Clean water is essential. Scientists at TU Wien are studying how the water quality in riparian floodplains, often used as drinking water resources, changes as a result of heavy rains and flooding.

Floodplain landscapes are essential for the supply of drinking water as they contain valuable water resources. It is therefore all the more important to protect them from contamination. Dr Julia Derx and a team of researchers wanted to know how certain pathogens excreted in feces enter water as a result of extreme weather events.

Thus, the interdisciplinary team studied the influence of heavy rainfall and flooding on water quality in alluvial areas. To this end, they developed a model, which they then successfully tested in a backwater area of ​​the Danube, near the border downstream from the city of Vienna. Researchers published the study results on July 14, 2021 in the journal Frontiers in microbiology.

Weather events can affect the quality of drinking water

On hot summer days, we often crave a refreshing rain shower. But when heavy rains or floods occur, they threaten the water resources of our floodplains. Contaminants can enter surface water from sewers, wildlife or livestock. This is a concern for several reasons, as Julia Derx of the Water Resources Management Research Unit explains, “Alluvial areas along large rivers are not only important and important natural habitats for the sea. flood control, but they also contain valuable resources for the production of drinking water. Human wastewater discharges and faecal deposits from livestock and wildlife therefore pose potential threats to these ecosystems in terms of water supply. “

Since heavy precipitation is expected to become more frequent and occur with higher intensity in the future, scenarios have been modeled to assess their consequences. Julia Derx and her team developed a model to determine the impact of different fecal sources, entering through flood water or rainwater, focusing on the safe extraction of drinking water from wells in riparian floodplains. The research team used data from fecal genetic indicators associated with humans and animals, called STD markers.

Who is the source of the contamination?

“MST markers are diagnostic DNA regions of microorganisms that live in the gastrointestinal tract of humans and animals and are associated with the host. Therefore, we can distinguish whether the fecal contaminants are of human origin or come from (wild) pigs, ruminants or other animals, explains Katalin Déméter. Integrated into the model (QMRAcatch), the model can thus be calibrated on the different entry routes into surface water. The team of the Interuniversity Cooperation Center “Water and Health” (ICC Water and Health) – made up of researchers from TU Wien, MedUni Wien and Karl Landsteiner Private University for Health Sciences – investigated the influence of heavy rains, which dissolve fecal pellets from the soil, as well as river water polluted by human sewage. “Our study shows that in our study area, the two pathways (release of pathogens induced by rain from animal faecal deposits and flooding) lead to similar exposures with regard to the two pathogens studied, Cryptosporidium and Giardia. In order to achieve sufficient protection against infections, the concentrations of pathogens must be reduced to a similar degree in raw water, ”said Professor Andreas Farnleitner, Director of ICC Water & Health.

In the production of drinking water, the soil takes over part of the treatment as the water seeps through different layers of sand and gravel. Further treatment is provided by subsequent disinfection of groundwater. The quality of drinking water is continuously monitored to ensure that the requirements of the Austrian Food Codex and the Drinking Water Directive are met.

Clean drinking water

In order to ensure a potable water supply, the system must be viewed holistically within the meaning of the World Health Organization (WHO) – from the point of extraction to the use of the water. “Our modeling approach allows this for different river floodplains by quantifying the different entry routes and their effects on the microbiological quality of the water”, explains Professor Alfred Paul Blaschke. In order to be able to take concrete measures for the protection of water bodies, site-specific measures of the microbiological quality of the water are necessary, both at the level of the sources of pathogens and at the point of use of the water. ‘water. The microbiological toolkit should contain standard fecal indicators, host associated STD markers as well as pathogens.