Evapotranspiration is a crucial component for water cycle and thus essential to accurately quantify for water management across irrigated landscapes. Typical landscapes possess a high degree of spatial variability, which in turn, can have impacts on the rate of evapotranspiration at field scales. To account for this spatial variability, and improve the formulation of evaporation into the atmosphere, new generation modeling and measurement techniques must be developed for water planning and applications in precision agriculture. This presentation will give an overview of some recent developments in simulation tools and measurement techniques that can lead to an improved understanding of the water vapor, heat, and momentum fluxes over patchy land surfaces and rugged topography. New generation Large Eddy Simulation (LES) is ideally suited to model evapotranspiration in complex regions while Raman Lidar and sensor networks are the experimental counterparts that fulfill the data density requirements.