Flooding of brown coal opencast mines could take longer than planned

The flooding of the still active brown coal mines United Schleenhain in Saxony and Profen in Saxony-Anhalt could take longer than previously assumed. Low water levels in the rivers and falling groundwater levels could have an impact on current plans, said Patrick Halka, head of the Leipzig Regional Planning Office, to the German Press Agency. Specialist working groups are currently investigating, among other things, what quantities of water will be available for flooding in the future and what minimum ecological flows must be maintained in the rivers. However, it is currently impossible to estimate whether this would have any concrete consequences for the planned lakes.

From the perspective of mining rehabilitation expert Martin Kreßner from the TU Bergakademie Freiberg, a lower water supply could lead to longer rehabilitation periods, increasing technical effort and higher costs. Companies would have to prepare for “extended project times until the recultivation work is completed,” Kreßner told the dpa. According to the expert, the idea of ​​accelerating the flooding of the remaining opencast mines with water from rivers is increasingly being abandoned in planning today.

Expert: “It will burden us in terms of costs”

If the water level rises more slowly than previously planned, increasing technical measures to stabilize the embankments could become necessary. “That will definitely burden us financially,” says Kreßner. However, he does not see a fundamental alternative to flooding: after the end of the artificial drainage of the mining fields, the groundwater will automatically rise again. There is therefore “in fact no alternative to creating a residual lake”.

The mining company Mibrag, which is responsible for the opencast mines, does not see the basic planning in question. Spokesman Sebastian Exner said that multi-year precipitation series would be used to predict the duration of flooding. Individual years with little precipitation are taken into account. Some of the planned open-cast mine residue lakes will already be flooded and will be created parallel to active operations. The water that would have to be pumped out anyway to keep the deposit free can be used for this purpose.

Pereser Lake is set to become the largest of all post-mining lakes in the region

For the last remaining hole, however, water must be supplied from outside - usually from surrounding watercourses, said Exner. The current public planning includes water from the Mulde and the White Elster, among other things. The target water levels are set by the authorities. Lake Pereser is one of the lakes planned for the future. According to plans that have been publicly presented so far, it will become the largest body of water in the Leipzig Neuseenland with an area of ​​around twelve square kilometers, a water volume of around 430 million cubic meters and a depth of up to 80 meters. According to Mibrag, the flooding should begin around 2039. In Saxony-Anhalt, Lake Schwerzauer and Lake Domsen are to be created in the area of ​​the Profen open-cast mine.

The responsible authorities in Saxony and Saxony-Anhalt are currently reporting groundwater levels almost everywhere that are half a meter below the long-term average. After the persistent drought in summer, the rivers also still only carry a fraction of the usual amount of water.