Comparing Methodologies of Measuring Evaporation From Urban Watersheds

For this research, evaporation was measured from two contrasting land cover types within the Humber River watershed over a two year period. Multi-level Bowen ratio energy balance (BREB) systems were used to collect hourly estimates of the surface latent heat flux and surface water budget. Results showed that despite similar rainfall receipt, the naturalized site evaporated 73.0% on average of precipitation back to the atmosphere. In contrast, the impervious site only evaporated 23 .5% of precipitation. The second part of the research explored the theory behind the complementary relationship (CR), based on Bouchet's (1963) hypothesis, between potential and real (or actual) evaporation. The experiment occurred at the naturalized flux site using traditional aerodynamic theory to derive hourly estimates of canopy and aerodynamic resistances in combination with estimates of true potential evaporation from a Class A evaporation pan in order to examine the behavior of the critical resistance.