Rivers in cities are a breath of fresh air. The “forgotten” River Bièvre in Paris has long been buried underground but there are now plans to revive part of it, not only to bring back natural plants and wildlife but also to help to reduce the heat in summer (World News, August 2).
It isn’t just Paris — cities such as Seoul in South Korea have reinstated rivers to improve the environment and cool urban places.
Take a boat ride on the Thames and even on the calmest days an invigorating breeze can blow along the river and refresh the city air. A study several years ago mapped the air flow along the Thames in central London for three months in the winter and spring of 2011. The air was often funnelled along the river, especially where the riverbanks were built up with tall buildings, squeezing and accelerating the air as if it was a canyon.
Rivers can also behave as air conditioners that cool the local environment in an overheated city. A study of the River Don flowing through Sheffield showed that the impact of this small river spread into surrounding areas up to 30m away, especially in green open areas or streets open to the river.
“We monitored temperatures at a number of sites and discovered that in hot weather and during the daytime the river has a significant cooling effect,” Dr Abigail Hathway, a senior lecturer at the University of Sheffield, said.
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Cities such as London also have an extensive network of underground rivers that once flowed above ground but over the centuries became relegated to underground waterways. Even though these subterranean rivers are largely forgotten, they too have their uses and can now be tapped as an energy source for heating buildings. The water is too cool to directly heat buildings but heat pumps can be used and the method can help to reduce greenhouse gas emissions. Heat pumps can also be used the opposite way round, to cool buildings in hot weather.
