Changes in the quality of water in the lower Vistula River in 1986–2009 Authors

The results of more than twenty years of own research and state environmental protection authority reports show that from 1986–2009 the quality of water in the lower Vistula, representative of the eastern (right bank) part of Poland, continuously and significantly improved. This improvement was the result of changes in water and sewage management in the Vistula basin. Earlier, in the 1970s, the Vistula was quite heavily polluted, but it has never been the dirtiest river in Europe. It has been shown that Włocławek Reservoir has improved the water quality in the Vistula, substantially reducing all the indicators examined (Tab. 2). The only exception is concentration of oxygen, lower in the reservoir than in the undammed Vistula, but not to such an extent that it would threaten the development of its biocoenosis, which is richer than in the undammed Vistula. Reduction in the nitrogen (by 12.4%) and phosphorus (by 21.5%) load carried by the Vistula in the reservoir is particularly important for protection of the Baltic Sea against excessive eutrophication. This way, Włocławek Reservoir contributes to fulfilment of Poland’s obligations under the Helsinki Convention ratified in 1999. DOI: 10.12736/issn.2300-3022.2013207 Introduction Comprehensive chemical and biological research on the lower Vistula (dolna Wisła), mainly Włocławek Reservoir, began in the first half of the 1980s. The research was conducted by the Hydrobiology Department of the Institute of Environmental Protection at the NCU (Faculty of Biology and Environmental Protection since 2012) in collaboration with other research units, with only minor interruptions. The research resulted in about 100 theses, including several dozen publications, nine PhD dissertations and one habilitation thesis. The results of research were also presented at many scientific and popular science conferences dedicated to necessary transformations of the lower Vistula (dolna Wisła). They were also the basis for the expertises prepared for the Sejm of the Republic of Poland [4] and the Marshal of Kujawsko-Pomorskie Voivodeship [5], which estimated the ecological effects of construction of the planned cascade below Włocławek. All the above-mentioned sources and – what is particularly important – the reports of the Provincial Inspectorate for Environmental Protection in Bydgoszcz clearly refute the theses that the Vistula (Wisła) is the most polluted river in Europe and Włocławek Reservoir damages the natural environment of the Vistula (Wisła), propagated by defenders of the Vistula (Wisła) – journalists, non-governmental organizations, and even some professionals – and harmful to the Polish economy and environment. The aim of this study is to provide arguments for the absurdity of both of the mentioned theses for the community of power engineers and hydraulic engineers. We add a new argument to the ones already known and included in various publications – it concerns a substantial reduction in phytoplankton biomass, thus also of the concentration of chlorophyll “a” in Włocławek Reservoir. In the third issue of the series the same team of authors will present the opportunity to broaden and clear the green corridor of the lower Vistula (dolna Wisła), provided by an eco-friendly construction of a cascade in Siarzewo. Description of the area The Vistula (Wisła) is the longest river in the Baltic Sea basin. Its length is 1047 km, of which 941 km are navigable. It is second after the Neva in terms of the volume of water flowing into the Baltic Sea (Neva – 2400 m3/s, Vistula (Wisła): 1050 m3/s). There are three sections of the river, indicated by the mouths of the largest tributaries, i.e. San and Narew (Fig. 1). A. Kentzer, A. Giziński | Acta Energetica 2/15 (2013) | 97–101