Water as a coolant of cities

Since more than half of the world population already lives in cities, it is important to understand the urban climate and its particularities. One of the typical aspects of urban areas is that cities are generally warmer than their rural surrounding. This phenomenon was first time described 200 years ago in the case of London and is commonly referred to as the Urban Heat Island (UHI). Urban heat island roots from a wide scale of factors typical for cities. Increased heat storage caused by higher specific heat capacities of construction materials together with darker color of urban surfaces, lack of vegetation and open water bodies, anthropogenic heat added by industry, traffic or air-conditioning, or the specific geometry of the street canyons are just few examples of how cities become warmer than rural areas. One of the often suggested ways to mitigate UHI is increasing evaporation by reintroducing vegetation and open water back to urban areas...