Changes

<h4>Water Quality</h4>

<h4>Water Quality</h4>

<p>Many green roofs receive only rainwater, which is relatively clean when it lands. As such green roofs can contribute contamination, most notably in nutrient leaching during early establishment. But, in dense urban centres, green roofs are increasingly being used to receive irrigation from harvested rainwater. Current Ontario Building Code permits the use of rooftop runoff to be reused in this manner, so long as it is 'free of solids'.</p>

<p>Many green roofs receive only rainwater, which is relatively clean when it lands. As such green roofs can contribute contamination, most notably in [[Water Quality#Nutrient|nutrient]] leaching during early establishment. But, in dense urban centres, green roofs are increasingly being used to receive irrigation from harvested rainwater. Current Ontario Building Code permits the use of rooftop runoff to be reused in this manner, so long as it is 'free of solids'.</p>

<p> Where rainwater is harvested and reused to irrigate a green roof, there is no significant discharge of stormwater from the system, and no loading of contaminants downstream.</p>

<p>A 'closed loop' system can be created by coupling a rainwater harvesting system to a green roof.  by catching and reusing runoff, the only water leaving the system is through evapotranspiration. This prevents any runoff from leaving the site and so prevents any nutrient loading to the environment. </p>

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