Hydrological connectivity creates additional cooling effects for urban wetland complexes

With respect to urbanization, the use of wetlands to mitigate the urban heat island effect has received increasing attention. Among the many factors affecting the cooling effect of wetlands, hydrological connectivity plays an important role, but how it influences the cooling effect of urban wetlands still remains unclear. In this study, the ENVI-met model was used to simulate the thermal environments and cooling effects of wetlands in Chengdu, Southwest China, and to explore the causes of the cooling effects induced by hydrological connectivity. The results showed that, in the summer daytime, the cooling capacity of hydrologically connected wetlands was significantly better than that of a single large wetland or discrete wetland of equal area, especially during the peak air temperature (15:00–17:00); the additional cooling effect induced by hydrologically connected wetlands reached 0.79 °C under the parallel wind direction and 0.14 °C under the perpendicular wind direction. The additional cooling effect induced by hydrological connectivity was partly due to the ventilation corridor created by connectivity (contribution rate 24 %) and the relatively low temperature effect of the wetland connection (contribution rate 17 %). In the case of limited space in an urban setting, connecting multiple discrete wetlands is a low-cost, nature-based solution (Nbs) for alleviating the heat island effect.