Urban canals cooling : As cities deal with hotter and more frequent heatwaves, an unexpected source of relief could already be running through them: urban canals.
Researchers at the University of Manchester modelled more than 2,300 canal sections across Great Britain and Ireland to understand how much these waterways can cool their surroundings. Their findings suggest canals lower nearby daytime temperatures by about 0.8°C on average, with the effect becoming much stronger during heatwaves.
During periods of extreme heat, the cooling effect reached between 1.5°C and 2.3°C in nearby areas. The study is believed to be the first to assess the cooling effects of urban canals at a national scale across the canal network of Great Britain and Ireland.
Researchers modelled more than 2,300 canal sections
The research team developed a new energy balance model to simulate the thermal behaviour of more than 2,300 canal sections over an entire year.
The model showed that canals generally cool their immediate surroundings during the day, with the strongest effects typically found within 20 to 50 metres of the water. On an average day, the cooling effect was around 0.8°C.
That effect was stronger during spring and early summer, when canals reduced nearby temperatures by around 1.2°C to 1.4°C. But the biggest difference appeared during heatwaves. During those periods, canals could lower surrounding temperatures by between 1.5°C and 2.3°C.
The cooling effect becomes more important during heatwaves
The researchers also looked at what the temperature reductions could mean for people living and spending time near canals.
Their modelling found that including the cooling effect of canals reduced the number of hours classified as posing a moderate heat risk by around 58%. Hours of high heat risk fell by around 74%.
In some locations, the cooling provided by canals eliminated periods of extreme heat risk altogether. However, the researchers noted that higher humidity around the waterways can also affect people's thermal comfort, partly counterbalancing the cooling effect.
Millions of people live near Britain's urban canals
The potential reach of this cooling effect is significant because around 6.2 million people live within one kilometre of Britain's urban canal network.
That means millions of people could potentially benefit from the cooler conditions created around these waterways.
The researchers say the findings point to a role for canals in helping cities adapt as heatwaves become more frequent and intense.
Lead author Dr Matt Tomkins said, "As climate change makes heatwaves more frequent and intense, cities need every available tool to help people stay safe and comfortable,” adding, “Our research shows that canals, which were originally built to power the Industrial Revolution, could now play an important role in helping cities adapt to climate change,” as quoted by The University of Manchester's website.
Canals can cool cities during the day but retain heat overnight
The modelling also found that canals can have a small warming effect overnight.
Water retains heat for longer than surrounding surfaces, meaning nearby temperatures can remain slightly higher after dark. However, the researchers said this effect is relatively minor compared with the cooling benefits provided during the day.
The strongest cooling was observed when temperatures were highest, making the waterways particularly relevant during heatwaves.
Canals could support health and wellbeing
The researchers say cooler conditions around canals could have benefits beyond simply lowering temperatures.
Reducing heat exposure could help reduce heat-related illness and improve wellbeing. Cooler surroundings could also make it easier for people to remain active and walk or cycle during hotter weather.
Dr Joanne Tippett, a co-author of the study, said, “Accessible blue and green spaces result in wider health and wellbeing benefits for society” adding, “The cooling that canals offer could help more people to stay active and access these spaces even during hot days. This highlights the importance of not only protecting our urban canals, but also thinking about how to increase signposting and access, connectivity with other green infrastructure, and wider awareness of these vital networks of urban cooling," as quoted by The University of Manchester.
The researchers also point to the possibility that canals could support active transport during hotter periods, potentially contributing to lower carbon emissions and reducing demand for energy-intensive air conditioning.
Canals are not a replacement for parks and trees
The researchers stress that canals cannot solve the problem of rising urban temperatures on their own.
Instead, they argue that waterways should be considered alongside parks, trees, sustainable drainage and other forms of green and blue infrastructure when cities plan for hotter conditions.
They also suggest that improving signposting, access and connections between canals and other green infrastructure could help more people benefit from these spaces.
Tomkins said, "Urban canals have often been overlooked in discussions about climate resilience, compared with parks and trees. Our findings suggest they should be recognised as part of climate-responsive urban design alongside green spaces, particularly because millions of people already live and work within walking distance of the canal network," as quoted by The University of Manchester.
A new way to study the cooling effect of waterways
The research also introduces a modelling approach that could be used to examine how similar waterways affect temperatures in other cities around the world.
The researchers say the model could complement information gathered through field measurements, climate modelling and satellite observations.
