Since 1996, Pieter has worked as a hydrogeologist in private consulting for GHT Consulting Scientists, GCS Water & Environmental and for AngloGold Ashanti in the mining sector. This deep experience brings diverse stakeholder perspectives on the impacts of and effects of groundwater.

Pieter has participated in various groundwater impact, management, and supply projects. Some of his key capabilities include groundwater liability, risk assessments, and mine closure studies for both metalliferous and coal mining clients. He has developed and implemented groundwater management and monitoring programs, resource assessments, and feasibility studies for mining projects across Africa, Australia and South America.

Some of the most recent highlights include:

• Groundwater resource assessments and establishing a well-field in the Sahara Desert (Mauritania) and a feasibility assessment for a well-field in the Nubian Desert (Sudan) for gold mine projects.
• Participating in groundwater resource assessments for more than 300 schools in rural Kwazulu-Natal, South Africa, as part of an emergency drought relief program between 2016 and 2019.
• Assisting mining companies to manage operational and post-closure groundwater liability and risk due to acid mine drainage and sulfate drainage through practical and innovative approaches.
• Participating in community-based projects involving water conservation with local schools in the Durban area, South Africa, and supporting two community-based nature trail-run events (3 Falls Trail Run and Kwa-Ximba Trail Run).
• Developing long-standing relationships with clients and learning every day from both my colleagues and clients.

Equipped with a Master of Hydrogeology from the University of the Free State (UFS) in Bloemfontein, South Africa and over 20 years of hydrogeology experience, Pieter Labuschagne is a valuable addition to the AGE team.

Pieter and his family relocated to Brisbane from Durban earlier this year, which is no mean feat considering quarantine requirements and trying to find a house in a time of COVID-19.

Connect with Pieter via LinkedIn ~ https://www.linkedin.com/in/pieter-labuschagne-44119229/

View our AGE team ~ https://ageconsultants.com.au/about/team/

In Australia, almost 17% of available water resources come from groundwater. So, understanding the environmental impact of that use is vital in ensuring access and usage of groundwater resources is safe, compliant, respectful of all stakeholders and considerate of the future.

For a range of sectors, from resource mining to agricultural and infrastructure projects, having an intimate understanding of groundwater-related operational issues is critical in ensuring safe practices and avoiding unforeseen risk. At Australasian Groundwater and Environmental (AGE) Consultants, our highly skilled team delivers robust and rigorously researched end-to-end groundwater and environmental advice to help clients understand the complexities of the underground environment whilst ensuring compliance with all regulations.

Groundwater modelling is a powerful methodical tool that creates computer simulations of underground water systems and helps predict impacts from mining, infrastructure and agricultural projects on aquifer conditions, vegetation, and ecosystems. These groundwater model predictions ultimately underline project and environmental risks relating to groundwater.

Developing a strong relationship with the client is the first step in understanding their specific needs and discussing areas of legal, environmental, or cultural significance which might impact the modelling. Data is then collected from the client and government databases. Armed with scientific and technical expertise, our groundwater modellers then begin the process of collecting and inputting data to develop predictive models:

• A conceptual model provides a simple representation of the natural system, describing the direction of groundwater flow and the relationships between groundwater, climate, surface water and features of cultural and ecological significance.
• Analytical modelling can be used to assess the impacts of smaller projects on water resources. If risks and uncertainties are low, these models may suffice in providing all necessary information.
• Numerical models are expected for significant projects and include many parameters that are needed to replicate the groundwater system accurately. Calibrating the model facilitates the best match between the observed data and the model predictions.

Each member of our team of highly trained hydrogeologists and engineers brings not only a thorough understanding of the regulatory and legislative groundwater requirements to their modelling but is able to apply specialised calibration and uncertainty analysis methodology. When the modelling begins, the modeller takes the conceptual understanding of the groundwater system and uses it to first build the model structure, before assigning hundreds of parameters to the software. Calibration allows for fine tuning to optimise model predictions, and uncertainty analysis provides a range of potential impacts on the groundwater system. The calibrated model predictions and uncertainty analysis are used together when the project is reviewed and then assessed by the regulator.

End to end, large projects can take up to a year, while smaller projects may be delivered within a couple of months. Comprehensive groundwater modelling provides a deeper understanding of a groundwater system, facilitates the preparation of impact predictions, and quantifies uncertainty around the model predictions. This comprehensive analysis of the system benefits both the client and the regulator.

Environmental Impact Statements are an integral part of operations in multiple sectors, and governments require that they be taken seriously, not treated as a mere ‘tick-box’ exercise. Our team at AGE are proud to conduct groundwater modelling with rigour and integrity, not only for the success of projects but for the future of our environment.

Discover more > https://ageconsultants.com.au/our-services/groundwater-modelling/

Queensland’s mine rehabilitation and closure reforms ensure that almost all active and closed open cut mines require a Progressive Rehabilitation and Closure Plan (PRCP). Until recently, void modelling has been quite unsophisticated, with annual average stresses, such as rainfall, used for modelling. Traditionally a number of discrete methods are used to model surface water, groundwater and contaminant transport. These systems do not communicate or align closely. This compromises the reliability of recovery predictions.

Traditionally, these predictions were calculated in isolation, with no sophisticated feedback loops between climate, surface water interactions, the final landform, and surrounding groundwater systems. Data needed to be simplified to integrate system predictions, which limited our ability to predict how stresses interacted. Furthermore, the ability to view the true cumulative effects was inadequate.

Neil Manewell, Technical Modelling Lead at AGE Consultants, describes this method as ‘problematic’, especially when there are significant volumes of dry coal seams and spoils, with varied permeability, that surface water models often misrepresent. This can have the effect of overstating future water levels in the pit lake and surrounding strata and can speed up the expected recovery of the groundwater system and pit lake.

A 3D groundwater model is the best way to assess the complex nature of groundwater flows patterns and contaminant transport. At AGE, when simulating post-mining recovery, we have devised an alternative method to simulate pit lake recovery. Using the 3D groundwater model, so that groundwater can be accurately simulated, a ‘reservoir node’ is built into the pit void. The reservoir node is where information is integrated from the surface water model. The inflows and outflows prescribed to the reservoir node are calculated from other analytical models, such as AWBM or SWAT+. We can also make use of particle tracking (mp3du), basic contaminant transport (BCT), and reactive-active transport simulators (BCT + PHT-USG).

By integrating surface water, groundwater and possibly geochemical data onto one platform, the data and outputs can be managed consistently over time. Detailed daily representations of climate (rainfall, surface water, and evaporation) and the impacts of short, sharp incidents can be simulated as a system. Landform disturbances or a major climatic event, are automatically updated throughout the model. High-level chemical reaction modelling can be embedded to manage the risks of salinity and other contaminant interactions with the aquifer. These models could be used to calculate the probability of various risks to groundwater dependent assets, prompting proactive redesigns of mine plans to avoid future impacts and ensure compliance.

When the data is integrated, the risk of errors is reduced, saving time in meeting PRCP reporting requirements. AGE has used this modelling in feasibility studies of various landform configurations, and future applications could include comparative analysis of various closure and rehabilitation options.

We have applied this new modelling method to models of the Glendell, Mt Owen, Hunter Valley and Liddell operations.  We successfully implemented a reservoir node into a MODFLOW USG model, and particle tracking for several different scenarios was simulated to confirm contaminants would not migrate to local groundwater dependent assets.

Future modelling will work on increasingly complex systems and simulate the interactions between systems with live monitoring data. We will continue to work at the forefront of this technology to improve the information and analysis required for optimised decisions and planning.

Ultimately, this new method of integrated water level predictions in mine voids, surrounding groundwater systems and connected streams helps our industry improve rehabilitation outcomes, leading to better financial assurance after the closure of a mine. The reservoir node approach maintains consistency with the surface water modelling, enabling reliable predictions of groundwater drawdown, thus improving governance and planning decisions.

We’ve been providing groundwater and environmental advisory for more than 20 years, empowering informed water decisions that help our clients, communities and the environment thrive, so we thought it was about time that we launch a new look that better reflects our position as Australia’s groundwater specialists.

Our team of hydrogeologists, hydrogeochemists, and numerical modellers specialise in end-to-end groundwater services, from field work and modelling to analysis and reports, to expert advisory and peer review.

We have an in-built curiosity for the latest opportunities, modelling techniques, research and thinking in geoscience and global environmental issues. With a single-minded focus on our work’s impact and the outcomes for our clients, we are proud to help solve our clients’ greatest problems.

One way in which we are demonstrating this curiosity, innovation, and better outcomes for our clients is through improved modelling approaches, such as those involved in mine closure planning.

To discover more about how we deliver advice that advances projects in an ever-changing world, read our latest blog entitled “Improved modelling of voids for mine closure planning”.

2017 marked an exciting anniversary for AGE – our 20th year in business.

Back in 1997, John Howard was prime minister, Titanic was the highest grossing movie of all time, Ford Falcon station wagons were all over our roads, and chambray shirts were all the rage. In this environment Errol Briese and Lindsay Furness bravely left secure jobs and co-founded AGE in a small office in Bowen Hills. Lindsay soon moved on to pursue a passion for overseas opportunities, prompting Errol to open ownership of AGE to other employees, a model that continues to this day.

The business quickly flourished and the team rapidly grew necessitating a move to a larger premises. A 100 year old heritage listed ‘Queenslander’ in Bowen Hills fit the bill and served the company well for over 10 years. An office was also set up to serve North Queensland from Innisfail. The iconic green Queenslander on Jeays Street is still standing today and can still be seen from the current AGE offices.

In 2014, AGE setup the Newcastle office to service the pre-existing clients within the Hunter Valley and greater New South Wales area. The office has operated successfully for three years with three hydrogeologists providing services to the Hunter Valley and wider region. Whilst serving Australian clients has always been our core business, we have enjoyed many opportunities to travel overseas and assist with projects in Laos, Vietnam, Kuwait, Papua New Guinea, Argentina, Brazil, Philippines, and Senegal.

Looking back like any child we have had growing pains. The transition from a small team of five to a larger group of 20 was challenging. We implemented better human resource frameworks and workflow systems for the company to ensure we look after our most precious resources – our people. The downturn in the mining industry in 2012 also forced us to focus on providing competitive services and maintaining a commercial edge over other companies. Our continued profitability, low staff turnover and maintenance of a 20 person team is a source of pride for us that we have navigated this challenge well and continue to provide high quality services.

2021 has already been an exciting year for our company and we intend to celebrate with our people and clients. Of course, whilst we celebrate, we will continue to focus on what has made us successful to date – our core capabilities and high quality deliverables.

We are also looking forward to the next five years at AGE Consultants and the further evolution of the company with some big announcements imminent. Stay tuned!

By Neil Manewell

Although we try our best to add sufficient complexity to a model, e.g. numerous layers, hydraulic zonation/pilot points, there will always be uncertainty, simply because it is impossible to measure the aquifer and recharge parameters of every square metre of the model domain.

To reduce uncertainty as far as reasonably possible, we calibrate our models to as much observation data as possible, e.g. groundwater levels, sump pumping observations, and hydraulic testing results.

There are an infinite number of combinations of parameters that will produce a ‘calibrated model’, and therefore is it important to explore impact predictions across these parameter interactions.

The uncertainty in the predictions of a model can be explored using a number of methods. A relatively quick process is to undertake a predictive linear analysis. This method assumes a normal distribution of parameters, based around an initial calibrated value.

The probability and range of predictions is calculated by making very small changes to each parameter during the predictive simulation, then projecting the likely impacts out, assuming a normal distribution. One advantage this method has is the quantification of parameters contributing to uncertainty, for example hydraulic conductivity of a layer is contributing ±1 ML/day to mine inflows.

It will also provide information on which groundwater observations most enhance the calibration, therefore reducing uncertainty of predictions.

Because parameter iterations are rarely linear, relying on linearly derived results from complex groundwater systems may not be appropriate in some cases. Non-linear uncertainty analysis actually tests parameter interactions across their predicted ranges to derive the likelihood of groundwater impacts.

One method is a null-space Monte Carlo technique, which uses the information from the calibration dataset to constrain the range and frequency of the parameters attributed to each unit in the model. This process creates several hundred ‘realisations’ of a calibrated groundwater model, which can be used to analyse the range in predictive impacts. Similar to linear predictive analysis, the process of assigning the frequency of parameter values usually assumes a normal distribution.

In reality, aquifer and recharge parameters rarely adopt a normal distribution. Parameters can have skewed, flat, or multi-normal distribution. Neglecting the possibility of a non-normal distribution can have significant implications to the range of groundwater impact predictions. AGE prefer the use of a calibration constrained GLUE (generalised likelihood uncertainty estimation) approach.

GLUE works by starting with a random suite of non-normally distributed models. Each model is tested to ensure calibration is maintained, and parameter distributions are refined by neglecting models outside a measurement threshold, e.g. objective function increase of 100%. One drawback is the many thousands of ‘realisations’ required to properly explore all possible parameter combinations.

DREAM (DiffeRential Evolution Adaptive Metropolis) uncertainty analysis is in our opinion currently the best method to quantify uncertainty. Similar to GLUE, the process assumes non-normal distributions of parameters. Parameter distributions are generated using a generic algorithm, meaning there is no requirement for calibration rejection, as eventually all realisations generated in the analysis are ‘calibrated’.

The results from the above analyses can produce the probability of drawdown, change in groundwater flux, baseflow, or dewatering predictions as a composite result across all ‘realisations’, e.g. 95th percentile drawdown estimates predict Bore_1a will go dry in 2028, or cumulative 80th percentile dewatering requirements will be 120 GL.

By Andrew Durick

Historically, the other limitation of particular note was simulating dewatered or unsaturated conditions, which occur around excavations. MODFLOW does have a ‘drying and rewetting’ function, however this invariably proves numerically unstable because of the threshold nature to trigger the wet or dry condition. Furthermore, having a cell convert to dry conditions usually increased the chances of neighbouring cells going dry, an effect referred to as cascading dry cells.

In the late 1990s, the bulk of groundwater modellers were using graphical user interfaces (GUI) such as PMWin, Visual MODFLOW and GMS. A handful of users had developed customised code to generate a series of input files and batch files to run those files with MODFLOW executable. Early utilities such as those developed by John Doherty were early examples of simplistic coding to manipulate and transform input and output data. During this time I was lucky to work with John Doherty and his utilities at the then Queensland Department of Primary Industries while at the same time gaining exposure into regional and local scale modelling for groundwater resource developments.

When I joined AGE in 2006, I brought this methodology of using code to manipulate and process data to make development of complex models easier. This use of coding enabled numerous start/stop models and time variant changes to be made for hydraulic properties – critical to simulating the impacts from longwall mining. This was occurring at AGE well before any commercial time variant hydraulic property package was available.

In 2006, our modelling transitioned from the standard MODFLOW and FEFLOW software packages to be dominated by MODFLOW SURFACT. SURFACT provided the ability to simulate unsaturated conditions and bypassed the inherent problems of the standard MODFLOW’s drying – rewetting function. Transitioning existing models from MODFLOW to MODFLOW SURFACT was simple because of the majority of the model setup remained the same.

In the recent past, we have again seen a transition at AGE, this time from SURFACT to the latest version of MODFLOW – MODFLOW-USG, with ‘USG’ referring to the ability to have unstructured grids. There are advantages in this for us and our involvement in mining applications where complex or sub-cropping geologies are generally represented. The ability to truncate a model layer where the geology pinches out in real life is something that was missing from all previous versions of MODFLOW. In the past, we developed a method of thinning and ‘wrapping’ these non-existent layers, which were assigned appropriate hydraulic properties, but it would have been better to have the overlying and underlying units directly connected. The other advantage of MODFLOW-USG is the step away from rectangular/orthogonal meshes to variable shaped meshes. We have found that the majority of our work is ideally suited to the voronoi mesh option, where we can add detail to the model where we have data and where refinement is required, and then rapidly coarsen the grid away from those areas. The voronoi mesh combined with the truncation of layers results in reduced number of model cells, meaning shorter model run times which is significant for calibration and other analysis involving significant number of model runs.

Model calibration in the last 20 years has certainly been revolutionised by PEST. While PEST is a great tool, it must be used appropriately and with constraints that relate back to the field data and to the resulting conceptualisation. PEST is continuing to evolve with ever expanding functions supporting the changing demands of not only calibrating a model, but also about quantifying the potential wrongness in the model predictions. This level of wrongness is more commonly referred to as uncertainty.

Uncertainty analysis has become a focus for the industry in the last five years and this will certainly continue with requirements for it written into legislative guidelines. Uncertainty was not commonly undertaken within the industry five years ago because the Monte Carlo technique available at the time was too cumbersome to undertake efficiently. Sensitivity analysis was used as a substitute, where it was extended from the usual calibration period, to the predictive simulation to examine the potential variation in model results. At AGE, we have embraced the challenge of uncertainty analysis by applying clever techniques (both linear and nonlinear) to address requirements for uncertainty analysis. We have also purchased ‘supercomputing’ resources to enable the significant model runs required during the analysis to occur as efficiently as possible.

In terms of modelling at AGE in the last 20 years, we have thankfully seen some significant changes. We would not like to be answering today’s questions with only the tools available 20 years ago. It is an exciting time for modelling at AGE, and it is mind boggling to think where we could be in another 20 years, with software, with computational power and with the types of questions needing answers.

By Neil Manewell

With classic MODFLOW, our only saving grace was grid telescoping, whereby we reduce the cell size until we gradually narrowed down to our intended grid resolution. This was generally restricted to a factor of 10% of the largest cell in the model, and couldn’t be reduced greater than 1.5 x smaller than the neighbouring cell. Model layers had to be continuous, meaning the modeller would have to ‘wrap’ the layers so that a minimum layer thickness was achieved across the model domain.

Finite-element mesh designs were therefore more favourable, particularly when groundwater interactions between the surface water and groundwater systems were high and required a high level of detail. Only the problem was the finite-element method often resulted in slow-runtimes due to high element counts, large water balance errors, and the requirement for continuous layers across the model domain.

MODFLOW-USG is the latest derivative of a long line of MODFLOW releases and represents a breakthrough for modelling efficiency. The code is essentially unrestricted in terms of layer presence, cell resolution changes, cell shape, and cell connectivity. A finite-element style mesh can be used to easily increase resolution where required, e.g. along rivers/creeks/mining areas. Voronoi meshes further reduce cell count by effectively halving the number of cells compared to a triangular mesh. Layers can be ‘pinched’ out, which is particularly useful in coal basins, where a number of units terminate at the surface.

We are currently converting many of our older models to MODFLOW-USG to make them faster, better represent connected and disconnected geological units and more suited to uncertainty analysis.

Enquiries can be directed to Brisbane@ageconsultants.com.au.

Sustainable Well: Maintenance, Problem Prevention, and Rehabilitation

Authors: Stuart A. Smith, Allen E. Comeskey

Publisher: CRC Press Taylor & Francis Group

Authors Smith and Comeskey bring a combined 80 years of expertise in bore deterioration monitoring, management and remediation into one handy, compact book. The book outlines the causes and effects of bore deterioration. This includes a great (hitchhiker’s) guide to biofouling, which they describe as “the number one contributor to reduced well performance… across the globe”

The first indicator of biofouling is normally increased concentrations of iron, manganese and sulphur within the groundwater. Further indicators of hydrochemical change include increased turbidity, odour and corrosion of pump components. Biofouling involves the oxidation of chemical compounds (i.e. iron, manganese and sulphur), which largely occurs within the redox fringe. The redox fringe is the interface between zones depleted of oxygen and those with free oxygen, which is important for the development of biofouling organisms.

Bore performance depends on a variety of environmental, hydraulic, and use factors. Biofouling can reduce this performance clogging pumps, pipes and screens, and reducing hydraulic conductivity. The effects of hydraulic conductivity reduction due to biofouling are largely controlled by the transmissivity of the aquifer. Highly transmissive gravels for example, are much less likely to display noticeable plugging effects from biofouling compared to a poorly transmissive, fine grained aquifers.

Biofouling may also encrust or loosely plug bore screens, pumps, and other equipment over a period of weeks, months, or years, depending on the environment. The book draws attention to the importance of regular assessments into the condition of groundwater bores. Without regular monitoring of water quality and aquifer performance, it is possible that the effects of biofouling may not be detected until they are in advanced stages. This can pose health risks to users, degradation of infrastructure, and increased remediation and maintenance costs.

The effects of biofouling extend beyond operational issues, with several potential detrimental health effects resulting from the presence of microorganisms. This can include bioaccumulation of arsenic, heavy metals, and radionuclide contamination. The book provides in-depth details on options to treat and prevent biofouling. Treatment options include a range of non-oxidising chemicals (i.e. acids) and mechanical aids for surging and agitating the bore to physically dislodge materials.

We have found the book to be very useful for the treatment of bores affected by biofouling in regional Queensland. Water supply and monitoring bores require a significant capital investment for many, so managing and maintaining the performance of bores is vital. This is a great book for anyone who owns or manages monitoring and water supply bores.

Another useful resource for landholders is the government’s recently established National Groundwater Information System (NGIS) database (www.bom.gov.au/water/groundwater/ngis). The interactive site provides easy access to information about groundwater bores across Australia. You can zoom to your location and find out details such as the use, geology and depth of bores and wells registered in your area.

We have significant experience in bore testing and assessment. Get in touch with us if you have any queries regarding bore performance and fouling.

A key piece of Commonwealth legislation that aims to protect groundwater resources is the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). The EPBC Act captures biodiversity commitments from the UN Convention on Biological Diversity (CBD), and outlines measures to protect listed Ramsar wetlands and World Heritage areas. These are referred to in the EPBC Act as matters of national environmental significance (NES). Water resources are also covered by the EPBC Amendment Act 2013, in relation to coal seam gas (CSG) and a large coal mining developments.

The EPBC Act relates to activities conducted across Australia; however, each State and Territory also has its own environmental legislation. In Queensland, key environmental legislation includes the:

• Environmental Protection Act 1994 (EP Act): to protect environmental values and ensure sustainable management of an environmentally relevant activity (ERA). These activities include an agricultural ERA, geothermal activity, greenhouse gas (GHG) storage activity, mining or petroleum. The EP Act outlines key environmental values and categorises the risk or level of harm caused to the environment as material or serious.
• Water Act 2000 (Water Act): outlines how water resources are vested in the State, and the act covers water resource planning, water access licensing and tradeable rights.
• Sustainability Planning Act 2009: aims to achieve ecological sustainability in planning and developments. Developments under the act include buildings, civil infrastructure and vegetation clearing.

In 2014, the Newman government amended the Water Act, as part of the election commitment for ‘red tape reduction’ and to encourage economic development in regional Queensland. This included changes to the Water Act with introduction of the Water Reform and Other Legislation Amendment Act 2014 (WROLA Act). The WROLA Act aimed to phase in a streamlined water management framework. This included changes to the Water Act (Chapter 2) regarding licensing requirements within regulated areas, and giving new mines a limited statutory right to take groundwater they intercepted. This groundwater is referred to as ‘associated water’.

With a change in government in 2015, we saw another change in election commitments regarding groundwater management. In November 2016, changes to the WROLA Act were made with the introduction of the Water Legislation Amendment Act 2015 and the Environmental Protection (Underground Water Management) and Other Legislation Amendment Act 2016 (EPOLA Act), which came into effect on 6th December 2016. The EPOLA Act amends the EP Act and Water Act (Chapter 3), and aims to strengthen the powers of DEHP in the environmental assessment process, as well as approval commitments to groundwater management. There are considerations in the new legislation for projects that proceeded through the approvals and application process prior to the changes. For future projects, these changes will involve:

• greater requirements for proponents of mine applications in regards to the collection of baseline data and environmental assessment;
• strengthening ‘make good’ obligations by giving landholders greater rights where scientific uncertainty exists, and onus of the proponent to pay reasonable costs associated with engaging a hydrogeologist to assist in ‘make good’ negotiations;
• linking the EP Act and Water Act means approval of groundwater impact predictions will need to be verified and updated within an underground water impact report (UWIR) three years following approval, or at a frequency prescribed by the chief executive. This already applies to petroleum leases, but now extends to mineral development lease (MDL) and mining lease (ML) applications, and can apply to an existing MDL or ML; and
• increased public consultation and allowance for third party appeals during application of a groundwater licence within a regulated area, in relation to predicted mine dewatering volumes.

AGE has significant experience in groundwater assessments and management across Australia. We can assist you with any queries you may have regarding these legislative changes, and how they may affect you. Enquiries can be directed to: brisbane@ageconsultants.com.au.

For further information about the EPOLA Act

For further details about UWIR requirements