Abstract Summary
The amount and dynamics of urban water storage play an important role in mitigating urban flooding and heat. The storage capacity serves on one hand as a buffer to prevent flooding during heavy rainfall. On the other hand, in absence of rain, it provides the water needed for evaporation to cool the city preventing heat stress. Assessment of the capacity of cities to store water remains challenging due to the extreme heterogeneity of the urban surface. The way the storage gradually empties during dry periods, can provide insight on the water storage capacity of urban surfaces. Assuming evaporation is the only outgoing flux, the water storage capacity can be estimated based on the timescale and intercept of its recession. In this paper, we test the proposed approach to estimate the water storage capacity at neighborhood scale with latent heat flux data collected by eddy covariance flux towers in twelve contrasting urban sites with different local climate zones, vegetation cover and characteristics and background climates (Amsterdam, Arnhem, Basel, Berlin, Helsinki, Herakleion, Łódź, Melbourne, Mexico City, Seoul, Singapore, Vancouver). Water storage capacities ranging between 1 and 28 mm were found. Additionally, the amount of stored water and the related evaporation halve every 1.5 to 7 days. According to our results, urban water storage capacity is at least five times smaller and evaporation decreases at least five times faster than what is found in natural forests and grassland.
