A new study by Columbia University researchers has revealed that green roofs such as the ones on the Con Edison building located in Long Island City, Queens, prevent rain water from reaching the sewer systems, thus preventing overflows.
The green roof on Con Edison occupies around quarter acre of space of the Learning Center. It has over 21,000 green plants. The plant retains 30% of the rainwater, which is then released by the plants in the form of water vapor. The green roof was built by Con Edison, which went for a research partnership with Columbia in the year 2008.
According to the study conducted by Stuart Gaffin, a researcher at Columbia's Center for Climate Systems Research, over 10 billion gallons of water can be prevented from reaching the sewer systems by transforming 1 billion square feet of roofs into green roofs. The NY city like any other urban city incorporates a combined sewer system that channels wastewater as well as storm water. During rainy seasons, the systems reach its capacity flow and dispatch sewage and storm water into the Hudson River, the East River, the New York Harbor and other waterways.
The researchers used equipment to gauge the amount of sunlight and other energy entering and exiting the green roof and utilized the data to check the amount of energy going out of the green roof in water vapor form. The research resolved that by incorporating a green roof, one gallon of water can be saved just by spending 2 cents every year.
Source: http://www.columbia.edu/