In 2022, Europe faced extreme heat and severe drought, among the worst ever observed. Italy experienced its hottest and driest year since 1800, leading to agricultural challenges, reduced hydroelectric production, public health issues, and significant melting of Alpine glaciers. Tourism, particularly in ski resorts and water parks, was also impacted.
Despite the prolonged drought, extreme weather events occurred, such as heavy flooding on September 15 in the Marche region and on November 26 on the island of Ischia. The first quarter of 2023 saw above-average temperatures and a high rainfall deficit. Winter water resources for 2022-2023 were approximately half compared to the previous year, leading to critical situations for rivers, ecosystems, and human uses.
Meteorological studies have highlighted the link between extreme heat and drought values and anthropogenic global warming-induced climate change. Regarding precipitation, Italy is witnessing an increase in the frequency and intensity of extreme precipitation events nationwide. Geographic, hydrogeological, and urban features, coupled with urbanization, make cities particularly vulnerable to climate risk, including flooding and inadequate drainage networks. Many Italian municipalities face hydraulic hazards, landslides, and coastal erosion, affecting a large population. In the context of climate change and considerations for future scenarios, it is evident that traditional approaches to water management and mitigating hydro-geological risks need radical reconsideration. Sectoral and fragmented approaches, reflecting historical divisions in skills and expertise, as well as barriers between entities based on water resource use and different territories, are no longer sufficient or effective. Instead, new approaches and solutions must be adopted, integrating diverse skills and expertise.
In this context, "soft" engineering relies on engineered natural solutions to manage urban drainage and harness the various ecosystem services they offer. These include atmospheric, climatic, and water regulation, erosion and sediment control, nutrient balance, pollution reduction through natural processes, biodiversity enhancement, biomass production, soil creation, expansion of recreational areas, and environmental education. Solutions and projects must be multifunctional and multilevel, aiming to reduce hydrological risks, improve water quality, and promote urban regeneration, health, and quality of life. Each intervention should contribute to mitigating and adapting to climate change, with a positive impact on the environment, territory, and involved communities. A key element in addressing climate change challenges is the adoption of Nature-Based Solutions (NBS), which can provide ecosystem services by improving stormwater management and helping to mitigate the urban heat island effect, creating more livable environments for communities. These solutions have spread since the 1990s in the UK and have since expanded across Europe, the United States, and Australia.
The adoption of Nature-Based Solutions (NBS) in drainage systems entails a shift in approach from a focus on rapid removal of stormwater through traditional drainage networks to more sustainable systems that involve interception and infiltration of water at both local and widespread levels. This is achieved through various solutions such as surface depressions, vegetation, permeable pavements, and rainwater harvesting and reuse systems.
Extreme heat and drought are claiming more victims, with cities at the forefront of humanity's battle against extreme heat. An inspiring example is seen in the city of Seville. The streets of Seville, in southern Spain, are so intensely hot that it's almost impossible to be outdoors. As temperatures soar close to 42°C, the population rushes to seek shelter in air-conditioned homes, offices, and public buildings. However, less than two miles from the city center, a refreshing breeze blows under an imposing white roof.
This building is part of CartujaQanat, an experimental architectural project for cooling solutions that does not rely on environmentally harmful fossil fuels. The site, covering approximately two soccer fields, includes two auditoriums, green spaces, a boulevard, and a shaded area with benches. But the real star remains hidden: the qanat, a network of underground conduits inspired by ancient Persian canals.
This aqueduct system can lower surrounding temperatures by up to 10°C using only air, water, and solar energy. The system is modeled after ancient tunnels dug to irrigate agricultural fields, first documented in what is now Iran. Persians noticed this phenomenon 1,000 years ago, realizing that flowing water also contributed to cooling the air in the canals, leading them to create vertical wells to bring this air to the surface.
The CartujaQanat project is the result of research conducted at the University of Seville, where scholars have applied modern innovations to the magnificent Persian engineering feat that inspired its creation.
During the night, water flows through an external aqueduct system, transported over solar panels installed on the roof and channeled into large underground tanks. Interacting with lower temperatures, this process cools the water, while a closed circuit minimizes waste. As temperatures rise with the dawn, solar-powered pumps push the same water through smaller pipes placed in front of fans to produce fresh air. Through openings in the floor and steps, this refreshing airflow permeates the surrounding square.
The square itself is designed with features to maintain lower temperatures even without the qanat system in operation. Situated two meters below ground level, it is covered by a white roof that reflects heat and surrounded by columns and vegetation, further contributing to its cooling.
To truly save human lives, projects like CartujaQanat must be complemented by low-tech solutions such as tree planting. Around one-third of the 6,700 premature heat-related deaths in 2015, an average European summer, could have been prevented if 30% of urban surfaces were covered by trees.
In an effort to raise awareness about the dangers of extreme temperatures and the need for more effective protective measures, some researchers have started naming heatwaves in a similar manner to hurricanes. Led by the Adrienne Arsht-Rockefeller Foundation Resilience Center, this initiative is testing solutions to tackle heat globally, including an insurance program for outdoor workers in India.