Predicting “regular” dam deformations for prevailing conditions and comparing them with observed deformations is an essential part of dam surveillance. In many cases prediction and comparison are carried out automatically and an alarm is triggered in the case of larger deviations.The main contributors to the deformations of arch dams are water loading and the fluctuation of concrete temperature. In general, the deformations exhibit an instantaneous elastic part, a time dependent reversible part and an irreversible part. Prediction of dam deformations can be based on deterministic models, purely statistical models or so-called hybrid models, which are a combination of the first two. Deterministic models rely on static analyses, statistical models on the statistical analysis of previous deformation data.For annual reservoirs, both water loading and temperature vary in cycles over a period of one year and it is extremely difficult to identify the various factors contributing to an observed deformation. This is particularly true for time-dependent reversible displacements due to the water loading and the portion caused by temperature variation.The present article deals with the analysis of arch dam deformations based on hybrid models. Particular attention is given to the analysis of the deformations due to temperature fluctuation and to the long-term deformations. The proposed procedure is employed for the analysis of the deformations of the 186 m high Zillergruendl arch dam.