Session D10 - Evapotranspiration in SCMs

Evapotranspiration (ET) rates from Sustainable Drainage Systems (SuDS) differ significantly from reference ET rates due to differences in vegetation types, water availability and the urban setting. A technique capable of quantifying ET rates in situ would be of considerable value to urban drainage design and modelling professionals. In this paper we present and discuss findings from a continuous field monitoring exercise aimed at assessing whether the 3T method can deliver robust ET data in this context. The 3T method is based on the measurement of three temperatures: the surface temperatures of a transpiring leaf and an imitation leaf, alongside the air temperature. Estimates/measurements of the net radiation at both the vegetated and imitation leaf surfaces are also required. Results from a continuous monitoring study show a strong correlation between 3T-ET and ET losses determined directly using a weighing lysimeter. However, care must be taken to ensure that the measurements are made under valid atmospheric conditions, which may restrict time windows available for its deployment.

Biofiltration systems often clog over time due primarily to influent sediment loads, leading to reduced infiltration and failure. Most biofiltration systems are planted with sedges and rushes, which have high pollutant removal efficiency and tolerance, resulting in low species diversity. Incorporating woody plant species, particularly shrubs, into biofiltration systems could potentially improve plant diversity, aesthetic appeal, infiltration under high sediment loads and volumetric runoff reduction via increased evapotranspiration (ET). Therefore, we undertook a biofilter column experiment to determine whether shrub species can maintain high infiltration and ET under high sediment loads and related their performance to plant traits to improve biofilter plant selection. Most shrub species maintained high infiltration rates despite sediment loads, outperforming the standard biofilter sedge (Carex apressa) in Australia. Shrubs with higher infiltration also showed increased evapotranspiration, potentially reducing runoff volumes. Greater total biomass and root length were associated with better performance. Integrating shrubs in biofilters could alleviate clogging, increase runoff retention, and expand species options for these systems to enhance both biodiversity and functionality.

Biofiltration systems often clog over time due primarily to influent sediment loads, leading to reduced infiltration and failure. Most biofiltration systems are planted with sedges and rushes, which have high pollutant removal efficiency and tolerance, resulting in low species diversity. Incorporating woody plant species, particularly shrubs, into biofiltration systems could potentially improve plant diversity, aesthetic appeal, infiltration under high sediment loads and volumetric runoff reduction via increased evapotranspiration (ET). Therefore, we undertook a biofilter column experiment to determine whether shrub species can maintain high infiltration and ET under high sediment loads and related their performance to plant traits to improve biofilter plant selection. Most shrub species maintained high infiltration rates despite sediment loads, outperforming the standard biofilter sedge (Carex apressa) in Australia. Shrubs with higher infiltration also showed increased evapotranspiration, potentially reducing runoff volumes. Greater total biomass and root length were associated with better performance. Integrating shrubs in biofilters could alleviate clogging, increase runoff retention, and expand species options for these systems to enhance both biodiversity and functionality.

Cities in Mediterranean climates face increasing water scarcity, heat stress and short, intense rainfall events. At the same time, large-scale adoption of blue–green roofs (BGRs) is limited by irrigation demands and the lack of robust, continuous performance monitoring. This study evaluates a water-efficient BGR configuration in which a roof-level reservoir supplies water to the substrate by passive capillary rise, with seasonal supplemental inputs designed to be comparable to on-site air-conditioner condensate volumes. An experimental roof at the Technion (Haifa, Israel) comprises two identical 100 m² plots: a reference plot with conventional surface drip irrigation and a test plot receiving water into the storage layer. High-resolution meteorological and hydrological observations are used within a two-layer (blue-green) water-balance framework to quantify evapotranspiration (ET), storage dynamics, internal fluxes and stormwater retention under constrained water supply. Sentinel-2 satellite imagery is processed to derive crop and stress coefficients (Kc, Ks), which are then used to estimate ET and support continuous roof-scale performance and water-stress monitoring. The findings are expected to advance practical, scalable approaches for designing and evaluating water-efficient BGR systems in drought-prone urban environments.