Multifunctional flood protection reservoirs of regional importance have been controversial for many years due to their significant environmental impact. The impact is especially observed at the implementation stage. Undeniably, properly managed large water reservoirs are the most effective element of active flood protection and significantly reduce the flood wave, thus limiting losses in housing, infrastructure, industry, or agriculture. At the same time, multifunctional reservoirs pursue other goals that are related to reducing shortages and counteracting the effects of drought, water supply, hydropower, or recreation. In the era of rapidly advancing climate and geopolitical changes, their role seems indispensable when it comes to responsible and coordinated water management in Poland. An open question is how to fully use the potential and to what extent it is possible for the system of reservoirs located on different watercourses to work together in the era of the progressive development of the country resulting in significant changes in land use (sealing large catchment areas) in relation to design assumptions. The article presents an analysis of the work of selected water reservoirs located in the basin of the upper Vistula during the floods that took place in the last decade. On the basis of the obtained conclusions, the authors present recommendations on how to effectively manage the network of reservoirs during a flood while minimizing losses of the water retained in them, which should be used to meet other goals of water management.

Based on new policies of the European Union, green technologies are to be mostly considered for power generation. Hydropower generation is one of the essential elements of sustainable energy production. Therefore, specific attention, both economically and technically, needs to be given to this sector of energy production. The Vistula River in Poland is considered an international waterway. The power production potential of the river has been taken into account over the years. However, further configurations are needed to obtain a more in-depth ecological knowledge-base and economic plans, which are socially approved. In an attempt to make the project environmentally friendly, specific attention was put into sustainable transport. Different methods of transport were researched to find the most renewable transport combination, mainly based on waterways. Having performed a cost–benefit analysis related to the economic aspects of the project, it was found that such an investment is highly profitable (B/C = 2.81).

Retention reservoirs are one of the basic elements of water management. Multifunctional, they are used for flood protection, drought prevention and other purposes. Water reservoirs can also play a fundamental role in improving navigability on the lower section of the Vistula River from the Włocławek barrage to the mouth of the Gdansk Bay. Their implementation is a determinant for the possibility of restoring the economic role of the river in question. Therefore, the purpose of this research was to determine the current navigation conditions and the state of the regulatory buildings on the Lower Vistula. The investments necessary to achieve international parameters of the waterway were also determined, together with the calculation of financial benefits related to their implementation. This was possible based on the conducted bathymetric measurements, spatial analyses, economic calculations and queries of the obtained studies. It was established that fairway depths of 1.4 m are ensured for 180 days per year on average. On the other hand, the construction of five barrages (Siarzewo, Solec Kujawski, Chełmno, Grudziądz and Gniew) will make it possible to achieve at least a navigability class IV (international) on the section of the Vistula River waterway. In addition, the barrages will enable the retention of 1.2 billion m³ of water and will be associated with financial benefits such as shipping use, flood protection and counteracting the effects of drought. On this account, annual revenues may amount to approximately PLN 3.5 billion. This shows that the construction of the reservoirs is profitable, and the proposed solutions should be implemented in the context of sustainable water management and adaptation to climate change.

Construction of the Włocławek Barrage on the Vistula River in 1970 became an important source of energy; however, it discontinued sediment transport in the Vistula River. This phenomenon resulted in accumulation before and erosion below the barrage; a similar problem can be expected due to the planned construction of the Lower Vistula Cascade. This study is dedicated to finding an effective and feasible solution to sediment transport management, acceptable to a wide group of users (e.g., navigation, energy producers, and ecologists). A numerical 1D model was applied to carry out analysis of hydrodynamics and sediment transport in the river section from Włocławek Barrage to the Vistula River mouth in the Baltic Sea. For calibration, historical data describing the accumulation and erosion created by the Włocławek Barrage were used. The proposed model allowed incorporation of new barrages chronologically, in accordance with the proposed time schedules. Analysis was carried out in a 50-year horizon, using a set of historical flow data. For sediment flushing, it was proposed to use natural flooding events exceeding Q_10% discharge and to control sediment management of the adjacent barrages. To use this method in practice requires verification.

Analizowano straty filtracyjne wzdłuż około 80-kilometrowego odcinka rzeki, powstałe w wyniku spiętrzenia wody w rzece Warcie wywołanego zrzutami ze zbiornika retencyjnego Jeziorsko realizowanymi w celu zapewnienia przepływów niżówkowych (minimalnych) Warty. Przeanalizowano 12 hipotetycznych przebiegów fali w zależności od wielkości i czasu trwania zrzutu. Parametry określające właściwości filtracyjne podłoża wyznaczono na podstawie badań terenowych przeprowadzonych na terenie polderu Majdany, w przekroju znajdującym się w połowie analizowanego odcinka rzeki. Wyznaczono skumulowane wydatki filtracyjne, będące sumą strat, oraz jednostkowe wydatki przez dno koryta rzeki. Straty porównano z objętościami zrzutów w poszczególnych symulacjach. Wykazano iż straty na rozpatrywanym odcinku nie są duże i sięgają maksymalnie 1,3% objętości zrzutu a udział procentowy maleje wraz ze zwiększaniem się wielkości zrzutu oraz czasem jego trwania. Rozwiązania uzyskano z wykorzystaniem MES zaimplementowanej w pakiecie oprogramowania komputerowego Hydrus, umożliwiającego analizowanie zagadnień niestacjonarnych ze zmiennymi w czasie warunkami brzegowymi.