Large-scale hydropower development provides substantial socio-economic and energy benefits but simultaneously introduces complex ecological and environmental challenges that require comprehensive scientific assessment. This study systematically evaluates the effects of the leading reservoir (Longpan hydropower station, referring to the uppermost and principal flow-regulating dam in the cascade) in the middle reaches of the Jinsha River's operation on the water environment of the mainstream Yangtze River, China, with the aim of clarifying its water quality responses and supporting evidence-based basin management. Based on an analysis of the current water quality conditions of the Yangtze River and a comparative review of the operational experience of the Three Gorges Reservoir, this research explores the mechanisms through which large reservoirs alter hydrological and ecological processes. These mechanisms include reduced flow velocity, prolonged water residence time, weakened pollutant dispersion, and increased risk of algal blooms in tributaries. To quantitatively assess these impacts, an improved river dilution-mixing model was developed and applied to simulate the water quality response during the dry season (February-April) under different discharge scenarios. Key downstream monitoring sections were examined. The modeling results indicate that the operation of the Leading reservoir can moderately reduce dry-season concentrations of key pollutants (e.g., total phosphorus, permanganate index) at downstream sections by approximately 2-5% on average, with spatially heterogeneous effects. Although the overall improvement magnitude remains limited, the combined effects of sediment deposition and in situ degradation may yield more pronounced real-world benefits. The findings underscore the importance of optimizing the regulatory function of the Longpan Reservoir through coordinated operation within the cascade reservoir system. It is recommended to integrate water resource allocation, water quality management, and aquatic ecosystem protection, alongside enhanced pollution control and ecological restoration in key zones. The methodology and findings provide a referenced framework for assessing the water-environmental implications of large-scale reservoir regulation in other major river systems.

Qionghai Lake is an important freshwater source in the Yunnan–Guizhou Plateau. However, cyanobacterial blooms have been observed recently in Qionghai Lake, but their formation mechanism and control management are not well understood. Herein, phytoplankton, zooplankton, eutrophication, nutrients, and biochemical indices were measured in Qionghai Lake from May 2022 to April 2023. The results showed that cyanobacterial blooms in Qionghai Lake predominated in Anabaena sp. with a density of 1.11 × 107–18.87 × 107 cells/L. Anabaena blooms started in the northwestern area of Qionghai Lake in November 2022 and then expanded to the entire lake until it peaked and subsided in February 2023. Protozoa dominated in zooplankton while having no significant relationship with Anabaena blooms in Qionghai Lake. The trophic level index and chlorophyll a showed similar spatiotemporal trends with Anabaena sp. density, and water quality in the northwest of the Qionghai Lake was worse than in other parts. Total nitrogen (TN) and total phosphorus (TP) were 0.41–0.54 and 0.021–0.045 mg/L from November 2022 to February 2023. TN and TP were positively correlated with Anabaena sp. density, but TP was the most significant environmental factor affecting Anabaena bloom in Qionghai Lake. These findings might provide essential information for improving bloom control and water quality remediation in Qionghai Lake.

Spring dinoflagellate blooms are always severe in the Three Gorges Reservoir (TGR), China, threatening water ecological health. Many dinoflagellates are capable of mixotrophism, yet the influence of dissolved organic matter (DOM) on their growth and blooms in spring remains unclear. This study characterized the source and composition of DOM from sediment, soil, and plant, and assessed their effects on the growth of bloom-forming algal species (Peridiniopsis sp. and Microcystis aeruginosa) under different temperatures. The results showed that sediment and soil DOM promoted Peridiniopsis sp. growth, plant DOM slightly inhibited it. However, DOM had no significant effect on M. aeruginosa growth. The promotion of sediment and soil DOM on Peridiniopsis sp. growth was higher at 15 °C and 20 °C than at 25 °C. Moreover, the effect of DOM on Peridiniopsis sp. growth was more significant than that of high nitrogen and phosphorus. Fulvic acid-like, humic-like and tyrosine-like substances of DOM in sediment and soil might be the effective components promoting the Peridiniopsis sp. growth, while tryptophan-like substance of plant DOM might hinder it. Sediment and soil DOM might promote the Peridiniopsis sp. growth mainly by providing adequate organic carbon, increasing protein content, and improving photosynthesis. The findings will provide important information for the formation and control of dinoflagellate blooms in TGR.

Reservoir water level regulation induces intricate processes of phosphorus (P) migration and release within the water-level fluctuation zone (WLFZ). These dynamic interactions pose significant challenges for effective pollution management strategies. This study focused on two typical tributary WLFZs (narrow gorges type and wide river type) in Three Gorges Reservoir (TGR), aiming to quantify P sources and assess their release potentials across two operational periods. Results showed that the deposition of suspended particulate P (SS-P) transported from the upstream was the dominant P source in the two WLFZs during the low water level period (August 2022). During the drainage period, the main P source of the ‘narrow gorges type’ WLFZ was P loss from slope soil above the WLFZ, but the ‘wide river type’ WLFZ had a mix of P sources, including P loss from slope soil, SS-P depositions from the TGR backwater and the tributary upstream. Among the three P sources, the slope soil source exhibited a relatively higher degree of P saturation (DPS) values (0.5–18.8%), indicating a greater potential for P release. Given that P loss from slope soil is the primary P source in the WLFZs during the drainage period, which coincides with the spring plowing season, it is crucial to implement measures to prevent P loss from slope soils to safeguard water quality in the TGR.

Substituting chemical fertilizers with compost is anticipated to facilitate the disposal of organic waste and mitigate nonpoint source pollution. However, research investigating the impact of diverse-compost utilization on the chemical reactivity of soil at the molecular-level remains lacking. Herein, the quantification and identification of molecular-scale redox sites and intermolecular interactions of soil dissolved organic matter (DOM) using diverse composts during a crop rotation cycle were investigated using the unified theoretical modeling approach VSOMM2 and Schrodinger. Results showed that compost use considerably altered the molecular weight and composition of soil DOM. In particular, we successfully optimized the validity coefficient of the unit model's molecular number to construct 38 molecular models of DOM molecules to identify and quantify the distribution of redox sites and intermolecular interactions within soil DOM molecules. Moreover, the distinct roles of different composts in modulating redox molecules within the soil DOM were determined during a crop rotation cycle. The application of cow manure compost considerably increased the quinone, Ar-COOH, and Ar-SH contents in Model(EAC+), while application of food waste compost enhanced the Ar-OH and Ar-NH2 in Model(EDC+). Finally, rotatable bonds, cation-pi interactions, aromatic H-bonds, pi-stacking, and salt bridges were identified to facilitate electron transfer within the redox molecules of soil DOM, which can be further enhanced via compost use. The findings of this study provide insights into the environmental biochemical reactions involving microcatalysts, metal reduction fate, pollution fate, and molecular composition of soil, providing a theoretical basis for enhancing soil reactivity using organic fertilizers instead of chemical fertilizers.

Fulvic acids (FAs) is formed during the bioconversion of organic matter (OM) to biogas during anaerobic digestion (AD) and has a complex structure and redox function. However, the evolutionary mechanisms of FAs during AD and its interactions with acid and methane production have not been sufficiently investigated, especially at different stages of AD. Intermittent AD experiments by chicken manure and rice husk showed significant structural changes and reduced aromatization of FAs (e.g., O-H stretch6, 14.10-0%; SR, 0.22-0.60). The electron donating capacity (EDC) [9.76-45.39 mu mole /(g C)] and electron accepting capacity (EAC) [2.55-5.20 mu mole  /(g C)] of FAs showed a tendency of decreasing and then increasing, and FAs had a stronger electron transfer capacity (ETC) in the methanogenic stage. Correlation analysis showed that the EDC of FAs was influenced by their own structure (C-O stretch2, C-H bend1, C-H bend4, and N-H bend) and also had an inhibitory effect on propionic production, which further inhibited acetic production. The EAC of FAs was affected by molecular weight and had a promoting effect on methane production. Structural equation modelling identified three possible pathways for AD. The C-O stretch2 structure of FAs alone inhibits the production of propionic. In addition, pH can directly affect the EDC of FAs. This study provides a theoretical basis for the structural and functional evolution of FAs in AD of chicken manure on the mechanism of methane production.

Dissolved organic matter (DOM) is a key component of aquatic ecosystem function and biogeochemical processes. The characteristics of DOM in tributaries of the Three Gorges Reservoir (TGR) during the severe spring algal bloom period and their relationship with algal growth are unclear. In this study, the content, composition, and source of DOM in the Pengxi River (PXR) and Ruxi River (RXR) exhibiting typical TGR bloom problems were analyzed using various physicochemical indexes, carbon isotopes, fatty acids, and metagenomics. The results showed that chlorophyll a content increased with rising DOM concentration in the PXR and RXR. The dissolved organic carbon (DOC) and chromophoric dissolved organic matter (CDOM) contents in the two rivers were 4.656-16.560 mg/L and 14.373-50.848 μg/L, respectively, and increased during the bloom period. Four fluorescent components were identified, namely, two humic-like substances, and two protein-like substances. Proteobacteria, bacteroidetes, and actinobacteria were the greatest contributors to DOM content. The carbon fixation pathway of microorganisms increased the DOC concentration in both rivers during the bloom period. Physicochemical parameters (WT, pH, DO, and PAR) affected the DOM concentration by influencing microbial activity and DOM degradation. DOM in both rivers was derived from allochthonous and autogenous sources. Meanwhile, the DOC content was more strongly correlated with allochthonous sources. These findings might provide essential information for improving water environment management and algal bloom control in the TGR.

为了解东洞庭湖水域的碳汇特征,于2022年4月涨水期对东洞庭湖区域进行调查采样,并同步监测关键环境因子.运用垂向归纳模型和薄边界层法分别研究了东洞庭湖涨水期浮游植物的初级生产力以及水-气界面CO2和CH4的交换通量,基于碳收支关系计算水域净碳汇通量并分析其影响因素.结果表明:东洞庭湖涨水期水域碳汇能力存在空间差异性,总体表现出碳源的特征.湖区出口、城陵矶、岳阳楼、扁山、鹿角、湖中岛、蝴蝶口、大小西湖、六门闸上游、红星洲净碳汇通量为负值,表现为碳源,通量波动范围为-4.92～-0.17(mmol/(m2·h)),平均值为-1.95mmol/(m2·h);东湖区、六门闸下游净碳汇通量为正值,表现为碳汇,通量波动范围为1.10～2.24(mmol/(m2·h)),平均值为1.67mmol/(m2·h).东洞庭湖水域的净碳汇通量(NPP)主要受CO2通量(FcO2)、CO2分压(PCO2)及溶解氧(DO)影响.此外水位波动、水体营养盐、温度、水体碱度也会通过改变水体PCO2含量对碳汇能力造成较大影响.

2022年4月平水期及2022年7月丰水期对洞庭湖区域进行调查采样,同步检测各环境因子;基于水体酸碱平衡、亨利定律及室内实验,计算水体各碳素赋存含量,并分析各影响因素.结果表明:不同时期东洞庭湖水域各碳素赋存含量均呈现出溶解性无机碳(DIC)＞溶解态有机碳(DOC)＞颗粒态有机碳(POC)＞颗粒态无机碳(PIC)的特征.水位变动、水体理化因子、湘江来流和温室气体分压对东洞庭湖水域碳素赋存含量有较大影响;不同时期水温(Temp)、pH值、溶解氧(DO)与叶绿素a(Chl-a)含量对碳素赋存含量影响差异性显著.

采用2013-2017 年洞庭湖主要出入湖断面水质、水量监测数据,估算洞庭湖经由"四水"(湘江、资水、沅江、澧水)和长江"三口"(松滋口、太平口、藕池口)入湖及城陵矶出湖氮、磷通量,分析其时空变化特征及滞留效应.结果表明:时间上,2013-2016 年"四水""三口"年均入湖氮、磷通量总体呈增加趋势,但2017 年受入湖水质改善、水量减小的同步影响,相比2016 年入湖氮、磷通量分别减小了19.93%、23.14%,受水情影响,入湖氮、磷通量在年内分配不均,70%以上集中在4-9 月;空间上,入湖氮、磷通量主要来源于"四水"水系,分别占78.48%和71.77%,其中湘江和沅江的贡献较大."四水"受点、面源污染的综合作用,而"三口"的面源污染是其主要污染来源.此外,洞庭湖氮、磷滞留率很低,藻类浓度不高,但湖区氮、磷浓度(1.73、0.075 mg/L)仍远高于湖泊藻类暴发的临界值(0.20、0.02 mg/L).为降低湖泊水华的发生风险,关键是保持湖泊的连通性,警惕长江"三口"区域总磷风险,并兼顾湖滨区污染物控制.

A comprehensive 3-dimensional hydrodynamic and eutrophication model, the environmental fluid dynamics code model (EFDC) with three functional phytoplankton groups, was applied to simulate the algal dynamics in a mesotrophic P-limited subtropical plateau lake, Lake Erhai, Southwestern China. Field investigations revealed the seasonal patterns in external total phosphorus (TP) input and TP concentration, as well as the composition of the phytoplankton community. The model was calibrated to reproduce qualitative features and the succession of phytoplankton communities, and the net primary production was calculated. The modeled daily net primary production (NPP) ranged between −16.89 and 15.12 mg C/m2/d and exhibited significant seasonal variation. The competition for phosphorus and temperature was identified as the primary governing factor of NPP by analyzing the parameter sensitivity and limitation factors of the lake. The simulation of four nutrient loading reduction scenarios suggested high phytoplankton biomass and NPP sensitivity to the external TP reduction. A significant positive correlation was found among NPP, total phytoplankton biomass and TP concentration. Overall, this work offers an alternative approach to estimating lake NPP, which has the potential to improve sustainable lake management.

The input of pollutants into the lake has ainfluence on the water quality of the lake. Detailing the contribution of water and nutrients from the inflow rivers are essential for lake water management. Major ions Na+ and Cl− were applied to trace contributions of water and total nitrogen (TN) from the inflow rivers to West Dongting Lake. By using the two-source mixing model and the two-component TN mixing model, the results showed that water and TN in West Dongting Lake were mainly contributed by local rivers rather than the three outfalls, in which the contribution of Yuan River was larger than that of Li River. However, the contribution rates of water and TN of the three outfalls to West Dongting Lake during the wet season reached above 20% and 30%, respectively, indicating that the contribution of the three outfalls to West Dongting Lake could not be ignored. Among them, the contributions of Songzi outfall were higher than those from Taiping and Ouchi outfalls. Therefore, we suggest that the relevant departments should identify key river management targets during different water periods, implement refined management over water pollution in West Dongting Lake, and prioritize the pollutant input of Yuran River and Songzi outfall (especially during the wet season). This study demonstrates that major ion tracing is suitable for estimating the contribution rates of different nutrient sources in the river-lake system, which will provide valuable information for protecting the water quality of West Dongting Lake in the future.

为了解洞庭湖流域水体叶绿素a的时空分布及其与环境因子的关系,于2019年1～12月对洞庭湖进行采样调查分析,运用广义可加模型(GAM)分析了叶绿素a浓度与各环境因子间的关系.结果显示,洞庭湖水体叶绿素a浓度存在较为显著的时空分布差异,其年均值为5.77μg/L,变化范围为1.00～67.33μg/L.叶绿素a浓度变化的单因素GAM模型中,不同季节环境因子对叶绿素a浓度变化影响解释率较高的单一因素有所不同,春季为高锰酸盐指数(CODMn)、电导率(Cond)和总磷(TP);夏秋季为CODMn、水温(WT)和电导率;冬季为氨氮(NH4+-N)、电导率.叶绿素a浓度变化的多因素GAM模型中,对叶绿素a浓度变化的总体解释率为97.5％,解释效果较好.影响叶绿素a浓度变化的环境因子排序为CODMn＞TP＞电导率＞NH4+-N＞TN/TP,均与叶绿素a浓度呈非线性相关.

藻类生长与营养盐浓度存在藻类几何级数增长的营养盐浓度变化的下限阈值和藻类生长不受氮磷浓度增加影响的上限阈值，但由于蓝藻水华的形成受多种因素的综合影响，不同湖泊、不同区域及不同时段的氮磷浓度对蓝藻水华的影响差别较大，使得蓝藻生长的氮磷控制阈值难以确定.针对控制蓝藻水华暴发的氮磷阈值的研究虽然有所开展，但多集中在实验室研究阶段或对经验值的判断，虽然也有基于野外实测数据的研究，但也限制于某一特定区域，而基于野外长序列实测数据并且覆盖整个湖泊的氮磷阈值研究则是空白.太湖作为具有较高营养背景的富营养化浅水湖泊，蓝藻水华的发生受氮磷影响较大.对太湖总磷（TP）、总氮（TN）和叶绿素a（Chl.a）浓度的时空变化分析发现，太湖西北湖区的TP、TN与Chl.a浓度明显较高，并且TP、TN与Chl.a均呈显著性正相关.为探究太湖蓝藻水华暴发的TP和TN控制阈值，以轻富营养化等级下的Chl.a分级标准(10, 26]作为表征水华暴发的条件，采用郑丙辉等的频率分布法，确定了太湖蓝藻水华暴发的TP和TN控制阈值分别为0.05～0.06和1.71～1.72 mg/L；通过空间验证，太湖藻型区TP和TN浓度远高于同级营养水平下全湖区TP和TN控制阈值，表明藻型区高氮磷水平为蓝藻水华发生提供充足营养盐条件，即使氮磷全湖平均浓度控制在蓝藻水华暴发的氮磷阈值水平之下，但在气象水文等因素适宜条件下，藻型区水华发生风险仍然较高；并且在高氮磷背景下，即便在水华发生风险低的季节，水华发生风险仍然较大.近十几年来，虽然太湖经历了大规模的高强度治理，但由于环太湖流域的湖西区入湖负荷占比大，导致太湖藻型区氮磷浓度仍处于高位运行状态，为蓝藻水华的暴发提供了充足的营养盐基础，因此，湖西区的控源减排仍然是太湖富营养化及蓝藻水华防控的重点.

The Three Gorges Reservoir (TGR) underwent staged impoundment during 2003-2010. Periodic water impoundment included drainage (March to early June), low water level (June to August), impoundment (September to October), and high water level (November to February) periods. However, the impacts of the Three Gorges Dam (TGD) and impoundment on water quality of TGR tributaries remain poorly understood, especially in the long term and across the entire TGR drainage basin. Herein, water quality and hydrological indices of 27 tributaries, eutrophication of 38 tributaries, and pollution load of the TGR were determined during 2000-2015 to explore spatiotemporal variations in water quality. The results revealed slower flow velocity in tributaries and an extended residence time with the water level rising, and the water quality of tributaries was mainly affected by the mainstream backwater movement. Water quality was good in more than 60% of tested sites, had the best condition in the impoundment period, and it increased over time. Spatially, water quality in tributary upstream was better than in the backwater area, and worst in the tributary estuary. Among water quality indices, total nitrogen (TN) and total phosphorus (TP) were the key pollution indices, with median range of 1.619- 2.739 and 0.088-0.277 mg/L, respectively. Additionally, water quality indices of TGR tributaries displayed temporal and spatial heterogeneity due to different hydrodynamic and pollution load conditions. A total of 38 tributaries displayed eutrophication, the frequency of blooms concentrated in spring and increased from the upper tributaries to the downstream area. These results expanded the theory of hydrodynamic variation and the associated evolution of the water environment after impoundment, could provide theoretical references for water quality management in river-type reservoir. (C) 2021 Elsevier Ltd. All rights reserved.

梳理了国内外排污许可制度的发展历程,分析总结了国家水体污染控制与治理科技重大专项(简称"水专项")实施初期太湖流域排污许可管理体系存在的问题和科技需求.根据对"十一五"、"十二五"水专项太湖技术成果的梳理总结,从控制单元划分、控制单元污染负荷核定、控制单元水环境容量核算、重点行业水污染控制与治理技术评估、排污许可量分配和证后动态监管角度集成形成工业点源排污许可管理成套技术.同时阐释了成套技术在太湖流域的应用成效,以期为太湖流域排污许可管理制度的实施提供经验和借鉴.

Impounding the Three Gorges Reservoir (TGR) has altered the water-sediment transportation regime in the Yangtze River (YR) downstream, with inevitable effects on phosphorus (P) transport behavior in river-connected lakes. In this study, we investigate the characteristics of water, suspended sediment (SS), and P transportation, adsorption, and bioavailability at the three inlets along YR diverted to Dongting Lake through field surveys, adsorption experiments, and historical data analysis. The results showed that P transportation was significantly correlated with sediment (p < 0.01) and fine sediment particles dominated the transportation of particulate phosphorus (PP) and bioavailable phosphorus (Bio-P). Before the TGR impoundment, the dissolved inorganic phosphorus (DIP) concentration (0.03 mg/L) at the three inlets maintained a low level despite high P input, which was mainly due to the P adsorption and removal effect by sediment with high concentration and finegrained texture. In addition, we reveal two changes at the three inlets caused by the impoundment: (1) SS content and discharge were reduced by an order of magnitude and the particle size was coarsened by three times; (2) the PP flux and bioavailability significantly decreased, whereas the transportation proportion of DIP increased. Consequently, the P buffering and adjusting capacity by sediment in the pristine river ecosystem from dam upstream supplies and downstream resuspension were notably weakened. Currently, the SS content at the three inlets (0.07 g/L) is far below the lower critical threshold (0.20 g/L) obtained through experiments that can effectively remove phosphate. Additionally, the decline of water and sediment supply from YR to Dongting Lake increased water transparency and prolonged water retention time in lake. With continuous TGR regulation and construction of upstream cascade reservoirs, the risk of algal blooms in river-connected lakes is significantly exacerbated.

The Three Gorges Reservoir (TGR) underwent staged impoundment of water from 135 m to 175 m between 2003 and 2010. Periodic water impoundment was divided into drainage (March to early June), low water level (June to August), impoundment (September to October), and high water level (November to February) period. However, the impact of the Three Gorges Dam (TGD) and staged impoundment on water quality, especially in the long term, remains unclear. Herein, hydrological, pollution load, nutrient, and biochemical indices were determined for the TGR during 1998-2018. The Canadian Council of Ministers of the Environment Water Quality Index, a K-means clustering algorithm, and the Mann-Kendall (MK) test were applied to this data to explore the spatial and temporal distribution of water quality. The results show that water quality was good overall, but it before the full impoundment stage (2010) was worse than after that. The low water level period had the worst water quality among the four periods, and spatially, midstream was worst. Among water quality indices, the median total nitrogen (TN) and total phosphorus (TP) were in the range of 1.505-2.303 and 0.071-0.176 mg/L, respectively, and these were the key pollution indices. In addition, due to differences in hydrological and hydrodynamic conditions, and the regional distribution of pollution sources, water quality in the TGR displayed temporal and spatial heterogeneity. TN, TP, potassium permanganate index (CODMn), five-day biochemical oxygen demand (BOD5) and Escherichia coli (E. coli) were maximal during the low water level period, and TN, TP and E. coli were highest in midstream. MK test results revealed that nutrients pollution became worse midstream, and a gradual increase in TP caused severe algal blooms downstream. Therefore, nutritional water treatment and non-point source pollution control should be the focus of future work.

水量、泥沙和污染物交换作为河流与湖泊之间的关键过程,对湖泊生态环境演变具有复杂而深远的影响.以长江中游典型通江湖泊洞庭湖为研究对象,着眼于"江湖""河湖""人湖"三重作用关系变化,从水文情势、水质、富营养化3个层面剖析了近30年洞庭湖水环境演变态势及主控因素.结果表明:①"江湖"关系变化影响了洞庭湖水沙交换及其年内分配,是湖泊枯水期提前和延长、水沙关系突变等现象的主控因素;"河湖""人湖"关系变化协同加剧了该现象.②"河湖"关系的失衡和"河湖"统筹管理措施缺位,造成入湖河流长期输送大量营养物质,是湖体氮磷污染较重的根源;"江湖""人湖"关系变化协同影响着营养盐分布格局,但影响范围及程度有限.③在"江湖""河湖"作用关系复合影响下,藻类生长条件更为有利,增加了洞庭湖富营养化及水华风险.为保障洞庭湖水环境安全,建议:针对"江湖"作用主导的低枯水位问题,以水资源调控为核心,推进长江与流域上游水库联合生态调度,保障湖泊生态流量;针对"河湖"作用主导的水质恶化问题,以水污染防治为核心,强化流域污染控制,统筹"河湖"一体化监测管理模式,保障湖泊水环境质量;对于"人湖"作用主导的生态破坏问题,以生态空间管控为核心,划定并坚守生态红线,保障生态空间.

West Dongting Lake (WD) receives water from local rivers, the Yuan and Lishui Rivers, within the lake basin and is recharged by the Yangtze River outside the basin through three outfalls. Thus, water pollution control is more complicated in WD than in lakes disconnected from the Yangtze River. Here, major ion tracing which was a method rarely applied in the river-lake system was used to characterize the contribution of water and total nitrogen (TN) from the inflow rivers to WD, and 9 sampling sites in WD and its inflow rivers were investigated in December 2016 (the dry season, DS), April 2017 (the normal season, NS) and August 2017 (the wet season, WS). Na+ and Cl－ were suitable tracer ions used in the ion tracing model to estimate the water and TN contributions from inflow rivers to WD. Results showed that the water and TN in WD who presented river and lacustrine phases were mainly contributed by local rivers rather than the three outfalls, in which the contribution of Yuan River was larger than that of Lishui River. However, the contribution rates of water and TN of the three outfalls to WD during WS reached above 20% and 30% respectively, indicating that the contribution of the three outfalls could not be ignored, in which the contributions of water and TN from Songzi outfall were higher than those from Taiping and Ouchi outfalls. Therefore, we suggest that the relevant departments should identify key river management targets during different water periods, implement refined management over water pollution in WD, and prioritize the pollutant input of Yuran River and Songzi outfall (especially during WS).