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Published: 9 July 2012

Dr Dirk Mallants: expert on groundwater and patience

Groundwater specialist Dr Dirk Mallants of CSIRO understands the importance of patience. As he explains to ECOS in this interview, the timescales on which groundwater processes operate can be as long as millennia.

Dr Mallants, CSIRO Groundwater Hydrology Program Leader
Dr Mallants, CSIRO Groundwater Hydrology Program Leader
Credit: CSIRO

Dr Mallants is based in Adelaide, Australia's city of churches, and hails from the University of Leuven, Belgium, another city of churches.

An expert in soil and groundwater hydrology, Dr Mallants leads a team of CSIRO researchers working on understanding groundwater in Australia. Some of the issues the team addresses are:

  1. current and future availability of groundwater

  2. how groundwater reserves are naturally replenished

  3. how groundwater contributes to maintaining streamflow

  4. how climate change affects groundwater availability

  5. the degree to which ecosystems, plants and animals depend on groundwater for their survival.

Can you give an example of how findings from CSIRO groundwater hydrology projects have been applied in the real world?

In the irrigation-intensive areas of the Murray–Darling Basin, much of the land is salt affected. CSIRO has contributed to establishing a long-term management strategy for community-based groundwater and salinity in these areas.

Disposal basins are used to store subsurface drainage from irrigated land, so that farmers can remove salt from the plant root zone and decrease salt export from irrigated areas into rivers. In the Riverine Plain region of Victoria and New South Wales, the number of small, on-farm (1–5 ha) and large, community (20–100 ha) disposal basins has increased in recent years, due to regulations limiting the export of salt from irrigation areas. The design and management of on-farm and community basins vary widely, because they were developed under different administrative frameworks.

The CSIRO groundwater hydrology project team investigated and modelled the hydraulic, chemical, and groundwater processes occurring in disposal basins and surrounding land in the Riverine Plain region. From this, we developed tools to improve basin siting, design, management, and cost-effectiveness, as well as principles and guidelines for optimum design and management of small-scale basins.

What are some of the challenges Australia faces in better understanding and managing its groundwater resources?

One of the key science challenges relates to how groundwater is recharged, or replenished: a complex process that involves timescales ranging from years to millennia. Sustainable use of Australia’s groundwater resources is based on knowing the amount of recharge, as this determines the maximum level of renewable resource.

Over long timescales, diffuse recharge is the amount of precipitation that is not lost to the atmosphere by soil evaporation and plant transpiration, and to the rivers by surface runoff. However, recharge is difficult to measure or estimate, particularly considering the enormous spatial dimension of the Australian landscape.

Typically, recharge is calculated from the difference between precipitation on the one hand, and evaporation and transpiration on the other. But, small errors in these water balance components may lead to large errors in the recharge component: especially if the recharge is just a few millimetres per year.

Another approach to measuring recharge is to take specific measurements at different sites (point-scale estimates): for instance, based on an analysis of the chloride balance of soil profiles. But, these point-scale measurements are difficult to extrapolate or upscale to large areas, because of variability in soils, sediments, and vegetation.

The challenge is to develop a link between small-scale and large-scale representations of the recharge process in a physically consistent way. For example, on the small scale, recharge estimates may be made by determining the age of groundwater using isotopic techniques. On the larger scale, we have flow models for groundwater and for the movement of water through the ‘unsaturated’ zone1 of the ground. So, the question becomes: can we integrate some of these techniques to give us more certainty when we model groundwater, so that we can have greater confidence in our recharge estimates, and therefore in our determinations of the maximum level of renewable resources?

Steam emanates from a drain connected to the Mirra-Mitta bore, Great Artesian Basin, South Australia. Hot water flows constantly from this 1000-m deep bore, which was sunk in the year 1901.
Steam emanates from a drain connected to the Mirra-Mitta bore, Great Artesian Basin, South Australia. Hot water flows constantly from this 1000-m deep bore, which was sunk in the year 1901.
Credit: CSIRO. Photo by Jan Mahoney

Prior to joining CSIRO, you worked in Europe and elsewhere on waste and contamination management issues in the nuclear industry. How does your expertise in soil physics relate to how nuclear waste is managed or contamination avoided?

The basic principle of safe management of radioactive waste is based on the ‘concentrate and confine’ concept. The waste product is concentrated and immobilised in a relatively small volume and then disposed in natural materials, such as deep clay layers, or artificial materials, such as concrete, that are more impermeable to water. As a result, transport of the radionuclides2 through such materials is virtually zero. Principles of soil physics demonstrate that the contaminants remain safely within the repository until most of the radioactivity has decayed.

Principles of soil physics – such as transport of heat, water and matter through a porous soil – are applicable in any porous medium, whether soil, clay, granite or even concrete. Compared with soils, deep clay layers are easier to deal with, because they are relatively homogeneous, remain water-saturated, and their physical characteristics do not change over reasonable timescales.

Many of the research tools – such as numerical models and tracer data - I and my colleagues in the nuclear safety field used are identical to the ones being used in coal seam gas (CSG) studies. Coal seam gas studies must consider the same properties of aquitards (relatively impermeable rock or clay layers that limit groundwater movement into, or out of confined aquifers), to determine how CSG extraction from isolated aquifers impacts on aquifers that are a major source of water for other uses.

You have been involved in stakeholder engagement and collaboration – aimed at promoting greater understanding, and potentially, acceptance of potentially controversial government policy and decisions. Can you give an example of one of these issues that you worked on and perhaps the approach taken?

I have indeed been very fortunate to have interacted widely with different non-technical stakeholders throughout my career as a scientist. The science behind the development of nuclear waste repositories is still very contentious in western democracies, and so I have worked hard on advancing understanding of the science through community partnerships. In this approach, engagement, interaction and cooperation with local communities is central to the process of facilitating acceptance of potentially controversial government decisions.

Members of local partnerships – such as regulatory agencies and the public at large – become involved in the project at a very early stage. Also, real decision power is granted to the partnerships and a very intense dialogue is maintained between all parties. I believe that much of the success of the partnerships in which I was involved was due the extensive effort made to communicate complex science in accessible terms – through, for example, public lectures and workshops.

A mound spring known as ‘the bubbler’ on the western edge of the Great Artesian Basin, South Australia. This spring has been flowing for thousands of years.
A mound spring known as ‘the bubbler’ on the western edge of the Great Artesian Basin, South Australia. This spring has been flowing for thousands of years.
Credit: CSIRO. Photo by Glenn Harrington

Do you think the community partnership approach could be or has been useful for groundwater policy in Australia?

Elements of this approach have universal applicability in other domains, including the development of sustainable water resources management. It has become clear in recent years that any large or potentially controversial technical, infrastructure, or even groundwater management project requires broad political and social acceptance to be successful. This, in turn, requires both technical and social confidence that the project is necessary, environmentally sound and will be well implemented.

This holds true in the case of Australia’s groundwater, as well as water policy more generally. For stakeholders to have confidence in the results and conclusions drawn from hydrogeological assessments, they need information provided in a transparent and traceable manner. They also need to be confident that the science used – for example, the conceptual models and computer codes – are fit for purpose and have been used appropriately.

Confidence in hydrogeological assessments is also boosted by uncertainty management: the science of considering relevant uncertainties, and either addressing them or acknowledging their effects. Uncertainty analysis is also a key element of developing a long-term R&D program. It helps prioritise data collection – for example, directing research towards those subsurface hydrological processes and parameters that contribute most to model prediction uncertainty.

Who has inspired and motivated you in your career ?

Dr. Martinus (Rien) van Genuchten, who is by far the most-cited soil hydrologist, with more than 15 000 lifetime citations. He conducted most of his work at the United States Salinity Laboratory in Riverside, California.

However, it is not necessarily Rien’s citations that have inspired me, as much as his unsurpassable energy, his genuine desire to help and connect people, and his ability to make complex science comprehendible and accessible. Rien has given his profession enormous visibility and scientific credibility, while at the same time making his theories and models readily available to potential users. Despite his successes, he has remained a very humble and amiable person, always ready to share.

Radon sampling at Cockburn River, NSW.
Radon sampling at Cockburn River, NSW.
Credit: CSIRO

Do you have a favourite quote?

‘There is no greater impediment to progress in the sciences than the desire to see it take place too quickly’ – G.C. Lichtenberg, 1742–1799.

Can you tell us how this need for a long-term approach plays out in the field of groundwater hydrology?

Groundwater hydrology, especially in Australia, is complicated by the extraordinarily large dimensions of some of the aquifers (e.g. the Great Artesian Basin is one of the largest known groundwater reservoirs in the world, covering approximately 1.7 million square kilometres) and by their interfaces with surface environments, rivers and oceans.

For example, the aquifers of Australia’s sedimentary basins can cover thousands of square kilometres, and contain several permeable layers separated by poorly permeable layers (aquitards). Furthermore, the complex movement and interactions of different layers of water in aquifers are often difficult to detect.

Groundwater generally travels slowly in the subsurface, with groundwater age varying from several years to centuries or even millennia. Moreover, low flow rates through aquifers can cause considerable time lags before the consequences of groundwater abstraction by pumping are detected. Effects of climate change (e.g. reduced precipitation) can lead to less groundwater recharge, but in slowly reacting groundwater systems, this may not be quickly detected. Therefore, we need long-term monitoring of groundwater levels and pressures to detect such deferred consequences.

Long records of groundwater levels (and where relevant, surface-level records) – usually over several decades – are also needed, to calibrate and validate the groundwater models that we use to underpin sustainable groundwater management. Monitored aquifers can be considered as long-term natural laboratories used to characterize groundwater resources in specific climatic and land-use settings.

The art of science is being patient and cautiously observing changes in the data being collected. A long-term strategy provides a solid basis for capitalising on field-based research, and the return on previous research investments is amplified as more data are collected. Each new observational study within a natural laboratory adds to the database, improving the conditions and opportunities for future work.

More information

Groundwater Hydrology Program, CSIRO

Groundwater, National Water Commission

1 The zone in which the pore spaces and fractures in soil and rock contain both air and water. It contrasts with the saturated zone, in which all the pore spaces and fractures between soil and rock particles are saturated with water.
2 Nuclear radiation is radioactivity that comes from the nucleus of certain chemicals. These chemicals are called radionuclides and are unstable. Radionuclides give off energy and particles as they decay (break down).

Published: 25 November 2014

Things warm up as the East Australian Current heads south

Jaci Brown

Occasional erratic bursts southward of the East Australian Current (EAC) are thought to have moderated the weather of south-east Australia this autumn and winter and they continue to introduce tropical and sub-tropical marine species to Tasmanian waters.

Tasmania’s east coast: tropical and sub-tropical marine species normally found off NSW are finding their way further south, thanks to changes in the East Australian Current.
Tasmania’s east coast: tropical and sub-tropical marine species normally found off NSW are finding their way further south, thanks to changes in the East Australian Current.

Ocean monitoring by Australia’s Integrated Marine Observing System is providing scientists with significant new insights into the changing structure of the EAC. Over the past 50 years sporadic warm bursts have become more common as the EAC moves further south. With global warming, the warm burst we’ve seen this year may also become the norm.

Had our little friend Nemo the clownfish been riding the EAC this year he might have found himself holidaying in Tasmania rather than admiring the Sydney Opera House. He wouldn’t have been on the trip alone, though. Sea nettles (Chrysaora spp.) have headed from their usual home in Sydney to be found for the first time ever in Tasmania and the Gippsland Lakes.

<i>Chrysaora woodbridge</i>, or sea nettle, was found in surprising numbers in Tasmania this year.
Chrysaora woodbridge, or sea nettle, was found in surprising numbers in Tasmania this year.
Credit: copyright Lisa-ann Gershwin

Waters in the EAC travel southward along the east coast of Australia, with most of it splitting from the coast near Sydney and heading for New Zealand. A small part of the current, known as the EAC Extension, works its way southward past Victoria and Tasmania.

A typical signature in this region are the large eddies, around 200 kilometres across and hundreds of metres deep. Some of the warm water is trapped here along with marine life.

The EAC starts at the Great Barrier Reef and travels south to Sydney before turning eastward to New Zealand. Some of the water can still push southward via a series of strong eddies.
The EAC starts at the Great Barrier Reef and travels south to Sydney before turning eastward to New Zealand. Some of the water can still push southward via a series of strong eddies.
Credit: Eric Oliver

This year a larger proportion of the EAC was sent southward instead of breaking away to the east. Winter ocean temperatures off Bass Strait were around 19°C, an increase of 4°C. This impacted local fishing, beach conditions and the weather.

In the video (above) the animation on the left shows the actual sea surface temperature and speed of the ocean currents. The animation on the right shows the difference in the temperature from average conditions.

Through autumn and winter, you can see two interesting changes occur. A strong warm current heads down the coast from Sydney to the coast of Victoria. At the same time, warm water peels off from the EAC and swirls around in large eddies as it meanders toward Tasmania.

An unusual catch down south

One advantage of warm eddies is the refuge they provide for tuna. They congregate in the centre of the eddy where the waters are warm and dine at the nutrient-rich edges.

Local fishers in north-east Tasmania report a remarkable year that allowed them to fish longer than usual, providing game fishers with more opportunities to catch tuna.

Last summer’s (2013–2014) warmth provided an abundance of skipjack and striped marlin, while winter brought a run of bluefin tuna.

Redmap is a website where locals can report sightings of marine species that are unusual for a given area.

Last summer a manta ray, a tropical cartilaginous fish (in a group including rays and skates), was sighted off the north-eastern coast of Tasmania. Previously the southern-most sighting of a manta ray was just south of Sydney.

<i>Manta birostris</i> spotted off north-east Tasmania on Australia Day 2014.
Manta birostris spotted off north-east Tasmania on Australia Day 2014.
Credit: Redmap/Leo Miller

It’s not just new species visiting Tassie either. Local jellyfish such as the Lion’s Mane (Cyanea) – more commonly known as ‘snotty’ – are usually quite elusive, but turned up in unprecedented numbers last summer in Tasmania.

But there’s a catch

This movement south of the EAC may have an impact on other systems, including our health. We rely on fish such as those from the Tasman Sea as a source of omega-3 fatty acids for our brain health. But the concentration of omega-3 fatty acids in the fish is likely to decrease with global warming.

Algae are the original source of fatty acids. As our waters warm, we will see more of the algae from the tropics take up residence in the south-east.

But the algae from the tropics are much smaller, which means more steps in the food chain from the algae to the fish we eat. The more steps in the food chain, the more the omega-3 fatty acids in the fish are replaced by fatty acids that are less favourable to brain health.

The warmer coastal waters also contributed to the balmy autumn and winter in south-eastern Australia this year. Afternoon sea breezes cool coastal temperatures by drawing cool oceanic air onto the coast.

Sydney’s heat wave in May this year had 19 consecutive days of 22°C or more – this is partly due to the sea breezes failing to bring in the usual cooling air.

What’s causing the EAC to move south?

Over the past 50 years the EAC Extension has stretched about 350 km further south. This extension doesn’t happen smoothly but in erratic bursts.

The southward extent of the EAC is controlled by the collective behaviour of the winds between Australia and South America. Over that same 50-year period these winds changed their pattern due to a strengthening of a climate system known as the Southern Annular Mode.

The changes to this mode have been attributed to a combination of ozone depletion and increasing atmospheric CO2.

One of the most robust and consistent responses of the climate system to increasing CO2 is a further strengthening of the Southern Annular Mode.

So the result will likely be a further enhancement of the EAC extension southward and even warmer waters in the Tasman Sea.

Dr Jaci Brown is a senior research scientist with the Centre for Australian Weather and Climate Research (CAWCR), a partnership between CSIRO and the Bureau of Meteorology. Her research focuses on the El Nino Southern Oscillation (ENSO) and climate change. This article was originally published on The Conversation. Read the original article.

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