Considering the increasing use of water resources, hydrological forecasting is one of the most important item of applied hydrology. Forecasting is used for flood control, stream regulation, hydroelectric production, dimensioning hydraulic works, and pollution control. Hydrologists developed tools, called hydrological models, to answer these needs in a satisfactory manner. Such models have very rapidly evolved in the last few decades with the advent of increasingly powerful computers. CEQUEAU hydrological model, developed at the INRS-eau since 1971, is a water balance, distributed parametric model.