**2. Ecosystem benefits of evapotranspiration from green infrastructure**

Green infrastructure provides a wide spectrum of ecosystem services far beyond stormwater management as it is being accepted by more disciplines. Ecosystem services are the conditions and processes through which natural ecosystems, and the species that make them up, sustain and fulfill human life [8]. The ecosystem services of GI can be classified into four types: provisioning, regulating, cultural, and habitat [19]. Most current studies focused on its regulating service, since GI can regulate temperature [20] and air quality [21] as well as remedy stream-related water quantity and quality issues (so-called urban stream syndrome) such as

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*Evapotranspiration from Green Infrastructure: Benefit, Measurement, and Simulation*

alternations in flow regimes, morphology, water and sediment quality, and associated biological composition [22–24]. From the cultural perspective, GI creates more green space accessible by the public and adds amenity values to municipal infrastructures [25, 26]. Green infrastructure also can be used as arable space to promote urban agriculture and to supplement the local food chain [27–31]. A study in Bologna, Italy, found that 82 ha green roofs could provide more than 12,000 tons

GI provides habitats to protect biogeographic representativity, ecological coher-

Evapotranspiration is relevant to most of those ecosystem services such as improving urban air quality, carbon sinks, and biodiversity and enhancing the local rain-driven water cycle [35]. But most of the current publications mainly associate ET with three ecosystem services of GI including urban heat island relief, baseflow regulation, and water budget reestablishment. These three perspectives are dis-

Since dark paint and material of impervious surfaces tend to trap heat, urban environments usually have higher air temperature compared to surrounding suburban areas. This is referred to as the urban heat island (UHI) effect. In urban areas, material heating and anthropogenic heat release warm the near-ground air, maintaining the UHI effect and increasing building's energy consumption [36]. During drought periods, cities may have to restrict irrigation use, which further facilitates the development of uncomfortable urban climates with intensified heating and drying [1]. Introducing green and blue space in cities is often seen as a cost-effective strategy for mitigating UHI effect, since ET process is able to convert a large portion of incoming solar radiation into latent heat leaving from the urban surface [37–39]. Such active cooling can be realized by common GI which contains a vegetation layer and a moisture storage. Active cooling can also come from nonvegetated GI such as pervious pavement and water bodies where soil or open water evaporates [11–13]. Though the cooling effect of water bodies is not widely agreed [40]. Furthermore, GI takes advantage of the space (e.g. rooftop, external wall, and subsurface) that is rarely used otherwise. Therefore, although a single GI only takes a limited space, the network of GI can overall increase the ET strength of a city and contribute to

A green roof is a GI type that is commonly adopted and studied to mitigate UHI effect and reduce building energy cost, because it does not take ground area in a dense city. The rooftop usually represents the top elevation of an urban valley and receives the intensive sunshine without much shade, so planting rooftops tends to provide effective cooling benefit. A study based on EnergyPlus simulations found that green roofs could reduce the annual building energy consumption by 3.7% [41]. The cooling effect depends on the green roof coverage and climate zones. An observation has shown that green roof reduced the temperature of the urban boundary layer (from the rooftop level up to a few kilometers in elevation) by 0.3 and 0.2°C per 10% increase of green roof coverage at daytime and nighttime, respectively [42]. The same study also shows that the cooling effect of green roof can be even stronger than the reflective (cool) roof with the same roof coverage. The reduction in highest electricity peak because of green roof implementation ranges from 5.2% in hot-dry

The cooling effect of the green roof highly depends on its roof coverage and the substrate moisture content. Irrigation can improve the cooling performance of

vegetables that satisfy 77% of the city's yearly demand [28]. Lastly, vegetated

*DOI: http://dx.doi.org/10.5772/intechopen.80910*

ence, and landscape connectivity [28, 32–34].

year<sup>−</sup><sup>1</sup>

cussed in detail.

**2.1 Urban heat island relief**

mitigating the UHI effect.

climate to 0.3% in temperate climate [43].

## *Evapotranspiration from Green Infrastructure: Benefit, Measurement, and Simulation DOI: http://dx.doi.org/10.5772/intechopen.80910*

alternations in flow regimes, morphology, water and sediment quality, and associated biological composition [22–24]. From the cultural perspective, GI creates more green space accessible by the public and adds amenity values to municipal infrastructures [25, 26]. Green infrastructure also can be used as arable space to promote urban agriculture and to supplement the local food chain [27–31]. A study in Bologna, Italy, found that 82 ha green roofs could provide more than 12,000 tons year<sup>−</sup><sup>1</sup> vegetables that satisfy 77% of the city's yearly demand [28]. Lastly, vegetated GI provides habitats to protect biogeographic representativity, ecological coherence, and landscape connectivity [28, 32–34].

Evapotranspiration is relevant to most of those ecosystem services such as improving urban air quality, carbon sinks, and biodiversity and enhancing the local rain-driven water cycle [35]. But most of the current publications mainly associate ET with three ecosystem services of GI including urban heat island relief, baseflow regulation, and water budget reestablishment. These three perspectives are discussed in detail.
