CLIMATE CHANGE AND MINE WATER MANAGEMENT

According to the World Bank’s Climate Change Knowledge Portal (CCKP), South Africa is experiencing a warming trend that is about 1.5 times the global average. Kirsten Kelly talks to Mehmetcan Özkadıoğlu, hydrologist at SRK Consulting, about the impact of climate change on mine water management.

South Africa is currently undergoing notable climate transformations – a trend that’s becoming more and more evident,” explains Özkadıoğlu. “Climate change projections are predicting a temperature increase of 1°C to 2°C across the country by mid-century. Accompanying this, we are anticipating a shift in rainfall patterns, leading to an increase in rainfall for some of the areas and a decrease in overall rainfall trends in other areas, which could potentially lead to drier and wetter mining conditions. At the same time, the climate models project an increase in the intensity of rainfall and the frequency of storm events, increasing the risk of mine flooding. The probability of extreme heat events, which can intensify evaporative losses, is also expected to rise. These changing climate patterns are essential to incorporate in the mine water management strategies, highlighting the urgency of climate change considerations in our decision-making processes.”

Climate change significantly impacts water resources, and the following are key considerations for the mining industry and mine water management in South Africa.

• Water scarcity: Climate change is projected to significantly impact on water resources, with a major concern being the potential decrease in water availability. This can result in water scarcity, posing a challenge to waterintensive mining operations.

• Extreme weather events: A key principle in thermodynamics is that as air temperature increases, so does the atmosphere’s ability to hold water vapour. This can lead to more severe and frequent storm events. These extreme storm events can disrupt mining operations, damage crucial infrastructures – such as stormwater structures, tailings, water supply dams, open-pit operations and waste rock dams, among others – and pose safety risks.

• Changes in water quality: Changes in temperature and precipitation due to climate change can affect the quality of water. Increased rainfall intensity, for instance, can lead to a rise in sediment loads in the surface run-off, affecting the quality of water used as the mine process water. On the other hand, decreased rainfall and increased temperature can result in higher concentrations in contact waters and reduce the water quality.

• Increased energy consumption: For mining operations that are delving deeper and encountering lower ore grades, there is an escalating demand for water and an increase in mine waste. This situation contributes to a rise in energy consumption and expands the industry’s carbon footprint.

• Reputational risks: Failure to adequately factor in the impacts of climate change on mining operations could lead to disputes with host communities, potentially affecting the social licence to operate, as water supply may be reduced for the communities.

Adaptive strategies and precautions

Mining companies must anticipate different climate change scenarios and then consider the impact on the operational and closure phases of a mine’s life. There are various adaptive strategies:

• Climate risk assessments: Mining companies should integrate climate change risks into their risk assessment processes. This includes considering future climate scenarios in the planning and design of mining operations and infrastructure. Given the dynamic nature of climate conditions and the evolution of methods to understand future climatic models, these studies are recommended to be updated at intervals of 5-10 years.

• Water efficiency: Improving water efficiency can help mining companies adapt to water scarcity. This can be achieved through measures such as water recycling and reuse, using alternative water sources, and implementing watersaving technologies.

• Stakeholder engagement: Engaging with local communities, governments and other stakeholders can help mining companies understand local issues related to water management and develop appropriate strategies.

• Innovation and technology: By incorporating innovative technologies, mining companies can effectively adapt to the challenges posed by climate change, enhancing their resilience and sustainability.

Understanding the potential impacts of climate change is key for the design, construction, operation, and closure of tailings storage facilities (TSFs).

The Global Industry Standard on Tailings Management (GISTM) is a framework developed to prevent tailings dam failures. It aims to achieve the safe and secure management of tailings facilities by establishing clear expectations for companies, governments and other stakeholders. In the context of climate change, GISTM can help mining companies adapt by promoting the use of best practices in tailings management, considering climate change in risk assessments and improving the resilience of tailings facilities to extreme weather events.

“The design and construction of current tailings dams have not fully considered the fluctuating climate patterns and the recent intensification of extreme weather events. It is now imperative to incorporate planning for an uncertain climate future into risk management strategies. Take, for example, the lifespan of certain tailings dams, which are projected to continue operation for the next three to five decades before the closure phase. Despite their closure, these dams will continue to be vulnerable to the impacts of climate change. Therefore, it’s critical that we factor in future climate conditions not just during the operational stages, but also throughout the subsequent closure and post-closure phases of these dams,” says Özkadıoğlu.

Considering a future where a region experiences a rise in rainfall patterns, it’s essential to acknowledge the impact this shift in rainfall pattens will have on a range of operational aspects, hydrological and hydraulic processes. These include, but are not limited to, the infiltration of precipitation into TSFs, the decant from the TSF impoundment area, and the storage conditions of both the TSF and downstream return water dams. TSFs must be capable of storing and effectively releasing extreme storm volumes to prevent uncontrolled discharges from TSF. The design of diversion channels, which redirect excess run-off away from the TSFs, may need to be re-evaluated in response to these changes.

The increase in air and surface temperature, alterations in wind patterns, variations in cloud cover, and other factors will affect the evaporation

CLIMATE CHANGE STUDIES WITH SRK CONSULTING INVOLVE:

• Historical climate review: This involves historical data screening, gap analysis and baseline data evaluation to understand and compare current conditions with the projection models.

• Climate change review: It includes evaluating climate change data, focusing on four greenhouse gas emissions scenarios known as the Shared Socioeconomic Pathways. The aim is to understand how the climate is changing (rate of change) for the near-, mid- and long-term future, and what the projected trends are. The studies also include a review of short-duration storm events (2-yr, 5-yr, 10-yr, 20-yr, 50-yr, 100-yr, 200-yr and probable maximum precipitation).

• Detailed desktop modelling, impact assessments and mitigations: Using the projected climate conditions, the modelling and impact assessment studies may vary based on the specific needs of mining projects in line with water management, Global Industry Standard on Tailings Management, and tailings water management. The several studies performed:

- site-wide or facility-level water balance and climate change impact assessment

- stormwater management planning, including future hydraulic designs or review of existing structures under expected future climate scenarios process. Additionally, it is important to consider that extreme weather events may potentially cause damage to the structure, necessitating a more resilient and robust design. The impacts of climate change will vary for each mine, depending on its specific location.

- evaluations of hydrologic, hydrogeological, and geotechnical conditions and potential impacts on TSFs (planning and design, construction, operation, closure and post-closure).

Climate change assessment

“Traditionally, water resource infrastructure design has been based on the principle of ‘stationarity’, assuming that probabilistic characteristics of hydrologic and meteorologic processes remain consistent over time. However, it is evident that climate trends are shifting, making it insufficient to rely on historical climate data from the 1950s, for instance, when designing structures like TSFs. Therefore, it is necessary to incorporate future climate projection models into our studies, relying on modelling techniques to predict and anticipate future climate patterns,” states Özkadıoğlu.

SRK Consulting adopts a comprehensive approach to addressing climate change, starting with a thorough analysis of local climate trends to establish baseline climate readings. Through this analysis, we assess the accurately representative historical baseline climate conditions for the site, downscale existing climate change models to match the site-specific conditions, and evaluate the rate of change for various parameters, considering the near-, mid- and long-term future. By thoroughly studying the unique characteristics of each mine, potential risks associated with climate change are identified, leading to the development of effective solutions. This meticulous approach ensures that SRK Consulting is well equipped to address the challenges posed by climate change in an informed and proactive manner.

“It is important to remember that each mining operation is unique and, therefore, the climate change assessment should be tailored to suit the specific circumstances of each mine. The study should be a dynamic and ongoing process that can be updated as our understanding of climate change evolves and as more data become available,” adds Özkadıoğlu.

This process entails reconciling historical climate records obtained from on-site weather stations, regional weather stations and relevant climatic gridded models, if necessary, to address any gaps in physical data availability. Climatic gridded models (or climate reanalysis) are scientifically generated to provide a comprehensive historical climate record, ensuring the completion of missing datasets. It is important to note that the selection of the most representative models undergoes rigorous statistical bias correction and adjustment studies to ensure their accuracy and reliability.

The projected future climate models utilised in our analysis are based on global circulation models (GCMs). While historical datasets have traditionally been used to study climate patterns, GCMs are better suited for generating synthetic datasets to investigate the potential impacts of climate change on a global or continental scale. These computer-driven models can be scaled to provide site-specific projections, aiding in weather forecasting, enhancing our understanding of climate dynamics, and projecting climate change.

Currently, the latest climate change models detailed in the Intergovernmental Panel on Climate Change’s Sixth Assessment Report (AR6) – specifically the Coupled Model Intercomparison Project (CMIP6) – are used to predict different climate change scenarios. These scenarios incorporate the concept of Shared Socioeconomic Pathways (SSPs) to represent different future greenhouse gas emissions and socioeconomic conditions.

There are four different SSPs (SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5) within CMIP6. Each one represents a distinct pathway of future greenhouse gas emissions and socioeconomic conditions. SSP1-2.6 represents a lower-bound scenario where sustainability efforts are adopted globally, resulting in significant reductions in greenhouse gas emissions. On the other hand, SSP5-8.5 represents an upper-boundary scenario where fewer climate protection measures are being taken, leading to higher greenhouse gas emissions. Each SSP scenario includes 35 different models, creating a large dataset. This dataset requires detailed statistical analysis and risk profiling to support decision-making processes.

“We are already experiencing climate change. It is vital that we first identify the potential risks, and then actively develop strategies to mitigate and adapt to these future climate scenarios,” concludes Özkadıoğlu.