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Minewater is all water that has or had contact with mining activities located underground or on the surface. It is usually water that naturally occurs in the form of seepage and groundwater. It may share the same quality as the local natural water, or it may contain foreign substances, depending on its origins or previous uses. This means it is particularly important to monitor the quality of the water. But minewater also presents opportunities: its geothermal potential can be used to heat buildings above ground, for example.

Groundwater is subterranean water that fills the cavities of the outer more layer of the earth’s crust (the lithosphere). Its movements are determined solely by gravity. Groundwater is formed by rainwater that seeps into the ground, and penetrates through numerous layers of rock, deep down into the earth’s crust. Most of our drinking water is sourced from groundwater. Protecting it from contamination is therefore our highest priority – minewater and groundwater cannot be allowed to come into contact with one another.  

Now that coal mining activity has ceased, it is no longer strictly necessary to continuously pump the minewater away. So, it makes sense, both ecologically and economically, to allow it to rise in a controlled manner underground. This takes place through the inflow of groundwater and seepage over long periods of time.

From a technical perspective, the ascent of minewater within an underground minework is over once the water level stops changing. This can occur, for example, when a hydraulic balance is established between the inflow and outflow of the water. The duration and exact progression of the minewater ascent are influenced by a number of factors here, including the characteristics of the rock, and the incoming volumes and flow path.

This completely depends on what pumps are referred to here:

If the underground pumps were switched off, nothing much would happen at the outset. The large cavities of the mines could initially accommodate a large amount of ascending minewater. So much so, that it would take a few decades before the water rose to the surface in the Ruhr Area. However, this is not planned whatever happens: Huge immersion pumps will, in future, continue to keep the minewater at a certain level underground.

On the other hand, if the pumps located in areas of mining subsidence – known as “polders” – were switched off, then waterlogging would occur, with lakes forming relatively quickly. Certainly, large parts of the Ruhr Area would become submerged under water within only hours or a few days.

That is prohibited by the special responsibility that is owed to the people, nature and the environment living and existing in these former mining districts and beyond. In Germany and Europe, the decommissioning of mines is subject to stringent conditions. However, there is still a lag here internationally. This is another area in which the Research Institute of Post-Mining is engaged, passing on its knowledge in the effort to make the mining of raw materials a more sustainable and environmentally-friendly activity, worldwide.

From a technical perspective, it would be possible. But the costs would be considerable, making it economically non-viable – in the near future, at least.

By definition, mining damages are not part of the so-called perpetual tasks. And that's because, in the end, all mining damage is finite. This means that possible subsidence and uplift of the site, which are caused by mining, will be completed at some point.

After a mining process, a new long-term era is dawning: the post-mining era. The consequences of mining will occupy many more generations. A great deal of specialist knowledge is necessary to make the development of former mining regions sustainable. For discovering new potentials in old areas, it is important to understand the challenges as opportunities. Therefor our research is in demand worldwide: Technical innovations can be marketed globally, for example in the areas of monitoring or material science. In addition, we also need well-trained specialists in the future, especially for the long-term technical tasks that mining leaves behind. We educate these experts in our own Master's degree in "Geoengineering and Post-Mining" at the THGA in Bochum. Masterstudiengang „Geoingenieurwesen und Nachbergbau“ an der THGA in Bochum aus.

Post-mining is becoming increasingly important internationally. Other countries are taking a great interest in the activities ongoing in Germany, and the particular way in which we are managing the legacies of mining – from making sites technically safe, to the subsequent use of these sites as areas of recreation. Germany has a unique opportunity to assume a pioneering role in the post-mining area.