Abstract Body

The greening of cities is increasingly used as a measure against heat, and has other positive effects on biodiversity, health, quality of life and the financial benefits it provides through, for example, the amenity value of a city centre. However, greening also increases evaporation and thus the water demand in urban areas, while extremely high temperatures often occur in simultaneously dry periods. In practice, this can lead to a reduction in evaporation during drought and thus less effective cooling. The recent Dutch summers of 2018 and 2019 have highlighted the urgency of the linked problem between urban water management, drought and heat mitigation. There are many questions about the link between the heat and water requirement of urban green (for cooling down and even survival). With different stakeholders (governmental, private and entrepreneurs) Wageningen Environmental Research started with an inventory of existing and promising green for Dutch cities, in line with existing information and viewed from an ecosystem approach. Using atmospheric models, we establish the relationship between evaporation and cooling and we feed the National Hydrological Model with which the effect of urban evaporation on the groundwater level can be estimated. In a societal cost-benefit analysis we will evaluate and compare different options for greening. By combining existing knowledge about functional ecosystems with hydrological and atmospheric models, we develop examples of spatial designs for climate-resilient cities.