Animucha, LIFE Tree Check
Animucha, LIFE Tree Check

Adéla Mráčková  8. 6. 2022

How to Cool Overheated Cities? Using Trees and Water

With the summer ahead of us, the issues of heat waves, droughts and torrential rain come back as well. It is common that in the warm months of the year the temperature in cities is higher than in the surrounding countryside, which is mainly due to the large paved areas and facades. These retain heat on hot days and continue to radiate it even after dark. Surface temperatures in cities can then reach up to 70 ° C.

However, the phenomenon of overheating and drought is not limited to large cities. For example, the concreted centres of small villages, which lack greenery, or villages surrounded by bare fields, which heat up after the harvest, may suffer from it too.

There is a solution: working with the greenery and rainwater

“In the context of climate change, overheating, droughts and torrential rains are expected to be more frequent and intense. But that does not mean that we are powerless in this regard. We can work on how to reduce the effect of these problems in the future.”

Martin Ander, Czech Environmental Partnership Foundation

For this reason, too, many cities are developing their adaptation strategies and adaptation plans, which use concrete steps to increase their resilience to climatic events. They focus mainly on the expansion and addition of greenery and water features.

Rostock; Czech Environmental Partnership Foundation
Rostock; Czech Environmental Partnership Foundation

Why water and greenery? Because on hot days, thanks to the natural evaporation, they cool their surroundings. For example, a mature birch can evaporate up to 70 litres of water per day and, on tropical days, it can be up to 400 litres. There are differences between individual tree species, it can also depend on the age of the tree, the size of the crown and the total area of the leaves.

The new Tree Check mobile app, which is free to download on Google Play and the App Store, can help you determine how a particular tree can cool. From a mere picture of a tree, it recognizes the tree species, measures its trunk circumference, and determines its characteristic features. It then calculates how much water this tree evaporates in the summer, or how much shade it provides with its leaf area.

If the tree avenues, parks or individual trees are placed favourably, we can influence the temperature around houses, in a street or an entire block. However, in the fight against drought and overheating, we must not forget the infiltration and retention of rainwater, which then allows it to gradually evaporate on hot days.

Where possible, replace tarmac and concrete with permeable or semi-permeable surfaces – for example soakaway grids or grass on gravel lawns. We can retain rainwater with the help of infiltration swales, rain gardens, bioswales and infiltration basins. Leaving spaces in between kerbs can also be very useful and help drain rainwater into a larger grass area, whilst not bringing any additional costs in terms of construction.

Asio, oakaway grids
Asio, oakaway grids
The local communities can also take part in the fight against urban overheating

Efficient planning and development of adaptation measures to climate change requires more than just the involvement of the state and municipalities. The private sector, associations, schools and the general public should not be left out either, for they can improve their quality of life and health for themselves. The summer heat waves bring considerable health risks, which especially endanger those with long-term conditions (diabetics, cardiac patients), the elderly and children.

“We can build or modify our housing so that it does not overheat on hot days. Let’s paint the facade and roof with a light colour that reflects more sunlight back into the surroundings. Let's plant greenery around the house, use climbing plants or even a green roof. It is also important to shade from the outside using outdoor blinds, shutters, attached pergolas and awnings, and open windows in the early morning and evening.”

Martin Ander, Czech Environmental Partnership Foundation

We have prepared
a set of recommendations on how to adapt to the impacts of climate change


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