The objective of this study was to investigate the effect of the temporal resolution of hydrological data on an interception simulation. Hydrological data with different temporal resolutions generated from a 28-year hourly hydrological data set was applied to a simple interception model. The effect was significant and was quantified by a newly developed formula that relates the annual canopy evaporation with the annual effective potential evaporation, canopy capacity and temporal resolution. Using this formula, the true annual canopy evaporation invariant to the temporal resolution can be derived from the annual effective potential evaporation and canopy capacity. The concept of an operational parameter value and its calculation algorithm was proposed. The operational parameter values corresponding to their true values and the temporal resolutions were used in the model operation with the hydrological data of the same resolution, and the true annual canopy evaporation was reproduced very well. This implies the necessity of using operational parameters according to temporal resolution of the data in a hydrological simulation. Copyright © 2011 John Wiley & Sons, Ltd.