To combat urban floods, like those that are tragically affecting the state of Rio Grande do Sul at the moment after heavy rains, Barcelona, capital of Catalonia, in Spain, developed an ingenious solution: gigantic underground tanks, capable of storing thousands of liters of rainwater.
This innovation emerged as a response to one of the city’s greatest natural disasters, the 1995 storm, which resulted in intense rains that generated devastating floods and the loss of life.
The city, which often found itself submerged after heavy rain, sought technology as an ally to reverse this situation. The first tank was built in 1999, and Barcelona currently has 15 of these structures spread throughout its territory. These deposits, also known as “storm tanks”, not only prevent flooding but also contribute to reducing the contamination of wastewater before it is released into the environment.
It is estimated that annually 900 tons of waste are prevented from being discarded directly into the environment thanks to these tanks. Furthermore, the water stored on site, after being treated (a process that is carried out there), can be used to clean streets and irrigate green areas, contributing to urban sustainability.
Under the Joan Miró park, located in the south of Barcelona, for example, there is one of these tanks with a capacity of 55 thousand m³ of water, the equivalent of approximately 22 Olympic swimming pools. When rains are intense, the city’s automated system opens the floodgates, allowing the tank to accumulate water and prevent the streets from turning into rivers.
The implementation of these tanks has had a significant impact on reducing flooding episodes in Barcelona. A study published in 2022 in the journal Nature highlighted the city as a success story in natural risk management. However, Professor María del Carmen Llasat, from the University of Barcelona, who contributed to the study, emphasizes that, despite advances, there is still much to be done, such as increasing soil permeability and keeping streets and drainages clean.
“Soil permeability must be increased with paving that allows rain to filter, more areas must be reserved for green spaces and streets and drainage systems must be kept clean,” she told the Spanish website elDiário.
Intense rains that occurred in 2019 in Barcelona highlighted the importance of the rainwater management system in the city. That year, 79 episodes of rain were recorded, 10 of which were intense. The underground tank system, like the one located under the Joan Miró park, played a crucial role in mitigating possible flooding. Even with the maximum daily rainfall reaching a record, with 139 liters per square meter, according to the website elDiariothe tanks were able to store enough water to avoid flooding, only being filled to 60% of their capacity.
Barcelona is not alone on this journey. Other Spanish cities, such as Madrid (which currently has the largest tank of this type), Murcia and Bilbao, have also adopted similar tanks, showing that the Catalan capital’s solution can be successfully replicated in different urban contexts.
The city continues to expand its network of tanks, with plans to reach more than 30. The initiative both protects the population from future floods and also serves as a model for other cities around the world seeking innovative solutions to similar challenges.
Barcelona managed to turn an adversity into an opportunity, demonstrating that, with planning and investment in infrastructure, it is possible to mitigate the devastating effects of climate tragedies and protect urban life from future natural catastrophes.
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