Enhancing the synergy between the green and blue networks – a key contribution to the cities’ resilience

The use of nature-based solutions and the greening of urban spaces is a key strategy to improve the resilience of cities. Vegetation allows for carbon fixation and the abatement of air pollution, provides thermal regulation counteracting the effect of heat islands, and offers natural spaces for leisure and social interaction. Green areas also increase retention, bio-treatment and infiltration of water into the soil, providing opportunities to mitigate impacts from excessive waterproofing of the land. Thus, trees, green corridors, parks and urban gardens contribute to the improvement of the urban environment and the health and quality of life of citizens. Home gardens and the naturalisation of backyards can also play an important role in this process.

However, maintaining vegetation requires a regular supply of water, which is a challenge and often a serious obstacle to greening in regions subject to water scarcity. The use of green areas to enhance rainwater reuse, aquifer recharge and flood control also requires demanding planning, usually at both local and citywide level. Thus, enhancing the synergy between the green (land and vegetation) and blue (water) urban networks plays a key role in maximising ecosystem services and increasing the city’s resilience to climate and socio-economic changes. The grey network (i.e. the hard engineering infrastructures, consisting of reservoirs, conduits, sewers and other devices of the water, stormwater and sewage systems) and their management are obviously part of this process.

The construction of separate water supply networks for irrigation, the reuse of water from wastewater treatment plants, as well as the use of grey water from buildings and rainwater are increasingly being used to close the urban water cycle and lead to more efficient use of water and resources. New approaches of urban planning, landscape modelling and rainwater drainage have also promoted the creation of multiple use spaces, where green areas and drainage infrastructure are increasingly integrated. In addition to their social function, these spaces promote the naturalisation of the urban water cycle, attenuating stormwater flows, reducing polluted discharges into rivers and providing temporary storage of stormwater for flood control. The advantages of this integrated blue-green infrastructure can be further leveraged using local or central metering systems, remote management and smart technologies.

Promoting these synergies involves a broad range of stakeholders, including decision-makers, urban planners, various public and private services, as well as different specialities and levels of action, researchers and representatives of local communities and society. By developing a multisectorial approach focusing on water to improve resilience, the RESCCUE Project is contributing to the integration of blue-green infrastructure.