Water Quality Affected by Climate Change, New Study Finds

A new study published by Water Research has found that deforestation caused by climate change can have a negative impact on water quality in reservoirs. A team of researchers from the Helmholtz Centre for Environmental Research (UFZ) conducted a study on the Rappbode reservoir in the Harz region of Germany and found that the indirect consequences of climate change on water quality are being seriously underestimated.

The Rappbode reservoir is Germany’s largest and serves one million people. Periods of drought from 2015 to 2020 have weakened surrounding trees and made them more vulnerable to disease and plagues, reducing the tree population by 50%.Prof. Michael Rode, one of the authors and a UFZ hydrologist, said: “This massive forest dieback is advancing rapidly and is dramatic. This will have consequences for the drinking water reservoir." 

Forests, the study found, filter water and bind nutrients. This facilitates water treatment processes, as it diminishes the amount of algae in the reservoir’s waters. By retaining elements like nitrogen or phosphorous, waters leave less available nutrients for algae to flourish.The research found that an anticipated deforestation of 80% will result in an 85% increase in phosphorus and a 120% increase in nitrogen in the dam. As a result, there would be a 80% increase in diatoms (micro algae) and a 200% increase in green algae.

Prof. Rode stated: “Nutrient input to reservoir catchment areas should be reduced even more than previously, reforestation projects with drought-resistant tree species should be further promoted and waterworks should be adapted to the impending developments with selective water removal strategies.”

Dr. Xiangzhen Kong, the study’s main author, stated: “Forest dieback as an indirect consequence of climate change has a more pronounced effect on reservoir water quality than direct effects of climate change such as elevated water temperature. We were actually surprised by the extent of this effect.”