Diverging part of the river Neva discharge to the dry regions in the southern USSR has raised the question, to what extent such a river diversion will influence the hydrographic conditions in the Baltic Sea and the Danish Inland waters. In order to quantify the influence, the system has been divided into eight subareas, each of which is characterized by an equation for the mass, the volume and the dynamic balance (the mixing), respectively. The man-made change in the river runoff has been introduced in the equations, which have then been linearized and solved with respect to changes in the salinities, the discharges and the layer depths in the system.

As a quantitative example the hydrographic consequences of a 25% reduction in the river Neva discharge have been outlined. The most pronounced influence is on the salinities, which are increased by 0.2 to 0.4 ‰ allover in the system. Hence, if the river diversion had become executed in the beginning of this century a 30 to 40% higher salinity-variation would have been encountered in the Baltic Sea – compared to the actual variations during this century.

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