In the summer of 2022, an environmental disaster unfolded on the Oder River. Though the disaster was caused by humans, it was the river’s natural ecosystem that paid the heaviest price.

One more time we would like to pay attention of especially of the hydraulic engineer audience to bankfull stage and discharge. Along the paper we show commonly accepted definitions of it and ways of calculations. It is difficult to determine the size of the bankfull flow level, that is why the authors are presenting many selected methods. Some of the methods allow the determination of biotic bankfull flow through the occurrence of zones of vegetation characteristic and based on the observation of the occurrence of ground beetles (e.g. the Woodyer and the Radecki-Pawlik and Skalski methods). Some of the methods – most popular- are using morphometric parameters (e.g. the Williams, the Hey and Thorne, the Gauckler-Manning and finally the Lambor methods).

We believe that the value of bankfull discharge would be accepted as a supporting tool for designers, hydraulics engineers and managers, especially those who care about river channel environment and cooperate with fluvial geomorphologists- and biologists as well as environmental agencies.

On the Polish-Czech Odra river section between Chalupki (Poland) and the Olza river mouth there are unique in European scale meanders (km 21.3 - 26.8). In the 20th century the break-up of two meanders caused by floods in 1967 and 1997 occurred. The total length ofmeandering section has become shorter and the hydraulic gradient increased. The sediments eroded and transported by the stream have settled in different zones of the meandering section. In 1997 the inlet to the meander I was blocked by settled sediments causing the break-up of this meander. The paper presents the preliminary estimation ofmorphological changes of the river bed and the physical and rheological characteristics for settled sediments.

Water reaches a river in the form of surface runoff (precipitation that has not seeped into the ground) or underground outflow (groundwater). Both of these factors affect the erosion and river deposition processes that shape the river valley. Understanding them is crucial for effective river management.

The purpose of the research is to establish the total number of ponds in Ukraine and to analyse the territorial distribu-tion in the administrative areas, as well as in the river basin districts, as the main hydrographic units of water management. Cadastral data of the State Agency of Water Resources of Ukraine regional offices as of 2019 was used in the research (as to Crimea, Donetsk and Luhansk regions we applied the data as of 2014). According the researches there are 50,793 ponds in Ukraine with a total water table area of 2,92899 ha and the volume of 3,969.4 mln m3 of water in 2019. The quantitative distribution of ponds across Ukraine is unequal. Most of them are concentrated in the central part of the country (10.5% of the total number of ponds in the country are in Vinnytsia region). Least of them are in Luhansk region (0.7%). Almost half of the ponds are located in the Dnieper River Basin (48.5%). The lowest quantity of ponds is in the Black Sea Basin (1.2%). The regulation of river basins districts (the rivers of the Sea of Azov, Crimea and Black Sea Basins) reaches 0.71–0.77. As of 2019, 28% of the ponds are rented out. In order to identify the real status of the ponds (both quantitative and qualitative), their recreational role, the environmental impact and the regulation of the hydrographic network in Ukraine, it is necessary to increase the attention to ponds monitoring.

The study was conducted on the Biała Lądecka River which is a mountain river. It is similar to many European mountain rivers in terms of hydromorphology and catchment management. The aim of this study was to determine the bioconcentration factors of heavy metals (Pb, Cd, Hg, Ni, Cr, Cu and Zn) in Ranunculus aquatile (L.) Dumort., Fontinalis antipyretica (L. ex Hedw.), and Lemanea fluviatilis (L.) C.Ag. The content of metals in water, sediment, and submerged plants was determined. The metal concentrations in plants can be arranged as follows: Hg < Cd < Cr < Ni < Cu < Pb <Zn. The highest concentrations of Hg, Ni, Cr, and Cu were observed in F. antipyretica, but the highest concentrations of Pb, Cd, and Zn were in R. aquatile. L. fluviatilis always contained the least amounts of heavy metals. Bioconcentration factors (BCFs) were lowest in L. fluviatilis and highest in F. antipyretica. Among the analyzed metals, plants accumulated the highest amount of Zn, and the least of Hg. The BCFs for Zn were from 24111 (in L. fluviatilis) to 97574 (in R. aquatile), and BCFs for Hg were from 29 (in L. fluviatilis) to 226 (in F. antipyretica).

The paper aims to present directions of transformation of riverside areas in Wrocław implemented in 2012-2018 as well as planned investments within Przedmieście Oławskie revitalization program. Przedmieście Oławskie, a quarter housing estate from the turn of the 19th and 20th centuries is another area being regenerated in Wrocław after Nadodrze. The article outlines projects defined in the Local Revitalization Program for the years 2016-2018, responding to the identified deficits in spatial, social, environmental and economic spheres. The program proposes various projects that will create conditions for further actions. The challenges posed before the revitalization process mean the necessity of undertaking various projects and flexible planning for many years ahead. One of the key actions is a redevelopment of degraded Oława riverfront, which will be an activity and recreation space not only for residents of densely built-up and devoid of green areas Przedmieście Oławskie but also residents of Wroclaw. Modernization of the more than a kilometer section of the wharf can be an impulse for the development of the whole river corridor, that will have high natural, landscape and recreational values. The article discusses the planning process, objectives, principles and methodology of planned activities.

Careful study of river channel hydraulics is helping recover archeological treasures from the bottom of the Vistula River in Warsaw, lost by Swedish looters back in the seventeenth century.

Due to more and more increasing role of pollution surface waters in environment - particularly in populous regions - in this paper the problem of the influence of the town of Nakło city on purity of the Noteć river has been presented. Hydrochemical investigation of the Noteć river in the region of the community Nakło indicated II and III water quality classification. The town of Nakło discharges very much pollution into this river. In spite of recent certain improvement in comparison to 1993-1995 years the annual amount of pollution flowing from the town into the river is still too large and it is 3149 Mg of suspended matter, 266 Mg of nitrogen and 69 Mg of phosphorus.

Soil contamination with pesticide and biogenie compounds is a serious problem. The following compounds are detected most often and in largest quantities: lindan, DDT (not used for many years now), Simazine, Atrazine, Chlorfenvinphos and Fenitrothion. The presence of pesticides in surficial waters in the Żuławy Wiślane region has been described many times. Additionally, my own research con finned the presence of pesticides in superficial waters in Podlasie. This paper presents the results of the concentrations determination ofphenoxyacetic herbicides , biogenics and other pollutants in the Białka river. The samples were collected over a period of one year, from April 2000 to March 200 I. The analysis was carried out by reverse phase HPLC and TLC chromatography and colorimetric and spectrophotometric methods by HACH apparatus.

Research concerning chemical constitution of alluvial sediments was done in the lower course of the Obra River (Western Poland). The fragment of vertical profile, which consisted of various alluvial sediments (fine sands, peats and sandy silts) was chosen lor detailed analysis. Main research problem was to determine if lithology and chemical constitution or alluvial deposits arc interconnected in a distinct way within studied section of' the Obra river valley, and if changes of chemical clements concentration could be used to i I lustratc depositional processes which take place in river bed and floodplain. Concentrations ofFe, Mn, Cu, Zn, Ca, Mg and K were determined in collected sediment samples. Investigated changes of chemical clements concentration show that there is a distinct border between the organic sediments, which mark the place of former functioning of the Obra river bed, and sandy silts, which were deposited within floodplain during floods. Besides, dependence between lithologic variability of alluvial sediments and their chemical constitution was observed. However, this dependence is not clear in some cases. The authors concluded that it is necessary to use statistic analyses to define connection between lithology and chemical constitution or alluvial deposits (distinguishing geochemical groups of alluvial sediments).

This study presents the results of investigations, carried out on the Czamiawka River from December 2003 to June 2004. The results indicate the changes of physicochemical parameters of water quality. High concentration of ammonium nitrogen, COD and orthophosphates are probably caused by discharge of municipal waste-water. A drop of ammonium nitrogen, nitrite nitrogen, nitrate nitrogen concentration along the river course is probably caused by inflow of water without these components. High salinity and very high concentration of suspended solids below the "Makoszowy" coal-mine is caused by discharge of coalmine water and carbon dust from coal washer. All of the discussed parameters of water quality (except for pH-index and nitrate nitrogen) are beyond official classification. In comparison to previous analyses a slight improvement of water quality can be observed, especially in the top length. In the estuary water quality deteriorates. Although the Czarniawka River is small, it is one of the most important Kłodnica River contamination sources. Improvement of the existing situation will be possible only if firm waste-water management action will be taken, especially in the "Makoszowy" coal-mine area.

Professor Paweł Rowiński, Vice-President of the PAS and a researcher at the PAS Institute of Geophysics, explains why rivers are such a fascinating subject of study and describes the innovative approach being taken to organizing the IAHR Congress in Poland.

On “blue-green” aspects of climate change adaptation in cities.

This study includes the results of investigations carried out on the Bytomka River which were made from September 2003 to January 2004. The results emphasized the changes of physico-chemical parameters of water quality. Low concentration of dissolved oxygen and high concentration of ammonium nitrogen and COD are probably caused by the discharge of municipal waste-water. High salinity is caused by coal-mines water from the river basin area. All of the discussed parameters of water quality (except for pH-index and nitrate nitrogen) are beyond official classification. Although in the river basin area there are currently activities which protect the environment, no changes of water quality have been observed except for the salinity which is growing up all the time. Improvement of the existing situation will be possible only if firm waste-water managements action is taken.

Research concerning temporal variations of suspended sediment concentration during period of high water stages was done in the lower course of the Obra River near Międzyrzecz (Western Poland). The analysis regarding dependence of mean suspended sediment concentration and discharge allowed to determine the way of suspended sediment supply to the river bed during high water stages. It was supposed that exposures of glacial and fluvioglacial sediments in high concave banks could be an important factor influencing the amount of delivery of suspended material. Besides, normal hysteretic loops (oriented clockwise) were observed in cross-sections 4 and 5. That fact would suggest that transported material originates form the Obra River bed or its vicinity. The process of sediment accretion was observed on a fragment of drowned floodplain during high water stages. Collection of samples of freshly deposited sediment and grain size analysis allowed to illustrate the mechanism of forming floodplain sediments. It also was possible to draw near conditions of forming such sediments in the past.

Climate change, manifested by long term periods of drought to heavy rainfall, may remarkably modify river flow regimes. We hypothesize that flow prevailing in a given year determines water chemistry of the Carpathian Raba River above and below Dobczyce Reservoir (southern Poland), used for drinking purposes. Based on the mean annual river flow for years 1991‒2017, hydrologically dry (HD), hydrologically average (HA)and hydrologically wet (HW) years were distinguished. We found significant differences in the values of most studied physicochemical parameters of river water above and below the reservoir between studied hydrological years (for a period of April‒November). In HD years, the water above the dam had significantly higher temperature and values of conductivity (point pollution source, groundwater inflow), while lower ones of nutrients NO3- and P-tot (diffuse pollution) compared to those in HA and/or HW years. The best GLM models for mean monthly flows above and below the dam include 3‒5 factors among which conductivity and NO3- concentration were always present. The reservoir in different ways influences the water chemistry below the dam in HD, HA and HWyears. The impact of flow on the water quality in hydrologically varied years is discussed. The obtained results are important for appropriate management in catchment basins of mountain rivers and the protection of dam reservoirs against the eutrophication processes in changing climate and flow regime.

The Vistula’s riverbed is a treasure-trove of relics concealed by continually shifting sands and by the turbid river water. So what lies down there, hidden in the Vistula’s depths?

The objective of the study was to characterise the quality of surface waters in order to de-termine their vulnerability to pollution by nitrogen compounds from agricultural activity, as well as to specify the areas with increased exposure, where nitrogen runoff from agricultural sources has to be reduced. It was necessary to determine surface waters liable to pollution by these compounds due to the fact that agricultural production should be carried out in the way which limits and prevents water pollution by nitrogen compounds of agricultural origin. The study addressed the following is-sues: the concentration of nitrogen compounds in the surface waters of the Middle Odra Basin, and the extent of eutrophication in flowing inland waters (with nitrogen as the main nutrient). The results have been plotted in figures and gathered in tables.

Wetlands play a significant role in agricultural landscape. They are the areas of exception-ally great natural values able to regulate water cycling in river catchments. In many cases they are the basic food source for bred animals.

Large areas of wetlands (c. 4 million ha) have been drained for agricultural purposes in Poland. Nevertheless, there are still numerous natural (or close to natural) wetlands, part of which is protected in nature reserves or national parks.

Having in mind the transformation of agriculture and the need of protecting water resources and natural environment, it is necessary to regulate the principles of utilisation and management of re-claimed wetlands. Water management should be adjusted to the type of an area and to environmental requirements. Regardless of the type and intensity of agricultural use of wetlands one has to aim at limiting rapid outflow of spring thaw and rainfall waters which means the reconstruction and increas-ing of natural retention capacity of the river catchment. It is necessary to provide an appropriate num-ber of water lifting facilities and their proper exploitation in land reclamation objects.

It is as well necessary to create appropriate organizational, legal and financial conditions stimu-lating actions to improve water balance and wetland protection.

Many of already existing roads cross wetland river valleys. Also the roads nowadays planned are cutting through valuable wetlands. It is necessary to evaluate the range of their impact on the natural environment. This paper focuses only on the analysis of the road crossing impact on the groundwater level. Two options of crossing the wetlands were analyzed, building the road on embankments and in the bridge. It was assumed that the valley is filled with organic material under laid by permeable sands. Calculation results showed that building a road in the valley affects groundwater level only to the slight extend. Water conditions in the valley may be affected only during the construction of the road. Calculation results were confirmed by field observations.

It should be stressed that the object of this paper is the evaluation of water conditions. Environment might be influenced by other factors.

The Kelani River is the second largest watershed in Sri Lanka and the main water-supply intake point for the Greater Colombo. The present study focuses to identify the sources of pollutants of the meandering zone of the Kelani River, par-ticularly due to the absence of more recent information. Accordingly, a survey was conducted to obtain information on in-dustrial discharges, anthropological, and social activities within the area of 15 m from left and right banks of the river. The high contaminations (total and faecal coliform – 1100 MPN∙(100 cm3)–1; COD – 10 mg∙dm–3; BOD – 4 mg∙dm–3) of surface and groundwater are corroborated with the results obtained via the demographic and land usage statistics. Industrial pollu-tant sources and harmful anthropological practices were identified as major threats to the river basin. In this survey, agricul-ture and land degradation were identified as issues due to improper land use management. As policy recommendations based on the results of the study, it was identified that the awareness for Kelani River protection should be increased; moni-toring and evaluation of the Kelani River basin under a management plan should be implemented; and stakeholder and pri-vate partnerships contribution to the sustainability of the Kelani River basin should be established.

Monitoring of surface waters within the transboundary section of the Western Bug River showed, that during 2014–2018, a significant excess of the maximum permissible concentration (MPC) was observed for some substances for fish ponds. As a result of this, the water in the river for these substances was rated as “dirty” in terms of purity and correspond-ed to water quality class IV, namely: phosphorus was observed to exceed the MPC at the observation point Ambukіv vil-lage in 2015 (9.7 times), for manganese – an excess of the MPC at the observation point Ambukіv village in 2018 (9.7 times) and in point Zabuzhzhia village in 2014 (7.9 times), 2015 (8.0 times), 2017 (7.1 times), 2018 (8.3 times); for the total iron – the exceeding of MPC at the observation point Ambukіv village in 2016 (5.95 times) and 2017 (6.13 times); at the observation point Ustilug town in 2016 (5.23 times); in the observation point Zabuzhzhia village in 2016 (9.44 times) and 2017 (5.27 times). The assessment of the surface waters based on the determination of the pollution factor showed that during the study period their quality did not deteriorate but did not meet the norms. In general, surface waters of the river correspond to the second class of quality and are characterized as “poorly polluted” waters by the level of pollution.