The operation of multi-functional reservoirs, together with their benefits and risks, is a complex issue. The scientific and social discussion has been burgeoning recently, and all the more so as no planning and technological solutions for the realisation of storage reservoirs have yet been worked out that could represent a universal approach, assuming ecologically and socially sustainable operations, maximising economic returns and supporting the development of the region concerned. Although the creation of each reservoir facility involves different engineering and environmental considerations, this article attempts to isolate the key benefits of impounding reservoirs and to summarise the risks associated with their operation, considering flood protection, retention, environmental and social aspects and water quality. Based on a review of the scientific literature for each of these aspects, various sub-categories representing intensively developing sectors of research were distinguished, and the published results were used to formulate a register taking into account the spectrum of impact of a given factor and a proposal for remedial action. As a basic conclusion of this review, it can be pointed out that the current development of scientific research, technological progress in hydrotechnical engineering and information technology, as well as advanced data analysis capabilities, provide the basis for developing sustainable solutions to avoid or mitigate the negative impact of all the identified risks. In addition, remedial measures in the catchment area and the reservoir should be taken on board to counteract the negative effects of reservoirs. The results presented can be a valuable source of information for institutions responsible for the planning and implementation of investments in the construction of multi-functional reservoirs.

The purpose of this paper is to assess the hydromorphological status of watercourses above and below the hydropower plants. To this end, four methods were selected which represent various groups of methods used in various member states of the EU. Particular focus was on the RHS method (assessment of the physical habitats—the method used in Poland). The following methods were also used: LAWA (assessment of physical habitats, Germany), QBR (assessment of bank habitats, Spain), and HEM (comprehensive morphological assessment, the Czech Republic). For each of these methods, appropriate hydromorphological status indicators were calculated (assessment on a five grade scale). The analysis revealed that despite the different assumptions, the methods lead to similar results and can be used in various countries, especially in Europe. Because of the broad spectrum of space and time data used in the analysis, the results of HEM are the most reliable; however, this method is also the most difficult to use. All the methods meet the requirements of the Water Framework Directive, which calls for rational water management. Based on the hydromorphological assessment, the results obtained helped us to evaluate the environmental changes on the river sections above and below the hydropower plants.

Hydropower in Europe is playing an increasingly important role as a renewable source of energy. Its share of the final energy consumption varies from country to country, posing different challenges in each. The European Union member states are obliged, according to energy policy, to increase the share of renewable energy. This article presents the challenges related to the development of hydropower in four countries with different shares of domestic electricity production from hydropower plants: Albania (100% share in 2019), Slovenia (25.7%), Poland (1.1%), and Estonia (0.3%). Particular attention is paid to the issues of rational management of water resources in connection to Europe’s energy policy. As a result of the case study analysis, the challenges in the development of hydropower are identified, as well as ways to solve them. In addition, a comprehensive analysis of the impact of social, economic, environmental and climate change factors on the development of hydropower was conducted. At present, whether the assumed goals of the European Union’s energy policy will be achieved is impossible to determine for the whole of Europe. Achieving these goals will be possible only after individual countries prepare comprehensive reports on the topics of renewable energy sources, including hydropower.

The aim of this study is to analyze the toxicity of the sediments accumulated in the vicinity of hydropower plants (HPs) on the Ślęza and Bystrzyca rivers in Poland and the possibility of using these sediments for soil enrichment purposes. Thus far, there has been little comprehensive research related to the analysis of the impact of HPs on the properties of sediments. The analysis of the granulometric composition, physicochemical properties, heavy metals (HMs) content in sediments, and the growth of three plant species was carried out, including toxicity (HMs) and germination indices (plants). Most parameters were significant between the points upstream and downstream of the analyzed HPs. It has been shown that the most dangerous toxic factor is the high concentrations of Cu, Ni, and Zn in the sediments upstream of the HP on the Ślęza. In most cases, the HMs content was observed to decrease downstream of the HPs (e.g., Cu in Ślęza River: average of 13.44‐times), a result of changes in the particle size composition and accumulation of sediments at the site of the dam wall. Typically, the sediments tested stimulated growth in the plant species studied in comparison with the control groups (e.g., germination index for Sorghum saccharatum, Bystrzyca: 273.5% downstream of HPs). The C:N ratio increased downstream of the HPs by an average of 37.11% for the Ślęza River and 10.88% for the Bystrzyca River. The requirements for composting material were not met; however, the sediment could be used to enrich soils with an excessively wide C:N ratio.

Hydropower plants affect the distribution and composition of sediments. The main aim of this study was to analyze the spatial distribution of sediment pollution in the vicinity of a small hydropower plant. The grain composition of the sediments, the content of heavy metals (Cu, Ni, Cr, Zn, Pb, and Cd) and select physicochemical properties (pH, electrolytic conductivity) were tested at 14 points upstream and downstream of the hydropower plant on the Ślęza River in Poland, as well as at reference point. The interactions between the tested parameters were also verified. The results of the conducted analysis show that hydropower plants significantly affect the composition and properties of sediments. Large amounts of sediment are deposited on damming weirs, accumulating heavy metals and other substances. The differences in the concentrations of elements were significant, and Cu, Ni, Cr, Zn and Pb were 8.74, 9.53, 3.63, 8.26 and 6.33 times higher, respectively, than the median value at points upstream of the hydropower plant than downstream. It was shown that the tested parameters of the sediments interact with each other and are correlated; heavy metals showed a synergistic effect, while other parameters configurations showed an antagonistic effect. The higher content of heavy metals upstream of the hydropower plant resulted from the presence of finer sediment—classified as silt—in this section. Downstream of the hydropower plant, there were mainly sands, which showed a lower ability to absorb substances. This work contributes to improving the rational management of the worldwide issue of sediments within dams located in river valleys. Moreover, it is in line with the 2030 Sustainable Development Goals adopted by the United Nations, particularly in the fields of clean water and sanitation, clean and available energy, and responsible consumption and production.

This study innovatively evaluates the impact of hydropower plants located in a diversion channel on water quality dynamics. The spatial characteristics of water in the diversion channel above and below a hydropower plant were assessed; specifically, the investigation was conducted in the watercourse undeveloped by the hydropower plant and at reference points. Among the five analyzed points, the strongest statistically significant changes were observed in electrical conductivity, pH, and dissolved oxygen. Statistical analyses showed a similar, statistically significant relationship for most months. The water quality indicators proposed in this study help assess hydropower plants’ impact on water quality dynamics because they enable water comparison at different locations. The best water quality, as calculated using designated indices, was recorded below the hydropower plant. Among the physicochemical parameter values, the most noticeable change occurred in dissolved oxygen below the hydropower plant and below the fixed weir; its value was 8.10 and 5.32% higher in the two locations at the reference point below the hydropower facility. Moreover, the NH₄‐N content was higher by 7.06% below the weir than the point below the hydropower plant. In the long term, this research may help plant operators manage water resources on watercourses with hydropower development more efficiently, according to sustainable development principles. This research will contribute to the rational management of such facilities on diversion channels considering sustainable water management principles.