The long-distance migration of Oncomelania snails mainly occurs by attaching to floating objects during floods. However, the processes, characteristics and effects of migration are not fully understood. Here, a motion equation for floating objects with attached Oncomelania snails was constructed using the Lagrangian method. The equation can be numerically solved to simulate the movement of floating objects after parameter calibration. Then, the calibrated parameters were used to simulate the migration of Oncomelania snails in the lower Jingjiang River, where they had spread over a large area. The effects of flood conditions on the migration and spread of Oncomelania snails have been studied to a certain extent, but the impact of wind conditions on snail migration has rarely been reported. Therefore, based on the distribution of Oncomelania snails in China, the difficulties and key areas for the control of schistosomiasis and Oncomelania snails, and the morphological characteristics of the river reach, the Lower Jingjiang River section was selected as a practical application case. A theoretical model of the migration and spread of Oncomelania snails was established, and the characteristics of the Oncomelania snail migration were simulated and analyzed based on flood and distribution patterns under different wind conditions. The results indicate that wind conditions have little influence on the longitudinal spreading of Oncomelania snails but have a relatively large influence on the lateral spreading of snails. Compared with calm wind conditions, both northeasterly and southerly wind conditions can lead to longer longitudinal migration distances of snails, thereby increasing the risk of snail spreading and schistosomiasis transmission.

Flow characteristics are the driving force to the riverbed evolution in straight channel with crisscross bars.The variation laws of longitudinal velocity, transverse velocity and turbulent intensity were studied by flume experiment.The results show that: ① the longitudinal time-average velocity decreases along the channel direction and its transverse distribution presents the velocity at the edge of the bar is the largest, far from the bar takes the second, and on the bar is the smallest.The transverse time-average velocity is mainly the periodic change of flow direction.② the longitudinal turbulence intensity tends to increase along the channel, which the increase amplitude decreases from upstream to downstream.The transverse turbulence intensity is mainly the largest in the middle of the bar, followed by the head and the tail.

The quantitative analysis of hydrological connectivity between lakes and river systems serves as a fundamental guide for the conservation and management,and it represents a current focal point in the research on the ecological restoration of rivers and lakes.This paper introduces a quantitative calculation model for assessing the hydrological connectivity between lakes and rivers.The model requires minimal empirical or hydraulic simulation data for validation,enabling the quantification of hydrological con-nectivity in single or multiple connecting channels between rivers and lakes.Water level and its change rate are crucial parameters.The change rate of water level is linearly related to the intensity of water exchange,while the water level is positively correlated with the rate of increase.The proposed empirical formula for water exchange flow can effectively estimate the exchange flow between lakes and the Yangtze River.Under equivalent water levels and rates of water level changes,the efficiency of outflow from lakes to the Yangtze River exceeds that of inflow from the Yangtze River to lakes.The peak value of hydrological connectivity generally oc-curs at points of variation within the overall rising or falling range.Hydrological connectivity can be effectively increased by adjus-ting the process of water level rise or decline,which can guide ecological scheduling aimed at improving the aquatic ecosystem in lakes.

Under the background of rapid social and economic development in China, the demand for oil transportation has increased rapidly, resulting in the frequent occurrence of sudden water pollution accidents. To control and prevent pollution due to spilled oil effectively, a large reservoir in the northeastern area of China is taken as the study site and two scenarios are investigated: (1) onshore discharge of an accidental instant pollutant source and (2) offshore discharge of an accidental instant pollutant source. Spilled oil is discretized into a certain number of oil particles. The surface current field of the reservoir is extracted through three-dimensional hydrodynamic numerical simulations. Based on an oil particle model, the advection, wind-driven drift, and random walk of oil particles are accounted for, and the migration path of oil particles that land onshore is revised. Moreover, the migration and spatial distribution pattern of spilled oil with respect to time are simulated and analysed.

研究满足水质和水量需求的生态流量对于河湖水环境治理保护很有必要.以水质性缺水的河流举水新洲段为例,基于实测河道断面数据和污染源调查结果,运用MIKE11软件建立了河道水量水质模型,并根据实测资料对模型进行了率定.利用率定后的模型,以COD、NH3-N、TN、TP作为主要污染物指标,通过试算法计算了现状排污条件下,各月份中控制断面水质达标的生态流量,同时运用Tennant法和流量频率曲线法计算了满足河流生态系统基本水量需求的生态流量.对3类方法计算结果综合比较讨论,得出了统筹水质水量的举水新洲段各月份生态流量.

受流域来水来沙条件变化及河口大型工程建设的综合影响,长江口呈现新的冲淤格局,为预测未来演变趋势,本研究基于前期研究中建立的长江口年代际冲淤演变预测模型(Delft3D),未来情景考虑不同来沙量条件和相对海平面上升速率.预测结果表明,到2035年长江口整体以冲刷为主,口内河段主槽和浅滩边缘冲刷较明显,仅高滩局部淤积;到2050年口内河段保持净冲刷状态,拦门沙地区在现状来沙量条件下略有淤积,但在极端低来沙量条件下转变为净冲刷状态,海平面上升对拦门沙地区冲刷具有一定抵消作用,但不会使冲淤状态产生本质改变.本研究分析认为,长江口局部区域未来冲淤趋势可能对河口综合治理与保护产生不利影响,针对新格局条件下的滩槽河势稳定、重要洲滩保护、重大工程安全评估、冲刷致灾研判以及海堤防护标准再评估等方面提出了对策建议,可为新时期长江口综合治理与可持续发展提供参考.

如皋沙群河段位于长江下游澄通河段,其河道宽阔多汊,滩槽冲淤演变规律复杂,开展河道演变及其影响因素分析对该河段治理和保护具有重要意义.利用1977～2018年实测资料对如皋沙群河段的冲淤、深泓、滩槽以及典型断面的近期变化进行了系统分析,并在此基础上对河道演变的主要影响因素进行了探讨.结果表明:如皋沙群河段近年来河床总体呈冲刷发展趋势,深泓总体向左侧偏移,其中在如皋右汊最大偏移幅度达900 m;双涧沙防护部分左右缘小幅淤积,民主沙沙尾小幅下移,横港沙滩面淤积明显,2011～2018年横港沙在九圩港以上-5 m等高线以上河床平均淤积抬高0.62 m,深槽和典型横断面变化幅度趋小,总体呈缓慢刷深的态势,平面上表现为深槽的上提下挫;如皋沙群河段整体稳定性受河道边界条件、大洪水、来水来沙及人类活动的影响,其中人类活动影响较大,相关整治工程的实施使得该段总体河势趋于稳定.

近20 a来受长江入海泥沙锐减的影响,长江口滩槽系统发生相应冲淤调整,河势稳定面临新的挑战.选取长江口南支河段白茆沙和扁担沙滩槽系统为研究对象,分析了1997～2015年冲淤演变过程和主要特征.结果表明:白茆沙总体上冲刷萎缩,沙尾冲蚀消失,固沙潜堤工程的实施使得冲刷态势得到控制,但南北水道分流格局呈单向发展,南水道冲刷南靠,威胁太仓港岸线稳定;扁担沙处于自然演变状态,沙体局部出现切滩,沙尾不断下移并挤压新桥通道,影响南支总体河势稳定.基于此,提出了稳定白茆沙汊道分流格局,遏制扁担沙切滩和稳定新桥通道的河势控制对策.

This paper presents a study of the terminal settling velocity and drag coefficient of the Oncomelanias with highly irregular shape in the range of particle Reynolds number (10 < R ep < 600). The movement characteristics of the Oncomelanias with horizontal and slant postures are revealed using image analysis and wavelet analysis. The shape features of Oncomelanias with different dimensions are quantified and formulated. The authors propose a new model for predicting the drag coefficient of the dormant and active Oncomelanias, which is proven to be better than several widely-used formulas. Further, a simple settling velocity model that can predict the terminal velocity of the Oncomelanias fairly with several easy-to-measure parameters is developed. These findings provide a basis for the further improvement for the hydraulic schistosomiasis control project and supply reference for the settling characteristics and drag coefficient of cone-shaped particles.

徐六泾节点段控制着长江口的物质通量和南北支的分流分沙,其河槽稳定性和变化趋势在长江口的演变中具有重要地位.采用实测资料分析和物理模型试验相结合的方法研究了长江口徐六泾节点段河槽的稳定性及其影响因素.研究结果表明:①徐六泾节点段1992年前河槽呈右移态势;1992—2018年间,河槽演变趋缓,平面上主要表现为小幅度的上提下挫,垂向上呈缓慢刷深之势.②徐六泾节点段未来滩槽格局基本稳定,河槽仍以冲刷为主,且有向下游发展趋势,大洪水作用下局部河床会出现较大的调整(2009—2018年+百年一遇水文年试验条件下,在现有的-30 m深槽下游约910 m处出现一个新的-30 m槽).③徐六泾节点段河槽整体稳定性前期主要受两岸圈围工程、上下游河势、大洪水等的影响,近年来主要受流域减沙的影响,局部河床稳定性的主要影响因素是大洪水和人类活动.

依托位于孟加拉湾人海口的某大直径盾构隧道,基于有限的水文基础资料,得到合理的入海口深厚淤积地层冲刷深度.首先根据经验及分析确定糙率、流量等参数,通过数值模拟计算不同径流与潮水组合工况下的河床冲刷,同时每个工况分别考虑了饱和带沙和清水两种条件,得到了冲刷深度的包络线;然后对比分析了基于多种规范要求的满足抗浮的最小覆土厚度,探讨满足掘进稳定性要求的最小覆土厚度;最后结合冲刷的研究成果,建立了该工程隧道全线纵断面合理覆土厚度的确定方案.

Sound knowledge of the local distribution and diversity of freshwater snail intermediate hosts and the factors driving the occurrence and abundance of them is crucial to understanding snail-borne parasitic disease transmission and to setting up effective interventions in endemic areas. In this study, we investigated the freshwater snails, water quality parameters, physical characteristics of habitats, predators and competitors, and human activity variables at 102 sites during December 2018 and August 2019 in Shenzhen and adjacent areas in China. We used decision tree models and canonical correspondence analysis to identify the main environmental and biotic factors affecting the occurrence and abundance of snail species. A total of nine species of snail were collected throughout the study area, with Biomphalaria straminea, Sinotaia quadrata, and Physella acuta being the most predominant species. Our study showed that the most important variables affecting the abundance and occurrence of snail species were the presence of predators and competitors, macrophyte cover, chlorophyll-a, substrate type, river depth, and water velocity. In terms of human activities, snail species occurred more frequently and in larger numbers in water bodies affected by human disturbances, especially for sewage discharge, which may reduce the occurrence and abundance of snail predators and competitors. These findings suggest that proper management of water bodies to reduce water pollution may increase the abundance of snail predators and competitors, and should be considered in integrated snail control strategies in the study area.

在广泛查阅国内外相关文献的基础上,对长江中下游两大通江湖泊洞庭湖与鄱阳湖水沙输移规律、冲淤演变规律及对洪枯调控功能的影响这3个方面的研究进展进行了总结分析,并对当前研究中存在的不足提出了今后应加强的内容,主要包括:①自然和人为影响下两湖演变机制量化揭示,包括资料匮乏时期两湖的演变过程、各种自然因素对两湖冲淤演变的影响的识别、人类活动加剧时期两湖的自然冲淤过程等;②两湖未来长历时、大范围冲淤情势变化趋势预测,实现从两湖泥沙淤积总量预测到淤积时空分布格局变化预测转变;③两湖演变对洪枯调控功能影响的指标化评估,包括表征湖泊洪枯调控功能的指标研究及其与两湖未来不同冲淤情景的响应关系等方面.

为了探究长江河湖变迁与保护目标,以相关史料、文献和实测资料为基础,分析总结了地质时期以来长江河湖变迁和人水关系变化历程.研究表明,长江人水关系经历了从和谐共处—日渐紧张—日趋恶化—有所缓和的发展过程,其中,宋朝、新中国成立以来的工业化及城镇化建设和2016年以来"共抓大保护、不搞大开发"理念的贯彻实施是人水关系发生变化的转折时期.鉴于此,提出了长江保护目标是实现人水和谐共生,保障水沙通道、泄洪通道、航运通道、生态通道和文化通道5个通道畅通,并阐述了长江保护目标是否实现的3个判断准则:长江水生态系统健康、长江对人类发展的支持功能良好和人类为长江提供充分必要的保护.根据现阶段实际情况,提出改善长江人水关系,减少人水失衡带来的负面效应是现阶段保护目标,并建议现阶段应从解决防洪安全问题、实现水环境改善、加快水生态修复、做好长江水文化建设4个方面开展工作.

随着人们对河流生态环境要求的提高,河流生态研究引起了广泛关注,也取得了很大的进步.在广泛查阅国内外相关文献的基础上,对河流生境、河流生态流量、河流生态系统健康评价、河流生态修复4个热点问题的研究进展进行了总结和分析,并根据当前研究中的不足,提出了今后应加强的方面,主要包括:① 流域尺度的生境因子变化规律及其累积影响、河流生境与多种河流生物适配性关系、多尺度河流生境质量评价等;② 多目标河湖生态流量计算方法、分区分时生态流量的确定、生态流量动态过程、生态流量管理机制等;③ 长期河道生态因子监测、河流生态健康评价标准的制定、大尺度河流健康评价等;④ 多种修复技术的优化组合、流域尺度生态修复、河流生态修复后评估指标和标准的确定、修复后的生态系统动态演变过程等.

为了实现河湖岸线的保护与高效利用,需要加强河湖岸线洲滩利用对河湖功能影响的研究,提高认识水平.主要综述了河湖岸线利用模式及主控因子、河湖功能与岸线洲滩相互影响以及河湖岸线洲滩利用管理与策略研究等3个方面的研究现状.总结了分别考虑自然和社会功能的河湖岸线利用模式分类方法,初步厘清了河湖功能与岸线洲滩相互影响的研究思路,综合提出了岸线资源化管理、可持续利用2个指导思想和岸线利用"零增长"模式、岸线资源"节约型"、河湖功能"友好型"3点建议.研究可为河湖岸线的保护与高效利用提出更好的研究思想与解决方案.

River deltas are actively propagating systems as redundant fluvial sediment accumulated hereon after part of the amount being taken away by marine currents. Anthropogenic activities in drainage basins strongly modified such propagation processes by increasing sediment productions over the past millennia and decreasing sediment loads in the past century. The most significant feature is the delta erosion or flooding as a result of sediment trapping in upstream reservoirs in combination with relative sea-level rise. In addition, human interventions within deltaic regions may complicate the morphological patterns with strong spatial variations. Understanding the controlling factors and future trends of delta erosion is of high importance for sustainable development and comprehensive protection of these dense-populated areas.

五河入湖水沙通量及河道形态变化对五河尾闾演变、湖区低枯水位、江湖关系等研究有重要意义.以1956—2018年实测资料为基础,利用Mann-Kendall检验法和河道特征对五河入湖水沙通量、典型断面形态变化特性及其影响因素进行了研究.结果表明:①五河入湖径流量总体呈小幅度减小态势,2003—2018年五河入湖平均径流量较1956—2002年减小5.3％;②除饶河外,入湖泥沙通量均有不同幅度的减小,其中赣江和信江大幅度减小,2003年后分别减少约72.3％和52.6％;③五河典型断面形态2014年前变化较大,断面多呈锯齿状;随后逐渐恢复正常;④水利枢纽工程、水土保持工程和人工采砂是影响五河入湖泥沙通量和河道形态的主要人为因素.

絮凝沉降性能是河湖疏浚淤泥资源化处理中重要且未完善的研究课题.以武汉沙湖、官桥湖及南湖3种淤泥为研究对象,通过沉降筒试验,利用清浑交界面沉降速度和上清液浊度研究了粒径分布、初始含沙量及高分子聚合物对河湖淤泥絮凝沉降特性的影响规律,并探讨了沉降筒尺寸对试验结果的影响.试验结果表明:河湖淤泥粒径越小,淤泥絮凝沉降越慢,上清液浊度越小;随初始含沙量的增加,河湖淤泥整体沉降速度变小,但当初始含沙量增加到一定值后,初始含沙量的影响作用开始变弱;高分子聚合物会促进河湖淤泥絮凝沉降;沉降筒尺寸虽然对试验结果略有影响,但对于分析河湖淤泥絮凝沉降特性无较大影响.研究河湖淤泥絮凝沉降特性对于河湖通航、蓄洪、水质修复、疏浚淤泥的处理均有重要意义.