According to the study, climate change affects the quality of drinking water
Research has revealed that climate change affects the quality of drinking water. The study was published in the journal “Water Research”.
Heat waves, drought, floods, forest fires – the consequences of climate change are increasing and changing our environment.
A good example is the countryside in the catchment area of the Rappbode reservoir in the Eastern Harz region. This is Germany’s largest drinking water reservoir and provides drinking water for around one million people. The long droughts between 2015 and 2020 have weakened the tree population in the Harz region so seriously that parasites such as bark beetles have been able to spread. This made the effect even worse: the trees were further damaged and quickly died. “Over the past four years, the Rappbode catchment, which is characterized by conifers, mainly spruce, has lost more than 50 percent of its forest,” says UFZ hydrologist and last author prof. Michael Rode. “This massive deforestation is happening fast and is dramatic. This has implications for drinking water supplies.”
Forests play a key role in the water cycle. They filter water and bind nutrients and are therefore essential for good water quality. The fewer nutrients – i.e. nitrogen or phosphorus compounds – there are in the tank water, the better it is for drinking water treatment. “This makes it difficult for algae to develop, which makes the treatment of drinking water at the water plant more cost-effective and easier,” explains UFZ lake researcher and co-author Dr. Karsten Rinke. “Management of nutrients in water conservation areas is therefore very important. In recent decades, long-term concepts in close cooperation between forests and water management have promoted the development of large forest areas in the catchment area of the Rappbode reservoir.” The rapid decline of forests in the eastern Harz area is now a serious concern for operators of reservoir and water facilities.
Spurred on by this development, the UFZ team has studied the effects of climate-induced deforestation on reservoir water quality in their model study. This study was based on data from the TERENO (Terrestrial Environmental Observatories) environmental monitoring network, in which UFZ is involved with the Harz/Central German Lowland Observatory. “We were able to use environmental data from more than ten years, which provided us with a solid data set,” says Dr. Xiangzhen Kong, also a UFZ environmental researcher and lead author of the study. The group used information from the international ISIMIP project (Inter-sectoral Impact Model Intercomparison Project) to predict future climate changes. “We first fed this data into the model to assess climate-related impacts on the nutrient balance of the catchment,” explains Kong. “The resulting data was then processed in a reservoir ecosystem model, which allowed us to determine the effects of different deforestation scenarios on predicted water quality for 2035.
The Rappbode basin is supplied by three different catchment areas, two of which were included in the study. “The Hassel catchment is characterized by agriculture, while the Rappbode catchment is mainly forest – at least that was the case before the spruce forests died,” says Kong. Before the water from the two catchment areas flows into the large Rappbode basin, it is first held at the upstream forecourt. The impact of agriculture leads to a significantly higher concentration of nutrients in the water in the Hassel pre-dam than in the Rappbode pre-dam. “We were able to show that even from a predicted forest loss of 80 percent, the content of dissolved phosphorus in the Rappbode predam increases by 85 percent and the nitrogen content by more than 120 percent in just 15 years. The Rappbode pre-dam thus reaches almost the same nutrient concentrations as the Hassel pre-dam,” says Kong. This leads to an increase of more than 80 percent in the number of diatoms and a more than 200 percent increase in the number of green algae in the pre-dam area of Rappbode. These results highlight the future need for multiple adaptations in drinking water management. “The supply of nutrients to reservoir areas should be further reduced, reforestation projects of drought-resistant tree species should be further promoted and water utilities adapted to future development with selected drainage strategies,” says Rode. “And what is still important and needs to be further increased: broad, granular environmental monitoring.”
The results obtained in the Rappbode reservoir can be applied to other catchment areas in similar areas. “As an indirect result of climate change, deforestation has a stronger impact on reservoir water quality than the direct effects of climate change, such as rising water temperatures. We were actually surprised by the extent of this effect,” says Kong.
HT
Source: ANI