Green Roof Runoff Water Quality

Green roofs can improve stormwater management.

Green roof runoff water quality.

The use of any technique or approach that reduces the rate and volume of rainwater runoff has the potential to contribute to better management of the overall quality of rainwater one approach that is used more and more frequently in the management of rainwater i e. Enhanced stormwater management and water quality. Green roofs can help to reduce both storm water volume rate of run off entering the drainage system. Green roofs can reduce and slow stormwater runoff in the urban environment and also filter pollutants from rainfall.

Moreover the water that is released from a green roof is released slowly reducing the amount of runoff that rushes into a watershed all at once which curbs flooding and erosion. Note that there was very little if any runoff during the may 1 to sept 30 growing season. Figure 3 2 monthly average precipitation and runoff for green and asphalt roofs including unplanted media roof figure 3 6 precipitation and green and asphalt roof runoff from snow and mixed precipitation events in march 2005 figure 5 2 average water loss during the daylight or night from planted and unplanted green roof lysimeter test beds. As with other green infrastructure interventions.

Green roofs can retain nearly all storm related precipitation during the summer months with lower retention during the winter months 20. Green roofs can remove carbon dioxide and produce oxygen. Therefore green roofs have an important role to play in the urban realm. For water quality performance with respect to stormwater runoff we undertook a 16 month survey of stormwater runoff quality from five full scale green roofs including two built up systems one modular tray system and two vegetated mat systems.

The plants and growing medium of a green roof absorb water that would otherwise become runoff and research indicates that peak flow rates are reduced by 50 percent to 90 percent compared to conventional roofs. Figure 2 shows the daily rain and associated daily green roof runoff for 1993 in state college pa for a green roof having a maximum of 1 6 inches of water retention storage. Green roofs the key hydrological mechanism for interception storage and filtration of water. Green roofs influence runoff quality through making the ph higher from values between 5 and 6 in rain water to over between 7 and 8 in green roof runoff water bliss et al 2009 czemiel berndtsson et al 2009 teemusk and mander 2007.

This is an important function which contributes to lowering the degree of acidification of natural. Stormwater management is the.