity to train hydrogeologists, but their graduate output is clearly unable to match the growing demands placed on the sector.

A critical issue to my mind is not only the limited number of degree programs in hydrogeology across the country but also the fact that we face difficulty in attracting the very best and brightest students into hydrogeology degrees. We know that many are drawn to more popular non-science degree programs such as law, psychology, economics and business, as well as other high-tech fields such as electronic and computer systems, engineering, forensic science and genetic engineering.  It really hurts me to say this, but I also think hydrogeology has an image problem. I want to use the National Groundwater Centre to start to address this issue.

Working on the remediation of a landfill lacks the glamour compared to other high-tech fields, and lacks the sophistication, perhaps, as well. In my view we need to introduce hydrogeology to students at primary school, at high school and at university level as an exciting, interdisciplinary and challenging field in need of sophisticated attention and, importantly, one which has excellent career prospects.

I would like to talk briefly about international groundwater research perspectives.

About two years ago when I was charged with the responsibility of building the National Groundwater Centre we had to come up with our new program of research for the next five years across a whole range of universities and industry partners. We looked at national Australian issues that need urgent research attention and also international research drivers.

An interesting debate on the future of hydrogeology was triggered in 2001 by two professors, Frank Swartz and Motomu Ibaraki, in their paper 'Hydrogeological research: Beginning of the end or end of the beginning'. This was a fairly provocative paper as the authors used citation analysis alone. Scientists and other academics in the room might argue that, when treated alone, citation analysis may be a flawed way of looking at the system. But they argue that groundwater research is inefficient with much produce for little gain, that the field may be ranked as mature and close to ageing, and that the number of truly impactful problems will have dwindled to just a few.

If you read the paper more carefully, and talk to the authors, the main take-home message was not that we had reached the end of hydrogeology, but that if researchers can identify and understand the inefficiency in some of our research, and perhaps the mediocrity in some of our research, that we have an enormous opportunity to create more impact for work and discover new paradigms.

So I took that on as a challenge. And in what we saw as a response paper by Miller and Gray, 'Hydrogeological research: Just getting started', they argued, in stark contrast to Swartz and Ibaraki, that hydrogeology is not a mature research field, that many problems are fundamental, and societal importance still remains. They cited a whole range of examples, including population growth, sustainable development, global climate change, contamination in groundwater quality restoration, the underground storage of nuclear radioactive waste materials and the role of groundwater in global cycling of water, energy and chemicals. What they did stress was that hydrogeological research and its applications must maintain a focus on benefitting society, since ultimately it is society that will value our work as hydrogeologists and as researchers in hydrogeology on the basis of the service that it has received.

There are many issues that we are grappling with in hydrogeological research. We are struggling with how to characterise groundwater systems. You can imagine that it is quite difficult to see underground, how to better characterise it.

We are dealing with how to understand the nature of groundwater processes, and in particular the movement of contamination in highly heterogeneous and extremely complicated groundwater geologic systems. Todd Halohan from Oklahoma State University and I have done some research on the thousands and millions of cracks in the geographic material shown in this slide. How would we know where groundwater flows and where the contaminate plume moves in such complicated systems?

It was interesting that a fellow academic, not from hydrogeology, but another discipline of science, said to me a number of years ago that we put man on the moon in 1969 and nearly 40 years later hydrogeologists are still saying that we cannot predict the fate of a contaminant plume. My response was that if the pathway between the Earth and the moon had been anywhere near as complex and as heterogeneous as the sorts of geologic mess that we are dealing with in hydrogeology then there was a pretty good chance that man would not have got to the moon either.

This is slightly less serious for a moment. It is all about the cracks in hydrogeology. It's all about the heterogeneity. We weren't the first to work this out. Michelangelo's creation of Adam in the Sistine Chapel is already pointing out that the cracks are indeed where we need to focus.

We have got major issues in this part of our research area. Heterogeneity is probably, to my mind, the most significant challenge that faces hydrogeology and hydrogeologic prediction. We have also got issues with how to model, using computer simulation tools, these complicated environments. Hydrogeology is now getting more complicated. We are bringing in biochemistry, biology and all these other disciplines with more complicated processes, and our models need to keep pace.

You can imagine, as we are building these models, that more and more complexity needs to go into them. So development of modelling and optimisation techniques are critical challenges.

Miller and Gray concluded their paper with the statement that meaningful advances in hydrogeologic research will require an increased emphasis on fundamental understanding, interdisciplinary approaches, educational reforms and the attraction of excellent researchers to the field.

The special theme issue of the 2005 Hydrogeology Journal, titled 'The Future of Hydrogeology', contains some 30 papers on a wide range of topics in hydrogeology and speculated on the future of our profession.

It was clear when I read through most of those papers that there is a lot still to do. They were slightly biased because they were written by academics and other like-minded professors who outlined a massive amount of work that still remains for research in hydrogeology, but it is clear that there are exciting areas that are emerging as entirely new challenges in hydrogeologic research.

We are now investigating the use of underground aquifers for carbon sequestration, the process of removing carbon from the atmosphere and depositing it in underground geologic materials.

We are still grappling with the issue of radioactive waste disposal and geologic waste repositories such as at Yokum Mountain in the United States, shown in this slide.

One of my favourite research areas is stygofauna. I don't work in this area but I would love to. This is a new and emerging area of research. Stygofauna are fauna that live within groundwater systems such as caves and aquifers – a few are shown on the slide. These underground critters survive in the low carbon and low oxygen aquifer environment. To do this, these stygofauna have adapted over millions of years to have a very slow metabolism. They are long lived, extremely slow growing and they have very few young.

Another area of research which is interesting is looking at alternate water supplies on other planets in the solar system. We are not doing this work in the National Groundwater Centre. This is work that is being done in the US by NASA and a group of professors at the University of Arizona, Vic Baker and his team. There is an emerging new discipline or subdiscipline of hydrogeology called extraterrestrial hydrogeology.

As I read through Vic Baker's latest paper I discovered that we now know that groundwater currently exists as ice on Mars but, once upon a time when Mars had more Earth-like conditions, groundwater moved between the Martian highlands and its northern plains.

We also now believe that subsurface water which exists in ice form is probably very common for most planetary bodies in the solar system and beyond our solar system. It is all very exciting stuff.

It is very clear that there are many exciting and new areas of future enquiry and a healthy prognosis for groundwater research.

We are still grappling with hydrogeology on planet Earth. Hydrogeology is in a new era. We have moved beyond the classical golden age of hydrogeologic research and applications which focused almost exclusively on the hydraulics of aquifers and water supply problems. I have already talked about the issues to do with groundwater quality – contamination, critical linkages between groundwater/surface water, ecosystems, and planetary-scale processes such as climate change. These are just some of the technical and biophysical issues. There are also critical issues to do with social uncertainty and the social issues that relate to hydrogeology.  After all, all the work that we do as hydrogeologists serve social decisions.

It is clear that hydrogeology is getting more complicated and – this is important – it is getting much more interdisciplinary with time. There are still core problems that we are not able to work on and remain unresolved in hydrogeology today. They relate to the geologic complexity that I talked about earlier. As hydrogeologists, we are interested in measuring what we call the permeability of an underground aquifer. This is a property that tells us how fast or how slow water moves through that geologic material. We will often say things like, 'The permeability of a sandy aquifer is much higher than the permeability of a clay', for example.

What de Marsily said in 2005 struck me as probably the most profound sentence of the entire Hydrogeology Journal special theme issue. He said that until the large-scale permeability of an aquifer – this large-scale property that we are working on – can be reconstructed from small-scale measurements – because we go out and measure these things very locally with a bore – there will be a credibility problem for our discipline.

An important question arises. I see this as the biggest quandary for hydrogeology, both as a research discipline but also as a practice and in our applications. How many holes do you actually think we need to drill to obtain a detailed characterisation of the subsurface environment? One, 10, 1000, 10,000? The answer is that we don't actually know. What we do know is that each bore costs us anywhere between $10,000 and $50,000. They are not cheap to put down. Therefore, it is not uncommon for a groundwater field site to have just a small handful of these groundwater bores to monitor and investigate the system.

Obviously, the number of bores we need in order to understand and investigate groundwater depends critically on the question that we are asking in that particular case. For example, are we trying to work out how much water we can extract from an aquifer? Maybe a few bores are okay in that case. Or are we trying to predict the precise movement of a contaminant plume in a highly heterogeneous aquifer?

Here we see a field site in the US, the Cape Cod site in Massachusetts, which has thousands of measurements. We have obtained, as a research community, extraordinary amounts of data from this site. It is probably one of the most, if not the most, instrumented groundwater site in the world. However, research reveals that more data are still required to resolve detailed questions about the movement of the contaminant plumes in this system.

As hydrogeologists, we are constantly faced with the challenge of determining how simple or how complex our investigation needs to be.

This quote from Albert Einstein is one of my favourites: 'Everything should be made as simple as possible, but never simpler!' It is one that I think about daily and weekly in hydrogeology as I go about my business, because it is absolutely pertinent to hydrogeology today.

Just before I wrap up, I want to say a few words about the new National Centre for Groundwater Research and Training, which is the new Australian centre that I lead. We have heard about many of the groundwater challenges and issues, from management through to the need for coordinated research and development, and also the skills shortage in hydrogeology. I believe that the new National Centre for Groundwater Research and Training is really a positive news story that addresses many of these issues.

NCGRT was funded by the Australian Research Council and the National Water Commission. It was born on 10 June 2009, out of a national desire to undertake major reforms in groundwater research and groundwater training in Australia.

NCGRT is a $60 million investment from the Commonwealth and other university and industry partners. We have twelve university partners and eight industry partners. We are looking at a whole range of national and international groundwater research and training; importantly, training of the next generation of groundwater specialists. We are going to work on important areas of inquiry that I outlined earlier in my talk, to assist in groundwater management, groundwater understanding and hopefully also assisting and informing groundwater policy.

We have set a goal of training more than 200 students over the next five years at postdoctoral, PhD and Honours level. I am pleased to be able to share with you that we already have 70 postdocs, PhD students and Honours students who have commenced their studies and research in the last year.

So, to conclude, Australia's population is expected to double within the next 50 years. It is a driver for a lot of the ways in which we have to think about water in this country and, indeed, manage it.

We also face, in addition to a doubling of our population, the serious prospects of what may come with climate change and an even drier climate. As a country, we need to confront the serious and hard questions. Where will our water come from? Will there be enough water? Groundwater does offer a serious new water resource in some parts of Australia, whilst in other parts of Australia, in fact in many parts of Australia, it is already over-developed and in need of greatly improved management. A myriad of policy management, institutional, research, technical and educational matters need to be resolved with some urgency if the crisis we have seen in the last 20 or so years is not to accelerate over the next decade or two.

The good news is that we are seeing renewed interest from government and local communities, recognition that groundwater is a crucial asset and that groundwater will necessarily be part of any long-term solution, even for domestic water supplies. But there are miles to go before we sleep!

Discussion

Question: One of the most interesting days of my life was going out west of Narre with an Aboriginal man named Reg Dodds. He grew up in the area and loves his land.

I forget how many years he told me that the groundwater takes to come to Narre from the Atherton Tablelands and further north. Just across the hills from Narre is a big mining outfit. They are using an extraordinary amount of that groundwater to process the minerals they are taking out of the ground. The first question is: Do we have any knowledge, any scientific basis, to say that the amount of water they are taking is ecologically sound and sustainable?

Secondly, the chemicals they are using to extract the minerals, are we at risk of those going back into the aquifer?

Craig Simmons: In answer to your first question, obviously one of the key issues with hydrogeology is that each particular system or situation is very dependent on local conditions, so it is very difficult to be able to make broad and rash generalisations about all mining operations.

One of the things that we have to do before a mining operation can proceed to extract groundwater is an environmental impact statement. To do that, a whole range of hydrogeologic tools are brought into play, including computer modelling. So efforts are made to try and provide robust data and computer modelling in support of the amount of water that is being extracted.

There are complexities in these systems. None of this is black and white. The amount of data I use in a particular model may be quite different to the amount of data or particular conceptualisation that you use, for example. There are also critical social dimensions to this as well, and our values system. One critical issue I didn't talk about was that in many of these groundwater systems, such as the Great Artesian Basin, we believe that a lot of the recharge occurred over 10,000 years ago and there is very little modern recharge in those systems.

So, effectively, if we are taking groundwater out of those systems we have made a conscious decision, although we are not always explicit about it, to actually mine that groundwater resource.

On the second question, the way the chemicals or the tailings from the mining process are dealt with is largely through tailings dams. So these are ponds, essentially, where that tailing material is put out. The water evaporates and you concentrate those tailings, and you can remove those from that site. A lot of work has been done to look at how you best line those tailing dams to minimise the leakage. Clearly that is a critical issue that you just have to avoid, this leakage of the tailings back into the groundwater system, because you can potentially end up with what we saw in the Erin Brockovich example.

Question: In a previous lecture in this series an Aboriginal man claimed that Aboriginals had a very detailed knowledge both of groundwater and above-ground water, and they knew from experience of well levels and this sort of thing how water ran through their systems. He said the trouble was no-one asked them. I would like to have your opinion on whether in fact it is possible to integrate that sort of knowledge into what you are trying to do in any meaningful way.

Craig Simmons: That is a really good question and it is a topic that I am very passionate about myself. In the Centre we are already starting to have some discussions with Indigenous communities. I don't know the answer to the question necessarily, but I think we have to explore it.

In fact, the Centre is creating a number of scholarships for Indigenous students to work on projects that address some of these sorts of issues. I think we absolutely have to explore what we can learn from Indigenous peoples. I think that is critical.

Question: I wonder if you can tell us about the opportunities for remote sensing? You have pointed out that there is a lot of heterogeneity and it is a bit like Darcy trying to predict flows in porous media by measuring what is going on in individual core spaces.

I wonder also if you might like to comment on an alleged fact that I have heard about groundwater, that its transfer to the sea accounts for about a quarter of the rise in sea level that has been seen.

Craig Simmons: Let me address your first question. Remote sensing techniques are becoming increasingly important in groundwater hydrology. Obviously the surface boundary is a critical boundary for everything that happens in our underground geological systems and our groundwater systems. The remote sensing is particularly, at least at this stage, very good at giving us information, or increasingly so, on things like rainfall, evapotranspiration in plants, and open water bodies.

We are using other geophysical techniques which are really a form of remote sensing, like electromagnetics for measuring groundwater resources and their salinity. Groundwater is increasingly being investigated using remote sensing.

My personal view on this is that for a discipline that continues to claim that it is so data poor, we are faced with no choice but to explore how we increase the number of tools in the hydrogeologist's toolbox. Remote sensing is one of those. It is early days, but remote sensing communities are exploring those.

On the second question, I don't specifically know the answer. I know it has been hypothesised. I believe that a colleague at USGS, Leonard Konikow, may have written a paper to do with how groundwater depletion affects the total water balance, and that if this then ultimately ends up in the oceans that groundwater extraction could, at least in theory, account for some, but not all, of the sea level rises currently observed and/or predicted to increase.

Besides the potential hypothesis that that may be the case, I haven't read any more, and I don't think there are many papers. There are a couple that I am aware of. Some scientists have thrown that out there as an idea.

Question: You mentioned carbon sequestration. Does large-scale sequestration present a problem to groundwater and the aquifer? Secondly, only a couple of nights ago on TV there was a huge subsidence somewhere in the world, it may have been France. Could you just explain roughly the mechanism by which those huge subsidences occur, please?

Craig Simmons: In answer to your first question, I think it is early days with CO2 sequestration. We are starting to explore that in a practical sense with a pilot study here and similarly in the US. But in the last year or so I have probably reviewed anywhere between six and eight grants from Europe and North America from research communities undertaking field-based investigations – or who want to undertake field-based investigations – in numerical modelling. There is a lot still to be thought through here. Injecting different chemicals – it is multiple phase transport as well – there is a whole range of complex chemistry and phase chemistry we have to consider. I think the jury is out on the long-term future sustainability of that process. I am unaware of anything that would be more conclusive than I am prepared to be right now in answering that particular question.

In answer to your second question, you can just imagine that the underground aquifers are under pressure. We know that when we put in a bore, if the underground system is a confined one, where a sandy layer is squeezed between two clay layers, it is kind of like inflating a tyre. So it is sandwiched and water is flowing in. This thing is under pressure. You saw a really extreme example of that with Catfish Farm Well where it was punctured by accident, actually, some time ago, and this water just went like an oil gush.

These things are under pressure. If you extract groundwater at a rate that is greater than the rate at which it is being replenished then you start to depressurise that aquifer. The water in that system, if you can imagine it sitting – it is like a sponge – between all the grains of sand, and it is basically exerting a pressure or stress upwards. The grains are being held up by that water pressure. As I start to take water away and depressurise the spaces between those grains you start to get a compaction and consolidation. Slowly this geologic material will just begin to consolidate.

You can write out all the states of mechanical stress equations and show this. You can show it theoretically and we have seen in many parts of the globe that this will occur.

Question: When does surface water become groundwater? Is it on the assumption that all surface water comes from the sky and hits the ground and goes into the ground? When do you stop calling it surface water and start calling it groundwater?

And my second question is: can you put into perspective the timeframe associated with groundwater? Given the fact that you are talking about groundwater being hundreds of thousands or tens of thousands of years old, why do we have a problem now, given that only for the last 200 years have we had the ability to take out more than we can possibly put in?

Craig Simmons: The first question was, at what point do you say surface water becomes groundwater. I will try to keep my reply simple. There are differences of opinion on that, and certain textbooks define it slightly differently. I go with the definition that once water has infiltrated into the soil it has moved underground and is, therefore, on its way into the groundwater system.

Underground there are two zones. You can do this thought experiment. I am on the top of the surface of the Earth. As that water molecule goes underground the first thing that it starts to encounter is dry soil. There will also be some biodegrading biological material, leaves and organic matter. There might be a bit of soil moisture in there, but it is not completely saturated with water, it is what we call unsaturated. There is a bit of water but there is a bit of air in there and other biological material. But, strict groundwater definition is probably that once the water hits the watertable, where it is fully saturated, that's where groundwater science really takes over. Above the watertable, soil physics applies. In a sense I would argue that anything that goes underground is groundwater.

In answer to your second question, the age of the groundwater is largely a function of what we call the residence time in the system. So, how big it is. In the case of the Great Artesian Basin you can imagine that the water is recharging up in the highland area in parts of Queensland, for example. It has got to travel in the order of hundreds of kilometres and more. It moves extremely slowly. So we know that groundwater moves a metre per year – a metre per year is a fast groundwater flow rate. So, therefore, it takes a long time for that groundwater to move from the recharge zones in the mountains to the discharge zones, whether it is Lake Eyre or whatever in the case of the Great Artesian Basin.

That is what controls the age of the groundwater system. But you can imagine that that system is actually moving very slowly. It is exactly for that reason that it is so easy to determine, because the system is recharging slowly, if at all, in current climates. The groundwater is moving extremely slowly. So you can imagine now if we put 100 new bores in and create a bore field and suck those bores really, really hard, massive cones of depressions would be created within days to weeks in those systems, because we are taking water out at a much greater rate than the water can actually flow to that extraction bore. That is essentially what is happening.

In the last 20 years or so, or since the early 1990s, we have also had reduced rainfall to these systems. We have seen increased groundwater extraction. We are not getting recharge to the systems, but we are extracting more from these systems. So things can only go down in that sort of environment in terms of water levels.

Question: Given the example of California subsidence you gave, what are they actually doing about that?

Craig Simmons: I don't know what the response to the particular San Joaquin Valley one was. I know there has been a lot more computer modelling that has been done in recent times.

You have to remember that a lot of these processes were not discovered until the last 40 or 50 years in terms of our research knowledge. We saw in that example that the subsidence occurred between 1924 and 1977. It pre-dates almost all of our computational models. We wouldn't even have been doing environmental impact assessments. There weren't sophisticated groundwater modelling tools available there at that time.

We are now really quite focused on good practice across the globe, in using groundwater models as part of our ability to understand how these systems respond. I certainly hope and pray that we don't see more of those examples occurring over the next 10 to 50 years.

We have also got to redress some of these situations where over-pumping might be occurring now, and make sure that we learn from these experiences.

Question: Is all the groundwater ultimately hydrosphere? Would any of the groundwater actually get inside the Earth? I ask this question, having disputes with land development at Braidwood, because one of the experts there has said there is no problem with groundwater because it is being generated from deep within the Earth.

Craig Simmons: There are three sources of groundwater. The first is what we call 'meteoric water', and that is water that comes from rainfall or it can be from melting ice and snow. It is generally part of the active hydrological cycle. I should say from the outset that it represents literally 99.9 per cent of groundwater on the planet. So you could ignore the other bits and you would be okay.

The other really, really minuscule amount of groundwater can come from two other sources. The first is what we called 'juvenile water'.  It is water that can be released. This is so small that we almost never think about it and don't include it in our analysis. Juvenile water is water that comes out of water that was brought into hydrologic cycles from things like meteors, for example, impacting on the Earth. Really small and insignificant from the point of view of the total hydrologic cycle and the water balance on the planet.

The third is what we call 'connate water'. Connate water is water that was locked – you can imagine as a rock is forming you have got soil grains. You might have some water between those soil grains, and then slowly over thousands and millions of years the rock starts to settle, it lithophies and as it does it is effectively cementing those grains of sand and other minerals together. The moisture that was present in that process gets locked into the rock. We know that from the point of view of water supply and quantity, that connate water, this water that is stored in the rock as it is being formed, is virtually insignificant from the point of view of quantity, but we know that it is critical with respect to water quality, because the mineralogy in that connate water influences the chemistry in these systems.

So I think in answer to your question, if I was going to place bets on anything, I would be going for rainfall 99.9 per cent of the time.

There is some interesting work being done in some projects that I am aware of right now. These haven't been published yet, so I have to be careful about what I say here. Where we do know that there are traces that we are seeing in groundwater, in the Great Artesian Basin for example, that are derived from the Earth's mantle, I don't necessarily think that is actual active groundwater flowing up from the middle of the Earth. But I do think it is showing us that there are connections through fractured rock in these systems where gases escaping from the mantle can escape upwards and influence the chemistry of these shallower groundwater systems. I think that is quite fascinating stuff.