Increasing vulnerability to extreme floods and societal needs of hydrological forecasting

Recent climatic variability seems to be intensifying the hydrological extremes resulting in devastating hydrological hazards, especially floods all over the world, including the arid regions. Disasters are always more tragic in poor countries than in rich ones, as more poor people seem to suffer and die, and the economic losses have a greater impact. On the other hand, in advanced countries, although flood control can reduce the number of deaths, it cannot always reduce economic losses despite the large public investments that have long been applied. This is due to the ever increasing damage potential in a basin where reliance on safety has been created by flood control measures. It is proven that proper prediction and preparedness are the only practical means that can be relied upon to reduce the death toll and economic losses. In a time of climatic variation, physically-based distributed models are to be pursued to obtain reasonable predictions, since the climate is non-stationary and both basin land use and water use are constantly changing. The proper integration of a distributed watershed model with atmospheric circulation models, four-dimensional data assimilation and mesoscale hydrometeorological nested models is the direction for hydrologists to be heading.