Urban canals cut local temperatures by more than 2°C during heat waves, study finds

New research from the University of Manchester has quantified the cooling effect of urban canals across Great Britain and Ireland, finding that waterways reduce nearby daytime temperatures by an average of 0.8°C over a full year. During heat waves, the cooling effect increases to between 1.5°C and 2.3°C, according to a study published in Nature Communications.

The researchers developed an energy balance model to simulate the thermal behavior of more than 2,300 canal sections over an entire year. The model accounted for the finding that canals produce a slight warming effect overnight because water retains heat longer than surrounding surfaces, but this effect is relatively minor compared with daytime cooling benefits.

The study also assessed thermal comfort during hot weather. Incorporating canal cooling reduced the number of hours classified as moderate heat risk by about 58% and high heat risk hours by about 74%. In many locations, canals eliminated periods of extreme heat risk altogether, though the researchers caution that rising humidity partly counterbalances these gains.

Lead author Dr. Matt Tomkins said the findings highlight the overlooked role canals could play in climate adaptation as heat waves become more frequent and intense. Originally built to power the Industrial Revolution, the canal network now places millions of people within walking distance of a cooling resource.

Co-author Dr. Joanne Tippett emphasized that accessible blue and green spaces yield wider health and well-being benefits. The cooling canals provide could help more people stay active and access these spaces during hot days, reducing heat-related illness and encouraging walking and cycling.

The researchers estimate that urban heat-regulation services from canals provide economic benefits of £14.41 million per year by reducing labor productivity losses on hot days. Canals may also reduce carbon emissions by enabling active transportation during heat and potentially lowering demand for air conditioning.

The team stresses that canals are not a complete solution to rising urban temperatures but should form part of a wider package of adaptation measures alongside parks, trees, sustainable drainage and other green and blue infrastructure. The modeling approach developed in the study could be applied to assess similar waterways in other cities worldwide.