River Section Research Articles

Assessment of the impact of dam reservoirs on river ice cover – an example from the Carpathians (central Europe)

Abstract. This paper presents a method for determining the impact of dam reservoirs on the ice cover of rivers downstream of their locations based on a long measurement period (1950–2020) and synthetic-aperture radar (SAR) data. Two rivers and two sets of dam reservoirs located in the Carpathian Mountains (central Europe) were selected for this study. In order to estimate the influence of reservoirs, a logistic regression model was built to describe the relationship between the course of air temperature and the occurrence of ice cover (i.e., total ice cover and border ice) at water gauge cross sections upstream and downstream of the reservoirs. The influence of reservoirs was then defined as the differences between the number of days with ice cover predicted from air temperature and those observed at the water gauge cross sections. Additionally, the extent of the impact of the reservoirs was estimated based on SAR data (Sentinel-1) by identifying river sections downstream of the reservoirs on which total ice cover did not form despite the persistence of very low air temperatures. The study shows that dam reservoirs play an important role in decreasing the incidence of ice cover on rivers. The occurrence of ice cover as a result of reservoir operations could decrease by over 80 % in the sections immediately downstream of the reservoirs. The impact of the reservoir on river ice cover diminishes as the distance from the reservoir increases. Using SAR data, it was estimated that total ice cover did not form in sections 26–60 km downstream of the reservoirs, despite the presence of favorable thermal conditions. Based on the results of the study presented here, it can be assumed that in areas where many dam reservoirs are located, the ice regime of rivers is significantly transformed, which should be taken into account when studying river ice cover. This study also demonstrates that the logistic regression model and SAR data are useful tools for assessing the impact of dam reservoirs on river ice cover.

Estimates on age, growth, and mortality of Leuciscus chuanchicus (Kessler 1876) in the Ningxia section of the upper reaches of the Yellow River, China

To investigate the age structure, growth pattern, mortality and exploitation rates of Leuciscus chuanchicus in the upstream Ningxia section of the Yellow River, four sampling surveys were conducted between 2022 and 2023. A total of 472 individuals were measured for their total length (TL) and body weight (W). Age determination was performed using otoliths. The collected samples had a range of total lengths from 4.52 to 37.45 cm, body weights ranging from 0.68 to 552.43 g, and ages ranging from 1 to 7 years old. The relationship between total length and body weight was expressed as W = 0.0052 L3.19 for all samples, which indicates that the growth of L. chuanchicus adheres to allometry. The Von Bertalanffy growth equation revealed that the fish had an asymptotic total length (L∞) of approximately 37.9 cm with a growth coefficient (K) value of approximately 0.461 yr−1. Using the age-based catch curve method, the calculated total instantaneous mortality rate (Z) for all samples was determined as being equal to approximately 1.1302 yr−1. Additionally, three methods were used to estimate the average instantaneous rate of natural mortality (M), resulting in an approximate value of 0.7167 yr−1 for all samples. Furthermore, the instantaneous rate of fishing mortality (F) for all samples was calculated as 0.4134 yr−1, leading us to determine that the exploitation rate (E) is 0.3658. It was concluded that the growth rate of L. chuanchicus in the upstream of the Yellow River is relatively fast, and L. chuanchicus has not been subjected to excessive exploitation, yet its relatively high natural mortality rate underscores the need for targeted management measures aimed at preserving its habitat.

Design of Transport Organization Schemes for River Shipping Towing Transport

To improve the economic efficiency of ship transportation in the Jialing River section, this paper conducts an in-depth analysis of the factors affecting tugboat and barge operations during cornering and lockage. Based on a detailed analysis of existing problems, this study proposes the re-adoption of electric tugboat solutions as a keyway to enhance the economic efficiency and transport capacity of Jialing River shipping. By establishing a mathematical model and comparing the cost levels of electric-powered vessels with traditional oil-driven ones, the study further suggests strategies for applying electric-powered tugs to increase the average tonnage per lockage pass and achieve optimization of ship transport organization, including careful adjustment of ship types and lockage vessel combinations. The research results show that under current conditions, the optimal fleet organization scheme is a combination of A motorized ships and B barges with a specific carrying weight (each barge with a load of t), which can significantly enhance the economic efficiency level of Jialing River fleets under specific premises, while also increasing transport volume and reducing costs by approximately.

Deep Learning-Based Automatic River Flow Estimation Using RADARSAT Imagery

Estimating river flow is a key parameter for effective water resource management, flood risk prevention, and hydroelectric facilities planning. Yet, traditional gauging methods are not reliable under very high flows or extreme events. Hydrometric network stations are often sparse, and their spatial distribution is not optimal. Therefore, many river sections cannot be monitored using traditional flow measurements and observations. In the last few decades, satellite sensors have been considered as complementary observation sources to traditional water level and flow measurements. This kind of approach has provided a way to maintain and expand the hydrometric observation network. Remote sensing data can be used to estimate flow from rating curves that relate instantaneous flow (Q) to channel cross-section geometry (effective width or depth of the water surface). Yet, remote sensing has limitations, notably its dependence on rating curves. Due to their empirical nature, rating curves are limited to specific river sections (reaches) and cannot be applied to other watercourses. Recently, deep-learning techniques have been successfully applied to hydrology. The primary goal of this study is to develop a deep-learning approach for estimating river flow in the Boreal Shield ecozone of Eastern Canada using RADARSAT-1 and -2 imagery and convolutional neural networks (CNN). Data from 39 hydrographic sites in this region were used in modeling. A new CNN architecture was developed to provide a straightforward estimation of the instantaneous river flow rate. Our results yielded a coefficient of determination (R2) and a Nash–Sutcliffe value of 0.91 and a root mean square error of 33 m3/s. Notably, the model performs exceptionally well for rivers wider than 40 m, reflecting its capability to adapt to varied hydrological contexts. These results underscore the potential of integrating advanced satellite imagery with deep learning to enhance hydrological monitoring across vast and remote areas.

Low signs of territorial behavior in the Eurasian otter during low-water conditions in a Mediterranean river

The Eurasian otter Lutra lutra is a territorial semi-aquatic carnivore usually found at low densities in rivers, coastal areas, and wetlands. Its diet is based on prey associated with aquatic environments. Mediterranean rivers are highly seasonal, and suffer reduced flow during the summer, resulting in isolated river sections (pools) that sometimes can be left with a minimal amount of water, leading to concentrations of food for otters. To our knowledge, this process, which was known to field naturalists, has not been accurately described, nor have otter densities been estimated under these conditions. In this study, we describe the population size and movements of an aggregation of otters in an isolated pool in the Guadiana River in the Tablas de Daimiel National Park (central Spain), which progressively dried out during the spring–summer of 2022, in a context of low connectivity due to the absence of circulating water in the Guadiana and Gigüela rivers. Using non-invasive genetic sampling of 120 spraints collected along 79.4 km of sampling transects and spatial capture-recapture methods, we estimated the otter density at 1.71 individuals/km of river channel length (4.21 individuals/km2) in a progressively drying river pool, up to five times higher than previously described in the Iberian Peninsula. The movement patterns obtained with the spatial capture-recapture model are not quite different from those described in low density, which seems to indicate a wide home range overlap, with low signs of territoriality.

Combined effects of river hydromorphological disturbances on macroinvertebrate communities: Multispatial scales analysis of central European rivers

Hydro-morphological threats impact the natural physical characteristics of river ecosystems, such as flow regimes, sediment transport, and channel morphology. These negative effects can occur at multiple scales, ranging from local microhabitats to geographic regions. Understanding these interactions can be useful for an integrated conservation approach and is needed for effective freshwater management. The aim of the study was to elucidate the combined effects of hydro-morphological threats on macroinvertebrates at three spatial scales: macroscale, including whole catchments, mesoscale (hydro-morphological changes in individual river sections) and the microscale, describing the microhabitat conditions of European rivers. The diversity and trophic structure of 1120 local macroinvertebrate communities in 28 catchments of various hydro-morphological disturbance levels, ranging from 0 to 2400 m asl, were analyzed. The response of macroinvertebrates to the main disturbance gradient differed between mountain and lowland communities. Random forest analysis indicated that the most important predictor of the ecological, diversity, and trophic indices was described by flow rate reduction. Generalized additive mixed models showed that decreased flow combined with river incision explained most of the variation in macroinvertebrate indices. Our results emphasize that based on multi-spatial scale analysis, hydro-morphological threats are very important factors in invertebrates biodiversity loss. Thus, to implement effective river management, we should pay more attention to the combined effects of geomorphological threats.

Evaluation of the Ecological Environment of the Fuhe River Based on the Diversity of Fish

This article takes the Fuhe River, which has water flowing into Baiyangdian all year round, as the research object. Through actual investigation and measurement of planktonic flora and fauna, benthic organisms, fish, and large vascular plants in the river, and based on fish diversity, the comprehensive evaluation index method is used to scientifically evaluate the ecological environment quality of the Fuhe River. The results showed that a total of 28 species of phytoplankton, 30 species of zooplankton, 11 species of benthic animals, 8 species of submerged plants, and 11 species of fish were detected in the survey area; From a diversity perspective, the diversity of the upstream and downstream river sections is higher than that of the downstream. Overall, the ecological environment quality of the Fuhe River in Baoding City ranges from medium to good, with good water quality in the upstream section and moderate water quality in the middle and downstream sections. This study provides a case study for the scientific evaluation of the ecological environment quality of the upper reaches of Baiyangdian.

Spatial distribution of benthic taxonomic and functional diversity in the Yellow River Basin: From ecological processes to associated determinant factors

One of the fundamental objectives in ecology is to investigate the ecological processes and associated factors governing the abundance and spatial distribution patterns of biodiversity. However, the reaction of biological communities to environmental degradation remains relatively unknown, even for ecologically crucial communities like macroinvertebrates in aquatic ecosystems. Here, we sampled 117 locations to quantify relative contributions of geographical and environmental factors, including water quality, land use, climate, and hydrological factors, to determine the absolute and relative compositions of macroinvertebrate communities and their spatial distribution in the Yellow River Basin (YRB), the sixth-longest river system on Earth. We assessed relative roles of species sorting and dispersal in determining macroinvertebrate community structure along YRB. Our results demonstrated that alpha and beta diversity indices showed an increase from the up- to low-reaches of YRB. The middle and low-reaches exhibited elevated species diversity and both regions exhibited relatively stable community compositions. The biodiversity of macroinvertebrates was influenced by a combination of geographical factors and environmental variables, with environmental factors predominantly serving as the principal determinants. Results of multiple linear regression and variance decomposition showed that the effect of environmental factors was approximately three times greater than that of spatial factors. These findings provide support for the hypothesis that species sorting, driven by environmental gradients, plays a significant role in shaping the community structure of macroinvertebrates in running water ecosystems at the basin scales. Moreover, the factors contributing to substantial shifts in biodiversity across different segments of YRB indicate that distinct river sections have been influenced by varying stressors, with downstream areas being more susceptible to the impacts of water pollution and urbanization resulting from human activities.

Challenges in downstream dam passage and the effect of dam removal on Atlantic salmon (Salmo salar) smolt migrations.

Migration is critical for life-cycle completion in diadromous fish species. River connectivity is vital in facilitating these large-scale movement events, but the extent of present-day river fragmentation can interfere with these migrations. Fish passage solutions (FPSs) are commonly implemented with the aim of improving river connectivity. In our study, we investigated the performance of two types of FPSs, spill regimes and complete dam removal, on Atlantic salmon (Salmo salar) smolt migrations. We used acoustic telemetry to monitor migration behavior and passage success of 120 wild smolts released in three different groups/sites: one group with two dams to pass to reach the river mouth, a second group with one dam to pass, and a control group without any barriers to pass (upstream of a recently removed hydroelectric dam). Smolt passage probabilities were similar for the two studied dams (87% and 86%) but showed variation in path choice, delay times, and loss rates. Passage success was influenced by several factors, such as body size, diel period, and water temperature, but not flow. Cumulative passage success to the river mouth was 61%, with most individuals being lost within lentic river stretches, either in the forebays of hydroelectric power stations or in naturally wide river stretches. Within the recently rehabilitated river sections (post dam removal), passage speeds were significantly faster than all other sections of the river (post-rehabilitation x¯ = 56.1 km/day) with significantly faster speeds compared to pre-rehabilitation (pre-x¯ = 28.0 km/day). Our findings provide valuable information on the benefits of dam removal and highlight the need for further rehabilitation measures in upriver reaches where barriers still affect downstream passage.

Multi-step ahead dissolved oxygen concentration prediction based on knowledge guided ensemble learning and explainable artificial intelligence

Accurate water quality prediction is crucial for effective environmental management and decision-making. However, previous studies have solely relied on historical data to simulate water quality, overlooking the potential discrepancies between predicted values and actual observations. Additionally, the opacity of machine learning models has posed challenges to the credibility of their predictions. Hence, considering the excellent nonlinear fitting ability of ensemble tree models, especially the Categorical Boosting (Catboost) model, this study proposes a knowledge-guided Catboost (KGCatboost) model for predicting the dissolved oxygen concentration, one of the vital water quality indicators, in 15 river sections of the Yangtze River Basin in Yunnan Province, China. Furthermore, to enhance the model’s interpretability, we employ the SHapley Additive exPlanations (SHAP) method to analyze the contributions of each input variable within the water body. The results demonstrate that on the test set of each dataset, the mean Nash-Sutcliffe Efficiency (NSE) value of KGCatboost is 0.874, which has improved by 0.34% and 3.07% compared to Catboost and eXtreme Gradient Boosting (Xgboost). In addition, this study reveals that pH has the most significant impact on DO concentrations. Specifically, as the pH increased, the DO concentration increased significantly. A regulatory mechanism has also been developed to alleviate the hazards caused by low DO concentrations. The KGCatboost model can provide valuable guidance for water resource management processes.

Characteristics of Microorganisms and Antibiotic Resistance Genes of the Riparian Soil in the Lanzhou Section of the Yellow River

Riparian soil is a critical area of watersheds. The characteristics of biological contaminants in riparian soil affect the pollution control of the watershed water environment. Thus, the microbial community structure, antibiotic resistance genes (ARGs), and mobile genetic elements (MGEs) in the riparian soil of the Lanzhou section of the Yellow River were investigated by analyzing the characteristics of soil samples collected from farmland, mountains, and industrial land. The results showed that the Proteobacteria, Bacteroidetes, and Actinobacteria were the dominant phyla in the riparian soil of Lanzhou section of the Yellow River. The microbial structure in the riparian soil was significantly correlated with the land use type (P < 0.05). The α diversity index of bacterial communities in land types was in the order of farmland > mountain > industry. Sulfonamide-typed ARGs were the most dominant genes in the soil of the Lanzhou section of the Yellow River Basin, among which the sul1 gene had the highest abundance, 20-36 000 times that of other detected ARGs. Moreover, the total absolute abundance of ARGs in industrial soil was the highest. Principal coordinate analysis (PCoA) displayed that the ARGs characteristics had a significant correlation with land types (P < 0.05), and intl1 and tnpA-04 drove the diffuseness of sulfonamide and tetracycline ARGs, respectively. Redundancy analysis (RDA) demonstrated that the content of inorganic salt ions and total phosphorus in the soil of the riparian zone of the Yellow River Lanzhou section were the main environmental factors, modifying the distribution of the microbial structure. Halobacterota and Acidobacteriota were the main microflora that drove the structural change in ARGs.

Environmental Restoration and Changes of Sediment and Hydrodynamic Parameters in a Section of a Renaturalised Lowland Watercourse

In Europe, the routes of most watercourses were straightened and shortened, leading to the destruction and degradation of many natural environments. Currently, in places where it is possible, as part of the implementation of the Water Framework Directive, efforts are made to improve environmental sustainability, including improving the ecological condition of rivers. This paper presents the impact of three in-stream deflectors on changes in the section of a small lowland river—the Flinta (Poland)—where (from 2018 to 2023) detailed, systematic geodetic, and hydrometric research and an assessment of the ecological conditions were carried out. The presented results show the influence of deflectors on the initiation of fluvial processes in the transverse and longitudinal layouts of the channel. The river channel was narrowed from 6 to 5 m, and the current line shifted by almost 3 m. Changes were observed in the distribution of velocities and shear stresses, varying along the surveyed section of the river. In the first year after their application, an increase in velocity at the deflectors can be observed (from 0.2 m∙s−1 to 0.6 m∙s−1 in the deflector cross-section). In the following years, on the other hand, a clear decrease in velocity was observed in the sections between the deflectors (to 0.3 m∙s−1). The introduction of deflectors resulted in a significant increase in the values of shear stresses (from an average value of 0.0241 N∙m−2 in 2018 to 0.2761 N∙m−2 in 2023) and local roughness coefficients (from 0.045 s∙m−1/3 before the introduction of the deflectors to 0.070 s∙m−1/3 in 2023). Based on analyses of sediment samples, erosion and accumulation of bottom material were initially observed, followed by a subsequent stabilisation of particle size. Differences in grain size were observed, especially in the cross-section of the deflectors (increase in granularity d50% downstream of the deflector from 0.31 mm to 3.9 mm already 2 years after the introduction of deflectors). This study confirmed the positive impact of using deflectors on hydromorphological processes as deflectors facilitate the achievement of a good ecological status, as required by the WFD. The innovation of this paper lies in demonstrating the possibility of using small, simple structures to initiate and intensify fluvial processes, which may contribute to improving the ecological conditions of watercourses.

Occupancy, movement, and behaviour of namew (lake sturgeon Acipenser fulvescens) in an intact river in Canada

Most sturgeon populations are imperilled and living in fragmented rivers. Here, we studied namew (lake sturgeon Acipenser fulvescens), fish important to Ililiwak (Moose Cree Peoples), in the North French River: a free-flowing, intact river in Kit Aski Nahnuun (the Moose Cree Homeland) in northern Ontario, Canada. This study was co-created alongside members of Moose Cree First Nation and used acoustic telemetry to passively track 20 tagged namew over 6 yr (2016-2022). Namew occupied the entire monitored river reach: about 45 km. Namew used 2 overwintering areas and occupied more overall river sections during spring and summer (out of 6 total seasons often used by Ililiwak). We did not detect namew moving upstream or downstream during freeze-up and winter. Generally, namew showed the greatest acceleration and travelled the longest distances during spring and summer, and they occupied shallower water during summer at lower water levels and deepest waters during freeze-up. We found an interaction between season and diurnal period, where namew occupied shallower depths and had higher acceleration at dawn and night relative to morning and afternoon in most seasons; dusk behaviour was variable among seasons. However, this pattern was absent in spring, when namew showed no diurnal pattern in acceleration and were in shallower water during morning and afternoon. Diurnal patterns were less pronounced, but detectable, during ice-affected seasons. This river provides year-round habitat for namew, and our data reveal distinct patterns of namew occupancy, movement, and behaviour in a free-flowing, intact river. Our work is an example of successfully co-creating research that addresses both scientific and community priorities.

Ammonoid and coleoid jaws from the Upper Cretaceous of northern Siberia (Nizhnyaya Agapa River sections)

The jaws of cephalopods, ammonites and especially coleoids, are rarely met in fossil state. The localities with diversified jaws, belonging to various groups of fossil cephalopods are even less common. We describe a diversified complex of cephalopod jaws from the upper Cenomanian–middle Turonian of Northern Siberia, which include the upper and lower jaws of Placenticeras ammonites (the oldest placenticeratid jaws known to date) and large-sized jaws of octobrachian coleoids. Although the lower jaws of Placenticeras belong to the aptychus type of ammonoid jaw apparatuses, they are characterized by the thickening of an inner organic layer in their anterior part, with a shape resembling a calcified conchorhynch known in the anterior portion of the lower jaws of Mesozoic nautilids and lytoceratid and phylloceratid ammonoids. The presence a conchorhynch-like structure supports the assumption that the feeding function in placenticeratid lower jaws most likely prevailed over the protective one. The upper jaws of Placenticeras show structure, typical for the jaws of aptychophoran ammonites: an inner lamella, divided into two wings, and a pointed outer lamella. Large-sized upper jaws of octobrachian coleoids demonstrate close affinities with the jaws of Octopoda suggesting that they could have belonged to representatives of this order, probably to large-sized gladius-bearing teudopseins. Judging by the jaws' size, both ammonites and octobrachians, which inhabited the marine basin in the Northern Siberia, were characterized by large body size. The cephalopod assemblage remained unchanged throughout the end of the Cenomanian and the first half of the Turonian.

Does willingness to pay for the traditional flood control measures kasumitei vary by river section of residential area?

Kasumitei (open levees) comprise a traditional flood mitigation measure used in Japan. Kasumitei allow floodwater to flow into surrounding paddy fields, which act as temporary flood mitigation basins. After flooding, debris accumulated in paddy fields often brings crop damage and debris removal costs. Therefore, in some areas, the disaster mitigation functions of kasumitei may bring about conflicts between beneficiaries (downstream residents) and burden bearers (midstream residents). Ensuring the continued use of kasumitei in the future requires a mechanism to support the burden bearers. This study aimed to test the hypothesis that the willingness to pay (WTP) for maintaining the kasumitei would be lower for midstream residents (potential burden bearers) than for upstream (irrelevant) and downstream residents (potential beneficiaries). The results showed that contrary to the hypothesis, WTP for maintaining kasumitei was not affected by the river sections of the respondents' residence. Thus, a financial support scheme for maintaining kasumitei might be acceptable regardless of the beneficiary or bearer in the surveyed respondents. In addition, respondents with higher interest in ecosystem conservation tended to have higher WTP. Therefore, to gain support for the maintenance and use of the kasumitei (a type of ecosystem-based disaster risk reduction), the authorities would promote awareness of the measure's contribution to ecosystem conservation. Based on the results, we discussed the potential financial support schemes for maintaining the kasumitei.

River plastic transport and storage budget

Rivers are one of the main conduits that deliver plastic from land into the sea, and also act as reservoirs for plastic retention. Yet, our understanding of the extent of river exposure to plastic pollution remains limited. In particular, there has been no comprehensive quantification of the contributions from different river compartments, such as the water surface, water column, riverbank and floodplain to the overall river plastic transport and storage. This study aims to provide an initial quantification of these contributions. We first identified the main relevant transport processes for each river compartment considered. We then estimated the transport and storage terms, by harmonizing available observations on surface, suspended and floodplain plastic. We applied our approach to two river sections in The Netherlands, with a focus on macroplastics (≥2.5 cm). Our analysis revealed that for the studied river sections, suspended plastics account for over 96% of item transport within the river channel, while their relative contribution to mass transport is only 30%–37% (depending on the river section considered). Surface plastics predominantly consisted of heavier items (mean mass: 7.1 g/#), whereas suspended plastics were dominated by lighter fragments (mean mass: 0.1 g/#). Additionally, the majority (98%) of plastic mass was stored within the floodplains, with the river channel accounting for only 2% of the total storage. Our study developed a harmonized approach for quantifying plastic transport and storage across different river compartments, providing a replicable methodology applicable to different regions. Our findings emphasize the importance of systematic monitoring programs across river compartments for comprehensive insights into riverine plastic pollution.

Assessing the water potential and wastewater load capacity of the La Tinh River, Binh Dinh province by MIKE 11AD and Ecolab model combined with GIS method

The study used the NAM model of flow simulation with a time series of 14 years (2008 - 2021), statistical analysis method, and MIKE 11 AD water quality model, and Ecolab combined with GIS method to calculate wastewater reception capacity and load capacity of the basin. The model validation is highly reliable with a model efficiency factor of R2 of 0.777 and BIAS = 5%. The results of the application of the NAM model have determined the daily flow series of 14 years (2008 - 2021) and the average flow characteristics of many years of the La Tinh basin such as Qo flow is about 5.9; 6.0 m3/s, total amount of Wo = 292.1; 188.8 million m3 flow modulus Mo = 19.3 l/s-km2 flow class Yo = 611 mm and flow coefficient α= 0.3 for all sub-basins. The results of the study show that the capacity of receiving wastewater, the capacity of most river sections in the La Tinh basin is still received with five parameters at a relatively high level, the section of the Binh Tri river upstream alone has exceeded its capacity to receive. This is one of the very useful tools in integrated management and effective use management of river basin water resources.

Generation of High‐Resolution Water Surface Slopes From Multi‐Mission Satellite Altimetry

AbstractFor nearly three decades, satellite radar altimetry has provided measurements of the water surface elevation (WSE) of rivers. These observations can be used to calculate the water surface slope (WSS), which is an essential parameter for estimating flow velocity and river discharge. In this study, we calculate a non time‐varying high‐resolution WSS of 11 Polish rivers based on multi‐mission altimetry observations from 11 satellites in the period from 1994 to 2023. The proposed approach is based on a weighted least squares adjustment with an additional Laplace condition and an a priori gradient condition. The processing is divided into river sections not interrupted by dams and reservoirs. After proper determination of the WSE for each river kilometer (bin), the WSS between adjacent bins is calculated. To assess the accuracy of the estimated WSS, it is compared with slopes between gauge stations, which are referenced to a common vertical datum. Such gauge stations are available for 8 studied rivers. The root mean squared error (RMSE) ranges from 4 mm/km to 77 mm/km, with an average of 27 mm/km. However, the mean RMSE decreases to 11 mm/km when the 2 mountain rivers are excluded. The WSS accuracies are also compared with slope data sets based on digital elevation models, ICESat‐2 altimetry, and lidar. For 6 rivers the estimated WSS shows the highest accuracy. The improvement was particularly significant for mountain rivers. The proposed approach allows an accurate, non time‐varying high‐resolution WSS even for small and medium‐sized rivers and can be applied to almost any river worldwide.

Health assessment of the current situation of rivers and discussion on ecological restoration strategies: A case study of the Gansu province section of the Bailong river

The health of watershed ecology is mutually constrained by the sustainable development of the regional economy and society, and health assessment helps to identify the ecological status quo. As one of the “ethnic corridors”, the Bailong River has become a region of human solid interference. Therefore, this study constructed an indicator evaluation system to reflect rivers' natural attributes and functionality by analyzing candidate indicators' sensitivity, principal components, and independence. The weight of the indicators was determined using the Analytic Hierarchy Process combined with expert opinions. The ecological status of the Bailong River was evaluated through field monitoring data, and ecological restoration suggestions were proposed. The results show that Bailong River's comprehensive score is 58.27, indicating sub-health. The constructed evaluation system includes thirteen indicators, of which 53.84% are in an ideal state, 15.39% are healthy, 7.69% are sub-health, 15.39% are unhealthy, and 7.69% are pathological, with weak spatial heterogeneity. The evaluation results of the guidelines show that the state of “cleanliness” and “service” is ideal, “circulation” and “life” are healthy, and “physical structure” is worrying. Based on this, the ecological restoration and protection of the Bailong River in the future should focus on the following aspects: improving methods and theories, restoring the habitat environment of the river, ensuring water quantity, improving water quality, and conserving fish species. This study can provide necessary theoretical support for the ecological restoration of severely disturbed water-deficient rivers and lakes in northern China.

Effects of freeze–thaw on bank soil mechanical properties and bank stability

Riverbank instability in the seasonally frozen zone is primarily caused by freeze–thaw erosion. Using the triaxial freeze–thaw test on the bank of Shisifenzi Bend in the Yellow River section of Inner Mongolia, we investigated the changes in the mechanical properties of the soil at different freezing temperatures and freeze–thaw times, and analyzed the bank’s stability before and after freezing based on the finite element strength reduction method. The results showed that the elastic modulus, cohesion, internal friction angle and shear strength of the soil tended to decrease with the increase in the number of freeze–thaw cycles and the decrease in freezing temperature. After 10 freezing cycles at − 5 ℃, − 10 ℃, − 15 ℃ and − 20 ℃, the modulus of elasticity of soil decreased by 40.84 ~ 68.70%, the cohesion decreased by 41.96 ~ 56.66%, the shear strength decreased by 41.92 ~ 57.32%, respectively. Moreover, the stability safety coefficient of bank slope decreased by 18.58% after freeze–thaw, indicating that the freeze–thaw effect will significantly reduce the stability of bank slope, and the bank slope is more likely to be destabilized and damaged after freeze–thaw.