River Network Area Research Articles

Variability in soil characteristics in the field–bund transition area increases water loss potential in paddy fields

Water loss in paddy fields occurs through various pathways, and previous studies have primarily focused on water seepage in the field, often overlooking the potential for the field-bund area. In this study, 3 typical paddy fields in the plain river network area of southeastern China were selected to clarify the differences in the soil structure and hydraulic characteristics at different positions within the field–bund area: the field, inner bund, middle bund and outer bund. The interactions between basic soil properties and hydraulic characteristics were also evaluated. The results revealed that the outer bund presented the lowest soil porosity (6.92 %), followed by the field (7.52 %), middle bund (7.77 %), and inner bund (8.09 %). The soil pores in the field presented the smallest mean diameter and fractal dimension and the highest degree of anisotropy. The deep layer of the bund contained more macropores, and the soil pores exhibited greater spatial distribution heterogeneity. The bottom layer in the field and bund presented the lowest average Ks value of only 0.05 mm min−1, indicating the presence of a plow pan and a notable tendency for lateral seepage. Differences in the soil structure and hydraulic parameters between the field and bund created a driving force for lateral seepage and rendered the field–bund area a hotspot for water loss. For the analysis of the underlying water loss mechanism, the structural equation model represented 65 % of the total variance in the hydraulic parameters. The micropore characteristics had the greatest positive direct effect on the hydraulic parameters, with a standardized path coefficient of 0.39 (p < 0.001). The soil physical properties were not directly related to the hydraulic parameters but exerted an indirect effect through aggregate stability and micropore and macropore characteristics, with a total indirect standardized path coefficient of −0.41.

Assessing Watershed Flood Resilience Based on a Grid-Scale System Performance Curve That Considers Double Thresholds

Enhancing flood resilience has become crucial for watershed flood prevention. However, current methods for quantifying resilience often exhibit coarse spatiotemporal granularity, leading to insufficient precision in watershed resilience assessments and hindering the accurate implementation of resilience enhancement measures. This study proposes a watershed flood resilience assessment method based on a system performance curve that considers thresholds of inundation depth and duration. A nested one- and two-dimensional coupled hydrodynamic model, spanning two spatial scales, was utilized to simulate flood processes in plain river network areas with detailed and complex hydraulic connections. The proposed framework was applied to the Hangjiahu area (Taihu Basin, China). The results indicated that the overall trend of resilience curves across different underlying surfaces initially decreased and then increase, with a significant decline observed within 20–50 h. The resilience of paddy fields and forests was the highest, while that of drylands and grasslands was the lowest, but the former had less recovery ability than the latter. The resilience of urban systems sharply declined within the first 40 h and showed no signs of recovery, with the curve remaining at a low level. In some regions, the flood tolerance depth and duration for all land use types exceeded the upper threshold. The resilience of the western part of the Hangjiahu area was higher than that of other regions, whereas the resilience of the southern region was lower compared to the northern region. The terrain and tolerance thresholds of inundation depth were the main factors affecting watershed flood resilience. The findings of this study provide a basis for a deeper understanding of the spatiotemporal evolution patterns of flood resilience and for precisely guiding the implementation and management of flood resilience enhancement projects in the watershed.

Understanding the Water Quality Changes of the Typical Plain River Network Area Using Comprehensive Assessment Methods

Understanding the Water Quality Changes of the Typical Plain River Network Area Using Comprehensive Assessment Methods

A Study on the Construction and Evaluation of the Water Resource Reutilization System for Farmland Diversion and Drainage

Water is an essential resource for both rural and agricultural areas; it can be wisely distributed and used in the field to protect daily life, production, the natural environment, and the safety and stability of regional drainage and flood control systems. Our research selected a typical plains rural river network area with agriculture as the main industry to investigate the most effective method of farmland diversion and drainage. We comprehensively planned and transformed the water system flow, water conservation engineering, and the ecological environment in the irrigation area through the reutilization system. The reutilization system’s operation and scheduling design is implemented for four specific periods: the water replenishment cycle, agricultural irrigation, agricultural drainage and the rainy period of the flood season. The research period ranges from 2020 to 2023 after the completion of the system. We used monitoring, the recording of hydraulic equipment parameters and data collection to evaluate the balance of water supply and demand in the study area. At the same time, we have tracked and evaluated the four aspects of water quality enhancement, water conservation and flood control, and agricultural irrigation. The results show that the total agricultural water consumption decreased by 2.9%, and the amount of water saved increased by 9.6%. The current segment creates the rivers’ embankment standards. With a 92% irrigation guarantee rate, the current section forms and the embankment standards of the rivers satisfy the design storage volume and the flood level of one in twenty years. The water quality of all the rivers in the area has decreased by 5~10% compared to the average concentration prior to establishment. This study verifies the comprehensive effect and the suitability of the system by comparing the before and after effects, and provides a scientific basis for the method of efficient recycling and utilization of water resources in the rural plains river network area; we also propose the guidance of increasing the digital twin control and long-term operation mechanism to ensure the long-term stable operation of the technology.

Study of flood protection water levels for railway projects in the plains river network area

The Taihu Lake basin is characterised by a developed water system and a longitudinal river network, which is prone to flooding during the flood season. This poses a threat to the construction and operation of river-related railways, bridges, and other infrastructures, and therefore the design value of the water level of the river channel must be provided prior to the construction of roads and bridges in the basin. The Yanyi Railway traverses numerous river systems without the benefit of measured hydrological data. In order to address this deficiency, two methods were constructed using the Taihu Lake basin model: the historical water level frequency analysis method and the typical design storm method of the basin. These methods were employed to calculate the flood protection water level of each river under different design schemes and to analyze the reasons for the differences in the results. The results indicate that the water level results of the historical water level frequency analysis method are also applicable to the construction of the Yanyi Railway, provided that an economic perspective is taken.

Identification of agricultural surface source pollution in plain river network areas based on 3D-EEMs and convolutional neural networks.

Agricultural non-point sources, as major sources of organic pollution, continue to flow into the river network area of the Jiangnan Plain, posing a serious threat to the quality of water bodies, the ecological environment, and human health. Therefore, there is an urgent need for a method that can accurately identify various types of agricultural organic pollution to prevent the water ecosystems in the region from significant organic pollution. In this study, a network model called RA-GoogLeNet is proposed for accurately identifying agricultural organic pollution in the river network area of the Jiangnan Plain. RA-GoogLeNet uses fluorescence spectral data of agricultural non-point source water quality in Changzhou Changdang Lake Basin, based on GoogLeNet architecture, and adds an efficient channel attention (ECA) mechanism to its A-Inception module, which enables the model to automatically learn the importance of independent channel features. ResNet are used to connect each A-Reception module. The experimental results show that RA-GoogLeNet performs well in fluorescence spectral classification of water quality, with an accuracy of 96.3%, which is 1.2% higher than the baseline model, and has good recall and F1 score. This study provides powerful technical support for the traceability of agricultural organic pollution.

High Spatiotemporal Resolution River Networks Mapping on Catchment Scale Using Satellite Remote Sensing Imagery and DEM Data

AbstractCharacterizing and understanding the changes in the flow regimes of rivers have been challenging. Existing global river network data sets are not updated and can only identify rivers wider than 30 m. We propose a novel automated method to map river networks on a monthly basin scale for the first time at 10‐m resolution using Sentinel‐1 Synthetic Aperture Radar, Sentinel‐2 multispectral images, and the AW3D30 Digital Surface Model. This method achieved an overall accuracy of 95.8%. The total length of the Yellow River network produced is 40,280 km, approximately 3.2 times that of the Global River Widths from Landsat (GRWL) database, more effectively covering small and medium rivers. The monthly river geometry revealed a positive correlation between river network area and precipitation. This study is expected to provide a cost‐effective alternative to accurately mapping global river networks and advance our understanding of the changes and drivers of river systems.

Joint Optimization of Urban Water Quantity and Quality Allocation in the Plain River Network Area

Cities located in the plain river network area possess abundant water resources. However, due to urbanization and industrialization, there is a severe water shortage problem caused by poor water quality. To overcome this issue, a multi-objective optimal allocation model of water quantity and quality is proposed. The model considers regional water resources, economic, social, and environmental requirements and uses the NSGA-II genetic algorithm for model solution. Furthermore, to evaluate and analyze the degree of spatial equilibrium of regional water resources and how it relates to economic factors, the study uses the spatial equilibrium theory of water resources and the Gini coefficient of water resources. Jingjiang, a city in Jiangsu Province characterized by a typical plain river network area, was selected as the study area. The results of the optimal allocation of water resources in Jingjiang City show that: (1) total water consumption and chemical oxygen demand (COD) emissions for the current planning period are within their respective limits. In addition, the implementation of the water conservation program has resulted in a 5% reduction in total water shortages and a reduction of COD emissions by 1276 tons, (2) the structure of the water supply in Jingjiang City has been optimized; more than 90% of Ⅳ~V surface water is used for agriculture, and the domestic water supply is mainly from transit water, which effectively ensures that high-quality water is used in the domestic water supply, (3) the spatial equilibrium coefficient of water resources per sub-area is between 0.33 and 0.74, indicating an unbalanced or almost unbalanced level. The application of a water conservation program has resulted in the improvement of the spatial equilibrium level of water resources in each sub-area, with an overall spatial equilibrium of 0.64, indicating a more balanced level; the degree of matching of water resources with population, GDP, and land area is at the matching level, (4) according to the Gini coefficient of the distribution of water resources, the plains river network area displays a better match between water resources and economic and social factors of each water receiving area, thanks to its unique geographical location and natural conditions. This study can serve as a decision-making reference for addressing the urban water quality water shortage problem in the plain river network area.

The Risk of Water Quality Deterioration with Urban Flood Control—A Case in Wuxi

There is a demand for flood control in densely populated river network areas. Therefore, small floodgates are used for long-term and rapid water flow regulation in such contexts. However, people often disregard these floodgates’ potential interference with the natural water environment. This study focused on an urban floodgate-controlled reach and monitored the monthly data of four main pollutant indicators (TN, TP, CODMn, and NH3-N) from 2016 to 2018 at six fixed sampling points (S1–S6). The difference analysis and cluster analysis results indicated that floodgate adjustments were the dominant driving factor of water quality changes in the reach, with pollutant concentration differences observed between the floodgate opening and closing periods. The results of the Canadian Council of Ministers of the Environment Water Quality Index evaluation showed that the water quality of the floodgate-controlled reach was categorized as “marginal” or “poor”. It is particularly important to note that the concentration of nitrogen compounds exceeded the allowable limits. The results of the Mann–Kendall trend and time series analyses revealed an overall upward trend in NH3-N concentration and a localized upward trend in TP concentration and presented periodic concentration fluctuations of four pollutants (TN, TP, CODMn, and NH3-N). This study highlights that flood control management using small floodgates can pose a risk of deteriorating water quality. Therefore, it is necessary to develop scientific water quality management methods.

Tracing sediment sources in a plain river network area by using optimized experimental design and reflectance spectroscopy

Soil erosion in a plain river network area with dense rivers, fertile land, and agricultural development is easily causes river siltation, agricultural non-point source pollution, and water eutrophication. Therefore, the negative impact of the sediment on the environment cannot be underestimated. Most traditional sediment fingerprint tracing studies have focused on mountain basins and lack a scheme suitable for plain river network sediment tracing. Here, a typical plain river network in the Taihu Basin was selected as the study area. The flow structure and characteristics were analysed, and a sampling scheme for the stream segment and a two-step model of sediment tracing in a plain river network were proposed to quantitatively distinguish the types of sediment sources. The results indicated that the traditional discriminant function analysis adequately distinguishes the contribution rate of basin soil and has a good validation accuracy (R2 = 0.96, root mean square error of calibration = 5.91 %), whereas Random Forest obtains better discrimination results by mining non-linear information in the soil spectra of different land types, with R2 values of 0.89, 0.83, and 0.80 for farmland, forest, and grassland, respectively. The average proportion of soil in the sediment in the watershed was 23 %, and the proportion of soil in the watershed increased from upstream to downstream. The sediment sources of the Caoqiao, Yincun, and Shaoxiang Rivers mainly came from grassland (44 %), forest (39 %), and farmland (42 %), respectively. Land-use distribution, water conservation facilities, and soil particle size were the main factors affecting these sources. Each river adopts measures to remove the corresponding pollutants, optimise water and soil conservation measures for riverbank green belts and forest, and regularly clean up silt in water conservancy ditches and rivers, which can reduce the pollution impact caused by sediment.

Temporal and Spatial Characterization of Sediment Bacterial Communities from Lake Wetlands in a Plain River Network Region

Sediment bacterial communities are a vital component of microbial communities in aquatic and terrestrial ecosystems and they play a critical role in lake wetlands. We aimed to investigate the effect of season, depth and regional environmental factors on the composition and diversity of bacterial communities in a plain river network area from Taihu Basin. The millions of Illumina reads (16S rRNA gene amplicons) at the surface 25 cm inside samples of the study area were examined using a technically consistent approach. Results from the diversity index, relative abundance, principal component analysis (PCA), redundancy analysis (RDA) and linear discriminant analysis effect size (LEfSe) analysis indicated that the diversity of the bacterial community in summer was generally higher than in other seasons. Proteobacteria were the most abundant phylum in the sediment samples in different seasons (43.15–57.41%) and different layers (39.66–77.97%); the autumn sediments were enriched with Firmicutes (5.67%) and Chloroflexi (12.5%); in all four seasons the sediments were enriched with Betaproteobacteria (14.98–23.45%), Gammaproteobacteria (11.98–14.36%) and Deltaproteobacteria (8.68–14.45%). In the bottom sediments (10–25 cm), Chloroflexi were abundant (average value 10.42%), while Bacteroidetes was the dominant phylum in the surface sediments; redundancy analysis found that total phosphorus (TP) (p = 0.036) was the main environmental factor influencing the sediment bacterial community in different layers. This study provides a reference for further understanding the effects of seasonal changes on sediment microorganisms in lake wetlands.

Deciphering the spatiotemporal trade-offs and synergies between ecosystem services and their socio-ecological drivers in the plain river network area

Understanding changes in ecosystem services (ESs) and quantitatively identifying the drivers that influence these changes are essential for achieving sustainable ecosystem development. In this study, multiple data sources and techniques, including meteorological data, land use/cover data, soil data, the InVEST model, and ArcGIS, were used to analyze the spatiotemporal variation characteristics of carbon storage, habitat quality, soil retention, water yield, and crop product supply in Xinghua City from 2000 to 2015. Additionally, we explored the causes of these changes and the interrelationships among these ESs. The results showed that: (1) During the study period, carbon storage and habitat quality declined, water yield fluctuated and increased, and soil retention had small interannual variations. The supply capacity of crop products first increased rapidly and then stabilized. (2) ESs were influenced by multiple drivers, with altitude having the strongest explanatory power for habitat quality and soil retention, and food production having the strongest explanatory power for crop product supply. (3) Relationships between different ESs were variable and changed over time. This study could enrich the understanding of spatial and temporal changes and drivers of ESs in the plain river network area, which has important implications for future land use planning and sustainable development of ESs.

Quantifying cumulative changes in water quality caused by small floodgates in Taihu Lake Basin — A case in Wuxi

Small floodgates in the river network area own some characteristics: considerable quantity, wide range and short adjustment time, and intercepts the one-dimensional constant flow of rivers, which induce a great impact on riverine water quality. In this study, a typical urban floodgate-controlled reach was selected, and analyzed through the monthly data of four pollutant indicators TN, TP, CODMn and NH3-N at six sampling sites S1–S6 in 2016–2018. The principal component analysis and correlation analysis showed that TP was a representative indicator and there was a positive correlation between various pollutants. The difference test and linear regression showed that the concentration of pollutants at different sampling points varied greatly, and the pollutant concentrations in the longitudinal direction of the river showed a cubic-linear regression. The cluster system and CCME WQI showed that the water quality in the urban floodgate-controlled reach is “marginal” state, and TN and NH3-N are severely exceeding the standard. The “cumulative changes” of the floodgate on the pollutant input to the environment appeared spatial heterogeneity.

A deep learning model with spatio-temporal graph convolutional networks for river water quality prediction

Abstract High-precision water quality prediction plays a vital role in preventing and controlling river pollution. However, river water's highly nonlinear and complex spatio-temporal dependencies pose significant challenges to water quality prediction tasks. In order to capture the spatial and temporal characteristics of water quality data simultaneously, this paper combines deep learning algorithms for river water quality prediction in the river network area of Jiangnan Plain, China. A water quality prediction method based on graph convolutional network (GCN) and long short-term memory neural network (LSTM), namely spatio-temporal graph convolutional network model (ST-GCN), is proposed. Specifically, the spatio-temporal graph is constructed based on the spatio-temporal correlation between river stations, the spatial features in the river network are extracted using GCN, and the temporal correlation of water quality data is obtained by integrating LSTM. The model was evaluated using R2, MAE, and RMSE, and the experimental results were 0.977, 0.238, and 0.291, respectively. Compared with traditional water quality prediction models, the ST-GCN model has significantly improved prediction accuracy, better stability, and generalization ability.

Scenario-based performance assessment of green-grey-blue infrastructure for flood-resilient spatial solution: A case study of Pazhou, Guangzhou, greater Bay area

Flood resilience has aroused significant interest in coastal areas dealing with a growing frequency of severe rainstorms caused by climate change and urbanisation. At the core of flood resilience is the development of a resilient green-grey-blue infrastructure system that can resist, absorb, and recover from floods in a timely manner. Current flood resilience research, however, is limited to evaluating single infrastructure systems, failing to examine the dynamic process or find ideal spatial infrastructure designs for decision-makers. This research proposes a scenario-based assessment framework for integrated green-grey-blue infrastructure systems to improve flood resilience during urban design decision-making. Rainfall-runoff, drainage networks, and river system models are interlinked to provide quantitative simulation evaluations of water quantity and urban impact in various spatial organisations of infrastructure design. A dynamic, multi-criteria decision-making process is used to reveal the importance of five temporal indicators and rank design alternatives. In Guangzhou, China, the efficiency of this architecture is demonstrated on Pazhou Island, a typical river network area. Given the limited water and green space available, the results demonstrate that submerged areas exert a greater influence during peak rainfall, and blue infrastructure storage becomes an essential factor following rainfall. Furthermore, from a spatial perspective, the looped network of green-blue infrastructure enhances flood resilience, and downstream waterway connections and green space-aligned waterways boost the water storage capacity of green-grey-blue infrastructure. This paradigm can improve flood resilience in the Greater Bay Area in the future, especially in response to heavy rainstorms and river floods.

Agricultural non-point source pollution and rural transformation in a plain river network: Insights from Jiaxing city, China

Recently, agricultural non-point source pollution (ANPSP) has gained increasing attention in China. However, using a uniform paradigm to analyze ANPSP in all regions is difficult, considering their geographical, economic, and policy differences. In this study, we adopted the inventory analysis method to estimate the ANPSP of Jiaxing City, Zhejiang Province as a representative region of the plain river network area from 2001 to 2020 and analyzed it in the framework of policies and rural transformation development (RTD). The ANPSP showed an overall decreasing trend over 20 years. Compared to 2001, total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD) decreased by 33.93%, 25.77%, and 43.94%, respectively, in 2020. COD accounted for the largest annual average (67.02%), whereas TP contributed the most to the equivalent emissions (50.9%). The highest contribution of TN, TP, and COD, which fluctuated and decreased over the past 20 years, originated from livestock and poultry farming. However, the contribution of TN and TP from aquaculture increased. The overall trend of RTD and ANPSP showed an inverted “U” shape with time, and the evolution of both showed similar stage characteristics. With the gradual stabilization of RTD, ANPSP successively went through three stages: high-level stabilization (2001–2009), rapid-decreasing (2010–2014), and low-level stabilization (2015–2020). Additionally, the relationships between pollution loads from different agricultural sources and indicators of different dimensions of RTD varied. These findings provide a reference for the governance and planning of ANPSP in the plain river network area and a new perspective for investigating the relationship between rural development and the environment.

Practice of ecological remediation and restoration in plain river network -- a Case Study of Gehu Lake in Changzhou, China

This study provides a design diagram which involves a series of pragmatic strategies for ecological remediation and restoration of plain river networks in the Yangtze River Delta. The design diagram is composed of two stages: the first concerns the reduction of pollutants, including those from non-point sources, point sources, and river sediments; the second, the restoration of the biological habitat, including the riparian zone and aquatic habitat. A case study of Gehu Lake was used as an example for the implementation of the suggested design diagram, and further suggestions were provided for the improvement of remediation work in plain river network areas. This research provides valuable insights into the methods of ecological restoration, and demonstrates the potential for multidisciplinary collaboration to help improve the environmental health of plain river networks.

Comparative Analysis of the Hydrodynamic Performance of Arc and Linear Flapping Hydrofoils

In order to improve the hydrodynamic performance of flapping hydrofoils and solve the problem of insufficient hydrodynamic force in plain river network areas, in this study, we consider the more realistic swing of fish tails and propose an arc flapping method, the coupled motion of which has three degrees of freedom: heave, pitch, and lateral displacement. Two flapping methods, positive arcs and negative arcs, were derived on the basis of the lateral displacement direction. By using the finite volume method (FVM) and overlapping grid technology, a numerical simulation was conducted to compare and analyze the pumping performance of three types of flapping hydrofoil, namely, linear, positive arcs, and negative arcs, in order to further provide guidance for the structural optimization of bionic pumping devices. The results showed that the wake vortex structures of the three flapping modes all had anti-Kármán vortex streets, but the wake vortex of linear flapping deflected upward, and the wake vortex of positive arc flapping tended to be further away in the flow field. In one cycle, thrust was always generated by the positive arc flapping hydrofoil and the linear flapping hydrofoil, but the thrust coefficient curve of the positive arc flapping hydrofoil was more stable than that of the linear flapping hydrofoil, and the peak value was reduced by 46.5%. In addition, under the conditions of a flow rate of 750 L·s−1 and an average head of 0.006 m, the pumping efficiency of the positive arc flapping hydrofoil reached 35%, thus showing better pumping performance than the traditional linear flapping hydrofoil under conditions with ultra-low head.

Theory and Practice of Hydrodynamic Reconstruction in Plain River Networks

The river networks in the plains of China are in low-lying terrain with mild bed slopes and weak hydrodynamics conditions. Filled with intense human activities, these areas are characterized by serious water security problems, e.g., frequent floods, poor water self-purification capabilities, and fragile water ecosystems. In this paper, it’s found that all these problems are related to hydrodynamics, and the spatiotemporal imbalance of river network hydrodynamics is identified as the common cause of these water-related problems. From this, a theory for the hydrodynamic reconstruction of plain river networks is proposed. In addition to the importance of the flow volume, this theory highlights the role of hydrodynamics and limited energy in improving the ecological water environment. The layout of water conservancy project systems (e.g., sluices and pumping stations) is optimized to fully tapping the potential integrative benefit of projects. The optimal temporal and spatial distributions of hydrodynamic patterns is reconstructed in order to meet the needs of the integrated management of complex water-related problems in river networks. On this basis, a complete theoretical method and technical system for multiscale hydrodynamic reconstruction and multi-objective hydraulic regulation in plain river networks with weak hydrodynamics is established. The principles of the integrated management of water problems in river network areas are put forward. The practical application and efficacy of the theory are demonstrated through a case study aiming to improve the water quality of the river network in the main urban area of Yangzhou City.

Co-occurrence patterns and assembly processes of abundant and rare bacterioplankton in plain river network areas of eastern China

In the context of anthropogenic impacts on riverine ecosystems globally, understanding the response of bacterioplankton to anthropogenic stress is important for human and environmental health. Bacterioplankton communities are critical for maintaining ecosystem stability, but little is known about their co-occurrence networks and assembly processes in intense human-impacted plains river networks. By applying cooccurrence networks, variance partitioning, and null model analysis, we investigated the mechanisms of interaction and assembly of abundant (>1% relative abundance) and rare (<0.01%) taxa at 32 sites in river networks along an urbanization gradient (urban, suburban, and agricultural areas). Our results show that interactions between the bacterioplankton communities were more complex in urban areas than in other areas, and that environmental factors (primarily fluoride, nitrate nitrogen, and dissolved organic carbon) as well as spatial factors (i.e., Moran’s Eigenvector Maps) explained most of the variation in bacterioplankton communities. Abundant taxa showed stronger spatial turnover than rare taxa, indicating that spatial factors played a greater role in the assemblage of abundant taxa. Land use types, especially impervious surfaces, had a unique influence on rare taxa, but contributed less to community change than other factors. In addition, rare taxa were mainly influenced by deterministic processes, whereas abundant taxa were more influenced by stochastic processes, especially in agricultural areas. These findings suggest that the shares of abundant and rare taxa mediate disturbances in local environmental conditions in anthropogenic river network areas, while deterministic processes play a greater role in shaping bacterioplankton communities. Overall, our study provides important insights for environmental monitoring and management in areas of intense human activity, emphasizing the need to consider both abundant and rare taxa when assessing the impact of human activities on riverine ecosystems.