March 2023

Sponge city. An issue of heavy rains and heat solved?



Heavy rains are increasingly threatening urban and suburban areas. Flash flooding becomes dangerous for people, plants, crops and welfare at the same time. On the other hand, we are dealing with expand of dry periods, in which there is a lack of water, i.e. to maintain greenery in the city, and use massive amount for watering gardens causes pressure drops in the plumbing systems.. The Sponge City can be the answer to both phenomena in the urban area.

What exactly is the idea of a "sponge city"?

It is an idea to work for urban transport that provides an approach to water resource management in order to minimize the effects of rainfall and droughts. The main goal is to use the source’s ability to absorb water, primarily through the use of green infrastructure, such as parks, gardens and streets with greenery, which act as a “sponge” – they absorb rainwater and its gradual release into the environment. As part of the “Sponge City” concept, technologies such as systems for collecting and storing rainwater, cleaning rainwater and irrigation of water drawn from the economy are also used. In this way, cities can manage flood and drought risks to ensure groundwater quality and create an additional urban environment for residents.

Examples of the implementation Sponge City concept

There are many cities around the world that implement the idea of Sponge City, implementing various projects and solutions to minimize the negative effects of rainfall. Here are some examples:

1. Shanghai, China – one of the pioneers in the implementation of the Sponge City concept. As part of the Shanghai Sponge City program, the city is building rainwater storage systems, green roofs, rain gardens, and parks that provide flood protection.

2. Copenhagen, Denmark – implements green roofs and walls, rainwater treatment plants, as well as the “Harbor Bath” project, which transforms the harbor district into a recreation area, enabling residents to bathe in tanks with natural water.

3. Philadelphia, USA – introduced the “Green City, Clean Waters” program, which aims to clean the polluted waters of the city’s rivers and tributaries. As part of the program, the city builds new parks, rain gardens, and uses modern water purification technologies.

4. Singapore – implements the “Active, Beautiful, Clean Waters” (ABC Waters) project, which aims to transform the urban water chain into beautiful, clean and active places for recreation. As part of the program, parks, rain gardens, but also artificial retention reservoirs and rainwater recovery systems are built.

5. Berlin, Germany – transforms existing canals and water systems into recreational zones, providing residents with access to natural waters and green spaces. The city also implements flood protection and climate change programs using green technologies.

The problem with retention is felt by other areas, in 2021 the authorities of the states of California and Arizona (USA) banned watering home lawns, as many local communities suffered from lack of water supply in the network due to excessive watering [i]. On a local scale, the emerging Retention Map of Poland is important, where each bottom-up and public initiative can be marked. On this website, everyone can mark the capacity of the tank, indicating for what purposes the water is collected in it, it can be washing, watering or any other purpose. Currently, access to water is a problem for over 365 places in Poland that have been marked. In addition, over 45 municipalities in the summer of 2022 introduced a total ban on watering gardens and lawns[ii]. Municipalities may impose fines of up to  120 USD for this reason.

Are there any cities in Poland where the idea of a “sponge city” is implemented?

Projects related to the concept of the sponge city are also being implemented in our country. It is worth mentioning Łódź, Wrocław and Gdańsk, where they have taken measures to minimize the negative effects of rainfall, using green infrastructure and innovative technologies.

In Łódź, the project “Ecozielona Łódź” was implemented, which assumes, among others, construction of rain parks, green roofs and rainwater treatment plants. Wrocław, on the other hand, is implementing the “City on Water” project, which aims to protect the city against flooding by building rain parks and rain gardens, but also by implementing rainwater collection and storage systems. Gdańsk, on the other hand, is implementing the “Gdańsk City Sustainable” program, which aims to improve the quality of groundwater through the construction of rain parks, green roofs and the introduction of green technologies.


There are also many other projects and initiatives in Poland aimed at introducing the concept of a sponge city, including Warsaw, where many companies from the water, urban and green industries work to improve retention. The Hadart company, which specializes in building gardens on roofs, green walls and parking lots, flower meadows or retention reservoirs, has been promoting the idea of sustainable water retention, especially in urban areas, for many years.


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