The Citypoll project warns of the damage to ecosystems caused by the urban flow of rainwater

2025/08/08 Galarraga Aiestaran, Ana - Elhuyar Zientzia Iturria: Elhuyar aldizkaria

• Ingurumena
• Hidrologia
• Ekologia

When it rains in cities, rainwater is polluted with pollutants, through which there is a high risk of pollutants reaching aquatic ecosystems. In the Citypoll project, researchers have studied the impact of these contaminated rain waters in cities on biodiversity and ecosystem functioning under the leadership of the University of the Basque Country, the Catalan Institute for Water Research ICRA and the University of Barcelona. The potential impact of the climate emergency has also been investigated.

Thus, a long list of pollutants has been identified, with the highest concentrations reported to be those of heavy metals and compounds derived from tire wear. In addition, it has been shown that the flow of these waters has a direct effect on aquatic organisms. In fact, it damages growth, reproduction and vital functions, so it can have repercussions on the functioning of freshwater ecosystems connected to drainage waters. In any case, they have observed that there are significant differences between the different areas of the same city, as well as between the rains. This complicates the detection and analysis of urban fluidity.

On the other hand, they have demonstrated the effectiveness of green filters to mitigate the impact generated on the environment. They have also found that a compound associated with tire wear, diphenyl guanidine, is an ideal chemical indicator.

With this in mind, they warn that while it is a good idea to completely separate rainwater and wastewater collection networks, rainwater is also the source of pollutants into ecosystems. According to them, urban flows should be treated through nature-based solutions.

In conclusion, it is expected that due to climate change, there will be less but more severe torrential rains. Researchers believe that this can aggravate the impact of pollution on urban flow in aquatic ecosystems. For this reason, the need to adapt urban systems has been recalled.