Exploring Influencing Factors and Innovative Solutions for Sustainable Water Management on Green Roofs: A Systematic Quantitative Review

Abstract

Green roofs are becoming popular in urban areas due to their potential benefits, including energy efficiency, urban heat island mitigation, and stormwater management. However, their water consumption can negatively impact water resources. Therefore, carefully managing the water consumption of green roofs is crucial to ensure they do not exacerbate existing water scarcity issues. This review explores the influencing factors and innovative solutions that increase the sustainability of water management on green roofs. A systematic quantitative review was conducted on published studies on green roofs. The review highlighted that while small-scale experimental studies are almost saturated, large-scale monitoring studies are still lacking. Modelling and assessing green roof settings based on climatic conditions and water availability and consumption are essential for successful water management. Using integrated technologies and sensing systems can increase water management efficiency and sustainability. Rainwater may be sufficient as a water source for green roofs in wet climates, while irrigation is still needed in other climates. Phytoremediation and biosorption can potentially increase runoff water quality. Improving hydrological performance by increasing rainwater retention and reducing water consumption capacity can reduce demand for other water resources and effectively manage small storms, mitigating pressure on city infrastructure and increasing water quality. Seeking non-potable sources, such as greywater, or harvesting enough rainwater to be used for irrigation during dry weather periods is highly advantageous for improving the sustainability of green roofs.

Simulation-Based Study on the Effect of Green Roofs on Summer Energy Performance in Melbourne

“…These results suggest that a soil moisture content of around 50% is optimal for reducing HVAC system electric consumption while implementing green roofs. These findings are consistent with previous research highlighting the importance of proper irrigation and soil moisture management in optimising the cooling performance of green roofs [57,69] The impact of plant height on energy reduction was also examined. Both reducing and increasing the plant heights had a negative effect on energy consumption.…”

“…Understanding the effects of soil moisture is essential for informing sustainable irrigation and water management strategies that can optimise the ecological functions of green roofs. Proper irrigation practices can ensure that soil moisture levels are maintained at appropriate levels, promoting healthy vegetation and efficient ET [57]. Efficient water management contributes to the cooling effects of green roofs, reducing UHI effects and enhancing the overall thermal comfort in urban environments.…”

Which Plant Species for Green Roofs in the Mediterranean Environment?

“…Among the main and typical ones, there is rainfall interception and prevention of flash floods in urban areas, consequently decreasing the load on sewer systems. To this end, vegetation plays an important role because it significantly influences the moisture content of the substrate and runoff rate [48,49]. The reduction in runoff occurs through various processes such as water interception, plant transpiration, root absorption, retention, and storage of water in plant tissues [50].…”