Water Through Green Roofs

Abstract

How green roofs process water is a critical component of their function and effective management. As green roof technology has spread from northern Europe's relatively cool and humid climate, green roof designs have had to adapt to regional variations in the timing and availability of water. The development of regionally appropriate designs requires a mechanistic understanding of green roof water relations, plant eco-physiology and irrigation technology. Emerging designs effectively match environmental conditions, substrate characteristics, plant physiological traits, plant community interactions, and expert systems for applying supplemental water.Keywords Evapotranspiration · Hydrology · Irrigation · Plant selection · Plant water use strategies · Xeric climates Green Roofs as Hydrological SystemsThe vast majority of the water that lands on a conventional roof quickly flows off. In sharp contrast, water that lands on a green roof enters a complex hydrological system (Fig. 4.1). Stocks of water are held on and within plants, in substrate, and in various layered materials such as drainage and water retention fabrics. Water exits the system through evaporation from the substrate and plant surfaces, transpiration, and runoff. The magnitude of the various stocks of water as well as the flux of water between stocks and out of the system is governed by complex interactions among green roof components and the physical environment. This complexity makes green roof performance inherently dynamic and contingent on the details of system design and local conditions (Berndtsson 2010).Nevertheless, most extensive green roofs share broadly similar hydrological characteristics. The bulk of the standing stock of water on a green roof is held in the substrate. The amount of water intercepted and held by vegetation is comparatively

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A revised terminology for vegetated rooftops based on function and vegetation

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