Plain River Network Research Articles

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.

Spatial variation in the community structure and response of benthic macroinvertebrates to multiple environmental factors in mountain rivers

Exploring the response between benthic community changes and environmental variables has significance for restoring the health of river ecosystems. However, little is known of the impact on communities of interactions between multiple environmental factors, and frequent changes in the flow of mountain rivers are different from those in the flow of plain river networks, which also impact differently the benthic community. Thus, there is a need for research on the response of benthic communities to environmental changes in mountain rivers under flow regulation. In this study, we collected samples from the Jiangshan River in the dry season (November 2021) and the wet season (July 2022) to investigate the aquatic ecology and benthic macroinvertebrate communities in the watershed. Multi-dimension analyses were used to analyze the spatial variation in the community structure and response of benthic macroinvertebrates to multiple environmental factors. In addition, the explanatory power of the interaction between multiple factors on the spatial variation of communities, and the distribution characteristics of benthic community and their causes were investigated. The results showed that herbivores are the most abundant forms in the benthic community of mountain rivers. The structure of benthic community in Jiangshan River was significantly affected by water quality and substrate, whereas the overall community structure was affected by river flow conditions. Furthermore, nitrite nitrogen and ammonium nitrogen were the key environmental factors impacting the spatial heterogeneity of communities during the dry and wet season, respectively. Meanwhile, the interaction between these environmental factors showed a synergistic effect, enhancing the influence of these environmental factors on community structure. Thus, controlling urban and agricultural pollution and releasing ecological flow would be effective strategies to improve benthic biodiversity. Our study showed that using the interaction of environmental factors was a suitable way to evaluate the association between environmental variables and variation in benthic macroinvertebrate community structure in river ecosystems.

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.

Hydrochemical characteristics of groundwater in a plain river network region: Establishing linkages between source and water quality variables

The chemical characteristics of groundwater can indicate water quality condition and provide useful information for pollution source identification. This study aimed to understand the effects of dissolved organic matter (DOM) on ionic composition of groundwater and identify the main ions and sources of pollution. The Lake Taihu is a typical eutrophic lake in China. In this study, the hydrochemical composition of groundwater in the surrounding aquifer of Lake Taihu Basin was analyzed. The results showed that the values of water quality index (WQI) range from 13.29 to 56.26 (good water quality). The dominant hydrochemical type of groundwater was Ca–Mg–HCO3 type, and the rock dominance was the major mechanism controlling the groundwater chemistry. With an increasing concentration in dissolved organic carbon (DOC), the Na+, Mg2+, and HCO3– concentrations all showed a sharp increase followed by a slow increase, while the NO3– concentration showed an opposite trend, indicating the DOM can affect the ions composition. In addition, K+ was positively correlated with NO3–, As, and Cd. Hence, DOM input may directly or indirectly change the hydrochemistry of groundwater. Besides, the NO3– concentration in groundwater was much higher than that in Lake Taihu, indicating that the NO3– in groundwater mainly came from surface soil leaching. The anthropogenic sources are probably the main sources of different ions, including K+, NO3–, As, and Cd. This study can help to better understand the effects of lake eutrophication on groundwater and its pathways.

Removal efficacy of fly ash composite filler on tailwater nitrogen and phosphorus and its application in constructed wetlands.

Constructed wetlands (CWs) have been widely used in tailwater treatment. However, it is difficult to achieve considerable removal efficiency of nitrogen and phosphorus in tailwater solely by CWs-an efficient green wetland filler is also important. This study investigated 160 domestic sewage treatment facilities (DSTFs) in rural areas from two urban areas in Jiaxing for TP and NH3-N and found that TP and NH3-N concentrations in rural domestic sewage (RDS) in this plain river network are still high. Therefore, we selected a new synthetic filler (FA-SFe) to enhance nitrogen and phosphorus reduction, and we discuss the importance of filler in constructed wetlands. Experiments revealed the adsorption capacity of the new filler: the maximum adsorption amounts of TP and NH3-N reached 0.47g m-2 d-1 and 0.91gm-2 d-1, respectively. The application potential of FA-SFe was verified in actual wastewater treatment, with the removal rates of ammonia nitrogen and TP reaching 71.3% and 62.7%, respectively. This study provides a promising pathway for nitrogen and phosphorus removal from rural tailwaters.

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.

Water Level Simulation in River Network by Data Assimilation Using Ensemble Kalman Filter

Water level simulation for complex water river networks is complex, and existing forecasting models are mainly used for single-channel rivers. In this paper, we present a new data assimilation model based on the ensemble Kalman filter (EnKF) for accurate water level simulation in complex river networks. The EnKF-based data model was tested on simulated water level data from a river network hydrodynamic model and optimized through parameter analysis. It was then applied to a real mountainous single-channel river and plain river network and compared with a data assimilation model based on the extended Kalman filter (EKF). The results showed that the EnKF-based model, with a medium ensemble sample size of 100–150, normal observation noise of 0.0001–0.01 m, and a high standard deviation of 0.01–0.1 m, outperformed the EKF-based model, with a 49% reduction in simulation errors, a 45% reduction in calculation cost, and a 43% reduction in filtering time. Furthermore, the EnKF-based data assimilation model predicted the water level in the plain river network better than the mountainous single-channel river. Around 5 to 8 h were required for data assimilation; afterwards, the model could make accurate predictions covering 20 to 30 h. The EnKF-based data assimilation model offers a potential solution for water level predictions in river networks.

Coupled improvements on hydrodynamics and water quality by flowing water in towns with lakes.

With the worsening environmental problems in the plain river network, flowing water has become important because of its obvious improvement effect. In order to solve water quality and water mobility problems of the river network in Shengze Town, this paper establishes four flowing water scenarios and compares the associated improvements in water quality and hydrodynamics of the river network with the use of coupled hydrodynamic and water quality models. It is identified as the best scenario to dispatch 20 m3/s of water from the Xiegang River downstream of the Qingxi River and 20 m3/s of water from Lake Xiangjiadang to Lake Beiyandang. Results of this scenario show a significant improvement in the water mobility of the river network in the southern area of the Qingxi River, with the flow rate increasing by 38.23%. The water quality in Lake Beiyandang has upgraded from Class V to Class IV (based on the Chinese water quality standards), and the water quality downstream of the Qingxi River has improved a lot. Findings in this work could provide references for the development of flowing water scenarios in similar watersheds.

Differences in bacterial community composition, structure and function between sediments in waterways and non-navigable channels in a plain river network area.

Bacterial communities greatly help maintain the balance of river ecosystems and are highly sensitive to changes in environmental conditions. Plain river network areas (PRNs) are characterized by dense river networks, low-lying terrain, and slow water flow, where the bottom sediment is frequently disturbed by ship navigation due to the limited water depth and width of waterways, providing a unique ecological niche for bacterial growth. Hence, understanding how bacterial communities in PRNs respond to changes in hydrodynamic conditions, physicochemical parameters, and pollutants under ship navigation is essential to maintaining the stability of inland waterway ecosystems. The Taihu Lake Basin, a typical PRN, was selected to explore the differences in bacterial community composition, structure and function between sediments in waterways (WS) and non-navigable channels (NS). The results indicate that the sediment from NS possessed more diverse and complex bacterial communities than WS. NMDS and ANOSIM analyses further verified the significant differences in bacterial community structure between WS and NS. Combined with LEfSe, we observed the highly differential taxonomy between WS and NS from phylum to order. Moreover, a comparison of beta diversity dissimilarity indices revealed that although species replacement dominated both the WS and NS beta-diversity patterns, species loss caused the differences in the overall beta diversity between them. Variance partitioning analysis revealed that physicochemical parameters (clay content, pH, ORP, and others) and ship traffic volume (STV) were the main driving factors for bacterial community distribution between WS and NS, while pollutants (heavy metals, perfluoroalkyl acids, and others) had a relatively minor influence. PICRUSt2 analysis revealed that the changes in pH, ORP, and STV under ship navigation might inhibit the bacterial ability to metabolize carbohydrates. The results reveal the comprehensive effects of ship navigation disturbance on sediment bacterial communities in the PRN and contribute to further understanding of inland waterway ecosystems.

Characteristics and Changing Trend of Water Pollution in North Plain of Shang Yu

The plain river network area is strongly influenced by human activities, with flat terrain, weak hydrodynamics and poor water quality. Previous studies have mostly focused on water quality categories, lacking an overall study of the pollution characteristics of water bodies and their changing trends. In order to comprehensively grasp the water pollution situation of the river network in the northern Yu Plain, this study scientifically analysed the water quality characteristics of the river network in the northern Yu Plain and its correlation with rainfall through regression analysis and MK mutation test based on the long series of water quality and rainfall data of the Dongjin River and Unity River in the northern Yu Plain from 2017-2021. The results show that the correlation between water quality and rainfall in the river network of the northern Yu Plain is not significant, reflecting that the pollution in the watershed is still controlled by point sources, but there is a trend for the Unity River to change to non-point source control; the CODMn, NH3-N and TP of the Dongjin River and Unity River all show a high positive correlation, and the correlation of the Dongjin River is higher than that of the Unity River; the MK mutation test shows that there is no significant mutation point in the Dongjin River in the last five years, and the Unity River has no significant mutation point in the last five years. The MK mutation test shows that there is no significant mutation point in Dongjin River in the past 5 years, and there is a sudden change in water quality in Unity River from 2017 to 2018, and the water quality indexes show a decreasing trend in general, but remain stable in recent years. The study aims to academically reveal the dominant factors, pollutant characteristics and water quality trends of pollutants in rivers in the northern Yu Plain, and to propose scientific references for the pollution prevention and control of other plain river networks.

Configuration of Submerged Plants for Plain River Networks Based on Transparency Improvement

The configuration of submerged plants plays an important role in the restoration of river networks. In this study, the Sudong River, a typical plain river network in southern China, was selected for submerged plant configuration research to improve water transparency. Analysis of historical and field research data of Sudong River showed that most of the water was in a state of eutrophication. The main factors affecting transparency were water temperature, ammonia nitrogen, chlorophyll a, total phosphorus, and permanganate index, which were identified through correlation analysis using SPSS. Submerged plants are important for water ecological restoration, and a plant selection evaluation system was constructed to screen six suitable local submerged plants in Suzhou for ecological restoration based on secondary indicators divided into five segments. Each plant was evaluated and scored. Finally, a combination of three submerged plants, Ceratophyllum demersum, Watermifoil, and Foxtail algae, was selected based on their scores. This combination effectively improved the eutrophication status of water and increased water transparency while adhering to the laws of submerged plant succession and facilitating the construction of a stable aquatic ecosystem.

平原河网生态流量计算方法及其适宜性研究

平原河网生态流量计算方法及其适宜性研究

Multiple-criteria determination and preventive measures of river ecological water level in the Northern Jiangsu plain

It is vital to employ efficient methods to calculate and determine the threshold of river ecological flow. These methods help to get the river ecological status control countermeasures in the plain river networks and construct a flawless long-term mechanism of ecological flow control (water level). According to the river's current environment and the actual circumstances surrounding its operation and administration, the upper, middle, and lower reaches make up the three sections of the Zong-Liutang River in the Plain of Northern Jiangsu. Furthermore, the ecological water level governing factor for each reach was analyzed and studied. The ecological water level threshold in the upper and lower reaches of the Zong-Liutang River adopted the specified values of Jiangsu Provincial Department of water resources. The threshold of the middle reach was thoroughly analyzed by using the determination method with multi-criteria, which consisted of the hydrological and hydraulic methods (including yearly minimum water level with a 90% assured rate method; wetted perimeter method; minimum monthly average water level method), aquatic living conditions method, and river landscape entertainment factor method. Taking into account the hydrological and hydrodynamic characteristics, observed hydrological data conditions of rivers, and the actual operation rules of rivers and water projects regulations in the Northern Jiangsu plain. Through comparing and contrasting actual operation and management plans, the target values of the ecological water level for the river's upper, middle, and lower reaches were 17.4 m, 8.96 m, and 7.5 m, respectively. Based on the river's ecological water level's control value, which was found through a thorough analysis, and the river's real operation and management conditions, specific measures to protect the river's ecological water level were suggested. These included developing a perfect and workable ecological flow control method, speeding up the development of an ecological water level goal assurance early warning system, and an ecological flow and inlet system.

Assessing the mechanism for flood control: a case of plain river network cities under extreme rainfalls.

In recent years, frequent floods hit Chinese cities and caused heavy casualties and property losses, making China faced with severe flood problems. In this study, Nanhai Future City in the IX Flood Control Area of Yancheng City, Jiangsu Province, was selected as the research area to simulate water-level changes under different control schemes meeting extreme rainfalls. MIKE model simulated the inundation with the designed storm of different return periods. The results showed that flooding inside the research area was severe. Higher drainage capacity of the pump stations with more engineering and non-engineering measures can reduce the adverse effect of extreme rainfall. The results provide a reference for planning future infrastructure and flood control decisions for Nanhai Future City and the surrounding areas.

Analysis of water source contributions and their impacts on hydrological structural connectivity in plain urban river network areas based on stable isotopes (δ2H, δ18O)

AbstractWater sources carry chemicals that can have a significant impact on the water environment of a river network, and understanding the contribution of different water sources to the river network can help to manage the pollution of the river network at its source. The hydrological connectivity of a river network affects the self‐purification capacity and flood prevention capacity of the river. Therefore, an isotope tracer approach was applied to determine the contribution rate of different water bodies to a river network and hydrological connectivity was quantified by introducing the retention rate. Changzhou city was selected as the study area because it is an urbanized city with the characteristics of a plain river network and it is faced with poor hydrological connectivity due to artificial constructions (dams and pumps) and human activity (urbanization). River water, well water (shallow groundwater), lake water and rainfall were collected during the flood season and nonflood season, and hydrogen and oxygen isotopes were determined. The temporal and spatial variations in hydrogen and oxygen isotopes in different water bodies and the state of the water cycle in different water bodies were analysed. IsoSource and MixSIAR models were established to analyse the contribution rate of river network water sources in the study area, and their effectiveness was compared. The results of the MixSIAR model were selected to evaluate the hydrological connectivity of the river network in the study area, providing a method to quantify the hydrological connectivity of specific rivers of the river network in Changzhou city. This method could also be applied to other urban plain river network areas to study river connectivity.

How anthropogenic factors influence the dissolved oxygen in surface water over three decades in eastern China?

The aquatic environment, linked to the sustainable development of human existence and ecological environment, is influenced comprehensively by anthropogenic and natural activities. In light of the continuously low concentration of dissolved oxygen (DO) in surface water in plain river networks and the phenomenon of delay in the improvement of surface water quality, this research aims to introduce a method that may be utilized in identifying the critical driving forces of DO in surface water and their lagging characteristics, which will contribute to the assessment and adjustment of water quality drivers and/or policies. The research analyzes a typical small watershed in a river network region of the Yangtze River Delta plain as the study area, collecting 35-year (1986–2020) data on several water quality parameters, decades of anthropogenic activities, and two natural factors. The time series methods of vector autoregressive model, Granger causality tests, forecast error variance decompositions, and impulse response functions (hereinafter referred to as VAR+), which are rarely applied in related research, were employed in this study and proved helpful for screening out pivotal drivers and capturing the lagging responses of DO level to driving forces at each lagged time. Results show that there exists a fluctuating drop in DO level in surface water from 1986 to 2008 and a steady climb from 2008 to 2020, with the lowest DO level being present in 2008. The impulsive perturbations of phosphate fertilizer consumption (PFC), motor vessel number, and precipitation minimally increase DO concentration, while the impulsive perturbation of gross domestic product (GDP) causes the sharpest drop in DO level. With these perturbations, the driving force of PFC persists for approximately seven years, and the driving forces of water temperature, permanent population, and GDP persist for only five years. Future research could be conducted with spatial hysteresis, selection of lag order and variable quantity within the model, as well as intermediate variables between drivers and DO level for exploring driving pathways and mechanisms.

Assessment and Optimization of Water Resources Regulation for River Networks in the Tidal Plain—A Case Study of the Qingsong Area in Shanghai

The plain river network area has a developed economy, a large population, a complex water system, and weak hydrodynamics. In order to improve the hydrodynamic conditions of the plain river network area, clean water sources are introduced through water resources regulation to supplement the ecological water quantity of the river and effectively improve the water environment of the river. In this paper, the Qingsong area in Shanghai is used as the research object. Prototype observation, numerical simulation, and other methods are used to build a hydrodynamic mathematical model of the river network in the Qingsong area, evaluate the water resources regulation effect of the Qingsong area, and put forward two optimization schemes. The results indicate that the overall flow of the Qingsong area is from north to south and west to east, with a maximum flow of 10–68 m3/s in the north–south backbone, exchange cycle between the backbone river, and the peripheral water bodies in the Qingsong area is 4.3 days. The largest amount of water is diverted along the Wusong River, accounting for 53% of the total water diversion; the drainage mainly relies on the gates along the Huangpu River and the Diandong Pumping Gate, accounting for 43% and 42%, respectively. In view of the lowering of the water level in the slice during the low tide period, an optimal regulation scheme has been developed for more diversion and less drainage along the Huangpu River, which can raise the water level in the slice by 0.05–0.10 m. Assessment and optimization of water resources scheduling in the Qingsong area can provide a reference for hydrodynamic enhancement in the river network area of the tidal plain.

Traceability of nitrate polluted hotspots in plain river networks of the Yangtze River delta by nitrogen and oxygen isotopes coupling bayesian model

The adverse effects of increased nitrate (NO3−) pollution especially from the non-point source on the hydrosphere and anthroposphere are becoming more prominent. The non-point-derived NO3− in the rivers supplying the upstream threatens the aquatic ecosystem of Taihu Lake. Here, dual-stable isotopes (δ15N and δ18O) of NO3− were applied to the Bayesian model (SIAR) for quantitative source identification of reactive nitrogen (Nr) in a mixed agricultural and urban region along the complex river network of the Yangze River delta. The results showed that the NO3− concentrations in the rivers ranged from 1.09 to 4.44 mg L−1 and decreased from the highly urbanized areas to the lakeside rural areas. The specific isotopic characteristics of four sources (atmospheric deposition, AD; chemical fertilizer, CF; manure and sewage, MS; and soil leachate, SL) by the SIAR isotope model indicated that the MS source made the greatest contribution (46.56%) to the total NO3− load, followed by SL (27.86%), CF (23.77%), and AD (1.81%). The highly urbanized areas and the hybrid areas, which contained a mix of industrialized, populated, and agricultural areas, were identified as hotspot areas with heavy Nr pollution, responsible for spatial patterns of δ15N–NO3- and δ18O–NO3-. These hotspot areas were characterized by a less well-developed sewage pipeline system with high Nr emissions from cash crops. The changes in wastewater treatment level, the agricultural production structure, and meteorological changes were the main factors of spatial variation of Nr concentration and source in the upstream Taihu Lake Basin. The variation in Nr concentration across Taihu Lake would respond to these anthropogenic-driven Nr loads. These findings suggest that MS was the predominant source had the strongest effect on the overall riverine NO3− source which was the primary problem that needed to be solved.

Online Storage Technology of the Separate Sewage System: Demonstration Study in a Typical Plain River Network City

Due to the high underground water level, frequent rainfall, and large amounts of infiltration and inflow (I/I) into the sewage system, a city in the plain river network region had to face a series of problems caused by the high water-level operation of the drainage system. Suzhou, a city in the Yangtze River Delta region of China, can be a representative of cities in plain river networks, where this research was carried out. The amount of I/I into the sewage system was evaluated, and the storm water management model (SWMM) was used to further calculate the sewer water storage capacity under dry and wet weather with multi-year average rainfall. Based on the offline model calculation and artificial experiences, the rule-based online regulation and storage real-time control strategy (RTC) is verified, and the online regulation and storage intelligent scheduling demonstration is carried out in the central-city district of Suzhou. The results showed that the infiltration in dry weather accounted for about 20–25% of the total collected wastewater; in wet weather (36 mm precipitation), the extraneous water induced by I/I peaked at 73.64%. The collaborative control of regional multi-stage pumping stations through RTC of the sewage system can effectively avoid the high water-level operation caused by peak sewage flows on dry days. In combination with rainfall forecasting, the coordinated control of plants and pumping stations to pre-empty the sewer pipelines prior to rainfall can, to some extent (up to 35 mm of rainfall in this study), cope with the increase in I/I induced by rainfall.

Exploring the Cumulative Selectivity of Polycyclic Aromatic Hydrocarbons in Phytoplankton, Water, and Sediment in Typical Urban Water Bodies

To understand the interactions among eutrophication, algal bloom, and POPs (persistent organic pollutants) in freshwater ecosystems, the cumulative selectivity of PAHs (polycyclic aromatic hydrocarbons) in phytoplankton, water, and sediment with different eutrophication level waters were identified in a typical plain river network region located in Nanjing City. Results showed that a total of 33 algal species belonging to 27 genera and 4 phyla were identified in 15 sites of urban water bodies, and most of them belonged to the type Cyanobacteria–Bacillariophyta. The eutrophication level of these rivers and lakes led to the sample site specificity of algal composition and abundance. The planktonic algae mainly accumulated the 2-ring and 3-ring PAHs, and the sediment mainly enriched the high-ring PAHs. However, the enrichment capacity of planktonic algae on PAHs was much higher than that of sediment. Cyanophyta and some species of Bacillariophyta and Chlorophyta in mesotrophic (βm) and meso-eutrophic water bodies (ßαm) preferentially accumulated lower-ring PAHs (naphthalene, acenaphthylene, and phenanthrene). Some other specific algae species, such as Euglenophyta, some species of Bacillariophyta, and most Chlorophyta in mesotrophic and moderate eutrophic water bodies, had strong capacities to enrich high-ring PAHs subsuming benzo[a]anthracene, chrysene, and anthracene. The eutrophication level of water bodies affected the cumulative selectivity of PAHs by shaping the site specificity of phytoplankton composition, which may be related to water quality, sediment characteristics, phytoplankton composition, and the algal cell walls.