Development of evapotranspiration estimates from class A pan
Runoff prediction from urban watersheds relies on accurate parameterization of all components of the water budget. Evapotranspiration often consumes the largest proportion of rainfall but is poorly understood because it is rarely measured and highly variable. This deficiency has been partly addressed within the Humber R. watershed with the recent establishment of two automated Bowen ratio energy balance ET monitoring systems, over an open field and impervious rooftop, operated jointly by the Toronto and Region Conservation Authority (TRCA) and Geography Department of York University. Extending ET estimates to other surface types and different watersheds within Ontario would improve if the potential evaporation PET, measured using evaporation pans over past several decades could be transformed into estimates of real evaporation, ET. The objective of this project involves the experimental comparison of models utilizing class A pan evaporation, PET against real watershed ET estimates utilizing the BREB systems. This will improve the accuracy of water-budget models relying on these estimates and extend their spatial and temporal validity. Many meteorological stations world-wide measure water loss from stainless steel class A pans during the ice-free season. Therefore, this analysis holds the potential to broaden the reliability of class A pan data for estimates of actual ET as well as create historical ET datasets which could be valuable in assessing the affects of climate change on the hydrological cycle.