As industries strive for more sustainable resource management, groundwater protection remains a critical challenge – particularly in mining regions. One of the most pressing issues is inter-aquifer leakage, where poorly decommissioned wells can create unintended pathways for water movement, threatening both quantity and quality of groundwater resources.
Dr. Mark Hocking, a leading groundwater specialist, has dedicated his career to tackling these challenges. With 30 years of experience working with government agencies and major infrastructure projects across Australia, Mark has been at the forefront of hydrogeological research and applied solutions. His work in the Surat Basin in Queensland has shed light on the long-term impacts of historical mining and exploration practices, revealing how unsealed wells can potentially contribute to groundwater loss and contamination.
Using the Analytic Element Method (AEM), Mark has pioneered new approaches to quantify inter-aquifer leakage, improving risk assessments, and shaping best practices in groundwater monitoring and well decommissioning. His research not only informs better regulatory frameworks, but also provides mining companies with practical tools to manage groundwater more effectively throughout the entire mine lifecycle – from feasibility to closure.
At the heart of his research is a commitment to bridging the gap between theoretical models and real-world applications. By applying advanced mathematical concepts to environmental challenges, Mark is driving the next generation of groundwater assessment techniques – helping industry leaders and policymakers make more informed, data-driven decisions about our most precious resource: water.
What motivated your study of inter-aquifer leakage and its impact on aquifer management?
Legacy Scotia Mine, North East Tasmania
The study was driven by a need to improve predictions of groundwater movement in multi-aquifer systems, particularly in areas which haven’t been investigated before (i.e. greenfield sites). Environmental experts are often required to understand groundwater behaviour without sufficient long-term monitoring data.
In Queensland, for example, there was no regulatory requirement to decommission exploration wells before 2013 and wells were historically left open. This created unintended pathways for water to flow between aquifers, leading to potential water quality and quantity issues.
Today, mining companies take a lifecycle approach to groundwater management as part of their mine plans, ensuring the best possible outcomes to minimise impacts on our precious water resources.
What are the primary challenges caused by leaky wells in aquifer systems?
The biggest challenge is detecting and quantifying the leakage. When a well isn’t properly sealed, it acts as a leak between different aquifers.
One key issue is water quality degradation, where water from deeper aquifers (often of lower quality) mixes with shallower
Legacy Scotia Mine, North East Tasmania
groundwater which is used for agriculture or drinking water. Additionally, in cases where mining operations depressurise an aquifer to extract resources, leaky wells can lead to unexpected depletion of overlying water tables.
One of your studies aimed to address gaps in understanding or estimating inter-aquifer leakage. Can you elaborate?
Traditional groundwater models struggle to capture these small-scale point-source interactions. We used the Analytic Element Method (AEM), which allows for more detailed analysis of individual well impacts across the broader landscape.
Our study also employed uncertainty analysis, running over 4,200 simulations to evaluate a range of possible outcomes rather than relying on a single prediction. This approach helps to provide more reliable risk assessments and identify where additional data collection is needed to refine potential impacts.
How can these findings inform current aquifer management practices?
There are a few key takeaways for water managers and policymakers:
- Regulations for well decommissioning are important – The lack of legislation before 2013 in Queensland meant that hundreds of unsealed wells were left open, to potentially allow uncontrolled inter-aquifer flow. Stronger enforcement and regulation is essential to prevent similar issues in other regions.
- Groundwater monitoring alone isn’t enough – Simply tracking water levels won’t always reveal leakage issues. More advanced hydrogeology modelling and assessment techniques need to be integrated.
- Risk assessment should include uncertainty – Instead of relying on a single prediction, uncertainty analysis can help better predict the potential range of impacts and mitigate risks associated with multi-aquifer interactions.
What practical steps can operators take to mitigate the effects of leaky wells?
Mining companies should adopt a lifecycle approach to groundwater management, including:
- Better well decommissioning – Ensuring that all exploration wells are properly sealed to prevent leakage.
- Comprehensive aquifer assessments – Using multi-aquifer evaluation techniques like AEM modelling instead of relying on simplified single-aquifer assumptions.
- Early-stage planning – Incorporating hydrogeological studies at the exploration phase, rather than treating groundwater management as a later-stage issue.
- Investing in long-term groundwater monitoring to detect and address potential leakage issues before they become critical.
Legacy Scotia Mine, North East Tasmania
What are the broader implications of this study for global water resource management?
The challenges we identify in Australia aren’t unique—similar risks exist in b. The key lesson is that b. Activities that affect one aquifer can have unintended consequences for others.
By improving regulatory frameworks, modelling techniques, and well decommissioning standards, we can minimise water loss, prevent contamination, and ensure sustainable groundwater use for future generations.
Connect with Mark Hocking at [email protected]