RAINWATER MANAGEMENT How can water become a resource that is noticeable in our everyday life and that supports nature’s processes in the city? With everyday rain, rainwater management consists mainly of providing space for the water in the ground, in the form of rain beds that delay the flow of water. Runoff in the city can be reduced significantly by delaying, infiltrating or evaporating rainfall through the ecosystem’s soil structure, and the vegetation’s leaf structure and hydrological systems. In Copenhagen, 40% of the overall rainfall today becomes surface water, which is released into the Sound (Øresund) via the sewage system and treatment plants. Retaining and percolating rainwater in the city creates a better water balance with improved conditions for microclimate management. Rainwater management with its starting point in nature based climate adaptation, requires robust urban nature that can adapt to the weather alternating between dry and wet periods. A dynamic that is amplified by the city’s extreme conditions.
FACTS ”A single large tree can transpire 450 litres of water a day. This uses heat energy equivalent to 1000 MJ to drive the evaporation process. In this way, city trees can significantly reduce summer temperatures in the city.” Bolund P & Hunhammar S (1999) ”Urban landscapes with 50-90% impermeable surfaces can lose 40-83% of rainfall to surface runoff, compared to 13% in forested landscapes.” Goméz-Baggethun E et al. (2013) TIANJIN QIAOYUAN WETLAND PARK, KINA Inspired by the original marsh nature, this park has several hollows where rainwater is held and purified by means of versatile, indigenous vegetation. Water levels mirror the seasons, and the hollows can appear both as small lakes and as dry areas depending on the amount of rain.
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