River Flow Research Articles

Evaluation of the Water Quality and Distribution of Heavy Metals in the Gomti River Flowing Through the Urban Region of Lucknow, India

Evaluation of the Water Quality and Distribution of Heavy Metals in the Gomti River Flowing Through the Urban Region of Lucknow, India

Regulation of the Ural River Flow under Current and Projected Climate Conditions

Regulation of the Ural River Flow under Current and Projected Climate Conditions

A safe operating space for the major rivers in the Bangladesh Delta

Abstract The contributions of water to all Sustainable Development Goals (SDGs) are critical to achieving SDGs in the context of climate change. This poses a major challenge as nearly 40% of the global population lives under water scarcity, including areas such as Bangladesh, which is one of the largest, most populous and climate-vulnerable deltas (Ganges–Brahmaputra–Meghna: GBM) in the world. Here, we aim (first attempt) to analyse the historical dynamics (spatial and temporal) of river flows in 10 major rivers and provide policy implications using a safe operating space (SOS) concept for the Bangladesh delta. In general, the space just before the unsustainable state is defined as an SOS, within which humanity can safely thrive and beyond which is dangerous to humanity. Time series analysis highlights that all seasonal river flow shows a decreasing trend in the last three decades except in the winter season. The hydrological alteration using range of variability approach confirms that the majority of the river flow has been altered high to severely including three major rivers (Ganges, Jamuna, and Old Brahmaputra) in the Bangladesh delta. Our findings show that four out of ten rivers (Ganges (dry season), Gorai, Halda and Old Brahmaputra) exceeded the SOS, with the rest of the six rivers given cautious status considering the hydrological alteration (moderate to severe) in the Bangladesh delta. Our assessment provides scientific evidence to inform science and policy related to transboundary water disputes and achieving SDGs in Bangladesh and South Asia.

Fifty years marshland changes in a large floodplain lake: Natural driving or human impact?

Study region: Poyang Lake, the largest freshwater floodplain lake in China. Study focus: Marshlands in a floodplain, as the typical natural wetland offering vital habitats for various organisms, are sensitive to environmental changes. The spatiotemporal changes of marshlands were investigated and their driving forces from both natural factors and human activities were discussed. The remote sensing image data from 1973 to 2022 was adopted to explore the long-term changes of marshlands exposed in dry season. New hydrological insights for the region: Over the past fifty years, the total area of marshlands in Poyang Lake is around 2540–2718 km2 and has undergone substantial changes. It follows the bell-shaped curve pattern with continuous rise since 1970s and reach the maximum at the end of 20 century and then fluctuating decline. Different evolutionary patterns were identified in different lake regions owing to the combination of human activities and natural processes. The expanding marshlands mainly concentrate in the central lake, while the significant losses of marshlands are observed in the northern lake（By sand mining and dyke constructions）. In the southern lake, sediment input from inflow rivers deposited naturally in the river mouth elevated the lake bed and lead to delta expansion（A 3.1 km expansion has been observed）. The complex geomorphological processes and fishery activities also create the dish-shaped internal sub-lakes in marshlands.

Correlation between phytoplankton dynamics and hydrometeorological factors in the Three Gorges reservoir area tributary

ABSTRACT Phytoplankton blooms in reservoir areas’ rivers are a research problem of wide interest. To assess the influence of hydrometeorological factors on the occurrence and development of phytoplankton blooms in the Xiangxi River, a major tributary of the Three Gorges Reservoir. We employed the generalized additive model (GAM) and random forest importance analysis to evaluate the impact of hydrometeorological factors on phytoplankton dynamics. The findings revealed that river flow in the Xiangxi River is the most crucial factor affecting phytoplankton, with a significant decrease in phytoplankton observed when the flow exceeds 100 m3/s. At the Xiakou station within the perennial backwater area, phytoplankton exhibited correlations with river flow, temperature, solar radiation, and wind speed, with decreasing levels of importance. At the Pingyikou station and the Zhaojun station within the dynamic backwater area, phytoplankton was correlated with river flow, solar radiation, and precipitation. Furthermore, an increase in wind speed at the Xiakou station was significantly positively correlated with an increase in phytoplankton, suggesting that wind speed plays a promoting role in phytoplankton aggregation in the perennial backwater area. These results underscore the significance of hydrometeorological factors as key determinants in assessing the occurrence and development of phytoplankton blooms. This research provides valuable insights for phytoplankton blooms prediction and warning systems.

A Coupled River–Overland (1D-2D) Model for Fluvial Flooding Assessment with Cellular Automata

To provide accurate and efficient forecasting of fluvial flooding assessment in the river basin, the present study links the well-known CA-based urban inundation modeling (2D-OFM-CA) with a one-dimensional river flow model (1D-RFM) as a coupled 1D-2D river–overland modeling. Rules to delineate the geometric linking between the 1D-RFM and 2D-OFM-CA along embankments are developed. The corresponding exchanged water volume across an embankment is then computed by using the free and submerged weir flow formulas. The applicability of the proposed coupled model on fluvial flooding assessment is then assessed and compared with a well-recognized commercial software (HEC-RAS model) through an idealized fluvial case and an extensively studied real-scale fluvial case in the Severn River Basin. Based on the simulated results concerning the numerical accuracy, the coupled model is found to give similar results in the aspects of the river flow and overland flow modeling in both two study cases, which demonstrates the effectiveness of the linking methodology between the 1D-RFM and 2D-OFM-CA. From the viewpoint of numerical efficiency, the coupled model is 47% and 41% faster than the HEC-RAS model in the two cases, respectively. The above results indicate that the coupled model can reach almost the same accuracy as the HEC-RAS model with an obvious reduction in its computational time. Hence, it is concluded that the coupled model has considerable potential to be an effective alternative for fluvial flooding assessment in the river basin.

Temporal variability and ecological risks of pharmaceuticals and cocaine during the Christmas and New Year holidays in a beach area of North Coast of São Paulo, Brazil

This study assessed the occurrence and ecological potential risk of nine selected pharmaceuticals in water samples from the Juquehy River. The river flows continuously to Juquehy Beach, known as “the jewel of the north coast" of São Paulo, Brazil. Samples were collected during Christmas and the New Year (period of December 2023–January 2024), in addition to a previous baseline weekend, to compare the loads during “celebratory parties" versus “normal operational conditions." The findings indicated that the “mass gathering" during Christmas and New Year holidays contributed significantly to an increase of the mass load of the nine pharmaceuticals flowing along to the Juquehy River, i.e., caffeine (14.40–633.00 ng/L) > losartan (<LOQ: limit of quantification to 9.43 ng/L) > furosemide (< LOQ to 9.16 ng/L) > diclofenac (0.61–4.55 ng/L) > carbamazepine (< LOQ to 0.73 ng/L) > orphenadrine (< LOQ to 0.11 ng/L) showed higher concentrations during the New Year holiday. Conversely, atenolol (< LOQ to 13.10 ng/L) > benzoylecgonine (0.33–7.23 ng/L) > cocaine (0.12–6.59 ng/L) showed higher concentrations during the Christmas day. The individual ecological risk assessment in the Juquehy River revealed a clear environmental concern for the aquatic ecosystem. The threat to the aquatic biota is significant, with caffeine and losartan presenting a moderate level of risk. Moreover, the mixture ecological risk assessment of nine compounds indicates acute moderate risks to algae, crustaceans, and fishes, as well as chronic low risks to fishes.

Planning of Uwe River PLTMH Jayawijaya Regency Capacity 2 X 750 KW

Indonesia has great potential to develop renewable energy, especially through Micro Hydro Power Plants (MHP) that utilize river flow. The Papua region, including Jayawijaya Regency, has significant water resources potential but has not been optimally utilized to meet local energy needs. This study aims to evaluate the technical feasibility of building an MHP in Uwe River, Jayawijaya Regency, with a capacity of 2 x 750 kW as an effort to increase the electrification ratio in Papua Mountains. The research uses a quantitative approach with field survey methods and primary data collection, such as water discharge measurements and interviews with relevant parties. The data were analyzed using the FJ Mock method for water discharge estimation and hydraulic power calculation to assess the technical feasibility of MHP development. The results showed that Uwe River has a potential hydraulic power of 2063.965 kW with a capacity factor of 88%, which is able to support the operation of two turbines with a capacity of 733.76 kW each. The conclusion of this study shows that the construction of an MHP in Sungai Uwe is technically feasible and has great potential to increase the electrification ratio, support local economic development, and reduce dependence on fossil fuels in remote areas. The implication of these results is the importance of investment and policy support in the development of renewable energy projects in Papua to achieve national electrification targets.

River-estuary continuum highlighted by variabilities in carbon and nitrogen stable isotope ratios of the catadromous eel Anguilla japonica.

Estuaries exhibit high physicochemical variability and the properties of estuaries and the constituent segments are not yet systematically understood. This study aims to reveal the spatial heterogeneity of predominant organic sources using carbon and nitrogen stable isotope ratios (δ13C and δ15N, respectively) of Japanese eels (Anguilla japonica), one of the ideal natural samplers. In the Miyakoda River, Japan, our study site, the effectiveness of eel δ13C and δ15N values as standard indices of predominant organic sources was tested by employing the River Continuum Concept. This study then extended the application of these indices to the estuary, i.e., the Hamana Lake system, into which the Miyakoda River flows. Once in the upper estuary, eel δ13C and δ15N values became high, with the latter peaking in this river-estuary continuum, indicating that artificial labile subsidies (nutrients and organic matter) with high δ15N values were rapidly assimilated into the food web. Eel δ15N values decreased again in the middle estuary. Nevertheless, the influence of terrestrial organic subsidies extended into this segment, as evidenced by the low δ13C values of eels. These results suggest that refractory organic matter with low δ15N values, such as plant-derived ones, is slowly assimilated into the food web in the downstream estuarine segments. The higher δ13C values in the lower estuary suggested that the contribution of eelgrass or macroalgae occurred in addition to benthic microalgae. Thus, our results emphasize the need to consider the multiple energy flows to understand the estuary as a continuum.

Pemberdayaan Masyarakat dalam Upaya Pencegahan Vektor Penyakit Melalui Pelatihan Pembuatan Karbol Serai di Palangka Raya

Vector-borne diseases are influenced by physical, biological, and socio-cultural environmental conditions. Residents of Pahandut Village were chosen as the subjects of service because part of Pahandut Village is located on the edge of the Kahayan River. Therefore, a lot of rubbish carried by the river flows under people's stilt houses and becomes a habitat for mosquitoes, flies, and cockroaches which can transmit diseases to people. Disease vectors can be prevented by keeping the floors of the house clean by using natural ingredients such as lemongrass. Community service activities are expected to increase public knowledge regarding diseases caused by zoonotic vectors, recognize disease-causing insects in the environment, prevent disease vectors, and skills in making lemongrass carbol. Community service participants' knowledge increased as shown by the evaluation of pre-test and post-test scores. Community service participants were 15 people from the Pahandut sub-district with a pre-test average of 36% and a post-test average of 100%. A comparison of the pre-test and post-test scores shows that there is an increase in knowledge after the service activities are carried out. In conclusion, education about preventing disease vectors and the practical production of lemongrass carbole can increase community knowledge and skills in preventing disease vectors.

Requirements for the Development and Operation of a Freeze-Up Ice-Jam Flood Forecasting System

This article provides a comprehensive overview of ice-jam flood forecasting methodologies applicable to rivers during freezing. It emphasizes the importance of understanding river ice processes and fluvial geomorphology for developing a freeze-up ice-jam flood forecasting system. The article showcases a stochastic modelling approach, which involves simulating a deterministic river ice model multiple times with varying parameters and boundary conditions. This approach has been applied to the Exploits River at Badger in Newfoundland, Canada, a river that has experienced several freeze-up ice-jam floods. The forecasting involves two approaches: predicting the extent of the ice cover during river freezing and using an ensemble method to determine backwater flood level elevations. Other examples of current ice-jam flood forecasting systems for the Kokemäenjoki River (Pori, Finland), Saint John River (Edmundston, NB, Canada), and Churchill River (Mud Lake, NL, Canada) that are operational are also presented. The text provides a detailed explanation of the processes involved in river freeze-up and ice-jam formation, as well as the methodologies used for freeze-up ice-jam flood forecasting. Ice-jam flood forecasting systems used for freeze-up were compared to those employed for spring breakup. Spring breakup and freeze-up ice-jam flood forecasting systems differ in their driving factors and methodologies. Spring breakup, driven by snowmelt runoff, typically relies on deterministic and probabilistic approaches to predict peak flows. Freeze-up, driven by cold temperatures, focuses on the complex interactions between atmospheric conditions, river flow, and ice dynamics. Both systems require air temperature forecasts, but snowpack data are more crucial for spring breakup forecasting. To account for uncertainty, both approaches may employ ensemble forecasting techniques, generating multiple forecasts using slightly different initial conditions or model parameters. The objective of this review is to provide an overview of the current state-of-the-art in ice-jam flood forecasting systems and to identify gaps and areas for improvement in existing ice-jam flood forecasting approaches, with a focus on enhancing their accuracy, reliability, and decision-making potential. In conclusion, an effective freeze-up ice-jam flood forecasting system requires real-time data collection and analysis, historical data analysis, ice jam modeling, user interface design, alert systems, and integration with other relevant systems. This combination allows operators to better understand ice jam behavior and make informed decisions about potential risks or mitigation measures to protect people and property along rivers. The key findings of this review are as follows: (i) Ice-jam flood forecasting systems are often based on simple, empirical models that rely heavily on historical data and limited real-time monitoring information. (ii) There is a need for more sophisticated modeling techniques that can better capture the complex interactions between ice cover, water levels, and channel geometry. (iii) Combining data from multiple sources such as satellite imagery, ground-based sensors, numerical models, and machine learning algorithms can significantly improve the accuracy and reliability of ice-jam flood forecasts. (iv) Effective decision-support tools are crucial for integrating ice-jam flood forecasts into emergency response and mitigation strategies.

Tectono-thermal evolution from the proximal to hyperextended domains of the northern South China Sea margin since initial rifting

The Pearl River Mouth Basin (PRMB) is located on the northern margin of the South China Sea (SCS). Heat flow measurements indicate that the PRMB is a typical ‘hot basin' characterized by a high background heat flow. However, the tectono-thermal evolution of the PRMB and the mechanisms involved are still controversial due to the different input parameters used in tectono-thermal models, small datasets and the limited area of the basin studied. We used tectono-thermal modelling with a multi-stage finite stretching model, constrained by extensive well data, to systematically analyse the tectono-thermal evolution of the PRMB since the onset of rifting. The study area was expanded relative to previous studies to cover both the proximal and hyperextended regions of the northern SCS margin, providing a more comprehensive understanding of its tectono-thermal history. Numerous wells and seismic data covering the entire basin were used, along with appropriate input parameters, to address the gaps in previous studies and to enhance the accuracy of the results. Our findings indicate that the PRMB underwent two phases of heating, primarily due to thinning caused by lithospheric extension during rifting. By the end of rifting, the Northern Depression Zone and the Kaiping Sag had reached peak heat flow, while the Panyu Lower Uplift and Baiyun Sag saw their highest heat flow since the initial rifting. The PRMB experienced thermal decay during the post-rift stage, but a significant reheating event occurred from 23.03 to 13.82 Ma, likely due to northwards lower crustal flow from the Baiyun Sag. The Panyu Lower Uplift and the Baiyun Sag had reached their peak heat flow by 13.82 Ma and the heat flow generally increased by 1–3 mW m −2 in the other studied areas during this stage. The basin's thermal decay slowed at 5.33 Ma and localized heating events linked to magmatic activities in the southern Dongsha Uplift were observed. In general, the proximal domain of the northern SCS margin reached peak heat flow by the end of rifting, whereas the hyperextended domain reached peak heat flow by 13.82 Ma. The heat flow in the hyperextended domain was generally higher than that in the proximal domain as a result of the thinner crust of the hyperextended domain caused by intense multiple lithospheric detachment–extensional thinning processes. During the rifting stage, the lithospheric extensional thinning process was the most important factor influencing the tectono-thermal evolution of the northern SCS margin, while lower crustal flow and magmatism were the most important factors during the post-rift stage.

Hydrological and hydrodynamic modelling for flood management: A case study of the Yamuna River Basin in Delhi

Study regionYamuna River (Delhi), India. Study focusThe anthropogenic activities within the vicinity of the floodplain reduce the river's margin and subsequently alter the magnitude of the river's flow. The encroachment of riverbeds leads to waterlogging and flooding in urban areas, thereby causing damage to property, human life, etc. It necessitates a comprehensive study of the floodplain and changes in its proximity such as encroachment of floodplains to carry out any further activities with certainty. This study employs a two-dimensional model to simulate the Yamuna River's (YR) hydrodynamic characteristics, focusing on India's Delhi region. New hydrological insightsSimulated flood flows are employed to evaluate floods of once in 10, 20, 25, and 30-year return periods using the flood frequency analysis for 1951–2013. The model validation results indicated that the model could mimic the flood depth in YR. Simulation results revealed that the floodplain's encroachment had increased the severity of the floods. The increase in the extremeness of flooding events, i.e., from once in a 10-year return period to a 30-year return period event, is expected to increase the areas at risk of floods by 12 %. The model also offers a potential platform for evaluating other alternatives, such as further encroachment, for a business-as-usual scenario or for restoring the Yamuna floodplains. With such a comprehensive perspective, floodplains' role enhances river basin resilience to climate and anthropogenic changes and increases flood safety.

Hydrological model calibration in data-deficient basins using satellite altimetry and a hydrodynamic model

Large basins with insufficient hydrological station distribution and lacking sufficient meteorological data, such as water level and discharge, pose significant challenges in developing reliable hydrological models. These models are crucial for addressing water resource-related challenges such as climate change (e.g., floods and droughts) and human-induced activities (e.g., dams) impacts. Recent advancements in satellite altimetry offer an efficient alternative by providing water level data; however, integrating this data into hydrological models remains an ongoing challenge. Here we demonstrate that a properly developed hydrodynamic model can effectively translate the satellite-observed water levels at various river cross-sections (hereafter referred to as virtual stations (VSs)) into the required discharge data, facilitating reliable hydrological modeling for data-deficient basins. Our results, based on the assessment of water level data derived from a hydrodynamic model and satellite altimetry, showed high consistency (NSE > 0.96) in the Lancang-Mekong River (LMR) basin as a case study. We found that the distribution of stations along the mainstream, in terms of their number and distance from each other, can significantly impact the performance of hydrological modeling processes. The results revealed that when a large stretch of the river is not monitored by a station, a large uncertainty occurs in runoff generation, at least for that segment of the river. However, the inclusion of virtual stations in the modeling process improved the overall performance, indicating the advantages of satellite altimetry data in better modeling of data-deficient basins. Our findings revealed that virtual stations can be effectively utilized in physically based and spatially distributed hydrological models to develop a sub-basin modeling approach that addresses the regional contribution of sub-basins to downstream river flow. The integrated modeling framework holds potential for hydrological analysis and water resources management for basins lacking sufficient gauging data and provides insight into how the distribution of stations can influence the calibration of hydrological models.

Toward integrated dam assessment: evaluating multi-dimensional impacts of the Grand Ethiopian Renaissance Dam on Sudan

Abstract The Grand Ethiopian Renaissance Dam (GERD) on the Nile is expected to influence many ecosystem services, such as flood regulation, hydro-electricity production, food supply, and habitat provision, among others. Understanding these impacts (positive and negative) requires a comprehensive evaluation framework. This study develops and applies an integrated simulation framework for assessing the impacts of the GERD on Sudan, focusing on the simultaneous economywide effects of riverine flood hazards, irrigation water supply, hydropower generation, and floodplain-dependent industries, namely traditional fired clay brick production. The simulation framework incorporates three models: a river infrastructure system model, a flood model, and a Computable General Equilibrium Model. Results indicate positive impacts for hydropower generation and flood control, marginal benefits for water supply to existing irrigation, and negative consequences for brick production and the construction sector. Assuming that the GERD starts its long-term operation in 2025, we find an overall positive economic impact on Sudan’s Gross Domestic Product in 2025, with an increase of up to just over 0.1%, subject to river flow conditions. Recognizing the differences in impacts across sectors and income groups, the study emphasizes the need for interventions that ameliorate negative effects. While the study captures several impacts, other effects on the environment, recession agriculture, and soil fertility require further investigation. Still, our findings underscore the importance of adopting an integrated simulation approach to dam evaluation, acknowledging the interconnected nature of water and related sectors in national economies.

Diatom assemblages in glacial-fed streams of Italian Western Alps

ABSTRACT The rate of glacier retreat has recently increased, with changes in the glacier discharge, river flow and water characteristics, creating specific environmental conditions for highly specialized organisms. We here investigated diatom communities in glacier-fed rivers of the Valle d’Aosta region (NW-Italy), analyzing data collected between 2010 and 2019 for the WFD monitoring programs. We present a complete checklist of the species inhabiting this region, many of which are classified as endangered in the diatom Red List. We found significant differences between sites with different catchment glacier cover (CGC), in terms of taxonomic composition, ecological guilds and abundance of Red List taxa. In particular, we observed a significant increase in species richness with the decrease in CGC, as well as significant differences in terms of taxonomic composition. We highlighted the role of Achnanthidium lineare as an indicator species for streams with the highest glacial influence, together with Hannaea arcus, Eucocconeis laevis and other oligotrophic low profile species that are well adapted to physical stress induced by glacier runoff. On the other hand, streams with lower glacial influence were characterized by motile species mostly belonging to the genera Navicula and Nitzschia, due to the nutrient increase. Didymosphenia geminata was recorded in streams with marginal glacier cover; recently observed blooms indicate that conditions may become increasingly favorable for the spread of this species in Alpine environments, as glaciers retreat. The abundance of Red List diatoms increased significantly with increasing glacier cover suggesting that glacier-fed rivers are niches for the conservation of diatom biodiversity.

Changes in the air temperature regime across the Dniester River basin at the beginning of the 21st century

The relevance of the chosen topic is based on the goals and objectives of the Water Strategy of Ukraine until 2050 that provides for promotion of studies on the impact of climate change on the water content of Ukrainian rivers. The Dniester River is a transboundary river. It supplies water to Moldova and several regions of Ukraine. Predicting possible changes in the Dniester River's runoff due to global warming will help our society adapt to new climate conditions and take preventive measures. The research of the mountainous part of the watershed is of particular importance, as it is the area of runoff formation. Warming can change contribution of the snow component to the river's feed pattern and affect the total river flow. The object of the study: changes in air temperature due to global warming. The subject of the study: assessment of changes in the temperature regime within the Dniester watershed and impact of such changes on formation of its mountainous part's runoff. The study is aimed at assessing the changes in the air temperature regime within the Dniester River watershed at the beginning of the 21st century and assessing the impact of warming during winter season on formation of mountain rivers' spring floods. The main research methods include the method of difference integral curves and the method of regression analysis. The research materials include average monthly and annual air temperatures at 13 meteorological stations located within the Dniester watershed for the period of 1947-2021. The research indicated that the Dniester watershed is subject to warming. Statistically significant changes in air temperature began in 1988. Fluctuations in average annual air temperatures occur synchronously. Positive statistically significant trends over the entire observation period (1947-2021) were found for average annual air temperatures, average monthly temperatures of both warm and cold periods, and for the winter season. When considering two measurement periods (before 1989 and after), it was found that no statistically significant trends were observed before 1989. They were formed after 1989. It was also discovered that mountainous watersheds of the Ukrainian Carpathians respond to warming by forming negative trends in the fluctuations of average monthly runoff of spring floods.

Analysis of the environmental state of the Sarata River in Odesa Region

The relevance of the study is dictated by the need to preserve the water resources of southern Ukraine and ensure their good environmental condition. In the context of military operations, Odesa Region plays a key role in providing the country with agricultural products because of significant damage incurred to agricultural lands of Mykolaiv and Kherson Regions in the course of military actions. Hence the role of irrigation and the need to restore and modernize irrigation systems are growing. One of fresh water reservoirs of Odesa Region is Sasyk reservoir (artificially created as part of the estuary) which accumulates fresh water supplied from the Danube. The Kogylnyk and the Sarata rivers flow into the northern part of the reservoir and can worsen its hydroecological condition. The subject of the study: pollution of the rivers across North-Western Black Sea Coast by chemicals. The object of the study: the environmental state of the Sarata River. The study is aimed at assessing the environmental state and environmental risks of chemical pollution of the Sarata River. The water quality assessment was performed based on a modified version of water pollution index (WPI). Biogenic substances (ammonium nitrogen, nitrite nitrogen, nitrate nitrogen) were identified as the main pollutants. The content of chlorides and sulfates is also significant. The assessment of the pollution risks by biogenic substances is based on calculations of the statistical probit function. The source materials of the research include hydrochemical observations made by the State Agency of Water Resources of Ukraine for the period from 2007 to 2023 in the upper reaches of the Sarata River - village of Miniailivka (94 km from the mouth, near the border with Moldova) and in the lower reaches of the Sarata River - village of Bilolissya (14.3 km from the mouth). The analysis of probability of exceeding the MPC for fishery use indicated that, in terms of nitrite ions and nitrate ions, such probability is higher in the upper basin than in the lower one. According to other indicators, the probability of exceeding the MPC by pollutants is either almost the same or slightly increased in the lower reaches. The assessment of water quality according to the modified WPI (dissolved oxygen, BOD5, ammonium, nitrite and nitrate ions, phosphates) showed that the water quality in the Sarata River mainly belongs to the "moderately polluted" and "polluted" classes. According to the environmental risk indicators, it was established that the possibility of a "high" risk of contamination by biogenic substances does prevail. Its probability is 52.9% for the upper reaches and 60% for the lower reaches. The "high" level of class IV pollution (ER=0.60-0.79) corresponds to an "unsatisfactory" environmental condition. The probability of achieving the class of a "good" environmental condition (class II, ER=0.20-0.39) is quite small: 17.6% in the upper reaches and only 6.67% in the lower reaches. Thus, the Sarata River belongs to such rivers, the natural properties of which underwent significant changes as a result of sewage delivery from "Sarata Komunservis" utility enterprise, settlement of Sarata. Contaminated waters are unsuitable for drinking, household and sports purposes, as well as for fish farming. The quality of the Sarata River's water has a negative impact on the environmental state of Sasyk reservoir.

Fluvial responses to Holocene climatically induced coastline migration in the Iguape River estuary (Southeast Brazil)

AbstractRivers represent intricate geomorphological systems that exhibit sensitivity to even subtle base‐level changes. This study examines the geomorphological response of Ribeira de Iguape River, located along the southern coast of São Paulo state, Brazil, to hydrological changes and coastline migration resulting from Holocene climate pulses. Using a multidisciplinary approach, including geomorphological and stratigraphical analyses, optically stimulated luminescence dating, grain‐size analyses, interpretation of satellite images, mapping and reassessment of previous studies, we investigated the potential impacts of these geomorphological dynamics on the river system. Our study reveals two distinct orders of low fluvial terraces, typically inserted no more than 10 m above the average channel discharge, which are geochronologically correlated with the low marine terraces that document the former coastline position at the river mouth, as previously identified in other studies. Such findings indicate a deposition phase when the coastline was stabilised on the inner continent in the Medieval Warm Period, as well as an erosion phase when the coastline migrated seaward during the Little Ice Age. This research contributes to improving our understanding of how rivers can respond to base‐level changes and provides valuable insights into the dynamic interactions between river systems and coastal environments.

Framework for UAV-based river flow velocity determination employing optical recognition

The determination of river velocity is important for hydromorphological analyses and river monitoring systems. Indirect measurements of river velocity using videos recorded by unmanned aerial vehicles (UAV) allow fast and cost-effective processing of information about the river stretch. This paper presents a method for computing flow velocity of the river surface using deep supervised model RAFT to determine the optical flow in combination with image pre-processing by convolutional operations. Moreover, the windiness coefficients and variance score were proposed to evaluate reliability of the collected data and the obtained results of optical flow detection. Various image pre-processing techniques were applied, namely the selection of the analysed area and the number of convolutional operations to select the one with the lowest variance score. This score represents the consistency of the river flow velocity during the video and can be used to filter out unreliable results. The numerical experiments were performed using the videos and directly measured velocity values of 4 shallow rivers in Lithuania collected during the field surveys. The optical velocity estimation method showed good correspondence to the directly measured values for the velocity range from 0 m/s to 0.8 m/s in the points with low variance score up to 0.192 that represents the first quartile of the variance. The optical flow method tends to underestimate the velocity up to 0.5 m/s for the quartiles with the higher variance scores. It was shown that in most cases the lowest variance score value was obtained using pre-processing techniques without convolutional operations. However, the need to analyse various pre-processing techniques arises from the different origin of the objects moving on the river surface.