Drainage basin of the Gulf of Gdansk is dominated by the river Vistula, as regards both the catchment area size and the amount of discharged water. The remaining watercourses flowing directly into the Gulf of Gdansk or via the Vistula Lagoon (the Lagoon is a component of the Gulf of Gdansk system) contribute slightly over 1/8 of the total water volume. The presented calcula-tions of riverine outflow from the catchment area of the Gulf of Gdansk were conducted based on data either published in hydrological yearbooks or purchased from the Institute of Meteorology and Water Management. Other data sources included the archives of the Physical Oceanography Department at University of Gdansk, scientific publications and the author's expertise. Statistical characteristics of riverine outflow and water temperature were prepared as required by the model. The annual cycles of riverine outflow and water temperature at the mouth sections in the Gulf of Gdansk are expressed by trigonometric functions in an averaged climatic scale.