Modelling of man-made contribution to salinity increase into the Vistula Lagoon (Baltic Sea)

The man-made contribution to significant increase in salinity in the Vistula Lagoon (south-eastern Baltic) during the last century is discussed in this paper: (a) diversion of the main part of the Vistula River discharge from the Vistula Lagoon directly into the Baltic Sea at the beginning of this century; (b) the intensification of water exchange with the sea because of the deepening of the Lagoon entrance and (c) significant simplification of sea water penetration into the distant parts of Lagoon aquatory through deepened ship channels. The numerical modelling results (MIKE21) for salinity field annual dynamics in the whole Lagoon under different hydrological conditions are presented: before the reduction of the Vistula River inflow in 1916, under present-day conditions, if there are different ship channels in the Lagoon aquatory. The impacts of different man-made hydrological and morphological interventions that contribute to the salinity field variations are estimated and graded in order of effect. Temporal and spatial salinity variations, and mean annual values are discussed.