RESEARCH ON HYDRODYNAMIC AND WATER QUALITY MODEL FOR TIDAL RIVER NETWORKS

Hydrodynamic and water quality model for tidal river network is set up withMIKE11 modeling system, according to the features of tidal river networks in plain area. The modelwas calibrated using the hydrological and water quality data of 1999, and the results show that thesimulated values agree with the measured data very well. This model is used to numerically analyzethe effects of low flow augmentation on hydrodynamic and water quality conditions of Suzhou Creek.The simulation results show that the flow augmentation can increase net discharge of Suzhou Creekand improve its ability of re-aeration; and its concentration of dissolved oxygen in the rivernetworks can also increase correspondingly.

AN OPTIMIZATION METHOD OF AQUATIC ENVIRONMENTAL CAPACITY FOR TIDAL RIVER NETWORK

By using the high-efficiency of four-stage calculation method named ＂channel-junction-channel＂ and considering the influence of temporal and spatial variation of aquatic environmental capacity, an optimization method of aquatic environmental capacity for tidal river network was worked out. The method not only reflects characteristics of unsteady flow with variable directions, but also indicates that aquatic environmental capacity is influenced by boundary condition and water quality standard, etc. It has been applied to the regional program of Pudong area in Shanghai, and the computed results agree well with the practical data.

Modified Saint-Venant equations for flow simulation in tidal rivers

Flow in tidal rivers periodically propagates upstream or downstream under tidal influence. Hydrodynamic models based on the Saint-Venant equations （the SVN model） are extensively used to model tidal rivers. A force-corrected term expressed as the combination of flow velocity and the change rate of the tidal fevel was developed to represent tidal effects in the SVN model. A momentum equation incorporating with the corrected term was derived based on Newton＇s second law. By combing the modified momentum equation with the continuity equation, an improved SVN model for tidal rivers （the ISVN model） was constructed. The simulation of a tidal reach of the Qiantang River shows that the ISVN model performs better than the SVN model. It indicates that the corrected force derived for tidal effects is reasonable; the ISVN model provides an appropriate enhancement of the SVN model for flow simulation of tidal rivers.

Hydrodynamic Characteristics and Sediment Transport of A Tidal River Under Influence of Wading Engineering Groups

By taking the Yong River for example in this paper, based on the multiple measured data during 1957 to 2009, the change process of runoff, tide feature, tidal wave, tidal influx and sediment transport are analyzed. Then a mathematical model is used to reveal the influence mechanism on hydrodynamic characteristics and sediment transport of the wading engineering groups such as a tide gate, a breakwater, reservoirs, bridges and wharves, which were built in different periods. The results showed the hydrodynamic characteristics and sediment transport of the Yong River changed obviously due to the wading engineering groups. The tide gate induced deformation of the tidal wave, obvious reduction of the tidal influx and weakness of the tidal dynamic, decrease of the sediment yield of flood and ebb tide and channel deposition. The breakwater blocked estuarine entrances, resulting in the change of the tidal current and the reduction of the tidal influx in the estuarine area. The large-scale reservoirs gradually made the decrease of the Yong River runoff. The bridge and wharf groups took up cross-section areas, the cumulative affection of which caused the increase of tidal level in the tidal river.

A combined numerical tidal model for the Hangzhou Bay and Qiantang River

-In order to avoid prescribing open boundary condition on the upstream side of the Hangzhou Bay, in numerical simulation of the tides and residual currents of the Bay, a 1-D model for the Qiantang River is connected to the 2-D model for the Hangzhou Bay. The harmonic constants of diurnal constituent [ (K1+O1)/2],semidiurnal constituent (M2) and shallow water constituent (M4) are obtained. The results produced by the combined model are in better agreement with the observed ones than those produced solely by the original 2-D model. The combined model gives much more reliable results for tide-induced residual water level and current.

Engineering application of submerged water jets for sediment removal in a tidal riverbed

Sediment deposition problems have attracted the interest of engineers and researchers.Several experimental studies have been conducted on scour depth using turbulent jets.However,field observation and monitoring have rarely been reported.This study aimed to eliminate sediments on a tidal riverbed using a prototype device,which consisted of a set of submerged vertical water nozzles and submerged horizontal air nozzles.The effectiveness of the water jet in sediment removal during spring and neap tides was evaluated.The quantitative relationships of dimen-sionless parameters,such as(1)the relative sediment scour volume versus the number of flows from the jet exit,(2)the relative sediment scour volume versus the relative scour depth,and(3)the relative scour size versus the relative jet intensity,were analyzed.The results showed that the freshwater flowing to the sea affected the sediment scour volume during the falling cycle of spring tides.In contrast,the rising cycle of spring tides retarded the freshwater flow,resulting in a decrease in the sediment scour volume.A steep water surface slope accelerated the river flow and further influenced the cross-flow current around the study area.As a result,a highly diffusive turbulent flow was produced,causing sus-pended sediments to be rapidly removed from the scour hole center.An increase in the number of flows from the jets led to intensified diffusion of turbulent energy into the flow.The rapidly varying water depth caused jet energy to be dissipated before approaching the riverbed,and it significantly affected the scour process during the spring-tide period.The proposed equations can be used to estimate the scour volume,scour size,and re-suspended sediments in tidal rivers within defined ranges of parameters.

Application of equivalent resistance to simplification of Sutong Bridge piers in tidal river section modeling

This paper describes some details and procedural steps in the equivalent resistance （E-R） method for simplifying the pier group of the Sutong Bridge, which is located on the tidal reach of the lower Yangtze River, in Jiangsu Province. Using a two-dimensional tidal current numerical model, three different models were established： the non-bridge pier model, original bridge pier model, and simplified bridge pier model. The difference in hydrodynamic parameters, including water level, velocity, and diversion ratio, as well as time efficiency between these three models is discussed in detail. The results show that simplifying the pier group using the E-R method influences the water level and velocity near the piers, but has no influence on the diversion ratio of each cross-section of the Xuliujing reach located in the lower Yangtze River. Furthermore, the simplified bridge pier model takes half the calculation time that the original bridge pier model needs. Thus, it is concluded that the E-R method can be use to simplify bridge piers in tidal river section modeling reasonably and efficiently.

Seasonal dynamics of meiofaunal distribution in the Dagu River Estuary, Jiaozhou Bay, China

Sediment samples were collected in the intertidal zone of the Dagu River Estuary, Jiaozhou Bay, China in April,July and October 2010 and February 2011 for examining seasonal dynamics of meiofaunal distribution and their relationship with environmental variables. A total of ten meiofaunal taxa were identified, including free-living marine nematodes, benthic copepods, polychaetes, oligochaetes, bivalves, ostracods, cnidarians, turbellarians,tardigrades and other animals. Free-living marine nematodes were the most dominant group in both abundance and biomass. The abundances of marine nematodes were higher in winter and spring than those in summer and autumn. Most of the meiofauna distributed in the 0–2 cm sediment layer. The abundance of meiofauna in hightidal zone was lower than those in low-tidal and mid-tidal zones. Results of correlation analysis showed that Chlorophyll a was the most important factor to influence the seasonal dynamics of the abundance, biomass of meiofauna and abundances of nematodes and copepods. CLUSTER analysis divided the meiofaunal assemblages into three groups and BIOENV results indicated that salinity, concentration of organic matter, sediment sorting coefficient and sediment median diameter were the main environmental factors influencing the meiofaunal assemblages.

潮汐河网水环境容量的计算分析

介绍了河流水环境容量的几种常用计算方法。针对上海市河网污染源分布的特点,基于感潮河网的水动力模型,提出了河网动态水环境容量计算的方法,建立了河网水环境容量计算模型,并对蕴藻浜水系以及中心城区体系的水环境容量进行了计算分析。结果表明,该方法对于河网动态水环境容量计算是十分方便而有效的。

南通主城区纳潮置换水体及其绩效评估

南通属于平原感潮河网地区,在贯通工程的基础上充分利用现有的水利工程、充沛的过境水资源优势和感潮河网的潮汐水动力特性,形成南通主城区纳潮置换水体循环系统是改善南通主城区水环境质量的关键。在充分论证南通纳潮置换水体可行性的基础上,初步建立了一套现有条件下适合南通平原感潮河网水质改善需要的、具可操作性的纳潮置换水体的运行方案,并就区域引排能力的计算、引水路线的选择、引水时间及引水量的计算及论证、纳潮置换水体改善效应进行了分析。研究表明:该方案实施后可使景观连接度有所增加,整个水系形成网络结构,有利于水生生物的迁移;能有效梳理和贯通水系,提高河道物质交换和能量流动水平,增强河道的负荷能力。

DEVELOPMENT OF COUPLED 1D-2D MATHEMATICAL MODELS FOR TIDAL RIVERS

Some coupled 1D-2D hydrodynamic and water quality models depicting tidalwater bodies with complex topography were presented. For the coupled models, finite element methodwas used to solve the governing equations so as to study tidal rivers with complex topography. Sincethe 1D and 2D models were coupled, the principle of model coupling was proposed to accountappropriately for the factors of water level, flow and pollutant flux and the related dynamicalbehavior was simulated. Specifically the models were used to probe quantitative pollutioncontribution of receiving water from neighboring Jiangsu and Zhejiang Provinces to the pollution inthe Huangpu River passing through Shanghai City, Numerical examples indicated that the developedcoupled 1D-2D models are applicable in tidal river network region of Shanghai.

Sedimentary facies of the Silurian tide-dominated paleo-estuary of the Tazhong area in the Tarim Basin

As the relative sea-level rose, a paleo-estuary was formed by the marine inundation of the braided river incised valley during the period of the lower sub-member of the upper member of the Kalpingtage. formation of the Silurian in the Tarim Basin, west China. Sandstone-mudstone rhythmite, tidal structures and bimodal cross-bedding are common in these deposits, indicating that tides played a significant role in generating the sedimentary structures and the estuary type was tide-dominated. Five depositional facies were grouped： tidal river, sandy and muddy subtidal flat, tidal flat, tidal bar, tidal channel on the basis of lithology, electric properties, rhythmicity, sedimentary structure, fossil and the contact relationship. The sediment distribution showing first fining seaward and subsequent coarsening seaward from head to mouth, implies the two sediment sources in the paleo-estuary. The paleo-estuary of the Tarim Basin is very different from other representative estuaries. The most important distinction is that there are two adjacent estuaries joined by tidal flat onshore and by sandy and muddy subtidal flat in the sea at the same time, while the others only architecture model for the tide-dominated estuary. have one, So the Tazhong paleo-estuary shows a good

感潮河段整治线宽度确定方法

潮汐河口受海洋和径流的共同作用。径流有季节性和年际变化,而潮流有半日和半月潮周期变化,使得感潮河段和河口处的条件比无潮河流复杂得多,从而增加了航道整治的难度。航道整治事关通航安全、水利和生态环境等多个方面,整治线宽度是航道整治工程设计中的重要参数之一,它决定整治河段的断面形态及其尺度,整治线宽度的计算是否合理某种程度上决定了整治工程的成败。现有规范和标准的计算公式大多数是针对受径流作用的内河航道提出的,而考虑潮汐因素的理论方法相对较少。为此,有必要针对潮汐河段的特征,采用最大适合潮汐河段的净输沙能力法,阐述航道整治参数的确定方法,得出适用于感潮河段的整治线宽度计算新方法。运用实例进行验证,发现与工程实际符合良好,证明了该方法的可行性。

闸控潮汐河网区水环境调度模型研究

针对闸控潮汐河网区的水系条件和水动力特征,立足于水网区水环境改善的需求,构建了闸控潮汐河网区水环境调度模型。该模型由河网区一维水动力模型、河网一维水质模型和水闸调控模拟模型3个模型构成,采用实测资料对模型进行了率定和验证。选择珠江三角洲"中珠联围"作为研究区开展实证研究,提出了联围整体调度与局部重点改善相结合的调度方法。结果表明,统筹考虑中山和珠海的调度需求,实施"中珠联围"统一调度,形成"西北进、东南出"的水流格局,可有效地加快联围内河涌的水体更新速度,降低污染物平均浓度,对于"中珠联围"水环境的改善及供水水质安全的保障具有重要意义。

INVERSE PROBLEM METHOD FOR WATER ENVIRONMENT TOTAL CAPACITY CONTROL OF A TIDAL RIVER

In this paper, an improved method for water environment total capacity control of tidal rivers was presented. The maximal capacity of point pollution sources for the Huangpu River was computed by this method, and the result was compared with the practically observed data. The numerical result shows that the method is effective and efficient.

闸控感潮河网水环境容量计算研究

受潮汐影响的闸控河网的水环境容量计算是水环境控制的重要内容。针对闸控感潮河网的水流特点,介绍了基于动态水质模型的水环境容量的数值计算方法。其方法综合考虑了感潮河网地区水流运动复杂、易受水利工程设施运行影响的特点,并成功地应用到动态水环境容量计算。

黄浦江河口建闸挡潮效果初步分析

在探讨计算水情和水闸调度运行方案的基础上,采用3种尺度的河网模型对黄浦江河口建闸的挡潮效果进行定量分析,并研究了不同调度参数（起关潮位和关闸历时）对挡潮效果的影响。研究结果表明,在遭遇千年一遇风暴潮时通过合理调度黄浦江河口闸门可将进潮量减少约80%,闸内干流段高潮位降低1.7~2.4m,能有效提高上海市区的防汛能力。

THREE-DIMENSIONAL NUMERICAL MODEL FOR WINDING TIDAL RIVER WITH BRANCHES

Natural rivers are usually winding with branches and shoals, which are difficult to be simulated with rectangular grids. A 3-D current numerical model was established based on the orthogonal curvilinear coordinate system and vertical o coordinate system. The equations were discretisized using a semi-implicit scheme. The ＂predictor＂ and ＂corrector＂ steps were applied for the horizontal momentum equations to meet the basic requirement that the depth-integrated currents obtained from the equations for 2-D and 3-D modes have identical values. And a modification of traditional method of dry/wet discriminance was proposed to determine accurately the boundary and ensure the continuity of variable boundary in the simulation. This model was verified with the data measured in a winding tidal river with branches in April, 2004. The simulated data of water levels and velocities agree well with the measured ones, and the computed results reveal well the practical flow characteristics, including the vertical secondary flow in a winding reach.

Modelling of water quality of Minjiang estuary

In order to establish economic development region at Mawei districtwhich is nearby downstream of Minjiang river and to answer the question of impact of economic development on water quality of Minjiang estuary, the analyses of hydrologic and hydraulic characteristics of Mawei reach of Minjiang tidal river, a two-dimensional mathematical model has been established and simulation of water quality was studied. The results show that the flushing time of a conservative pollutant during dry and raining period are 12 and 7 days respectively from Mawei to Minjiang mouth, the decay rate constants of BOD and NH3-N are 0.1 to 0.4 and 0.18 to 0.45 d-1 respectively. The capacity of dilution and assimilation for pollutants is larger.

Numerical Analysis of the Mixing Zone for a Vertical Discharge into a Tidal River

This paper analyzes the mixing zone of a vertical discharge of sewage into a natural tidal river with strong tidal currents. The paper presents a numerical model, which combines 1 D and 2 D models to compute the mixing zone for the Sibao Segment of the Qiantang River. The simple 1 D model was used to model the flow for the entire river using field data as the boundary conditions. The complete depth averaged turbulence model was used for the 2 D computation. The calculated results agree well with the field observations. The analysis provides a practical method for the computation of mixing zones in tidal rivers.