Closure of coal mine will aggravate water scarcity in Berlin

Berlin has a drinking water system that relies entirely on groundwater. In the past the area had plenty of groundwater, but now the vital resource is under increasing pressure due to climate change and the planned closure of a coal mine that feeds the Spree River. The city is preparing for water scarcity with a ‘Masterplan Water’, supported by the European project IMPETUS.

Like many European cities safeguarding drinking water for an increasing number of citizens, combined with climate change, will be particularly challenging in the near future. The circumstances in Berlin are extra challenging because the city also depends on an artificial source of groundwater. Located approximately 110 km southeast of Berlin, the Welzow-Süd open-pit coal mine is one of the largest in the Lusatia region. The mine is expected to cease operations by 2038, aligning with Germany’s national coal phase-out plan. This is a problem because a considerable amount of groundwater is pumped into the Spree river. “So, ironically, the very industry that is often considered the most damaging to the climate serves as an additional vital source for the Spree river”, said Josefine Filter, project coordinator at Research and Development Department from the drinking water company Berliner Wasserbetriebe.

Implementation of ozonation

Supplying around 3.8 million people, Berlin’s drinking water system relies significantly on a process called bank filtration, whereby water from the Havel and Spree Rivers and neighbouring lakes is drawn through the soil. The water is naturally filtered through sand and gravel, which removes impurities before the water is used, treated, and returned to the ecosystem. Due to reduced groundwater coming from the coal mine and more extreme drought the share of treated wastewater in the Spree river is likely to be higher. To allow a higher share of treated wastewater in Berlin’s surface waters is the implementation of ozonation, an additional wastewater step to eliminate pharmaceutical residues. According to the new Urban Wastewater Treatment Directive (UWWTD) quaternary treatment removing a broad spectrum of micropollutants will be mandatory for all plants over 150.000 p.e. (and over 10.000 p.e. based on a risk assessment) by 2045.

Modelling changes in water bodies

The European IMPETUS-project is providing crucial support for the Masterplan Water of the city of Berlin that is aiming to develop strategies to improve the region’s responses to water scarcity in Berlin. The project’s researchers use computer models to simulate how droughts or changes in water bodies could impact Berlin’s drinking water and evaluate how various management strategies would perform under stress, such as extended droughts or the loss of coal mine water in the Spree River.

Groundwater imbalance

Not so long ago, in 2015, Berlin was struggling with too much groundwater. Since the early 1990’s the abstraction of groundwater was reduced due to the closure of beer breweries.  It caused extraordinary high levels of groundwater. Seven years later the situation had completely changed. The opening of Tesla factories were delayed by protests against the huge amounts of water that were needed to produce electric cars. And the water balance in the city needs to be found again the coming years.

This article was published with support of the German platform Science Stories.