subcatchments of the Meuse. The variation of the parameters is modelled by means of a random walk method. Some objective criteria for evaluation forecasting performance are introduced. It can be concluded that, in general, adaptive modelling improves the real
the use of an additive Q matrix into the recursive algorithms for the linear parameter estimation problem, are compared. It is found that, from an operational standpoint, the use of an additive Q matrix leads to better forecasting performance. The choice