The economic consequences of the fluctuations of discharge in the Swedish rivers are substantial. Around 60% of the total demand of electric energy is satisfied by hydroelectric power. The power plants are relying upon the proper operation of reservoirs and thus hydrologic forecasts become important. Flooding is a problem, which is not immediately associated to Sweden, but intense springfloods like the one in 1977, can cause heavy damage and costs for the society and the public.
Therefore forecasts of floods are of interest, particularly in rivers, where the damping effect of lakes is small. During extremely dry summers, like the one in 1976, forecasts can be of interest for the planning of local water supply in certain areas.
Since 1972 the Swedish Meteorological and Hydrological Institute (SMHI) has been engaged in the development of a conceptual runoff model suitable for operational forecasting and other applications under Scandinavian conditions.
The model is now in operation in ten catchments in Sweden, and forecasts are issued regularly every spring and on some occasions in autumn and winter.