Green Roof Actual Evapotranspiration

One truly cannot design a green roof without fully understanding the annual water balance and evapotranspiration rates of the plant palette in the making of green roof design.

Green roof actual evapotranspiration.

Actual evapotranspiration can be achieved by multiplying eto by ks. In coutts et al. Evaporation is the loss of water from any old surface such as leaves and stems soil particles or debris. Simpler equations have been applied to green roof such as the thornthwaite mather version neglecting the rooting depth and moisture stress or the soil moisture extraction function smef that further removes the restriction of wilting point 59 74 93 97.

On a green roof it s the same. If it s hot and windy the roof dries faster than if it s cool and still. Wind speed matters as it stirs up the so called boundary layer allowing water molecules to leave the surface as vapor. Needless to say this is a task best left to the experts.

Course eco roof and green technologies. Green roof systems which calculate the runoff by solving the water balance equation account for precipitation irrigation storage and evapotranspiration processes rossman 2015. She pang 2010. Green roofs reduce storm water runoff through soil moisture retention and evapotranspiration berndtsson et al.

In the literature available however it is still not clear how and how much the evapotranspiration affects the performance of a green roof. Green roofs on campus. 2013 the higher latent heat flux on soil with maximum value about 280 w m 2 compared to green roof with maximum value about 210 w m 2 suggested that wet soil freely evaporated while evapotranspiration from the green roof was limited by the lower surface temperatures and water uptake by vegetation. Green roof is one of the emerging lid technologies used for retaining rainfall volume and attenuating storm runoff peak flows.

Even though the green roofs might be a quite simple system consisting of several layers all the processes within each layer must be controlled dynamically. After irrigation there was a substantial increase in latent heat flux for both green roof and bare soil. Considering that the sun can account for about 95 of the excess heat coming in through a roof evapotranspiration alone would lower the temperature of a typical extensive green roof by only a few degrees and leave us with a bunch of fried sedum.