Evapotranspiration from urban green spaces in a Northeast United States city

Evapotranspiration from a temperate urban environment is the focus of the research presented in this dissertation manuscript. The research is conducted throughout New York City at a variety of monitored sites. Sites include a total of twelve existing and newly developed monitoring sites primarily in urban green spaces. New urban green space monitoring sites include engineered urban green spaces (e.g. bioretention areas and green roofs) as well as remnant local forests. Sites are intensively monitored with equipment including weighing lysimeters, soil sensors and climate stations. Monitoring at these sites yields novel previously unavailable data sets. Data sets from new and existing sites are used to quantify evapotranspiration using various methodologies, including weighing lysimeter, soil water depletion, evaporation pan, energy balance, Penman-Monteith based combination method (ASCE Standardized Reference Evapotranspiration Equation, short), crop coefficients and attenuating factors. Methods for the determination of evapotranspiration using onsite data sets from urban green spaces have been found to perform with fair or better agreement to actual evapotranspiration when certain conditions are met. Improved applicability of methods for the determination of evapotranspiration to urban green spaces has been demonstrated to be achievable through, for example, the development of crop coefficients. Data sets have also been used to evaluate the spatial variability in evapotranspiration and determinants of evapotranspiration across the heterogeneous urban environment. Findings suggest that engineered urban green spaces or green infrastructure installations in temperate urban environments generally evapotranspire at different rates amongst sites and in comparison to remnant forests due to physiological differences in vegetation and variable micrometeorological conditions, with the magnitude of these differences being dependent on runoff routing to installations. Furthermore, evapotranspiration has been compared to historic regional conditions finding that urban green spaces (specifically a green roof) may mimic historic evapotranspiration conditions at the site scale.