The study area of the Nida valley was examined to investigate variations in groundwater and surface water levels, as well as the interaction between them. In the valley, there were three branches. The two actives were the Nida River itself and the Smuga Umianowicka branch while the Stara Nida branch was dry during the measurement session. Over a 12-month period from June 2021 to June 2022, 7 monitoring points were equipped with piezometers, comprising 5 groundwater points and 2 surface water points. The monitoring frequency was set to 30 minutes. The results of this research indicate that there are significant differences in the water level at the same observed point at different times. This study demonstrates seasonal changes in both surface water and groundwater levels with higher levels in autumn and winter and lower levels in spring and summer, which are closely tied to the changes in meteorological conditions during the research period, such as precipitation and air temperature. The study results also indicate that during summer and winter at the Nida River and its riparian area, losing stream is the primary process occurring in the studied reach. Conversely, during autumn and spring, the main process is gaining stream. At the human-maintained Smuga Umianowicka branch and in its riparian area, losing stream is the main process during summer and autumn, and gaining stream is the main process during spring. During winter, losing stream and gaining stream processes can occur simultaneously, and neither process takes place mainly.

The investigation of Nida Valley water aimed to assess fluctuations in physicochemical properties. In this study, environmental monitoring method was utilized to evaluate the changes in physicochemical properties of water. Over a 24-month period, from June 2021 to May 2023, a total of 228 water samples were collected from 10 sampling sites, with a monthly sampling frequency. Statistical analyses were utilized including the Shapiro–Wilk test (α = 0.05), Kruskal–Wallis test and Wilcoxon (Mann–Whitney) rank sum test (α = 0.05), Pearson correlation analysis (α = 0.001) and principal component analysis (PCA). Statistical analyses revealed significant differences between months in GW samples for for temperature, dissolved oxygen, pH, total nitrogen, total phosphorus, chloride, manganese, and zinc in GW samples and for T and DO in SW samples. Pearson correlation coefficient analysis (α = 0.001) identified strong positive correlations within the SW dataset. Similarly, significant positive correlations were observed among the GW dataset. Noteworthy positive correlations were also detected between the GW and SW datasets. Principal component analysis (PCA) revealed a substantial dissimilarity between GW2 samples compared to others, characterized by elevated manganese, iron, and Sulfate content. Two distinct groups emerged: Group 1 included samples at GW1, GW2, GW3, GW5, and SW2, while Group 2 comprised all other samples. This study demonstrated the stability in the physicochemical properties of SW and underscore a discernible correlation between the hydrochemical compositions of both SW and GW in the riparian area. Outstanding characteristics in hydrochemical component of sample waters have been indicated.

Stara Nida represents one of the three hydrological channels traversing the Nadnidzianski Landscape Park, a locale characterized by ecological diversity within the Nida valley, Poland. Historically rendered inactive due to flow regulation, this specific river branch underwent restoration in February 2023 as a pivotal component of the "Restoration of the Inland Delta of the Nida River" project. The revitalization of Stara Nida has precipitated beneficial ecological metamorphoses within the landscape. To evaluate the impact of the restoration of the Stara Nida branch on the physicochemical characteristics of water in the landscape, systematic sampling of regional SW and GW was conducted. The sampling duration covered a 12 -month period, segmented into two phases: the first six months leading up to the restoration (from February 2022 to July 2022) and the subsequent six months following the restoration of the Stara Nida branch (from February 2023 to July 2023). A total of 114 water samples were collected from 10 distinct sampling locations. In -situ measurements of key indicators, including temperature (T), electrical conductivity (EC), dissolved oxygen (DO), pH, and total dissolved solids (TDS), were performed using handheld devices. Concurrently, laboratory analyses were carried out for total nitrogen (TN), total phosphorus (TP), chloride (Cl-), sulfate (SO42-), manganese (Mn2+), iron (Fe2+,3+), zinc (Zn2+), cadmium (Cd2+), lead (Pb2+), copper (Cu2+), and chemical oxygen demand (COD). Statistical analyses encompassed the Shapiro -Wilk test (alpha = 0.05) and the Wilcoxon (Mann -Whitney) rank sum test (alpha = 0.05) to discern significant disparities in physicochemical indicators at sampling points pre- and post -restoration of the Stara Nida branch. Additionally, Pearson correlation analysis (alpha = 0.001) was employed to evaluate overarching changes at the sampling points attributable to the impact of the Stara Nida branch restoration.

The groundwater of the Nida valley was investigated to assess the quality of water source and monthly variations of the physicochemical parameters. A total of 70 water samples were collected from 7 sampling sites during a 10 months period from June 2021 to March 2022. Sampling frequency was once per month. The parameters such as temperature ( T), electrical conductivity ( EC), dissolved oxygen (DO), pH, total dissolved solids (TDS) were measured in-situ by using handheld device. Meanwhile, total nitrogen (TN), total phosphorus (TP), chloride (Cl –), sulphate (SO42–), manganese (Mn), iron (Fe), zinc (Zn), cadmium (Cd), lead (Pb), copper (Cu), chemical oxygen demand (COD) were analysed in the laboratory. According to the classification of Ministry of Marine Economy and Inland Navigation in Poland (2019), some investigated parameters are classified as unsatisfactory quality waters (class 4) and poor-quality waters (class 5) for a few specific months. Such as, TP concentrations obtained in June and January are classified as class 4, SO 4 2– concentrations corresponded to classes 4 and 5 in June, July and August, and Mn concentrations (except in January) are settled in class 5. The high values of Fe in November are arranged in class 5 and in June, July to September and March are classified in class 4. Statistical methods were used as: Shapiro–Wilk test (α = 0.05), ANOVA test and post-hoc Tukey test (α = 0.05), Kruskal–Wallis test and Wilcoxon (Mann–Whitney) rank sum test (α = 0.05) estimated the significant differences in sampling months. Pearson correlation analysis (α = 0.01 and 0.05), principal component analysis (PCA) and cluster analysis showed correlation between the parameters and sampling months.

Aim of the study River channels are dynamic structures in which fluvial processes leading to equilibrium state between energy of flowing water and the stability of the bed material. The changes of river morphology is difficult to capture using the monitoring tools, however, physical or numerical modeling can be used instead to reflect these natural processes. Objective of the study is to analyze the variability of hydraulic parameters and their impact on morphological changes using numerical modeling of a regulated section of the Nida River. Material and methods On the basis of field measurements, numerical model of the river was built. In this section, the channel has been strengthened, which enables the process of its restoration. Numerical modeling was carried out for a range of flows from low to an overbank one. Bankfull discharge was determined using the Riley method. Calculations based of modeled parameters made it possible to analyze their impact on the bed dynamics. Results and conclusions The numerical modeling resutls (average velocity, shear stresses, and water depth) was used to calculate shear velocity, Reynolds Number, Grain Reynolds Number and settling velocity. The lack of clear trends of changes in individual parameters with increasing flows proves the existence of irregular connections between flowing water and riverbed. Changing discharge in the river affects not only the intensity of fluvial processes, but also their location. The bottom morphology created during low flows is completely changed at the passage of high water, as indicated by measurements and simulations of the examined section of the Nida River.

The channels of multi-threaded (braided) rivers occur commonly in areas that fulfill certain conditions such as substantial influx of bed material and gradients large enough to create significant energy of flowing water. Natural conditions favoring the formation of multithreaded channels are present in the Carpathians in Poland in Podhale – a large basin located in the piedmont area of the high-mountain Tatra massif. The area had experienced glaciation in the Pleistocene. Yet the 20th century – and especially its second half – was a period of rapid and irreversible elimination of braided channels across the region. The Białka is considered to be the last braided river in the Carpathians in Poland. Many parameters like: structure (morphologic reach sequence), degree of braiding (BI index, W/D) and also a number of hydrodynamic ones (unit stream power, critical stress, shear stress, others) were investigated in order to assess a current stage of development of the Białka river channel. The Białka river channel appears to be a complex system with a differentiated structure. Its channel system is a mosaic of different types described by the following sequence: straight-sinuous-braided. It represents an intermediate type that is somewhere between a single- and a multi-threaded channel. Future evolution of the Białka river channel appears to include further degradation and transformation into a poorer channel ecosystem.

The Nida valley study area underwent examination to investigate the hydrochemical components and the correlation between groundwater (GW) and surface water (SW). Over a 12-month period from November 2021 to October 2022, 9 monitoring points were established, consisting of 7 GW points and 2 SW points, with a monitoring frequency of once per month. The research findings indicate that the hydrochemical components and direction of GW flow in the study area can be classified into 3 distinct regions. The chemical composition is complex in areas near the Nida River, stable in the region near the Smuga Umianowicka branch, and different in other areas. It was observed that the SW in the Nida River and Smuga Umianowicka branch exhibits a relatively uncomplicated chemical composition due to minimal human impact in the natural area. However, dissimilarities between them were also identified and explained by the flow regulation of the dam built on the branch within the study area. The application of the Shapiro-Wilk test (α = 0.05) and Kruskal-Wallis test (α = 0.05) revealed statistically significant differences among the recorded hydrochemical component values throughout the measurement period. Furthermore, Pearson’s correlation coefficient analysis (α = 0.001) indicated correlations between the hydrochemical components of SW and GW in the riparian area and strong correlations among GW samples. Principal Component Analysis (PCA) identified significant dissimilarity and similarity between GW and SW samples based on their characteristics.

Trapezoidal-shaped hydrographs are typical of anthropized rivers, as this form is generally associated with the release of water from hydropower dams. To investigate how such unnatural waves can affect bedload rate, preliminary flume experiments were performed in Krakow, Poland, looking at bedload transport rate, bed shear stress and bed morphology. In addition, close-range bed surface photogrammetry was used to investigate bed changes due to the passage of the flood wave. Three scenarios, having the same water volume but different wave magnitudes, were tested. The lowest wave showed almost no sediment transport and no visible changes in bed morphology, while higher waves changed the bed morphology, creating erosion and accumulation zones. The highest wave was characterized by an 8-shaped hysteresis of the bedload rate with a peak during the wave maximum. The lag time between the maximum bedload rate and the wave plateau was longer than expected due to zero-slope conditions.

The objective of this study is to present the approach to assess needs of land consolidation to prepare rural areas for proper water resource management. The study presented links of water management with land consolidation, which is a new approach in rural development planning in Central Europe. The results of this research are presented in the form of a needs assessment matrix for water retention. The matrix includes the main groups of parameters that are related to water resource management systems and rural development planning, which are classified into three groups: (1) water resources and retention, (2) technical systems and water management measures, and (3) information about land space distribution in rural areas. A verification of the proposed matrix was carried out for two sites that differ in terms of factors influencing the retention size; one is located in southern Poland in Lower Silesia—in the village of Mokrzeszów—and the other is located in Strzelce Wielkie—a village located in Lesser Poland. Both sites were evaluated using different needs assessment methods in terms of retention. The main factors influencing a reduced retention potential are related to the insufficient retention capacity of river channels and valleys and the inadequate maintenance of melioration systems. In Strzelce Wielkie, the land consolidation favours longer catchment response on rainfall, which is an advantage to mitigating drought and flood problems. The developed matrix can be applied for an assessment of the retention potential of rural areas based on the relatively accessible data. The method is universal and can be used in different regions. The approach presents practical tools dedicated to authorities to deciding on land consolidation in regards to water resources management; it aims at resolving agricultural land use conflicts and sustainably using space in order to manage water domains.

Aim of the study: This study focuses on assessing the efficiency of the anaerobic digester combined with biological pond to provide overview data and can be used as a reference for similar studies in Nghe An province. Material and methods: Wastewater properties at 3 stages of livestock wastewater treatment process (input, after digester, after biological pond) in Nam Anh were investigated. A total of 81 samples were collected across 9 locations between March and May 2020. Shapiro-Wilk test (α = 0.05), Kruskal-Wallis test and Dunn test (α = 0.05) was preformed to estimate the significance differences. Cluster analysis was utilized to compare the parameters between the sampling locations and to classify the locations. Results and conclusions: The results showed that all parameters exceeded the allowable limit many times specified by QCVN 40:2011/BTNMT and TCN 678 – 2006. The wastewater after being treated by anaerobic digester was significantly reduced. The treatment efficiency for BOD5 was 66-73%, COD was 74-80%, SS reached 78-84%, reaching 10-27% for TN, 7-25% for TP and coliform ranged from 28.2-85.3%. Wastewater after being treated through the digester combined with the biological pond had a very high treatment efficiency: 95 - 97% for BOD5, 96- 97% with COD, SS was up to 96-97%, 45 - 57% with TN, 35 - 70% with TP and coliforms reached 77.4 - 98.4%. The treatment efficiency had a linear correlation between object locations. Applying anaerobic digestion in combination with biological pond has proven to be a highly effective solution, and should be prioritized in the treatment of livestock wastewater.

Flow regime and its variability play a fundamental role in preserving rivers' ecosystems. Effects of flow predictability modeling on macroinvertebrate community structure parameters and taxonomic composition were investigated. The main aim of the present work was to apply flow predictability as an indicator of river ecological health and to investigate the relationship between the flow predictability index and macroinvertebrate assemblages variation. Due to the high spatial variability in the abiotic and biotic characteristics of rivers, the classification and regression trees algorithm in respect to Polish Biological Monitoring Working Party (BMWP_PL) index on regional scale was done. The study was conducted in 30 catchments representing various rivers (from 0 m a.s.l. at the Baltic Sea, up to 2500 m a.s.l. in the Tatra Mountains) of Central Europe. Principal component analysis of macroinvertebrate habitat metrics indicated the presence of two groups of habitat characteristics. One of them is related to the quantitative characteristics of the regime, whereas is the second with the seasonality-predictability of the regime. Redundancy analysis showed that predictability of the hydrological regime was the most influential variables on macroinvertebrate community parameters. Generalized linear modeling showed that predictability (positively) and watershed area (negatively) influence on BMWP_PL index referred to the ecological statement of the river. Based on the main components analysis and CART algorithm in terms of the BMWP_PL index, analyzed catchments were divided into five groups according to predictability, high pulse durations, and catchments area. The predictability index is proposed as a good method for estimating the impact of human pressure on river biota without performing an extensive hydrobiological survey.

Flooding events in rivers are usually causing an increment in sediment transport.To investigate the relationships between bedload, bed shear stress and wave characteristics, laboratory experiments were performed in a 12-m-long flume at the University of Agriculture in Kraków, Poland.Three sets of experiments were conducted, imposing singular trapezoidal flood waves as forcing terms.The maximal wave height differed between runs, but the water volume and bed slope stayed the same.The bed was covered with mixed gravel, and the sediment was weighted using a trap at the end of the flume.The water level was measured at 5 points along the flume, while the velocity was measured in the middle of the flume by Acoustic Doppler Velocimeter at a point 7 cm above the bed.Preliminary results show that unsteadiness of flow induces the variation of bedload transport during the wave passage and that the total yield of sediment is positively correlated with the wave magnitude.

In this study, Digital Surface Model (DSM) was created to investigate to what extent unsteady flow affects gravel bed surface in laboratory conditions.Bed elevation was measured before and after the passage of unsteady flow using a Digital Close Range Photogrammetry (DCRP) technique and the processing of photographic data was performed using PhotoScan software.From these preliminary outcomes, it can be concluded that the DCRP technique can be considered as a complementary method to track the changes of gravel beds at the laboratory scale.

The economic use of rivers in many cases has led to the degradation of their beds, the interruption of ecological continuity, and its defragmentation. In Poland, the effect of restoration activities in the mountain river bed has rarely been analysed. The article presents an analysis of hydraulic conditions and habitat structure, as well as a hydromorphological assessment of the river in selected sections of the Wisloka River after completion of activities improving fish habitats. On a section of the Wisloka River, about 30 km long (from the weir in Mokrzec to Pustkow), ten sections were selected, which were subjected to restoration activities. These activities included spatial differentiation of water flow conditions in the channel to improve the habitat conditions that were obtained by (i) laying boulder clusters, (ii) depositing a bedload in the river bed, and (iii) forcing a change of the horizontal river system through controlled lateral erosion of the banks. As part of the restoration activities, the diversity of habitat types on the sections examined has significantly increased, which, in the future, should lead to an increase in the diversity of benthic fauna and macro-invertebrates.

Scientists have been researching processes leading to the formation of sand islands, but the process of their shaping when spate passes has not been accurately identified. Field measurements and numerical modelling of the Vistula river have been performed along a 1900 m section in which a sandy island with a nesting area for two species of tern exists. Numerical modelling covered a section with an island connected to the right bank of the river in 2017. As a result of observing changes in water levels and flows, two waves were selected and simplified to a uni-modal shape and run in the CCHE2D model. The following data were analysed: (i) survey measurements, discharge, and the flow velocity using an Acoustic Doppler Current Profiler; (ii) bars, islands, and water surface; (iii) the granulometric composition of bed material; and (iv) resources of the Head Office of Geodesy and Cartography in Poland (GUGiK). The purpose of the project is to determine limit discharges and related hydraulic parameters responsible for the growth or disappearance of a sand island. The limit discharge of the nesting is the moment when the whole island is submerged. The 2D modelling carried out provided data supporting the thesis that exceeding the conditions of bed material movement does not always lead to activating erosion processes. With the right load of material transported in the river bed, the transport capacity of the stream may be exhausted and, as a result, the bottom will not be eroded.

Although eutrophication of freshwaters is a natural process, the human impact often leads to inland waters becoming overloaded with nutrients, impoverishing many valuable and vanishing habitats, such as floodplain lakes. These changes need to be reversed if the occurrence of endangered aquatic species is to be restored. In this paper we analyse the impact of a change in the water regime of a naturally eutrophic floodplain lake, which harbours a large diversity of Unionidae (large freshwater mussels), a globally threatened taxonomic group that provides important ecosystem functions and services. We found that a slight increase in the discharge from this waterbody, following the construction of an additional outflow pipe, positively influenced recruitment in three of the five mussel species inhabiting the lake. We also found that, after the construction of this additional outflow, the niches of juveniles of Anodonta cygnea and Unio spp. changed, revealing differences in their hydrological requirements. Our results suggest that, as in lotic habitats, complex hydraulic parameters are highly significant to unionid mussels in lentic conditions.

Two sets of triangular hydrographs were generated in a 12-m-long laboratory flume for two sets of initial bed conditions: intact and water-worked gravel bed. Flowrate ranging from 0.0013 m 3 s -1 to 0.0456 m 3 s -1 , water level ranging from 0.02 m to 0.11 m, and cumulative mass of transported sediment ranging from 4.5 kg to 14.2 kg were measured. Then, bedload transport rate, water surface slope, bed shear stress, and stream power were evaluated. The results indicated the impact of initial bed conditions and flow unsteadiness on bedload transport rate and total sediment yield. Difference in ratio between the amount of supplied sediment and total sediment yield for tests with different initial conditions was observed. Bedload rate, bed shear stress, and stream power demonstrated clock-wise hysteretic relation with flowrate. The study revealed practical aspects of experimental design, performance, and data analysis. Water surface slope evaluation based on spatial water depth data was discussed. It was shown that for certain conditions stream power was more adequate for the analysis of sediment transport dynamics than the bed shear stress. The relations between bedload transport dynamics, and flow and sediment parameters obtained by dimensional and multiple regression analysis were presented.