Numerical Analysis of an Impact of Planned Location of Sewage Discharge on Natura 2000 Areas – The Dead Vistula Region Case Study

This article presents results of an analysis of impact of a designed discharge of contaminated water into the Dead Vistula (Wisła Martwa) in the region of the Isthmus (Przesmyk) with the aim of determination of a possible effect of the pollution onto protected areas of Natura 2000 (bird habitats and sites, especially the Bird Paradise – Ptasi Raj) nature reserve. The analysis was conducted on the basis of the two-dimensional modelling of unsteady transport of non-degradable dissolved matter. To this end, a numerical model of a section of the Dead Vistula was worked out. Four scenarios of hydro-dynamical conditions (2 – for average weather conditions and 2 – for stormy weather conditions) were selected. To solving the equation of pollution migration the finite volumes method (MOS) was applied. Two localizations of contaminated water discharge outlet were considered, namely: the first from the side of Siennicki Bridge before the Isthmus and the other in the section of the Brave Vistula (Wisła Śmiała) downstream the Isthmus. The obtained results made it possible to assess positively the first localization of the designed discharge outlet. In the other case there is a fear that at unfavourable hydro-meteorological conditions a water pollution may happen over Natura 2000 protected areas.