Leana Weissberg

Three methods for the measurement of evapotranspiration were tested for quantitative agreement and ease of implementation at the Yale Experimental Watershed on the Yale University campus. Methods were employed over the course of the 2016 growing season (July – October, 2016) and included a micrometeorological heat budget (Penman FAO 24 model), pan evaporation, and soil moisture profiles. Penman FAO 24 and pan evaporation showed a modest linear relationship in a multiple linear regression model accounting for seasonality. However, inter-method variability, calculated as the root mean square error, typically showed better agreement between pan evaporation and soil moisture profiles. The use of a micrometeorological heat budget was the most cost-effective and feasible method tested for the measurement of urban evapotranspiration. Quantifying this crucial water budget component in urban environments could incentivize urban design that either reduces runoff or increases storage on the landscape, depending on the requirements of the climate in question.