Nowcasting precipitation is a key point to anticipate risks in flood warning systems. In this environment, weather radars are very useful because of the high resolution of their measurements both in time and space. The aim of this study is to assess the performance of a recently proposed nowcasting technique (SPROG) from a hydrological point of view. This technique is based on the advection of radar precipitation fields and its main point is that the forecasted fields get smoothed as the forecasting time increases, to filter out the smallest scales of the field when they become unpredictable. The evaluation of the forecasted precipitation fields is done in two different ways: a) comparing them against the actually measured precipitation fields and b) according to the concept of “hydrological validation”, comparing the hydrographs calculated by a distributed rainfall-runoff model simulating operational conditions (using the forecasted precipitation fields) against the hydrographs calculated by the model with the entire series of radar measurements. This part of the study has been carried out in the framework of the Besos basin flood forecasting system.