Changes

==Infiltration and Filtration==

==Infiltration and Filtration==

“In particular, the frequency and magnitude of overflow from the systems substantially increased under the climate change scenarios. As this represents an increase in the amount of uncontrolled, untreated runoff from the contributing watersheds, it is of particular concern. Further modelling showed that between 9.0 and 31.0 cm of additional storage would be required under the climate change scenarios to restrict annual overflow to that of the base scenario. Bioretention surface storage volume and infiltration rate appeared important in determining a system’s ability to cope with increased yearly rainfall and higher rainfall magnitudes.”  Hathaway et al 2014 – modelling study in US to see how bioretention can mitigate climate change.

“In particular, the frequency and magnitude of overflow from the systems substantially increased under the climate change scenarios. As this represents an increase in the amount of uncontrolled, untreated runoff from the contributing watersheds, it is of particular concern. Further modelling showed that between 9.0 and 31.0 cm of additional storage would be required under the climate change scenarios to restrict annual overflow to that of the base scenario. Bioretention surface storage volume and infiltration rate appeared important in determining a system’s ability to cope with increased yearly rainfall and higher rainfall magnitudes.”<ref>Hathaway, J. M., R. A. Brown, J. S. Fu, and W. F. Hunt. 2014. “Bioretention Function under Climate Change Scenarios in North Carolina, USA.” Journal of Hydrology 519 (PA):503–11. https://doi.org/10.1016/j.jhydrol.2014.07.037.</ref>

*“This study shows that the current levels of SGI in two major Mid-Atlantic cities and surrounding areas do have small, but significant to marginally significant and positive impacts on hydrology and nitrogen exports. Specifically, this study found that at the watershed scale, when stormwater green infrastructure controls N5% of drainage area, flashy urban hydrology and nitrogen exports are reduced. The magnitude of impacts are small, but will likely increase with more SGI. There were also some promising trends towards reduced CSO levels with higher SGI in watersheds, but the differences between sewersheds create high variability in CSO levels.”  in Penino et al 2016 – already evidence of improvement

*“This study shows that the current levels of SGI in two major Mid-Atlantic cities and surrounding areas do have small, but significant to marginally significant and positive impacts on hydrology and nitrogen exports. Specifically, this study found that at the watershed scale, when stormwater green infrastructure controls > 5% of drainage area, flashy urban hydrology and nitrogen exports are reduced. The magnitude of impacts are small, but will likely increase with more SGI. There were also some promising trends towards reduced CSO levels with higher SGI in watersheds, but the differences between sewersheds create high variability in CSO levels.”<ref>Pennino, Michael J., Rob I. McDonald, and Peter R. Jaffe. 2016. “Watershed-Scale Impacts of Stormwater Green Infrastructure on Hydrology, Nutrient Fluxes, and Combined Sewer Overflows in the Mid-Atlantic Region.” Science of the Total Environment 565. The Authors:1044–53. https://doi.org/10.1016/j.scitotenv.2016.05.101.</ref>

==Simultaneous benefits for periods of drought and periods of excess water==

==Simultaneous benefits for periods of drought and periods of excess water==