There is seldom a gauging station at exactly the spot in a watercourse where you need information about the discharge. Because precipitation and temperature are measured more densely than the discharge of water, this information can be used as input data to calculate the flow at any point in a watercourse.
The calculations are carried out with regional coefficients in a hydrological runoff model, the HBV model. The results are supplied as weekly and monthly mean values, so-called PULS-data.
The model is calibrated to for all the discharge gauging stations in a region, finding regional parameter values (coefficients) which provide sufficient concordance between calculated and recorded discharge for all stations used. These parameters are then used for calculating the discharge in ungauged spots.
SMHI annually carries out calculations for approximately 450 points in Sweden. The results are used, among other things, by the county councils and the water management associations for transport calculations in recipient monitoring.