Water quantity and quality response of a green roof to storm events: Experimental and monitoring observations. (November 2016)

• Record Type: Journal Article
• Authors: Carpenter, Corey M.G.; Todorov, Dimitar; Driscoll, Charles T.; Montesdeoca, Mario
• Is Part Of: Environmental pollution. Volume 218(2016)
• Page Start: 664
• Page End: 672
• Publication Date: 2016-11
• Subjects: CSO -- Green roof -- Water quality -- Water quantity -- Nutrients; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2016.07.056
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: Syracuse, New York is working under a court-ordered agreement to limit combined sewer overflows (CSO) to local surface waters. Green infrastructure technologies, including green roofs, are being implemented as part of a CSO abatement strategy and to develop co-benefits of diminished stormwater runoff, including decreased loading of contaminants to the wastewater system and surface waters. The objective of this study was to examine the quantity and quality of discharge associated with precipitation events over an annual cycle from a green roof in Syracuse, NY and to compare measurements from this monitoring program with results from a roof irrigation experiment. Wet deposition, roof drainage, and water quality were measured for 87 storm events during an approximately 12 month period over 2011–2012. Water and nutrient (total phosphorus, total nitrogen, and dissolved organic carbon) mass balances were conducted on an event basis to evaluate retention annually and during the growing and non-growing seasons. These results are compared with a hydrological manipulation experiment, which comprised of artificially watering of the roof. Loadings of nutrients were calculated for experimental and actual storms using the concentration of nutrients and the flow data of water discharging the roof. The green roof was effective in retaining precipitation quantity from storm events (mean percent retention 96.8%, SD = 2.7%, n = 87), although the relative fraction of water retained decreased with increases in the size of the event. There was no difference in water retention of the green roof for the growing and non-growing seasons. Drainage waters exhibited high concentration of nutrients during the warm temperature growing season, particularly total nitrogen and dissolved organic carbon. Overall, nutrient losses were low because of the strong retention of water. However, there was marked variation in the retention of nutrients by season due to variations in concentrations in roof runoff. Graphical abstract: Highlights: Quantity and quality of stormwater runoff from an extensive green roof were examined. Monitoring observations were compared with a roof irrigation experiment. The mean retention of water over the monitoring period was 96.8% (SD2.7%, n = 87). Nutrient losses (TN, TP and DOC) were low associated with the strong water retention. There was marked seasonal variation in the retention of TN, TP and DOC. Abstract : The green roof was effective in retaining precipitation quantity from storm events with no seasonal dependency. Overall, nutrient losses were low but with marked seasonal variation.