Summary:

The article attempts to establish regional dependencies for calculation of the Snyder's model parameters. This model belongs to a group of synthetic unit hydrographs, whose parameters are determined based on the characteristics of catchments. This creates the possibility to use this model in uncontrolled catchments to calculate maximum probable flows and to construct hypothetical waves. In practice, this model is used worldwide. It is recommended for practical use in Poland, however due to the lack of established values of model parameters specific to Polish conditions, its use is rather unreliable. The optimization of the model parameters was carried out for the selected episodes of rainfall-runoff in the cat-chments of Rudawa, Kamienica, Grabinka, Stobnica, Jasiołka and Wielopolka. Hydrological data used in the calculations were provided by the Institute of Mete-orology and Water Management National Research Institute in Warsaw and were derived from the Annals of hydrology for the Vistula basin. The analysis revealed that the Snyder's model very well or well describes the observed flooding incidents (values of the effectiveness ratio E ranged from 68 to 93%). The parameter values of the Snyder's model, which depend on the shape of the catchments, levelled slope of the watercourse and the CN parameter, characterizing the watershed's coverage and ground permeability, were described using the multiple regression analysis. Although values of the multiple correlation coefficient R are not statistically significant in the established dependencies, which mainly results from the limited number of data used in the analysis, establishing of the dependencies may be applied in practice in the calculation of the Snyder‘s model parameters in un-controlled catchments. It should however be remembered that there is still the need for further research to revise the established dependencies, which should confirm the validity of their application in Poland.