River Conditions Research Articles

Analisis Keanekaragaman dan Kelimpahan Plankton di Sungai Way Awi dan Hubungannya dengan Kualitas Air

Plankton serves as a bioindicator that can be used as a marker for water quality related to water saprobity index. Way Awi River is a river flowing from the Susunan Baru area, passing through the Tandjungkarang region, and reaching the Garuntang area. Liquid waste from households is often directly discharged into the river, without passing through a containment system such as a septic tank, resulting in river pollution. To understand this relationship, this research was conducted to determine the biological condition of the Way Awi River based on plankton community structure, including abundance index, diversity index, evenness index, and dominance index, as well as its correlation with water quality using Pearson correlation test. The research was conducted in the Way Awi River with sampling taken at five different stations from October to December 2023. Water samples were analyzed using physical parameters including water temperature and turbidity, while chemical parameters observed were pH, DO, BOD, and COD. Based on the analysis of plankton community structure, it was found that the water of Way Awi River is in a moderately polluted condition.

PENGUKURAN pH, DISSOLVED OXYGEN (DO), DAN TOTAL DISSOLVED SOLID (TDS) PADA SUNGAI WILAYAH INDUSTRI COR LOGAM KABUPATEN HULU SUNGAI SELATAN

Water is essential for human life, used daily for drinking, cooking, bathing, washing, and various other purposes. The presence of industrial waste can significantly impact the water quality of rivers located in industrial areas. In North Daha District, South Kalimantan, there is a metal casting industry that discharges its waste into a nearby river. Therefore, measuring the water quality of the river is necessary to determine the level of pollution caused by industrial waste. The objective of this study is to obtain parameters from water quality tests, such as pH, dissolved oxygen (DO), and total dissolved solid (TDS), to assess the river's condition before and after metal casting processed. Additionally, the study aims to compare the test results against water quality standards for public consumption. The research method involves direct measurement of river water using a multiparameter water quality testing instrument. The test results before metal casting processed are pH 6,33 – 6,47; DO 1,03 – 2,18 ppm; and TDS 45 – 65 ppm. The test result after casting processed are pH 6,57 – 6,85; DO 6,66 – 13,19 ppm; and TDS 43 – 48 ppm. Comparing from PP RI Number 82 (2001) that the metal casting industry activities have water criterion within the range allowable values. That indicate the industry do not contaminate the river in the industrial area. The river pollution is primarily caused by tidal phenomena, particularly during low tide conditions.

Study on the Spatiotemporal Evolution Pattern of Frazil Ice Based on CFD-DEM Coupled Method

Frazil ice is the foundation for all other ice phenomena, and its spatiotemporal evolution is critical for regulating ice conditions in rivers and channels, as well as for preventing and controlling ice damage. This paper investigates the dynamic transport pattern of frazil ice during the early stages of winter freezing in water conveyance channels based on a CFD-DEM coupled numerical model, and derives predictive formulae for the spatiotemporal evolution of frazil ice and floating ice. First, static repose angle simulations and slope sliding simulations were used to calibrate the contact parameters between frazil ice particles and between frazil ice and the channel bed, ensuring the accurate calculation of contact forces in the model. On this basis, the processes of frazil ice transport, aggregation, and upward movement in water transfer channels were simulated, and the influence of contact parameters on simulation results was analyzed, showing a significant effect when the ice concentration was high. Numerical results indicate that the amount of suspended frazil ice is positively correlated with the frazil ice generation rate and water depth, with minimal influence from the flow velocity; the amount of floating ice increases linearly along the channel, with growth positively correlated with the frazil ice generation rate and water depth, and negatively correlated with the flow velocity. Predictive formulae correlating frazil ice and floating ice amounts with the flow velocity, water depth, and other factors were proposed based on numerical results. There is good agreement between the predictive and numerical results: the maximum APE between the predicted and simulated values of suspended frazil ice is 13.24%, and the MAPE is 6.32%; the maximum APE between the predicted and simulated values of floating ice increment is 7.80%, and the MAPE is 2.89%. The proposed prediction formulae can provide a theoretical basis for accurately predicting ice conditions during the early stages of winter freezing in rivers and channels.

Advanced high‐precision methodology for assessing sediment erosion in Pelton turbine buckets

AbstractDeveloping highly accurate sediment erosion testing methods for Pelton turbine overflow components is challenging due to their irregularly curved surfaces. In this study, we designed a method to evaluate the sediment erosion of the Pelton turbine bucket using test blocks with an accuracy of 0.0001 g. In addition, we conducted sediment erosion tests on a model Pelton turbine and conducted an in‐depth study on the installation design of the turbine runner and bucket, the design of the erosion test blocks, and the arrangement; we analyzed sediment abrasion distribution on the bucket's working surface. Our test results show that the bucket splitter edge, as well as the root of the working surface, are heavily worn. The maximum erosion rate of the working face is 0.7669 μm/h, and the maximum erosion rate of the splitter edge is close to 5 μm/h, which is highly consistent with the distribution of sediment erosion observed in Pelton turbines operating under sandy river conditions. This test method is essential for examining sediment erosion in Pelton turbines.

SNP Polymorphisms Are Associated with Environmental Factors in Sockeye Salmon Populations Across the Northwest Pacific: Insights from Redundancy Analysis.

The SNP variation in sockeye salmon across the Asian part of its range was studied in 23 samples from 16 lake-river systems of the West Pacific Coast to improve understanding of genetic adaptation in response to spawning watersheds conditions. Identification of candidate SNPs and environmental factors that can contribute to local adaptations in sockeye salmon populations was carried out using redundancy analysis (RDA), a powerful tool for landscape genetics proven to be effective in genotype-environment association studies. Climatic and hydrographic indices (7 indices in total), reflecting abiotic conditions in freshwater habitats of sockeye salmon and characterizing the temperature regime in the river basin, its variability during the year, the amount of precipitation, as well as the height of the maximum tide in the estuary, were used as predictor factors. Among the 45 analyzed SNPs, several loci (ALDOB-135, HGFA, and RAG3-93) correlated with predictors gradients along the northwest Pacific coast were identified. The putative candidate loci localized in genes involved in the immune and inflammatory responses, as well as genes encoding temperature-sensitive enzymes and some hormones regulating ion homeostasis in fish during the anadromous migration and smoltification, were potentially associated with environmental conditions in natal rivers. The findings could have implications for aquaculture, conservation, and resource management in the context of global climate change.

Geochemical fingerprints, evolution, and driving forces of groundwater in an alpine basin on Tibetan Plateau: Insights from unsupervised machine learning and objective weight allocation approaches

Study RegionTongde Basin, a typical alpine basin on the northeastern Tibetan Plateau Study focusResearch on the hydrochemical pattern and availability of groundwater is very limited in alpine regions, which greatly hinders the rational ulitilization and scientific management of groundwater resources. Multiple approaches integrating self-organizing map, K-means, entropy weight were employed to elucidate the distinct hydrochemical evolution patterns and controlling mechanisms of groundwater in alpine basins with dense human activities. New hydrological insights for the regionMultiple hydrochemical evolution patterns were discovered for groundwater in present alpine basin on northeastern Tibetan Plateau. Groundwater presents a gradual hydrochemical evolution from the piedmont to the riverside under the natural regulation with the increasing of TDS and major ions along the flow path. While, groundwater at some sporadic sites is featured with relatively high total alkalinity due to carbonate mineral dissolution. The riverine groundwaters are regulated by the strong hydrodynamic condition of river and demonstrate fresher hydrochemical characteristics. Groundwaters in the irrigation areas are featured by elevated nitrate levels with a maximum of 42.86 mg/L, attributed to agricultural pollution inputs. A conceptual model was established to illustrate the distinct hydrochemical fingerprints, evolution patterns and controlling mechanisms of groundwater in alpine basins that with dense human activities. This research can enhance the understanding of groundwater chemical status, genesis and availability, and is beneficial for the conservation and sustainable management of groundwater resources in ecologically fragile alpine regions worldwide.

A comprehensive review of effective parameters to improve the performance of the Savonius turbine using a computational model and comparison with practical results

Amidst growing global concerns over climate change and escalating greenhouse gas emissions from fossil fuels, the pursuit of renewable energy sources has become critical. This study focuses on harnessing hydropower using Savonius turbines, which are known for their efficiency in generating energy at lower flow rates. However, the intrinsic low efficiency of these turbines necessitates precise optimization tailored to specific river or channel conditions. In this research, we optimized the performance of Savonius turbines by analyzing key parameters such as the height-to-diameter ratio, blade twist, and the integration of multi-stage configurations with deflectors. Our findings reveal significant efficiency improvements through strategic modifications. Specifically, by reducing the height-to-diameter ratio from 1.2 to 0.8 and maintaining a Tip Speed Ratio (TSR) of 0.6, the power coefficient increased by 15%, from 0.33 to 0.38. Further optimization was achieved by adjusting the blade twist angle, with an increase in power coefficient up to an optimal angle of 45°, beyond which efficiency declined. Implementing a two-stage turbine setup with a 90-degree phase difference between stages further improved the power coefficient to 0.51 at the same TSR. Additionally, the use of deflectors, particularly at a 90° angle, significantly boosted the power coefficient, highlighting their effectiveness in optimizing water flow impact on the turbine. This comprehensive study not only advances the understanding of Savonius turbine optimization but also contributes to broader renewable energy applications. The research offers critical insights into sustainable hydroelectric power generation, providing practical solutions to enhance turbine performance for real-world applications.

Inferring sediment-discharge event types in an Alpine catchment from sub-daily time series

Abstract. Fluvial sediment dynamics in mountain rivers are changing rapidly in a degrading cryosphere, raising the potential for erosive rainfall and runoff and detrimental effects on downstream areas. Hence, we need to understand better what characterises and drives episodic pulses of water and suspended solids in rivers. Here, we infer different types of such sediment-discharge events from 959 automatically detected events based on 16 metrics derived from 15 min time series of streamflow and suspended sediment concentrations from Vent–Rofental in the high Ötztal Alps, Austria. We use principal component analysis to extract uncorrelated event characteristics and cluster event types with a Gaussian mixture model. We interpret the thus inferred event types with catchment metrics describing antecedent conditions, hydrometeorological forcing, and fraction of catchment area with freezing temperatures and snow cover. We find event magnitude, hysteresis, and event shape complexity to be the main factors characterising the overall event regime. The most important characteristics distinguishing the event types are suspended sediment and streamflow magnitude and complexity of the hydro- and sedigraphs. Sediment-discharge hysteresis is less relevant for discerning event types. We derive four event types that we attribute to (1) compound rainfall–melt extremes, (2) glacier and seasonal snowmelt, (3) freeze–thaw-modulated snowmelt and precipitation events, and (4) late-season glacier melt. Glacier and snowmelt events driven by warm conditions and high insolation were the most frequent and contributed some 40 % to annual suspended sediment yield on average; compound rainfall–melt extremes were the rarest but contributed the second-highest proportion (26 %). Our approach represents a reproducible method for objectively estimating the variety of event-scale suspended sediment transport conditions in mountain rivers, which can provide insights into the contribution of different drivers to annual sediment yields in current and future regimes. Our findings highlight the importance of both meltwater and rainfall–runoff as drivers of high-magnitude suspended sediment fluxes in mountain rivers.

Impact of Climate Deviation on Reproductive Profile of Nile Tilapia, Oreochromis niloticus (Linnaeus, 1758) from the Tons River, India

Nile tilapia, Oreochromis niloticus is among the leading farmed species around the world as well as a powerful invader in many countries globally. Studies were undertaken during the period from February 2019 to January 2020 from the lower stretch of the Tons River at Prayagraj, Uttar Pradesh, India. During the sampling period, 683 fish specimens of Nile Tilapia, Oreochromis niloticus (336 males and 347 females) were collected and studied for evaluation of sex ratio and sex structure. The sex ratios of male and female fishes were very close and reported 1.0:1.03 in the stock. The male ratio was higher in the small size group of fish with 81 to 200 mm size groups and 411 to 470 mm size group. The sex structure of males and females was observed at 49.19% and 50.81%, respectively in the case of stock. The female proportion was recorded as a minimum with 37.50% in the 441-470 cm size group and highest with 54.84% in the 381-410 mm size group. However, the male proportion was reported lowest at 45.16% in the 381-410 mm size group and highest at 62.50% in the 441-470 mm size group. In the present findings, O. niloticus was found to reach maturity starting below 138 mm of total length, taking individual fish. The fishes breed in the months of March to June and September to November of the year. The number of eggs per individual ranged from 393 to 4338 in the size of fish varied from 138-452 mm. The reported fecundity and sex ratio of O. niloticus indicated that the climatic condition or environmental condition of the Tons River was most suitable. The environmental condition (especially temperature) of the Tons River at Prayagraj is slightly warm compared to the Ganga River which is very favourable for O. niloticus. The water current velocity of the Tons River is very poor. Both parameters are very helpful for the stability of O. niloticus in the Tons River at Prayagraj. The high fecundity of O. niloticus in the Tons River at Prayagraj could probably be a result of a combination of different causes such as climatic conditions, habitat structure, food abundance, water quality, and quality of food. Therefore, the present study aimed to update the information on the sex ratio, sex structure, and fecundity of O. niloticus with respect to climate from the Tons River, India.

Quantitative Assessment of Ecological Flow in the Yellow River Under Changing Environments

ABSTRACTStudying the streamflow characteristics of the Yellow River mainstem under changing environmental conditions is crucial for the management and sustainable development of water resources within its basin. This research employs a long short‐term memory (LSTM) model to restore the flow characteristics of the Yellow River's mainstream under natural conditions. Additionally, the range of variation approach (RVA) and nonparametric kernel density estimation (KDE) method are integrated to quantitatively assess the impact of environmental changes on streamflow. The findings indicate that: (1) Hydrological variability in the Yellow River was observed in 1985, with a degree of variability ranging from 26% to 58%, classified as moderate. (2) The annual ecological flow value of the Yellow River is 560–1001 m3/s, and the average annual ecological flow assurance is 43%. (3) Based on LSTM simulation results (NSE > 0.7, R2 > 0.8), it is concluded that the ecological flow assurance under natural conditions in the Yellow River exceeds the measured values, primarily due to human activities, which contribute over 52% to this discrepancy. These results suggest that the river ecosystem of the Yellow River's mainstem is relatively unstable and requires further management.

Assessment and condition of a small river in urbanized areas (with the example of the river Kurdyum of the municipal formation “Saratov city”)

The results of the study of the ecological status of the Kurdyum river within the municipal formation “Saratov city” are presented. The hydrochemical regime, hydrophilic flora and vegetation of the watercourse were studied in the 2022–2023 field seasons. The ecological status of the river by structural parameters of macrophytes was assessed. The species composition of aquatic plants in the river Kurdyum was represented by 41 macrophyte species belonging to 32 genera, 23 families and three divisions (Charophyta, Polypodiophyta, and Magnoliophyta). The families Potamogetonaceae, Asteraceae, Poaceae, Typhaceae and Ranunculaceae predominated by the number of species. The genus Potamogeton contained the greatest number of species (four) while other genera were represented by one – two species. Hydrophytes were a numerous ecological group, accounting for 51% of the total number of species. New locations of species rare for the Saratov region (Myriophyllum verticillatum and Zannichellia palustris) were revealed. The vegetation cover of the Kurdyum river is characterized by the greatest phytocenotic diversity of true aquatic vegetation. The impoverishment of the phytocenotic composition of helophytic and hygrophytic vegetation is explained by the lack of favorable conditions for the development of their phytocenoses (the watercourse has abrasion banks along a significant length) or trampling and eating by grazing animals. The studied river is characterized by species diversity in comparison with previously studied urban watercourses. Index comparison has revealed an inverse relationship between species diversity and the level of anthropogenic load. Cluster analysis has revealed that the structure of flora and vegetation from the source to the mouth of the river is not homogeneous and is formed under the influence of a combination of hydrological, chemical and anthropogenic factors. The results of our chemical analysis of the water showed that the maximum permissible concentrations of Fe, Zn, Cu, surfactants, NO2 and NH3 were exceeded throughout the river. However, the environmental indicators assessed based on the structural parameters of macrophytes allow us to consider the ecological status of the watercourse satisfactory. Thus, the Kurdyum river is moderately polluted with a high trophic status.

Factors influencing harvest success for an Arctic under-ice subsistence fishery

Long-term fisheries datasets are particularly rare in Arctic environments and are essential to understanding the variability in harvest rates. We analyzed 30 years of harvest monitoring data and compared results to fish monitoring data from nearshore waters of Prudhoe Bay, Alaska, to determine the importance of age-0 recruitment and intra-annual factors on subsequent harvests of Arctic cisco in the Colville River delta (CRD), Alaska. While age-0 recruitment to Prudhoe Bay was positively associated with annual harvest success in the CRD, wind and salinity patterns and subsistence fishing location and timing also contributed significantly in explaining adult harvest variability. Harvest rates were highest closest to the river mouth and early in the season. Harvest rates increased with increasing salinity up to 25 ppt, then declined. As the climate changes in the region, we may see shifts in nearshore ocean and river conditions which will impact recruitment and fishing activity. These long-term monitoring efforts will continue to inform sustainable fisheries management in the face of a rapidly changing climate, and with ongoing infrastructure development in the region.

Avoiding Flood by Improving Cross-Sectional Capacity through River Normalization

Bekasi is one of the regions in Indonesia that often suffer from flooding. To overcome flooding problems in the Bekasi area, the Ciliwung Cisadane River Basin Center has begun a normalization project along the Bekasi River. This research aimed to evaluate the Bekasi River's cross-sectional capacity both before and after normalization. The analysis focused on the section where the Cileungsi and Cikeas rivers converge to the Bekasi weir. In this research, secondary data were employed, such as national digital elevation model data, detailed engineering designs of Bekasi River flood control activities, and rainfall data from the Cibinong Station that covers the period from 2006 to 2020. The result from planned flood discharge with the Nakayasu synthetic unit hydrograph method for a return period of 25 years on the Bekasi River was obtained at 665.81 m3/s. The results of hydraulic analysis before normalization with the HEC-RAS application show that flooding occurred at 102 out of 116 stations, with capacities of river cross-sections ranging from 453.49 m³/s to 665.71 m³/s at these overflow stations. Following the river normalization process, the cross-sectional capacity at all Bekasi River stations can accommodate flood discharge without any instances of overflow.Keywords: Flood, HEC-RAS, Nakayasu, Normalization, Rainfall.

Geochemical state of small rivers of Syrym District of West Kazakhstan region (on the example of the Rivers Buldyrty, Yesenankaty, Shiderty, Olenty)

Despite the fact that small rivers are called Small, their importance in terms of ecology is high. This is because the condition of large rivers will depend on smaller rivers. The degradation of small rivers negatively affects the state, is an important and urgent task. The purpose of the study was to geochemically analyze the composition of the waters of small rivers in the Syryms district and assess their quality. Water samples were taken from each river ecological state of medium and large rivers, because they feed at the expense of these small rivers. It is easy to see that every day the waters of these rivers are receding and the banks are expanding. Currently, one of the main tasks that environmental science sets for itself is to monitor the ecological state of water bodies. In connection with the conditions of increasing anthropogenic factors, determining the ecological state of small rivers plays an important role in maintaining the composition of the natural ecosystem. Small rivers are very sensitive to anthropogenic factors and react to these factors in the opposite way. The study of the chemical composition of small river waters, as well as their ecological state, is an important and urgent task. The aim of the study is a geochemical analysis of the composition of small river waters in the Syrymsky district and an assessment of their quality. Water samples were taken from each river to determine the composition of the water quality. The cameral stage was held in the laboratory of environmental and biogeochemical testing of M. Utemisov West Kazakhstan University. Chemical analysis was carried out using the widely used methods GOST 26449.1 — 85. After analyzing the indicators of water samples taken from the research area, it was found that the maximum raual concentration level did not exceed, except for the total hardness.

Analisis Beban Pencemar dan Kapasitas Asimilasi Sungai Klinter Nganjuk

Klinter River in Nganjuk is subjected to pollution loads from various pollution sources, including domestic and industrial waste. Water quality can affect the condition of Klinter River, which is still used by the local community to support daily activities. The parameters analyzed include TSS, COD, BOD, NO3-, NO2-, NH3, PO4, and oil and grease, taken from data provided by the Nganjuk Environmental Agency. The study aims to assess the carrying capacity of Klinter River by analyzing pollutant loads and the river's assimilative capacity. Regression analysis is conducted to obtain equations and graphs illustrating the relationship between pollutant concentration and assimilation capacity for each parameter. The analysis results indicate that COD, BOD, and NH3 parameters are no longer able to undergo self-purification.

Ecological flow research in response to hydrological variation: A case study of the Jinsha River Basin, China

Climate change and human activities have altered the natural state of rivers to a certain extent, leading to runoff variation and impacting the stability of riverine ecosystems. The ecological flow has emerged to balance the water relationship between humanity and riverine ecosystems and to safeguard the health and biodiversity of rivers. Presently, the scientific quantification of riverine ecological flow has become a focal point in water resource research. Addressing the quantification of ecological flow under hydrological variation conditions, the cumulative deviation method (CDM) and Pettitt methods were firstly employed to detect breakpoints in the runoff sequences. Then, the natural monthly runoff post-variation was restored using the Soil and Water Assessment Tool (SWAT) model, i.e., natural runoff restoration, and three testing methods were employed to determine the optimal hydrological distribution functions for natural monthly runoff. Subsequently, an improved frequency calculation method was used to calculate the ecological flow. The Jinsha River Basin was selected as the study area, and four crucial sections in the mainstream of the Jinsha River were studied, including Zhimenda (ZMD), Shigu (SG), Xiaodeshi (XDS), and Pingshan (PS). The results indicated: (1) the runoff sequences (1960–2017) at the four crucial sections exhibit different breakpoint times, with breakpoint years being 2004, 1986, 2005, and 1996, respectively; (2) the SWAT model, in simulating runoff at the four crucial sections, exhibited NSE values all exceeding 0.85, and r values all surpassing 0.9, demonstrating its effective ability to restore natural runoff in the Jinsha River basin; (3) the optimal hydrological distribution functions for natural monthly runoff at the four sections varied, and most natural monthly runoff conforms to the Generalized Extreme Value (GEV) distribution; (4) the average annual ecological flows for the ZMD, SG, XDS, and PS sections were 296 m3/s, 992 m3/s, 1238 m3/s, and 2755 m3/s, and the ecological flows derived using the improved frequency calculation method under the optimal hydrological distribution functions were more rational. This study can provide a scientific basis for the optimal allocation of water resources and the protection of riverine ecosystems in the Jinsha River basin.

Assessing ecological status using phytoplankton functional groups in three urban rivers in Hainan Island, China.

The urban rivers, including Changwang, Meishe, and Wuyuan in Haikou City, Hainan Island, are vital water sources for agricultural production and support industrial and domestic activities. Despite the rivers experiencing anthropogenic impacts, limited studies have assessed their water quality. Accordingly, this study assessed the phytoplankton community structure, utilized the river phytoplankton assemblage index (Qr index) to evaluate the ecological status, and compared its performance with the comprehensive trophic level index (TLI). Sample collection and microscopy analysis was conducted seasonally in 2019. Two hundred ninety-eight phytoplankton species belonging to 8 phyla were identified, predominated by Chlorophyta, Bacillariophyta, and Cyanophyta. The phytoplankton biomass ranged from 0.04 to 34.98mg L-1, with averages of 3.06 ± 0.71, 5.16 ± 1.92, and 2.70 ± 0.76mg L-1 in Changwang, Meishe, and Wuyuan, respectively. The phytoplankton biomass varied seasonally, recording the highest and lowest values in summer and autumn, respectively. The phytoplankton species were classified into 26 functional groups, which exhibited spatial and seasonal differences in their biomass and composition. The redundancy analysis (RDA) revealed that NH3-N, TP, CODMn, Chl-a, salinity, and temperature were the main environmental factors influencing phytoplankton functional groups. The average Qr index values in Changwang, Meishe, and Wuyuan were 3.39 ± 0.61, 3.44 ± 0.51, and 3.22 ± 0.67, and all the rivers were rated "good" in status. Seasonally, the Qr index and TLI revealed that the rivers' ecological condition was better in autumn and winter compared to spring and summer. Generally, the Qr index performed better, indicating that parameters such as NH3-N, CODMn, TP, and Chl-a decreased with improving ecological conditions from "poor" to "excellent" status. In addition, the Qr index exhibited a significant negative relationship with TLI, suggesting that low Qr index values may indicate increased eutrophication or deteriorated water quality. Thus, the ecological condition of the urban rivers could be adequately assessed using the Qr index to guide their water quality monitoring and management.

River quality management: Integrating uncertainty, failure probability, and assimilation capacity

Managing river water quality is challenging due to uncertainties in hydraulic and hydrologic parameters. This study integrates the symmetric exponential function (SEF) approach for solving the advection-dispersion equation with the Monte Carlo method in MATLAB. This combination allows us to explore the river's assimilation capacity and the failure probability (Pf) of maintaining desired water quality standards. Here, Pf represents the likelihood of pollutant concentrations exceeding acceptable limits under varying river conditions. A key contribution of this study is the introduction of a novel equation, developed using the Genetic Programming (GP) soft computing tool, to calculate assimilation capacity considering the failure probability of water quality provision. This equation provides a valuable tool for risk assessment in water resource management by quantifying pollutant assimilation dynamics. Its robustness is validated through high Coefficient of Determination (R2) and Overall Index (OI) values near 1, along with low Root Mean Square Error (RMSE) and Mean Absolute Error (MAE). The study identifies critical river characteristics, such as flow velocity and pollutant load, significantly influencing the reliability index (β). By outlining how adjustments in these parameters can achieve a target reliability index (β=4.526), our study offers a practical approach to safeguarding river ecosystems. For example, increasing flow velocity by 76 % can shift the river from a safe state (Pf=3×10−5) to a hazardous state (Pf=1), while a 44 % decrease in velocity allows for 57 % more pollutant assimilation. These findings highlight the importance of flow control as a cost-effective strategy for mitigating high pollutant concentrations and ensuring sustainable water quality management. By integrating numerical approaches with reliability sampling methods and soft computing techniques, this study enhances understanding of river system dynamics and supports informed decision-making for protecting water resources.

A novel optimal temporal lag air2stream model using dynamic time series matching

ABSTRACT In order to solve the problem that the current air2stream model does not consider the lag change of water temperature, this paper proposes a new method that combines empirical mode decomposition, power spectral density and dynamic time warping algorithm to determine the optimal time lag parameters, and then constructs the air2stream with the optimal time lag (a2swtl). Finally, the effectiveness and stability of the new method and model were verified based on the measured data from 2020-2022 at three hydrological stations in the middle and lower reaches of the Yangtze River that are close to natural river conditions. The results show that the new method overcomes the problem of low accuracy in determining the time lag of the existing correlation coefficient method. Compared with the original model, a2swtl has better stability without introducing additional observation data, and the average prediction accuracy is improved by about 6.33%. 8.36% and 15.4%.

State of the World's Rivers

In this review, we thoroughly analyze the state of global rivers, focusing on their physical and ecological characteristics as well as management strategies. The review results have helped us generate four recommendations. Firstly, rivers should be managed under a legally binding global accord at the basin level. Secondly, challenges related to river pollution and inappropriate project implementation can be mitigated by adopting newly defined strategic environmental assessments and the United Nations System of Environmental Economic Accounting. Thirdly, we need data from the latest scientific sources, such as geospatial sources, to better understand rivers at different scales as composite systems. The last recommendation calls for taking into account climate change concerns in river management approaches. We also outline a proposition for developing a river monitoring and assessment program in order to perform comprehensive and planet-wide river assessment. The article elaborates on the strategies for achieving these recommendations.