Reservoirs as Essential Drinking Water Sources: Climate Change Impacts Quality

Reservoirs play a crucial role in the drinking water supply in Germany, providing approximately 15% of the nation's drinking water. However, the increasing temperatures associated with climate change are posing significant threats to water quality.

Karsten Rinke from the Helmholtz Centre for Environmental Research in Magdeburg highlighted the challenges posed by climate change on the quality of drinking water derived from reservoirs. He noted that rising temperatures can lead to multiple problems, including oxygen depletion and the release of harmful substances.

Over the past 40 years, Germany has recorded an average temperature increase of about two degrees Celsius in its drinking water reservoirs. If this trend continues, the temperature could rise by an additional four to five degrees Celsius. This scenario would effectively transform some of the country's northernmost reservoirs into environments akin to those found in the southern Alps.

Lower oxygen levels in the water can lead to severe ecological consequences. Many reservoirs have experienced notable decreases in minimum oxygen concentrations, which are critical for fish, mollusks, snails, and crustaceans. A significant drop in oxygen could lead to the death of these aquatic life forms.

Additionally, the lack of oxygen can disrupt sediment processes at the bottom of these water bodies. This can result in the release of substances like manganese and iron into the water, which can render it unsuitable for drinking without substantial technical intervention.

To address these challenges, one potential solution is to extract water from different layers within the reservoirs that still contain sufficient oxygen. This approach has been implemented in various locations, such as the Mauthaus Reservoir in northern Bavaria, which supplies over ten million cubic meters of drinking water annually. The region has recently experienced an increase in hot and dry summers, leading to greater water consumption during peak periods.

Experts suggest that building new reservoirs in Germany, although feasible, is limited by high costs and the need to inundate large areas, often within protected zones. A more promising solution lies in expanding existing reservoirs. By raising dam heights, more water volume can be gained without significantly increasing the surface area.

Plans to enlarge facilities, such as the Granetalsperre in the Harz region, are currently being considered to better manage future water demands. As climate change continues to pose challenges, the need to maintain and adapt the country's reservoir systems becomes increasingly vital.