Methods of description of the nonlinear effects in dynamic hydrological systems have been surveyed. Particular reference was given to those sorts of nonlinear methods which do not require significantly more computational effort in comparison with classical linear models. Original concepts in the field of nonlinear state-space models, Volterra series models and the general framework of multilinear models were tackled in more detail. Illustrative numerical examples of flood routing and rainfall-runoff modelling were presented.