Influence of Hydrological Conditions During Climate Change on the Development of Waterways – Case Study of Polish Rivers

Considerable transformations of the main elements of the hydrological regime of rivers in the central part of the European Lowland have been observed over the last 30 years. They involve increasingly frequent occurrence of low flows caused by draughts, a decrease in the number of floods, and reduction of the duration of periods with ice phenomena on rivers. All those changes are an effect of climate warming. In the years 1961-2017, an evident increase in air temperature in the annual scale was recorded (by 0.32^oC/10 years^-1 on average), including during winter by 0.36^oC/10 years^-1, and in spring by as much as 0.44^oC/10 years^-1. Moreover, an increase in sunshine duration and wind speed is observed, causing an increase in evaporation (in some years even by 40%). Effects of the aforementioned meteorological and hydrological phenomena are particularly evident in rivers subject to only partial regulation, characterised by free flow along many sections. Several rivers of the type occur in Poland. The rivers are parts of European, international waterways designated as: E-40 (the Vistula River), E-30 (the Oder River), and E-70 (the Warta, Noteć, Nogat Rivers). The technical state of the aforementioned waterways is currently bad (apart from the Oder River). This prevents the functioning of water transport. In 2017, a decision was taken on the revitalisation of the aforementioned waterways for the purpose of their incorporation into the well-functioning system of the western part of Europe. The main works, with a total cost of more than 21 billion USD, were planned from 2020. Based on economic expert opinions it was evidenced that revitalisation of the main waterways in Poland is justified. Little attention was paid, however, to the changing hydrological conditions the effects of which can to a great degree hinder achieving the economic goals. Therefore, the primary objective of this study is the identification of negative and positive changes in the regime of rivers (waterways) from the point of view of development of water transport, as well as pointing to the current and potential future limitations in the development of waterways in this part of Europe, resulting from further climate transformations. The study was prepared based on daily data of water stages and water flows in rivers, and primary meteorological parameters from the period 1961-2017. The aforementioned data were provided to the authors by the Institute of Meteorology and Water Management in Warsaw.