As Climate Change Continues, Drinking Water Stored in Reservoirs Began Lose Quality

The water stored in reservoirs secures our drinking water supply. Water quality is consequently critical, yet it is under threat from climate change.

A research team illustrated how the climate-related removal of trees in the catchment area for Germany's largest drinking water reservoir, the Rappbode reservoir in the Harz region, might impair water quality in a model analysis of the reservoir.

According to experts, the problem of such indirect effects of climate change is vastly underappreciated. Water quality is crucial, particularly for drinking water reservoirs, because subsequent treatment in the waterworks must always exceed rigorous requirements.

Climate change is affecting drinking water quality

(Photo : Vedrana Filipović/Unsplash)

Heat waves, droughts, floods, and forest fires are all examples of how climate change is affecting our ecosystem, as per ScienceDaily.

The landscape in the catchment area for the Rappbode reservoir in the eastern Harz region is a classic example.

This is Germany's largest drinking water reservoir, serving around one million people. Long periods of drought from 2015 to 2020 significantly reduced the tree population in the Harz area, allowing parasites such as bark beetles to reproduce.

This aggravated the situation: the trees were severely harmed and died off soon. "Over the last four years, the Rappbode catchment region, which is dominated by conifers, particularly spruce, has lost more than half of its forest," says the report by UFZ hydrologist and last author Prof. Michael Rode

Forests are essential to the water cycle. They filter the water and bind nutrients, making them essential for optimal water quality. The fewer nutrients there are.

"This makes algae development more difficult, making drinking water treatment in the waterworks more cost-effective and easier," UFZ lake researcher and co-author Dr. Karsten Rinke adds.

Nutrient management is particularly critical in water conservation regions.

Long-term approaches with strong collaboration between forest and water management have progressed the development of significant tracts of forest in the Rappbode reservoir catchment region during the last decades.

The fast deforestation in the eastern Harz area is causing significant anxiety among reservoir and waterworks managers.

In response to this change, the UFZ team conducted model research to evaluate the consequences of climate-induced deforestation on reservoir water quality.

This study used data from the TERENO (Terrestrial Environmental Observatories) network, of which the UFZ and the Harz/Central German Lowland Observatory are members.

"We were able to acquire environmental data from over 10 years ago, presenting us with a robust collection of data," says Dr. Xiangzhen Kong, a UFZ environmental scientist and the study's primary author. To forecast future climate changes, the researchers analyzed data from the worldwide ISIMIP project (Inter-sectoral Impact Model Intercomparison Project).

"We first entered this data into a model to predict the climate-related effects on the nitrogen balance in the catchment area," Kong continues.

The obtained data were then analyzed in a reservoir ecosystem model, using which we were able to estimate the consequences of several deforestation scenarios on the expected water quality for 2035.

The Rappbode reservoir is fed by three different catchment areas, two of which were studied.

"The Hassel catchment area is characterized by agriculture, while the Rappbode catchment area is predominantly forest - at least that was the case before the spruce forests died," Kong says.

The agricultural effect causes the water in the Hassel pre-dam to have a much higher nutrient content than the water in the Rappbode pre-dam.

"We were able to demonstrate that, for an expected deforestation of up to 80%, the Rappbode pre-dam will experience an 85 percent increase in dissolved phosphorus concentration and a more than 120 percent increase in nitrogen concentration within only 15 years, achieving nearly the same nutrient levels as the Hassel pre-dam," Kong says.

This would result in an increase of more than 80% in diatoms and more than 200 percent in green algae in the Rappbode pre-dam.

These findings indicate the impending need for a wide variety of changes in drinking water management.

Read more: North American Birds Still Not Fully Adjusted Due to Climate Change, New Study Finds

Climate Change and Groundwater

Climate change is becoming a growing worry, and while this subject is receiving a lot of attention right now, its impact on groundwater is still being studied, as per the International Groundwater Resources Assessment Centre

As a result, IGRAC is committed to addressing this critical issue by participating in groundwater and climate change research and training programs.

Climate change-induced increased variability in precipitation and more intense weather events can lead to prolonged periods of drought and flooding, affecting groundwater availability and reliance.

Long periods of drought provide a greater danger of aquifer depletion, particularly for small and shallow aquifers.

Because of its buffer capability, groundwater will become increasingly important to people living in water-stressed areas.

Simultaneously, indirect climate change effects such as increased human activity and land use changes raise the demand for groundwater.

In a changing climate, strategic groundwater usage for global water and food security is becoming increasingly vital. Another reason why groundwater should be given more prominence in climate talks.

Read more: Eating Healthier Food Could Help Mitigate Climate Change, Find Out How