A backward-flowing River Spree in 2003, a dried-up Black Elster river, too little water in the dams and high sulphate levels in the Spree. The cause of all this is the low rainfall experienced by the region for several years in a row. In Brandenburg, droughts have been occurring more frequently over the past 60 years, and their intensity has increased with the rising number of warm summer days.
In addition, there have been an increasing number of reports of problems with the water supply across Brandenburg, including from the Tesla factory for electric cars currently under construction in Grünheide. “All this indicates that the region southeast of Berlin has a water problem,” says hydrogeologist Irina Engelhardt. Assessing how much water is available in a region requires an “integrated water resources management” system or IWRM for short. IWRM is used to compare water availability and demand as well as develop plans to deal with particular water-use scenarios. Interactions between hydrological, climatic and ecological conditions are taken into account, as are societal objectives. The safety of drinking water, as well as land use, industrial needs and socio-economic factors are weighed up and balanced against each other. “But such an integrated water resources management system does not exist in Brandenburg,” says Professor Dr. Irina Engelhardt, who heads the Chair of Hydrogeology at TU Berlin.
According to Engelhardt it is imperative for her as a hydrogeologist to know what water resources are available as the water balance in the Spree basin – the river’s entire water catchment area – has already been thrown out of kilter: Precipitation levels have long since ceased to meet the water needs of households, agriculture, industry and tourism as well as nature. This problem is exacerbated by the difficult geological conditions in the region: “The sandy soils formed during the glacial period provide poor water storage. Furthermore, there’s a lack of near-surface aquifers containing large volumes of water, and as soon as you go down to a depth of 300 meters you start to come across salty groundwater, which is not usable as a source of drinking water,” says Engelhardt.
And then there is the issue of the brown coal phase-out. Part of the process of brown coal mining in Lusatia involved allowing the groundwater that had been removed during the extraction of the brown coal – in order to drain the open-cast mine and keep it dry – to flow into the Spree. This artificially increased the river’s outward flow; dry periods had less of an impact on the water levels of the Spree and the Black Elster. With the decline in brown coal mining since 1989, less and less water has been pumped from open-cast mines into the Spree, and a water deficit has become apparent in the river’s basin as well as that of the Black Elster. This became visible when the Black Elster dried up in 2018, 2019 and 2020.
“Regional water suppliers require the implementation of a modern, transregional, model-based water management system in order to adjust the water balance in Brandenburg to both climate change and the structural change caused by the phasing out of brown coal mining,” Engelhardt stresses. The coupling of climate and groundwater models makes it possible to analyze the influence of predicted changes in the climate on water resources, to quantify long-term water availability, to detect at an early stage periods of water stress, to develop channels for risk communication and to compare seasonally available water levels with water demand. This information would enable regional water suppliers, such as the Strausberg-Erkner water board, in whose area the new Tesla factory is located, to prioritize certain consumers during dry periods. Prioritizing need in times of drought among factories, agriculture and nature, once drinking water supplies have been secured, will be unavoidable if there is too little rain and the mine water from brown coal production is no longer there.
As climate change progresses, the demand for water in agriculture will inevitably increase. “So far, there is not much in the way of irrigated agriculture in Brandenburg,” says Engelhardt. Currently, about 40 percent of the Spree’s basin is used for agriculture, but only two percent of this is irrigated. “Due to climate change, an increase in irrigated agriculture in Brandenburg to 20 percent of total agriculture over the coming decades is to be expected,” says Engelhardt. However, the water laws in Germany don’t yet allow for the prioritization of water use. “If the amount of precipitation in the Brandenburg region continues to decrease in summer, the new conditions arising from climate change will make amendments to the law inevitable,” says Irina Engelhardt. In some Mediterranean countries, which have long been suffering from water poverty, the implementation of IWRM, together with suitably adjusted irrigation farming and the prioritization of water users are already common practice.
And there is another issue Engelhardt would like to give her backing to, namely the storage of wastewater underground and the use of wastewater in agriculture. The technology to enable this has long been applied in water-poor areas around the Mediterranean, but has to date been banned in Germany due to fears that groundwater could become contaminated. “With modern modeling and online measuring technology, it’s possible to identify areas where water infiltration into the soil could be particularly efficient, where the soil has a high cleaning capacity and where the groundwater wouldn’t become contaminated. If dry periods become the new normal, droughts occur more frequently and groundwater levels continue to fall, then politicians in Germany will also be forced to rethink and reassess their long-standing positions in order to tap into new water resources or reuse resources that have already been used,” says Engelhardt.