The Soil Water Apportioning Method (SWAM): An approach for long-term, low-cost monitoring of green roof hydrologic performance

Evapotranspiration from Green Infrastructure: Benefit, Measurement, and Simulation

“…Penman-Monteith (P-M) equation, taking a full account of energy balance, convection, and canopy resistance while well documented by previous agricultural studies, is widely applied to estimate ET from almost all types of GI such as green roof [6,57,74,83,93,[96][97][98][99], bioretention [64,80,100], and permeable pavement [101]. Simpler models, such as Priest-Taylor equation without considering convection [102], or solely temperature-based Thornthwaite Equation [59,85,103] and Hargreaves Equation [96,104], have also applied for GI when fewer inputs and less calibration effort required.…”

“…However, without the adjustment for the substrate moisture content, ET a will be overestimated for unsaturated conditions [89,117]. Therefore, the water stress coefficient [105] is used to take account of moisture dynamics, and has been used as the benchmark for assessing other predictive ET a models in lieu of physically monitored data [90,97]. Actual evapotranspiration can be achieved by multiplying ET o by K s .…”

“…Actual evapotranspiration can be achieved by multiplying ET o by K s . Simpler equations have been applied to green roof, such as the Thornthwaite-Mather version neglecting the rooting depth and moisture stress [83], or the soil moisture extraction function (SMEF) that further removes the restriction of wilting point [59,74,93,97]. All these methods tend to exaggerate the magnitude of ET reduction during dry periods, since they do not account for processes that could increase the moisture availability such as depression storage, interception, vegetation storage, and ponding water, or factors that alter ET fluxes like the subsurface moisture movement and non-ideal environmental conditions [81].…”

Green Infrastructure and Urban Sustainability: Recent Advances and Future Challenges

“…The two major green roof categories include extensive green roofs, whose substrates are typically 15 cm thick or less and feature short rooting, drought resistant plants such as sedum, and intensive green roofs, whose substrates are greater than 15 cm thick and may be sowed with deeper rooting plants including shrubs and trees. Due to their lower cost, reduced maintenance requirements, and lighter weight per unit area, extensive green roofs are more frequently adopted than their intensive counterpart [27]. For this reason, the majority of green roof studies engaging the author and her colleagues involve extensive green roofs.…”

Sustainability

“…The simulation results indicated that both the "government participation" and "household participation" scenarios, (Liu and Li, 2016). The impact of landscape patterns on peak runoff for areas in Texas (USA) were evaluated finding that, "larger, less fragmented and more connected landscape patterns are likely to mediate the mean annual peak runoff," which has implications for design of green infrastructure and stormwater management (Kim and Park, 2016 (Hakimdavar et al, 2016). Curve numbers and runoff coefficients were developed for green roofs, across various climates, with a stepped approached proposed for the use of curve numbers.…”