Wetlands are characterized by frequent saturated conditions, dense vegetation growth and thus high evapotranspiration (ET) rates. Understanding wetland processes and water resource implications of wetland management and restoration requires estimates of ET rates. The analysis of diurnal groundwater fluctuations (DGFs) for estimating ET has been established for nearly 80 years, yet the method is not yet well utilized in practice due to inherent limitations. This paper assesses contemporary updates to the method to define a consistent tool and applies this to two contrasting riparian zones, in southeast England and northeast Germany. The method's accuracy is compared to reference ET evaluation methods and its utility for wetland hydrological management is assessed. Finally, practical guidance on how to apply the tool is provided, with a view to providing robust estimation of ET loss at wetland sites. Copyright © 2010 John Wiley & Sons, Ltd.