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The results of evaluating the statistical characteristics of the annual runoff of the Kuban River and its main tributaries, which was retrieved taking into account the influence of economic activity, are presented. The evaluation is based on the data for 1926–2021. Natural water resources of the river, including the "trans-Kuban" rivers, amounted to 14.8 km3/year. The features of long-term fluctuations in annual runoff of the rivers, taking into account their genesis, are considered. It has been found that under conditions of the warming progressing in recent decades in the Kuban River basin, a phase of increased water content is observed on the rivers, the bulk of whose runoff is formed during the spring-summer flood. The synphase pattern of long-term changes in annual runoff of the rivers and annual total precipitation in their basins has been revealed. The results of estimating the changes in annual runoff of the Kuban River under the influence of anthropogenic factors are presented. It is shown that the greatest impact on water resources is caused by irrevocable withdrawals of water outside the basin through the Great Stavropol and Nevinnomyssk canals. [ABSTRACT FROM AUTHOR]

Purpose: to determine the hydroecological condition of the different areas of the Zaporizhzhia (Dnipro) reservoir and its tributaries (Samara River, Konoplyanka River), which are under technogenic pressure. Methodology: classical methods of determining hydrochemical indicators (pH, dissolved oxygen, carbon dioxide, permanganate oxidizability, anions and cations of organic and inorganic compounds) and microbiological parameters (total count of microorganisms and count of saprophytes) were used during the study. The content of heavy metals was determined by atomic absorption spectrophotometry. Findings: The study of the current hydroecological state of the Zaporizhzhia (Dnipro) reservoir in the summer period showed that, according to most parameters, the water quality did not exceed the MAC (maximum allowable concentration) for fish farming. The exception was the reduced oxygen dissolved concentration (by 10-25%) in almost all areas of the reservoir, and the high mineralization of water in the Samara Bay (2 MAC), due to the discharge of highly mineralized waters of the Samara River. In the long-term aspect, there is an increase in the total mineralization of the Samara River (4 MAC, which is under the influence of the discharge mine waters of the coal mining industry of Western Donbas. The analysis of the content of heavy metals in the reservoir indicated an increase in the concentration of copper - from 13 MAC in the Samara Bay to 21 MAC in the lower part of the reservoir. The Samara River was characterized by a high content of cadmium (1.5 MAC), copper (13 MAC), and nickel (2.3 MAC). Indicators of the ecological state of the Konoplyanka River had significant differences in its different areas: in the upper reaches of the river, where the economic and domestic effluents of the city of Kamianske and the tailings storage facilities for radioactive waste are located, water did not meet the MAC for oxygen content, carbon dioxide, nitrites, nitrates, mineral ions (Ca2+, Mg2+, Cl’, SO4-2), general mineralization and the count of saprophytic microorganisms; at the mouth of the river, exceeding the MAC for nitrate content and saprophytic microflora was recorded. Originality: data on the hydroecological state of the Zaporizhzhia (Dnipro) reservoir and its tributaries in the conditions of the war have been obtained. Practical value: the results of the conducted study can be used to develop a strategic program for the restoration of the ecosystem of the Dnipro reservoirs in the post-war period.

Mthatha River is the main source of water for the fast-growing population of Mthatha communities and its surrounding. Human resident settlements, livestock grazing and watering, subsistence farming and commercial activities are the main water and land use activities in the catchment. Using the environmental forensic method, this study was carried out to assess water quality in Mthatha River and its selected tributaries for different uses (drinking and domestic use) and identify potential pollution sources. Seven sampling points were purposively selected for water quality testing along Mthatha River and the tributaries. Data was collected during wet and dry seasons of the year 2021. Microbiological and physico-chemical parameters were measured in this study. Microbiological samples (i.e., Total coliform and E. coli) were analysed in the laboratory within 24 h. Physico-chemical parameters (Dissolved Oxygen, water temperature, pH, Electrical Conductivity, Turbidity, Total Dissolved Solids and Nitrate) were measured in-situ. Multivariate statistical analysis, one-way analysis of variance (ANOVA), and Pearson's correlation analysis were employed to analyse the data using SPSS version 22, Primer version 7 and MS Excel 2013.The pH, turbidity and nitrate were found to be higher during wet season than dry season. Extremely high microbiological indicators (E. coli and total coliform counts) were recorded during both seasons and exceeding the WHO and DWAF permissible limits. The study also found that agricultural activities in the upper reaches of the river and a combination of refuse dumping and sewage pollution in the mid-stream section are the main causes of changes in the water quality of the Mthatha River and its tributaries. An assessment and monitoring of the river water quality is necessary for the Mthatha community and to communicate information on water quality for sustainable watershed management practices. [ABSTRACT FROM AUTHOR]

River temperature is a critical parameter influencing aquatic ecosystems and water quality. However, it can be changed by natural (e.g., flow and depth conditions) and human factors (e.g., waste and industrial water drainage). Satellite-based monitoring offers a valuable tool for assessing river temperature on a large scale, elucidating the impacts of various factors. This study aims to analyze the spatiotemporal dynamics of surface water temperature (SWT) in the medium-sized Tisza River in response to natural and anthropogenic influences, employing Landsat satellites and in situ water temperature data. The validity of the Landsat-based SWT estimates was assessed across different channel sections with varying sizes. The longitudinal thermal profile of the Tisza was analyzed by mosaicking, monthly, four Landsat 9 images, covering the entire 962 km length of the Tisza in 2023. The impact of climate change was evaluated by analyzing SWT trends at a specific site from 1984 to 2024, utilizing 483 Landsat 4–9 images. The findings indicated elevated accuracy for Landsat-based SWT estimation (R2 = 0.94; RMSE = 3.66 °C), particularly for channel sizes covering ≥ 3 pixels. Discharge, microclimatic conditions, and channel morphology significantly influence SWT, demonstrating a general increasing trend downstream with occasional decreases during the summer months. Dams were observed to lower the SWT downstream due to cooler bottom reservoir water discharge, with more pronounced differences during the summer months (1–3 °C). Tributaries predominantly (75%) elevated the SWT in the Tisza River, albeit with varying magnitudes across different months. Over the 40-year study period, an increasing trend in SWT was discerned, with an annual rise rate of 0.0684 °C. While the thermal band of Landsat satellites proved valuable for investigating the Tisza River's thermal profile at a broad scale, finer spatial resolution bands are necessary for detecting small-scale phenomena such as thermal plumes and localized temperature variations in rivers. [ABSTRACT FROM AUTHOR]

This study documents the first record of Lindernia tamilnadensis (M.G.Prasad & Sunojkumar) in the states of Uttar Pradesh, Bihar, Jharkhand, and West Bengal. Previously, 16 species of Lindernia have been reported from different parts of India. The newly acquired specimen exhibits distinct morphological characteristics compared to previously described taxa from the Indo-Gangetic plains. A brief description, field notes, photographs, location, and distribution of the species are provided to facilitate identification. [ABSTRACT FROM AUTHOR]

The concentration of major ions ( , Cl–, , Ca2+, Mg2+, Na+, and K+) in the water of tributaries of Lake Teletskoe (Northeastern Altai) was studied in 2016–2020. Seasonal variations were found in the ion composition of the water of lake tributaries and a relationship between this composition and the biogeochemical conditions in their drainage basins was established. The waters of eastern and western tributaries, which drain shores with different geological and landscape structure, differ in both the concentrations and proportions of the major ions. It is shown that most of the examined tributaries belong to the same hydrogeochemical facies and carry water of bicarbonate-magnesium-calcium type. Characteristics of ion runoff of three lake tributaries were calculated; chemical denudation in their drainage basins was evaluated. [ABSTRACT FROM AUTHOR]

Many populations migrate between two different habitats (e.g. wintering/foraging to breeding area, mainstem–tributary, river–lake, river–ocean, river–side channel) as part of their life history. Detection technologies, such as passive integrated transponder (PIT) antennas or sonic receivers, can be placed at boundaries between habitats (e.g. near the confluence of rivers) to detect migratory movements of marked animals. Often, these detection systems have high detection probabilities and detect many individuals but are limited in their ability to make inferences about abundance because only marked individuals can be detected.Here, we introduce a mark–recapture modelling approach that uses detections from a double‐array PIT antenna system to imply movement directionality from arrays and estimate migration timing. Additionally, when combined with physical captures, the model can be used to estimate abundances for both migratory and non‐migratory groups and help quantify partial migration. We first test our approach using simulation, and results indicate our approach displayed negligible bias for total abundance (less than ±1%) and slight biases for state‐specific abundance estimates (±1%–6%).We fit our model to array detections and physical captures of three native fishes (humpback chub [Gila cypha], flannelmouth sucker [Catostomus latipinnis] and bluehead sucker [Catostomus discobolus]) in the Little Colorado River (LCR) in Grand Canyon, AZ, a system that exhibits partial migration (i.e. includes residents and migrants). Abundance estimates from our model confirm that, for all three species, migratory individuals are much more numerous than residents.There was little difference in movement timing between 2021 (a year without preceding winter/spring floods) and 2022 (a year with a small flood occurring in early April). In both years, flannelmouth sucker arrived in mid‐March whereas humpback chub and bluehead sucker arrivals occurred early‐ to mid‐April. With humpback chub and flannelmouth sucker, movement timing was influenced by body size so that large individuals were more likely to arrive early compared to smaller individuals.With more years of data, this model framework could be used to evaluate ecological questions pertaining to flow cues and movement timing or intensity, relative trends in migrants versus residents and ecological drivers of skipped spawning. [ABSTRACT FROM AUTHOR]

Due to the impact of various types of pollution on the available water resources, inland waters are facing a decrease in water quantity and the quality of surface waters is deteriorating. Tributaries of the Saigon River are an important feature of the river, Ho Chi Minh City. The tributaries selected were mainly located in Binh Chanh District. In this context, assessing the quality of surface waters is an essential, critical and challenging activity to be undertaken to protect these waters. At 31 research sites (n = 31), surface water was collected from upstream to downstream tributaries. Monitoring parameters included Temperature, pH, Electrical conductivity (EC), Total dissolved solid (TDS), Ammonium nitrogen (NH4+-N), Nitrate nitrogen (NO³ –-N), Phosphate (PO4 ³ –), Iron (Fe), Zinc (Zn) and Copper (Cu). In terms of data analysis, the results of this study will provide valuable information for the improvement of water quality in the study area. Ecological and economic zoning through the 31 research sites has been mentioned. The results of these water parameters can be specifically discussed and have comparisons with the previous studies. Finally, the results were synthesised to describe the variation in water quality values across the study area in the wet season. [ABSTRACT FROM AUTHOR]

Effective management and conservation of fishes requires understanding habitat use across multiple life stages while ensuring necessary habitats are both available and accessible. Tributary habitats may play an important role in recruitment and dispersal of fishes in anthropogenically modified rivers such as the Mississippi and Illinois Rivers of the Midwest U.S.A. Identifying source locations that contribute to recruitment of fish populations can determine the importance of connectivity within river networks and pinpoint critical habitats that sustain fish populations. In the Upper Mississippi River System (UMRS), the environments that fish use in early life stages (i.e., natal origin) can be identified using otolith trace element analysis due to stability and distinctness in water chemistry (strontium: calcium [Sr:Ca]) among water bodies that is reflected in otoliths.Here, we used trace element analysis to determine natal origin of six small‐bodied fishes including bullhead minnow (Pimephales vigilax), emerald shiner (Notropis atherinoides), gizzard shad (Dorosoma cepedianum), bluegill (Lepomis macrochirus), orangespotted sunfish (Lepomis humilis), and yellow perch (Perca flavescens) across six reaches of the UMRS (Pools 4, 8, 13, 26, the Open River of the Middle Mississippi River, and the La Grange Pool of the Illinois River). Otolith core Sr:Ca for fishes was quantified using laser ablation inductively coupled plasma mass spectrometry. Using the resulting Sr:Ca chemical signatures of otolith cores, natal origin (tributary, immigrant, or potential resident) was determined for individual fish based on family‐specific relationships between otolith and water chemistries.We found that all species originated from tributaries and other reaches (i.e., were immigrants) to varying extents, which acted as evidence for network connectivity. Specifically, tributaries contributed up to 48% of individuals at a given reach. In certain reaches, Pool 26 and the Open River reach, up to 80% of individuals in a species immigrated from another mainstem river reach. Network connectivity was also important in both upstream and downstream directions. Contributions from network connectivity varied among species: bullhead minnow used less whereas orangespotted sunfish used more network connectivity than when all species were combined. Further, the use of network connectivity varied spatially where individuals captured in Pool 8 and the La Grange Pool less often and those from Pool 26 and the Open River more often originated from network connectivity compared to the whole assemblage across reaches.These results indicate that species' life history traits probably interacted with the physical environment, which differs spatially, to yield observed recruitment source patterns. Our results show that network connectivity contributes to established assemblages of native small‐bodied fishes throughout the UMRS and underscore the role of interjurisdictional management in maintaining network connectivity to sustain fish populations. [ABSTRACT FROM AUTHOR]

The physical integrity of the Ngerengere River and its three tributaries drains within Morogoro Municipality were evaluated by assessing the variations in land-use–land cover (LULC) in the river's buffer zone, the discharge, and the contamination of river water and sediment from nutrients and heavy metals. Integrated geospatial techniques were used to classify the LULC in the river's buffer zone. In contrast, the velocity area method and monitoring data from the Wami-Ruvu Basin were used for the discharge measurements. Furthermore, atomic absorption spectrophotometry was used during the laboratory analysis to determine the level of nutrients and heavy metals in the water and river sediment across the 13 sampling locations. The LULC assessment in the river's buffer during the sampling year of 2023 showed that bare land and built-up areas dominate the river's buffer, with a coverage of 28% and 38% of the area distribution. The higher discharge across the sampling stations was in the upstream reaches at 3.73 m3/s and 2.36 m3/s at the confluences. The highest concentrations of heavy metals in the water for the dry and wet seasons were 0.09 ± 0.01, 0.25 ± 0.01, 0.03 ± 0.02, 0.73 ± 0.04, 4.07 ± 0.08, and 3.07 ± 0.04 mg/L, respectively, for Pb, Cr, Cd, Cu, Zn, and Ni. The order of magnitude of the heavy metal concentration in the sediments was Zn > Ni > Cr > Cu > Cd > Pb, while the highest NO2−, NO3−, NH3, and PO43− in the water and sediment were 2.05 ± 0.01, 0.394 ± 0.527, 0.66 ± 0.05, and 0.63 ± 0.01 mg/L, and 2.64 ± 0.03, 0.63 ± 0.01, 2.36 ± 0.01, and 48.16 ± 0.01 mg/kg, respectively, across all sampling seasons. This study highlights the significant impact of urbanization on river integrity, revealing elevated levels of heavy metal contamination in both water and sediment, the variability of discharge, and alterations in the LULC in the rivers' buffer. This study recommends the continuous monitoring of the river water quality and quantity of the urban rivers, and the overall land-use plans for conserving river ecosystems. [ABSTRACT FROM AUTHOR]

Polychlorinated biphenyls (PCBs) are persistent organic pollutants that are ubiquitous in nature. In this study, the levels of PCBs were evaluated in sediments and fish samples obtained from dredged tributaries and creeks of River Ethiope. The work also assessed the possible relationship between the parameters and risks posed by polychlorinated biphenyls via several pollution indices. The mean concentrations of P PCBs on the sediments spanned from 645 - 3,977 μg/kg (wet season) to 252 - 1,219 μg/kg (dry season) dry weight. The concentrations of PCBs in fishes were 1,688 μg/kg (wet season) and 557 μg/kg (dry season). Higher bioaccumulation factors were observed with lower molecular weight PCBs than the higher ones (9 - Hexa - PCB, 8-Tetra-PCB). The results of the ecological risk (160 ≤ Eri < 320), and human health risk (≥ 10-4 to 10-3- ≤ 10-6), showed moderately to very high contamination and also moderately to very high cancer risk for children and adults. The strong positive correlation between PCB-114 and PCB-77, PCB-81, PCB-105 (r2 = 1.00, 0.99 & 1.00, p < 0.01) and the risks assessment values which ranged from 6.10 × 10-3 to 1.47 × 10-2 for children and 6.30 × 10-4 to 1.11 × 10-3 for adults (wet season), 1.04 × 10-3 to 2.99 × 10-2 for children and 7.80 × 10-5 to 5.61 × 10-1 for adults (dry season), showed rarely to adversely high potential ecological risk, biological effect and human health risk across the environment. The data show that higher levels of PCBs were observed in sediments and fish samples when compared with available standards. Considering the ILCR, hazard index, toxic equivalent, the sediments and fish obtained from these sites would be considered risky for humans. Dredging activities are majorly responsible for the high levels of PCBs across the sites. These have contributed significantly to the environmental status of the studied area. [ABSTRACT FROM AUTHOR]

The objective of the current research was to examine the water quality of the River Ravi and the River Sutlej, with a specific focus on potentially toxic elements (PTEs). Additionally, we sought to monitor the sources of pollution in these rivers by gathering samples from the primary drains that carry industrial and municipal waste into these water bodies. Furthermore, we aimed to evaluate the impact of PTEs in surface water on groundwater quality by collecting groundwater samples from nearby populated areas. A total of 30 samples were collected from these three sources: rivers (6 samples), drains (9 samples), and groundwater (15 samples). The analysis revealed that the levels of PTEs in the samples from these three resources having a mean value: arsenic (As) 23.5 µg/L, zinc (Zn) 2.35 mg/L, manganese (Mn) 0.51 mg/L, lead (Pb) 6.63 µg/L, and chromium (Cr) 10.9 µg/L, exceeded the recommended values set by the World Health Organization (WHO). Furthermore, PTEs including (As 84%), (Zn 65%), (Mn 69%), (Pb 53%), (Cr 53%), and (Ni 27%), samples were beyond the recommended values of WHO. The results of the Principal Component Analysis indicated that surface water and groundwater exhibited total variability of 83.87% and 85.97%, respectively. This indicates that the aquifers in the study area have been contaminated due to both natural geogenic factors and anthropogenic sources. These sources include the discharge of industrial effluents, wastewater from municipal sources, mining activities, agricultural practices, weathering of rocks, and interactions between rocks and water. Spatial distribution maps clearly illustrated the widespread mobilization of PTEs throughout the study area. Furthermore, a health risk assessment was conducted to evaluate the potential adverse health effects of PTEs through the ingestion of drinking groundwater by both children and adults. Health risk assessment result show the mean carcinogenic values for As, Cr, Pb and Ni in children are calculated to be (1.88E-04), (2.61E-04), (2.16E-02), and (5.74E-05), respectively. Similarly, the mean carcinogenic values for the above mentioned PTEs in adults were recorded to be (2.39E-05), (3.32E-05), (1.19E-03), and (7.29E-06) respectively. The total hazard index values for As, Zn, Cr, Pb, Mn, Cu, and Ni in children were observed to be (9.07E + 00), (9.95E-07), (4.59E-04), (5.75E-04), (4.72E-05), (2.78E-03), and (5.27E-05) respectively. The analysis revealed that As has an adverse effect on the population of the study area as compared to other PTEs investigated in this study. [ABSTRACT FROM AUTHOR]

Piscivorous waterbirds enhance wetlands’ diversity and have been seen as bio-indicators of ecological conditions within ecosystems. In addition to their ecological contribution, to wetlands functions and ecosystem services, these birds have been reported to be affected by fishing activities and to compete with fisheries. Despite their importance along wetlands, their populations are in serious decline on a global level. This study aimed at comparing piscivorous waterbirds community composition and functional diversity between a fish protected area (FPA) and a non-fish protected area (NFPA) in two tributaries of Zambezi River in Namibia. At each site, all the waterbirds within a radius of 50 metres were enumerated and identified using binoculars and guide books. For each tributary, species diversity, taxonomic diversity, functional diversity, and community-based trait diversity indices were calculated. A total of 40 carnivorous waterbirds species belonging to 9 orders were recorded during the survey. Of these 40 species, 10 (25%) predominantly feed on fish, 6 (15%) predominantly feed on insects and 24 (60%) species predominantly feed on both fish and insects. At the FPAs site, a total of 35 species were recorded, comprising 10 (29%) species that predominantly feed on fish, 4 (11%) species that predominantly feed on insects and 21 (60%) species that feed on both fish and insects. Generally, piscivorous waterbirds species diversities were not significantly different between a FPA and a NFPA (p 0.05). However, all piscivorous waterbirds functional diversities indices calculated were significantly different between FPAs and NFPAs (p 0.05). Conservation implications: In most riparian human communities, fish is an important source of protein. The effects of uncontrolled fishing in shaping the composition, structure, and diversity of piscivorous waterbirds worldwide have been reported. If we need to balance the two, regulating fishing loadings and season will improve piscivorous waterbirds conservation and human livelihoods.

Abstract Population growth combined with the need for electrical energy resulted in the construction of hundreds of hydroelectric plants in the state of São Paulo, Brazil. The consequence of these interventions was the fragmentation of rivers, forming barriers, that hinder the mobility of migratory fish species, generating an impact on the life cycle of these species, especially about movement between breeding and feeding areas. For this reason, this article aimed to evaluate the state-of-the-art knowledge regarding dams, free stretches, and migratory species in the three main river basins of the state of São Paulo and its tributaries. Through a systematic review from 2003 to 2023, 89 articles were obtained, 48 of which were about dams, 5 which addressed fish transposition systems, and 36 portraying migratory species. In the first half, research focused more on the impacts of dams on fish fauna, while in the second half of the period studied, studies of migratory fish were dominant. Most research was conducted in the main rivers, with few in the tributaries. Finally, 16 migratory species, considered long-distance, were studied, the most studied being P. lineatus, P. maculatus, L. friderici, M. obtusidens and S. hilarri and the ones that occurred most frequently in rivers are Prochilodus lineatus, Pimelodus maculatus, Megaleporinus obtusidens and Salminus hilarii. Therefore, we recommend maintaining the natural flow regime that still exists in the main rivers and tributaries of the state of São Paulo, to maintain healthy populations of the inventoried species.

Urbanization in watersheds leads to the introduction of sources of microplastics and other pollutants in water bodies. However, the effect of urbanization on microplastic pollution and the relationship between microplastics and water quality are not well understood. We assessed the distribution of microplastics in tributaries urbanized, non-urbanized and in the receiving lagoon body of Conceição Lagoon watershed. The results show that urbanization significantly affects water quality but does not differentiate tributaries in terms of microplastic concentrations. Microplastic concentrations were lower in the receiving lagoon body compared with the tributaries, highlighting their importance in microplastic pollution in the studied lagoon. Microplastic concentration was correlated with low N:P ratios in the lagoon and associated with high levels of total phosphorus, which indicate the discharge of effluents. The correlations between microplastic concentration, water temperature, and dissolved oxygen in the lagoon were based on the temporal variations of these variables. Precipitation and wind velocity had influence on microplastic distribution in the watershed. Our findings underscore the importance of evaluating water quality parameters and meteorological variables to comprehend the microplastic distribution at small watersheds. [ABSTRACT FROM AUTHOR]

The formation history of the Irkutsk Reservoir is considered along with its effect on changes in the nearby area and water chemistry. The results of hydrochemical studies, carried out by the authors in 2022 in reservoir bays and tributaries are analyzed and compared with earlier studies. The waters of rivers flowing into the Irkutsk Reservoir were found to belong to sulfate-hydrocarbonate magnesium-calcium type. The chemistry of the waters of rivers, bays of the Irkutsk Reservoir in the key areas, where inhabited localities, cottage settlements, and garden plots are situated, was found to differ from the background chemistry and to be chloride-hydrocarbonate magnesium-calcium. The microelement composition of water in the major portion of the reservoir corresponds to the ranges of the basic concentrations of microelements at the source of the Angara River. [ABSTRACT FROM AUTHOR]

The irrigation of soil is an important measure for achieving the desired agricultural productivity, especially in regions with deficit of precipitations. The presence of sodium in the irrigation water can exert an adverse influence on the soil structure by reducing the rate at which water reaches the roots of plants. The Vakhsh river basin with more than 220 000 hectares of the irrigated land area is among the largest river basins in Tajikistan, which contains irrigation channels and a collector–drainage system with lengths of about 5000 to 6000 kilometers, respectively. The Vakhsh River merging with the Pyanj River to form the transboundary Amudarya River, which is the largest river in Central Asia, is the main river of the Republic of Tajikistan. The Vakhsh River Basin (VRB) is among the largest river basins (39 100 km2) in the highest part of Central Asia. In the VRB territory, 1213 million m3/year of the waste and collector–drainage waters are formed, of which 4 million m3/year are used for irrigation and 1209.1 million m3/year flow into natural surface water bodies. Therefore, the issue of water quality in the river basin is an urgent one. This study is aimed at analyzing the chemical composition of the Vakhsh River and its main tributaries and determining the degree of their applicability for irrigation of agricultural lands. It has been established that the Vakhsh River and its tributaries meet the requirements for irrigation water when regarding the main parameters, namely, the fractions of adsorbed, soluble, and exchangeable sodium and magnesium. It has been shown that the chemical composition of rivers is primarily formed because of weathering the rocks and washing out the skin of basins. [ABSTRACT FROM AUTHOR]

The presented work deals with the numerical modeling of intense bedload-transport processes at confluences of mountain rivers and steep tributaries. Steep tributaries are characterized by having high transport capacities which supply large amounts of sediments to the confluence zone, where due to the sudden change in slope and the local hydraulic conditions, intense deposition can occur. The objectives of this study are to understand the potential applications and limitations of 2D numerical simulations for modeling these processes. The calibration of the applied 2D numerical model (BASEMENT, Basic Simulation Environment, v2.8) is based on comparing high-density point clouds of the confluence morphology at the end of flume experimental runs with numerical results. The calibrated numerical model is then used to test different discharge ratios and to investigate depositional patterns and mechanisms. The results show that key morphological features such as the confluence fan, the bank-attached bar and the scour hole can be accurately reproduced, showing that 2D numerical simulations are a valuable tool for modeling the complex interactions between morphodynamics and hydraulics at river confluences. Additionally, it is shown that the confluence morphology of steep tributaries and mountain rivers is strongly influenced by the sediment concentration in the tributary channel and the discharge in the main channel. [ABSTRACT FROM AUTHOR]

Abstract Conservation of the Atlantic salmon Salmo salar requires to monitor the spatial distribution and abundance of juveniles at a local scale in tributaries. However, tributaries are rarely accounted for in monitoring programs despite their importance for juvenile life stages. This is mainly because inventories of young salmon populations in tributaries can be technically challenging with traditional methods, as the number of tributaries in a watershed can be important and their access limited compared to the main stem. In this study, we tested the use of environmental DNA (eDNA) to quantify the abundance of juvenile Atlantic salmon in tributaries. We successfully detected eDNA of juvenile Atlantic salmon in 19 tributaries of three main rivers of the Gaspé Peninsula (Québec, Canada) using quantitative real‐time PCR analyses. By comparing the eDNA approach with electrofishing surveys conducted in parallel to water sampling, we found that eDNA concentrations positively correlated with juvenile abundance, total biomass, and body surface area. The use of the allometrically scaled mass (ASM) instead of abundance improved the correlation. Furthermore, we demonstrated that the levels of eDNA molecules detected for juvenile Atlantic salmon were also correlated with water temperature and canopy cover measured in each tributary. Finally, we tested if eDNA concentrations measured in a tributary could be used as a reliable indicator of juvenile abundance or biomass in that tributary. We found that our models slightly better predicted juvenile biomass than juvenile abundance. The use of ASM did not improve model prediction, suggesting that further refinement would be required in the future. Our method will facilitate the implementation of conservation practices appropriate to the ecology of juvenile Atlantic salmon in tributaries.

The anatomical variations in the lower limb veins play a critical role in venous reflux surgeries. This study presents an analysis of the great saphenous vein (GSV) proximal part’s anatomical peculiarities, with 257 patients included, who were operated for venous reflux. This study highlighted a progressive increase in the GSV diameter in conjunction with the complexity of the anatomical variations, ranging from no tributaries to more than five tributaries, an anterior accessory GSV, or venous aneurysms. Statistical analysis evidenced this expansion to be significantly correlated with the variations. Additionally, the progression of the chronic venous disease (CVD) stages was notably more prevalent in the complex anatomical variations, suggesting a nuanced interplay between the GSV anatomy and CVD severity. Conclusively, our research articulates the paramount importance of recognizing GSV anatomical variations in optimizing surgical outcomes for CVD patients. These insights not only pave the way for enhanced diagnostic accuracy but also support the strategic framework within which surgical and interventional treatments are devised, advocating for personalized approaches to venous reflux surgery.

Low-order streams contribute to the abiotic and biotic character of large rivers and are renowned for harboring unique forms of aquatic flora and fauna. However, most studies on headwater streams mainly focus on the mainstems and overlook the contribution of the tributary systems. Moreover, low-order streams are generally overlooked in legislation and bioassessment programs, and consequently not protected in many countries. To contribute to the recognition of the ecological importance of low-orders streams, this study focused on determining whether river network characteristics and associated physico-chemical parameters can be used to effectively predict the variabilities in macroinvertebrate assemblage characteristics between first-order and second-order streams in the headwaters of the Nzoia River Basin, Kenya. The study quantified the structural and functional community composition, diversity, similarity, and richness of macroinvertebrate communities between the two river systems. Dissolved oxygen, coarse particulate organic matter, conductivity, stream width, depth, discharge and flow velocity were the main predictors of the diversity and distribution of macroinvertebrates in the first order and second-order streams. The first order streams recorded higher abundance of macroinvertebrates than the second-order streams. Taxa from families Ephydridae, Elmidae, Gomphidae, and genera Euthraulus, Neoperla, Orthothrichia and Prosopistoma were limited to the second-order stream sites while families Ceratopogonidae, Pisuliidae, Dytiscidae and genus Trichosetodes occurred exclusively in the first-order stream sites. Collector-filterers and collector-gatherers were the most abundant functional feeding groups (FFGs) in the two river systems. Scrapers were abundant in the second-order stream while shredders were abundant in the first order streams. The distinctness in the structural and functional composition of macroinvertebrates between the two river systems suggests that linkages among streams in a network as exemplified in the Nzoia River Basin, support and foster biodiversity.

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The hydro-geomorphological background in microplastic (MP) deposition and mobilization is often neglected, though the sampling environment is the key point in a monitoring scheme. The aim of the study was to analyze the environmental driving factors of MP transport over three years (2020–2022) along a 750 km-long section of the Tisza River, Central Europe. The mean MP content of the fresh clayey sediments was 1291 ± 618 items/kg in 2020, and then it decreased (2021: 730 ± 568 items/kg; 2022: 766 ± 437 items/kg). The upstream and downstream sections were the most polluted due to improper local sewage treatment. In 2020, 63% of the sites were hotspot (≥2000 items/kg), but their number decreased to one-third in 2021 and 2022. MP pollution is influenced by highly variable environmental factors. (1) The geomorphological setting of a site is important, as most of the hotspots are on side bars. (2) The tributaries convey MP pollution to the Tisza River. (3) The bankfull or higher flood waves effectively rearrange the MP pollution. (4) The dams and their operation influence the downstream trend of MP pollution in the reservoir. (5) Downstream of a dam, the clear-water erosion increases the proportion of the pristine sediments; thus, the MP concentration decreases. [ABSTRACT FROM AUTHOR]

Inflows from unregulated tributaries change the physical, chemical, and biotic conditions in receiving regulated rivers, impacting microbial community structure and metabolic function. Understanding how tributary inflows affect bacterial carbon production (BCP) is integral to understanding energy transfer in riverine ecosystems. To investigate the role of tributary inflows on bacterial community composition and BCP, a ~90th percentile natural flow event was sampled over 5 days along the Lachlan River and its tributaries within the Murray-Darling Basin of eastern Australia. Increased tributary inflows after rainfall corresponded with a significantly different and more diverse bacterial community in the regulated mainstem. The major contributor to this difference was an increase in relative abundance of bacterial groups with a potential metabolic preference for humic substances (Burkholderiaceae Polynucleobacter, Alcaligenaceae GKS98 freshwater group, Saccharimonadia) and a significant decrease in Spirosomaceae Pseudarcicella, known to metabolise algal exudates. Increases in orthophosphate and river discharge explained 31% of community change, suggesting a combination of resource delivery and microbial community coalescence as major drivers. BCP initially decreased significantly with tributary inflows, but the total load of carbon assimilated by bacteria increased by up to 20 times with flow due to increased water volume. The significant drivers of BCP were dissolved organic carbon, water temperature, and conductivity. Notably, BCP was not correlated with bacterial diversity or community composition. Tributary inflows were shown to alter mainstem bacterial community structure and metabolic function to take advantage of fresh terrestrial dissolved organic material, resulting in substantial changes to riverine carbon assimilation over small times scales. [ABSTRACT FROM AUTHOR]

Fish morphology is incredibly plastic and local/resident morphology can be influenced by factors including habitat, predation, resource availability, and water velocity. Through analysis of body shape using geometric morphometrics, we describe the degree of phenotypic plasticity within a generalist fish species resident to low‐order tributaries of Green Bay and Lake Michigan. We predicted that isolated populations of creek chub (Semotilus atromaculatus) would display plastic responses in body shape due to differences in selective pressures imposed by stream environments. We show that body shape of creek chub was significantly different between streams which are considered to be isolated populations, and while we expected body shape variation to remain constant between study years, we found that shape was not fixed and changed over time in the same manner among focal streams. The diversity of creek chub diet and degree of agricultural land use in the watershed were significant predictors of body morphology. The effect of resource availability and land use within the watershed demonstrates how selective pressures influence phenotypes at the population level. Our study provides insight into morphological changes of stream fish populations, which may be important in the context of changing ecosystems and novel conditions. [ABSTRACT FROM AUTHOR]

The physical integrity of the Ngerengere River and its three tributaries drains within Morogoro Municipality were evaluated by assessing the variations in land-use–land cover (LULC) in the river’s buffer zone, the discharge, and the contamination of river water and sediment from nutrients and heavy metals. Integrated geospatial techniques were used to classify the LULC in the river’s buffer zone. In contrast, the velocity area method and monitoring data from the Wami-Ruvu Basin were used for the discharge measurements. Furthermore, atomic absorption spectrophotometry was used during the laboratory analysis to determine the level of nutrients and heavy metals in the water and river sediment across the 13 sampling locations. The LULC assessment in the river’s buffer during the sampling year of 2023 showed that bare land and built-up areas dominate the river’s buffer, with a coverage of 28% and 38% of the area distribution. The higher discharge across the sampling stations was in the upstream reaches at 3.73 m3/s and 2.36 m3/s at the confluences. The highest concentrations of heavy metals in the water for the dry and wet seasons were 0.09 ± 0.01, 0.25 ± 0.01, 0.03 ± 0.02, 0.73 ± 0.04, 4.07 ± 0.08, and 3.07 ± 0.04 mg/L, respectively, for Pb, Cr, Cd, Cu, Zn, and Ni. The order of magnitude of the heavy metal concentration in the sediments was Zn > Ni > Cr > Cu > Cd > Pb, while the highest NO2−, NO3−, NH3, and PO43− in the water and sediment were 2.05 ± 0.01, 0.394 ± 0.527, 0.66 ± 0.05, and 0.63 ± 0.01 mg/L, and 2.64 ± 0.03, 0.63 ± 0.01, 2.36 ± 0.01, and 48.16 ± 0.01 mg/kg, respectively, across all sampling seasons. This study highlights the significant impact of urbanization on river integrity, revealing elevated levels of heavy metal contamination in both water and sediment, the variability of discharge, and alterations in the LULC in the rivers’ buffer. This study recommends the continuous monitoring of the river water quality and quantity of the urban rivers, and the overall land-use plans for conserving river ecosystems.

Relevance. The need to expand and deepen the understanding of the influence of solar radiation indicators on chemical characteristics of surface water, since the dependence of hydrochemical processes on periodic changes in solar activity has so far been studied extremely poorly. In addition, special attention is paid worldwide to the study of iron content in waters of rivers and lakes. Iron increased concentrations are one of the reasons for the "brownification" of surface waters in a significant part of the Northern Hemisphere. Aim. To establish a relationship between iron content and dynamics in the waters of the tributaries of Lake Teletskoe with indicators of solar activity (sunspots number, F-index). Methods. Water samples from the tributaries of Lake Teletskoe were collected into clean new polyethylene bottles in the estuaries of the rivers, from a depth of 0.5 m during the spring-summer high water and autumn low water, in 2016–2020. Content of total and dissolved Fe in the waters was determined by the ISP-MS method and by the AAS method. We used the data on solar activity indicators from the Belgian Observatory, which are freely available. Results. The total Fe content in the rivers of Lake Teletskoe basin for the period from 2016 to 2020 changes from 5 to 340 µg/l. Concentrations of dissolved iron (4 to 200 µg/l) do not exceed Russian standards, but they are often noticeably higher than the global average for river waters established abroad. The highest iron content, as well as the proportion of its soluble forms in the tributaries of Lake Teletskoe and in lake waters, was noted in 2016. It is probably due to the highest rates of solar activity. They cause certain changes in the environment – such as an increase in air temperature and water evaporation, and decrease in river flow, which accompanied by growth in concentrations of chemical elements in surface waters. Since 2016, there has been a steady decrease in dissolved iron concentration in surface natural waters of Lake Teletskoe basin, which may be a consequence of a decrease in solar radiation intensity in recent years.

Analysis of the distribution of uranium concentrations in the water of conjugated components of the Baikal ecosystem (the water of Lake Baikal and its tributaries, headwaters of the Angara River, and groundwater from the wells drilled on Olkhon Island, and in the southwestern coastal part of Lake Baikal) has been carried out. The essential differences of the maximum uranium concentrations in groundwater of Lake Baikal and its inflows and the close average and median values of uranium in the water of Lake Baikal and the Angara River source were determined. The data obtained on the uranium distribution fix the influence of geological and geochemical peculiarities of the structure of the Baikal ecosystem and its surroundings and the climatic and catastrophic (earthquakes, seismic geodynamic activation, etc.) events that take place in the region. The changes in the uranium concentration in the water of Lake Baikal in relation to the seismic process were analyzed on the example of strong earthquakes (M ≥ 5) in the Lake Baikal area. [ABSTRACT FROM AUTHOR]

The evaluation of the trend of flood stage changes in alluvial rivers downstream of dams is important for flood management. However, the flood stage associated with a given discharge generally is nonstationary in river reaches with multiple tributaries. This is not only because of the dam-induced shifting in the cross-sectional area and/or channel roughness but also because of the backwater induced by high flows from the tributaries. To determine the total trend of the flood stage and quantify the separate contributions of hydrological and geomorphic effects, the current study proposed a framework approach consisting of hydrological analysis and multiscenario numerical modeling. By this means, the trend in the flood stage could be distinguished from the stage oscillation driven by varying factors, including extreme hydrologic events. The effects of chronic changes, including channel incision and flow resistance increase, also were quantitatively separated. This framework was applied to the Chenglingji–Datong (CD) reach downstream of the Three Gorges Dam (TGD) in the Yangtze River, China. The results indicated that the effect of the roughness increase counterbalanced the effect of channel incision when the flow discharge was beyond the bankfull level. The backwater effect induced by tributary inflow was the major cause of the flood stage rise in recent years. The method presented in the current study provides a useful tool for managers and engineers to obtain better insight into the driving mechanisms of flood stage changes in river reaches that are downstream of dams. These findings indicate that the flood stage may not decline or may even occasionally increase, although the cross-sectional area was enlarged by channel incision. Special attention should be given to the flood risk situation in the study reach after the TGD began operation. [ABSTRACT FROM AUTHOR]

Eco-hydraulic analyses begin with the arrangement of tributaries. This research aimed to minimize the discharge of flood run-off downstream and map the flood inundation by spatial analysis uses DEMNAS data and mapping of flood inundation areas using ArcGIS. Analysis of return period flood points using HEC-RAS version 5.0.7. The data needed is the cross section of the river, the distance between the sections, the Manning's roughness number, the return period flood discharge and the slope of the river. The integration between topographic maps, watersheds and flood water levels can display areas that are potentially affected by inundation floods, so that the flood inundation limits and flood inundation areas can be calculated. This research examined proper eco-hydraulics design so that it could reduce discharge, identify locations prone to flooding, and describe the magnitude of the flood impact quantitatively. The results eco-hydraulic method obtained the design border width of 100 m, the condition before the existing river border arrangement was carried out, the inundation height was 0.30 – 1.13 m and after the river border arrangement the discharge could be reduced to 113.09 – 209 m3/s and the inundation height is 0 – 0.31 m. Based on the research results, it is known that border arrangement can provide benefits for flood control measures.

Catastrophic floods in the Lim basin on the territory of Montenegro were registered in November, December 2010 and January 2011. Since 1952, historical hydrological data related to the occurrence of large waters have been analyzed. In the area of the small basin of the river Lim, 2,785 people and two facilities for the water supply of citizens were affected by the floods. High waters during floods can cause damage of exceptional proportions. The floods of 2010 covered the tributaries of the Lim in the upper reaches: Ljuča, Vruja, Grnčar, Đurička rijeka, Plavska rijeka in the territory of the Plav municipality, Zlorečica, Kraštica, Trepačka rijeka in Andrijevica, Lim with tributaries through Bijelo Polje and Lim in the territory of Beran. High waters were registered in 2012 at the Grlja watercourse, the hydrological station at Grlja, and in 2016 at the hydrological stations Bijelo Polje na Lim, the hydrological station Plav and hs Dobrakovo. The floods had torrential and riverine character. After the catastrophic floods in 2010, flood protection systems were installed. Little attention is paid to the biological and biotechnical works on the arrangement of streams, so the possibility of the appearance of torrential streams increases, especially in the upper reaches of Lim, where torrential streams have been active for years, such as Martinić potok, Bjelicko, Bijelo potok, and through the municipality of Bijelo Polje the tributaries of Lim: Lješnička, Bistrička , Boljanska river, Lipnica, Orahovicki stream.

According to the water quality Index calculated in different sections of the Dniester River tributaries the water was from medium pollution to polluted state, in Botna river (Causeni town) in 1995 and 2004 being very polluted. The water in Raut river in 2015 was of average pollution, at Balti town being polluted. A detailed study was carried out for the water from Bac river, Chisinau municipality, in 2009, through the calculated ICAcc, it was demonstrated that the water entering the territory of Chisinau municipality was already polluted, reaching very polluted downstream of the sewage treatment plant from the municipality

The aim of this study was the systematization and generalization of data obtained by authors during the last decade and the comparison of these data with those obtained by other authors. Gas chromatography (GC-MS) was used for the determination of PAHs and the positive matrix factorization (PMF) model and principal component analysis (PCA) were used for source apportionment of PAHs. It was found that the total concentration of 16 priority PAHs in surface waters varied from 5 to 200 ng/L, whereas the concentration of 16 PAHs in bottom sediments varied from 50 to 700 ng/g. The 2–3-ring PAHs were dominant in water, whereas the 4–6-ring PAHs were dominant in sediments. That was due to PAHs fractionation in the soil–water system. The source apportionment results showed that the PAHs in both water and sediments mostly originated from the combustion of biomass and fossil fuels. In contrast to sediments, there was a PAH fraction in water that did not originate from a single source. The pollution of freshwater ecosystems manifested itself in the lack of correlation between values of octanol/water partitioning coefficients and sediment/water partitioning coefficients of PAHs. [ABSTRACT FROM AUTHOR]

In 2009–2018, the isotopic composition of oxygen and hydrogen in the atmospheric precipitation, groundwater and river and lake water of Lake Onega basin was studied. The weighted annual isotope composition of precipitation at Petrozavodsk was δ18O = −11.7‰ and δ2H = −84‰ and varied from −30.9 to −4.1‰ for δ18O and from −23 to −22‰ for δ2H. The isotopic composition of the water in Lake Onega was relatively uniform from −11.5 to −9.3‰ for δ18O and from −85 to −71‰ for δ2H. In the bays, the isotopic composition of the water varied more substantially than in the central part of the lake due to the river runoff during springtime flooding. In late summer, the concentrations of deuterium and oxygen-18 increased in the lake water, and figurative points on the δ2H vs. δ18O diagram shifted above the meteoric line. The absorption of the isotopically heavy summer precipitation and disequilibrium isotope fractionation during evaporation led to the enrichment of the lake water by heavy isotopes. Experiments were conducted to estimate the evaporation influence on the isotope enrichment of the residual water, and a comparison of the obtained isotope data with the experimental function showed that commonly, about 4% and up to 12% of water was lost during the spring and summer, respectively. In the water of the tributaries, the abundance of the deuterium and oxygen-18 varied in a wider scale than in the lakes, from −14.4 to −9.1‰ for δ18O and from −102 to −73‰ for δ2H. An evaporation loss of up to 35% was found for the rivers in late summer, and this value was proportional to the area of lakes and wetlands in the elementary watershed. The initial isotope composition of the water in the tributaries prior to evaporation was estimated to be δ18O ≈ −14.1‰ and δ2H ≈ −103‰ on average and crossed the approximation and meteoric lines. This estimation was close to the average composition of the groundwater, i.e., δ18O ≈ −13.4‰ and δ2H ≈ −94‰ on the Lake Onega catchment. The slightly increased isotope depletion of the calculated composition in the initial river water in comparison with the groundwater was the result of the contribution of the spring snowmelt water, which had a significant influence on the lake water balance. [ABSTRACT FROM AUTHOR]

The structure and spatial distribution of macrozoobenthos in the mouth area of the small tributaries of the Rybinsk Reservoir, the Il'd, Syobla, Lam, and Yukhot rivers, was studied in different seasons, 2007–2008 and 2010–2011. The composition of the macrozoobenthos was identified: in the Il'd River, 222 species and forms, in other studied rivers, 140. Most of the discovered species were larvae of chironomids and other amphibiotic insects. The highest species richness and diversity of macrozoobenthos was recorded in the free-flow zone, and its highest abundance was recorded in the free-flow zone and in the transition zone of the tributary of the river mouth area. A significant decrease in flow in the frontal zone of river mouths leads to a decrease in species richness (due to the loss of rheophilic fauna) and creates conditions favorable for the dominance of limnophilic species adapted to oxygen deficiency, bloodworm larvae and oligochaetes. [ABSTRACT FROM AUTHOR]

The plant communities of riparian area, or cyclically flooding zone of the water reservoir depend on the diaspores accumulated in the ground and seed banks. Dramatic changes of habitat conditions of plants require the availability a wide ecological spectrum of species in the soil seed bank, from hydrophytes to mesophytes. The seed bank of the estuary region of the Il'd' River and neighboring areas consists of 44 plant species, including 38 species found in the mouth of the tributary and 20, in the approach channel. Most of the discovered species are typical to the study region and are found either on the shore or in the immediate vicinity of the river. Coastal plants that entered water represent the dominant (54%) ecological group in the seed bank. The observed patterns are similar for most stations. The proportion of hydrophytes at the vast majority of stations is low (15%), although at some stations (in the transition zone of the receiver) it reaches 23%. No hydrophytes have been found in the seed banks of the free flow and transition zones of the tributary. The floral diversity in the estuarine area is not evenly distributed; it increases with distance from the tributary. The level of floral similarity changes in a similar way, reaching a maximum of 41% in the transition zone of the receiver. Although Betulapendula, Chenopodiumalbum, and Phalaroidesarundinacea (R-strategy species) are found in all the studied zones, most species tend to certain areas of the estuarine region. [ABSTRACT FROM AUTHOR]

The diversity of transition zones is considered, the main features of ecotones are indicated, and the degree of knowledge of the mouth areas of tributaries of reservoirs is analyzed. A review and analysis of the concept of the estuary region and approaches to zoning the estuarine regions of rivers carrying water to the seas and oceans is provided. Based on the high biological potential, the great role in the life of receiving reservoirs, significant areas and extremely scarce data, the task is set of detailed comprehensive studies of the mixing zones of river and reservoir waters, as well as areas of bordering water bodies, that is, the tributary itself and the reservoir. The principles of identifying different types of zones in the mouth areas of tributaries of lowland reservoirs based on the electrical conductivity of water are presented, and the names of the selected areas are given. [ABSTRACT FROM AUTHOR]

In order to maintain fish life, the Council Directive of 18 July 1978 on the quality of freshwater, which must be protected or improved provides that non-ionized ammonia in salmon and cyprinid waters may be in concentrations of ≤ 0,005 mg/dm3 (indicative) and ≤ 0,025 mg/dm3 (mandatory). It presents a danger for aquatic biological diversity in concentrations from 0,03 to 2,00 mg/dm3 NH3 depending on the species and age. This conditions also are specified in Chapter II (Specific substances to be introduced into surface waters, pt. 8) of the Republic of Moldova Government Decision no. 802 of October 9, 2013. The study includes evaluation of non-ionized ammonia in the water of some portions of the Dniester and Prut river tributaries, which crosses the Central Development Region of the Republic of Moldova. In the rivers Răut (upstream of Bălți town and downstream of Varvareuca village), Ciulucul Mare, Ciulucul Mic, Camenca (Gura Camencii village) the ammonia concentration in different years (1981-2019) was low, but in the Răut river water, downstream of the Orhei town at 5OC was of 0,029-0,35 mg/dm3 and at 15OC - 0,065-0,528 mg/dm3. The calculation of the NH3 content in the water from the left tributaries of the Prut river that crosses the Central Development Region of the Republic of Moldova at a temperature of 5OC and 15OC shows high values in the water of the Gârla Mare river, Medeleni and Catranâc villages (0,394-0,818 mg/dm3), river Gârla Mică, liman (0,141-0,327 mg/dm3), Delia river, Pârlița village (0,84-1,78 mg/dm3), Nârnova river, Nisporeni town and Leușeni village (0,27-0,73 mg/dm3), Lăpusna river, Voinescu village (0,277-0,65 mg/dm3). Thus, in the water of different years (1981-2019) on many portions of the Dniester and Prut rivers tributaries, which crosses the Central Development Region of the Republic of Moldova, the concentration of ammonium (NH3 + NH4+) was high, and depending on the pH and temperature the calculated non-ionized ammonia content exceeded the value of 0,025 mg/dm3.

The hydro-geomorphological background in microplastic (MP) deposition and mobilization is often neglected, though the sampling environment is the key point in a monitoring scheme. The aim of the study was to analyze the environmental driving factors of MP transport over three years (2020–2022) along a 750 km-long section of the Tisza River, Central Europe. The mean MP content of the fresh clayey sediments was 1291 ± 618 items/kg in 2020, and then it decreased (2021: 730 ± 568 items/kg; 2022: 766 ± 437 items/kg). The upstream and downstream sections were the most polluted due to improper local sewage treatment. In 2020, 63% of the sites were hotspot (≥2000 items/kg), but their number decreased to one-third in 2021 and 2022. MP pollution is influenced by highly variable environmental factors. (1) The geomorphological setting of a site is important, as most of the hotspots are on side bars. (2) The tributaries convey MP pollution to the Tisza River. (3) The bankfull or higher flood waves effectively rearrange the MP pollution. (4) The dams and their operation influence the downstream trend of MP pollution in the reservoir. (5) Downstream of a dam, the clear-water erosion increases the proportion of the pristine sediments; thus, the MP concentration decreases.

The present work aims to assess the chemical and bacteriological quality of the two Ghiss-Nekôr tributaries of Al-Hoceima Bay. A set of field data collected, either from direct analysis or from satellite data, was used to conduct this study. We relied on GIS tools for data processing and analysis. The nutrient analysis indicates normal surface water quality, with nitrogen and phosphorus concentrations typical of less polluted waters. These nutrients originate from continental inputs due to runoff. Nitrates are the most common mineral nitrogen species, resulting from the leaching of nitrate-based fertilizers from agricultural and domestic sources. Bacterial analysis reveals water contamination by total coliforms (TC), Escherichia coli (EC), and intestinal enterococci (IE). Hinterland inputs from the two rivers are the primary source of liquid and solid pollutants in Al-Hoceima Bay. They are influenced by climatic and anthropogenic factors such as hydraulic development, agriculture and urbanization.

The relevance of the research is caused by the necessity to expand and deepen knowledge about the formation and functioning of large freshwater objects, the chemical composition of which is closely related to the peculiarities of biogeochemical processes and soil cover of the catchment, with type of the anthropogenic environmental impact of catchment basins. However, the mechanisms of these interactions in the mountainous territories have not been fully studied yet. The main aim of the research is to establish the relationship between the content of the major components in the tributaries waters of Lake Teletskoe and the features of their chemical denudation with the biogeochemical situation on the catchments. Methods. Water samples from the tributaries of Lake Teletskoe were collected in clean polyethylene dishes in the estuary of the rivers, during the spring-summer high water and autumn low water. Determination of the ionic composition of surface waters (HCO3–, Cl–, SO42–, Ca2+, Mg2+ Na+ and K+) was carried out according to standard methods, with titrimetric or spectrophotometric completion. Na+ and K+ in 2018 and 2019 were determined by atomic emission spectrometry on the IRIS Advantage Thermo Jarrell Ash Corp. instrument. (1999). Fe content in waters and water extracts from soils was determined by atomic absorption spectrometry using electrothermal atomization on the SOLAAR M-6 device. Results. It is established that the waters of the Lake Teletskoe tributaries are characterized by a low total mineralization (TDS), from 18 to 159 mg/L. It is shown that the seasonal dynamics of the major ions is determined by the biogeochemical processes in the catchment. It is revealed that the waters of the eastern and western tributaries, draining different geological and landscape structures, as well as the degree of recreational load of the coast, differ both in content and in the ratio of the major ions. Thus, Cl– and SO42–, K+ and Na+ make a greater contribution to the ionic composition of the waters of the eastern tributaries originating on the Korbu granite ridge, whereas in the waters of the western tributaries, draining sedimentary deposits for the most part, bicarbonates and calcium dominate. The influence of biogeochemical conditions of catchment on the content and ratio of iron in water and water extraction of soils is shown. It is revealed that most of the tributaries carry bicarbonate-magnesium-calcium type waters. The indicators of ion runoff of three tributaries of the lake of different sizes are calculated, chemical denudation in their catchment basins is estimated. In one year, 364 thousand tons of soluble salts enter the lake with the waters of the largest tributary – the Chulyshman River. 21 tons of salts are removed from 1 km2 of the Chulyshman River catchment (this is less than from the catchments of smaller tributaries), of which 12,8 tons are hydrocarbonates, 1,4 tons are chlorides, 1,6 tons are sulfates, 4,5 tons are calcium, 0,4 tons are magnesium.

The mouth areas of large rivers can serve as a good model of heterogeneity sites with a pronounced trophic gradient to assess the impact of the degree of eutrophication on different plankton communities. The aim of this research was to identify the possible response of the diversity indicators of phyto- and zooplankton communities to trophic gradients in the mouth area of two large tributaries of the reservoir, formed in the Middle Volga River (Russia). Both linear regression models and canonical correlation analysis (CCA) were used to assess the role of abiotic and biotic predictors in the structural organization of plankton communities and to assess the changes in the parameters of the species plankton community structure in the trophic gradient. It was found that the species diversity (Adjusted R2 = 0.116) and evenness (Adjusted R2 = 0.114) of phytoplankton significantly decreased with an increase in the degree of eutrophication, while the species diversity (Adjusted R2 = 0.059) and evenness (Adjusted R2 = 0.073) of zooplankton increased. According to the CCA models, electrical conductivity (EC) explained the largest proportion of the observed dispersion. The Trophic State Index (TSI) explained 3.0% of the total variance in the phytoplankton community species structure and 7.8% in the zooplankton one. The variation in phyto- and zooplankton dominant complexes generally corresponded to the well-known patterns of plankton species succession in the gradient of trophic conditions and can be considered as a classic manifestation of the cascade effect in the food chains of freshwater plankton communities. Our results highlight the necessity of studying the mouth river areas, as well as applying an integrated approach to investigating the response of plankton communities to eutrophication processes of continental water bodies. [ABSTRACT FROM AUTHOR]

Significant changes have been observed in the ecosystem of Lake Baikal in recent decades: there is a mass death of sponges and the development of algae atypical for the lake. In this regard, the study of small tributaries of Lake Baikal flowing in the areas of coastal settlements is of particular relevance. This article presents the results of a hydrochemical study of lake tributaries: the Krestovka River, the Kamenushka Stream, and the Malaya (M.) and Bol'shaya (B.) Cheremshanka streams flowing in the village of Listvyanka (one of the largest tourist areas of the lake). Interannual changes in the content of organic matter and biogenic elements and in mineralization are considered. The hydrochemical composition of tributaries in the modern period is compared with the results of a study from the 1950s. Changes in the relative composition of waters of the tributaries in 2015–2021 are shown. Factors of the formation of the chemical composition of the studied rivers are suggested. The impact of the anthropogenic factor on the formation of waters of the Kamenushka, M. Cheremshanka, and B. Cheremshanka streams is pointed out. [ABSTRACT FROM AUTHOR]

Reservoir cascades have cumulative effects on fish assemblages that can be less pronounced with the presence of incoming free-flowing tributaries. However, it is still poorly understood how the effects of cascade reservoirs on fish communities are driven. This study aimed to assess the fish assemblage distribution along two long free-flowing rivers that enter the first two reservoirs in cascade within the upper Grande River basin. Fishes were collected bi-monthly throughout 1 year along this cascade and were evaluated by composition and richness of native and non-native species. The transitional areas between the rivers and the first reservoir presented the highest richness. An increase of non-native species was observed from the uppermost (Rivers) to the downmost (lower reservoir) region. Although the seasonality did not influence fish composition in the Camargos-Itutinga cascade system, discharge-related variables (water level, transparency, and temperature), together with the position along the gradient, were the main drivers of the variation on fish assemblage's structure. The results reinforce the role of cascade systems in the increase of non-native species, as well as the importance of free-flowing rivers in structuring the fish fauna in such conditions. [ABSTRACT FROM AUTHOR]

Emerging aquatic insects constitute one of the main biological flows connecting aquatic and terrestrial ecosystems. In a landscape, there are many sources of emergence, which vary in space and time. Thus, they must be clearly defined when studying the inland dispersal of aquatic insects. In this study, we defined five types of hydrographic networks (including or not including ponds and ditches) on the basis of cartographic data of varying degrees of detail (from OpenStreetMap to field map) in order to explain the abundance of aquatic insects. We sampled Ephemeroptera, Plecoptera, Trichoptera, and Megaloptera (ETPM) with 64 sticky traps homogeneously covering a 75 ha agricultural landscape. The abundance of aquatic insects is logically better explained by the hydrographic networks recorded directly in the field than by the reference network, which is incomplete (OpenStreetMap). The results show that, depending on the sampling period, not all water bodies in the landscape are necessarily sources of emergence. To our knowledge, the issue of defining the sources of emerging aquatic insects has never been raised. Based on a practical example, this short note shows that, by refining the hydrographic network to better match the sources of emergence, the explanatory power of inland aquatic insect abundance can be greatly improved. [ABSTRACT FROM AUTHOR]