MATHEMATICAL MODEL FOR ALLUVIAL TIDAL WATER COURSE

This paper presents a mathematical model to predict the bed deformation of Jiang- men water course,a tributary of Xijiang River in South China,affected by navigation regula- tion.This model has been verified by the field data.

Mean water level setup/setdown in the inlet-lagoon system induced by tidal action—a case study of Xincun Inlet,Hainan Island in China

With the tides propagating from the open sea to the lagoon, the mean water level （MWL） in the inlet and lagoon becomes different from that at the open sea, and a setup/setdown is generated. The change of MWL （setup/setdown） in the system imposes a great impact on regulating the development of tidal marshes, on determining the long-term water level for harbor maintenance, on the planning for the water front development with the flood control for the possible inundation, and on the interpretation of the historical sea level change when using tidal marsh peat deposits in the lagoon as the indicator for open sea＇ s sea level. In this case study on the mechanisms which control the setup/setdown in Xincun Inlet, Hainan in China, the 2-D barotropic mode of Eulerian - Lagrangian CIRCulation （ELCIRC） model was utilized. After model calibration and verification, a series of numerical experiments were conducted to examine the effects of bottom friction and advection terms, wetting and drying of intertidal areas, bathymetry and boundary conditions on the setup/setdown in the system. The modeling results show that setup occurs over the inlet and lagoon areas with an order of one tenth of the tide range at the entrance. The larger the bottom friction is, a larger setup is generated. Without the advection term, the setup is reduced clue to a decrease of water level gradient to compensate for the disappearance of the advection term. Even without overtides, a setup can still be developed in the system. Sea level rise and dredging in the inlet and tidal channel can cause a decrease of setup in the system, whereas shoaling of the system can increase the setup. The uniqueness of the Xincun Inlet with respect to MWL change is that there is no evident setdown in the inlet, which can be attributed to the complex geometry and bathymetry associated with the inlet system.

Three-Dimensional Tidal Model and Its Application to Numerical Simulation of Water Quality in Coastal Waters

The turbulence mechanism plays an important part in the mixing process and momentum transfer of turbulence. A three-dimensional Prandtl mixing length tidal model has been developed to simulate tidal flows and water quality. The eddy viscosities and diffusivities are computed from the Prandtl mixing length model. In order to model the water quality of an estuary or coastal area many interdependent processes need to be simulated. These may be conveniently separated into three main groups: transport and mixing processes, biochemical interaction of water quality variables and the utilization and re-cycling of nutrients by living matter. The model simulates full oxygen and nutrient balance, primary productivity and the transport, reaction mechanism and fate of pollutants over tidal time-scales. The model is applied to numerical simulation of tidal flows and water quality in Dalian Bay. The model has been calibrated against a limited data set of historical water quality observations and in general demonstrates excellent agreement with all available data.

Integrated Water Resources Management (IWRM) Impacts in South West Coastal Zone of Bangladesh and Fact-Finding on Tidal River Management (TRM)

The south west coastal zone of Bangladesh have been affected by rampant water logging due to vulnerable climate, silted rivers and stumpy terrain;and introduction of IWRM and TRM at some places of the zone has substantially safeguarded the circumstance. This study aims to assess the benefits achieved due to implementation of IWRM in parts of Khulna and Jessore districts, and investigate some technical aspects evolving TRM. Analyses have been carried out using satellite images, RS and GIS technology, Digital Elevation Model (DEM) and field investigations. A mathematical formulation has been made to assess rate of tidal sedimentation due to TRM and selection strategies of tidal basins. The study comes up with evidences of considerable advancements in regional livelihood i.e. flood resistance, cultivated lands, cultivable area, cropping intensities and food security due to IWRM. Moreover, the technical facts established on TRM would help planners to have vivid perception regarding the process.

Impact of Tidal River Management (TRM) for Water Logging: A Geospatial Case Study on Coastal Zone of Bangladesh

Bangladesh is a floodplain dominated country. Coastal delta areas of Bangladesh convey multiple impacts of climate change worth-hit. Most of the rivers carry a huge amount of sediment from upstream piedmont area. The river bed rises due to insufficient upstream water supply. Similarly, the deposited sedimentation creates a large number of sandbars inside the river. That’s why, water logging and siltation turn into a serious problem in the south-western region of Bangladesh, especially in Satkhira, Khulna and Jessore district. In the middle of September, 2011 the Tidal River Management (TRM) project approved at the study site for four years to develop the water logging problem with basic consideration of silt management. In this circumstance, this study focused on the consequences of the TRM on water logging in the coastal area of Bangladesh. Primary and secondary data have been used. Geospatial analyses have been used following the NDWI in Arc GIS for water logging area detestation using Landsat Enhance Thematic Mapper (ETM) and Landsat Operational land Image (OLI) satellite images. The geo-spatial analysis denoted, about 5090 acres of agricultural land and about 729 acres of homestead land have been water logged during TRM implementation period.

Tidal Response Characteristics of the Well Water Level in the Sichuan-Yunnan Region

In this paper,the long time series data of the well water-level data of 12 wells in the Sichuan and Yunnan area is analyzed by the Baytap-G tidal analysis software,and well water level tidal response characteristic parameters( amplitude ratio and phase change)are extracted. We analyzed the features of the shape and stage change,and characteristic parameters of the tidal response of well water level before and after the earthquakes,which can provide a new method and approach to analyzing the response relationships between well water level and earth tide and barometric pressure. The results show that Luguhu Well and 9 other wells are affected by earth tides,and their well water level amplitude ratios and phases are relatively stable; the Nanxi Well and Dayao Well water level changes are affected by the barometric pressure combined with tide force,and their well water level amplitude ratios and phases are more discrete. The water level amplitude ratios and phases of Jiangyou Well,Luguhu Well and Dongchuan Well are significant to large earthquakes,and the relationship between seismic energy density and water level amplitude ratios and phases of M_2 wave of the three wells are presented.

Tidal Effects on the Bottom Thermal Front of North Yellow Sea Cold Water Mass near Zhangzi Island in Summer 2009

Three seabed-mounted TD/CTD chains and two upward-looking acoustic Doppler current profilers (ADCPs) in the southwest of Zhangzi Island are used and a simultaneous cruise observation in the northern North Yellow Sea (NYS) is conducted to study temperature variation in the bottom thermal front zone of the NYS Cold Water Mass (NYSCWM) during the summer of 2009. In the flood-ebb tidal cycles, the bottom temperature decreases (increases) during flood (ebb) tides, which are dominated by the tidal-current induced horizontal advection. The ebb tide-induced temperature increase is larger than the flood tide-induced tempera- ture decrease due to seasonal warming. In the spring-neap tidal cycles, the temperature and the vertical temperature structure show notable fortnightly variation from 16 July to 25 August. The bottom temperature increases from neap to spring tides and decreases from spring to neap. The Richardson number demonstrates strengthened vertical mixing during spring tides but enhanced stratifica- tion during neap tides. The spring-neap variation in vertical shear caused by tidal current is the dominant factor that induces the fort- nightly variation in vertical mixing and thus bottom temperature.

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.

Reaearch on Skempton’s coefficient B based on the observation of groundwater of Changping station

Based on isotropie linear poroelastic theory and under the undrained condition, we summarize three equations connecting the Skempton＇s coefficient B with the groundwater level. After analysis, we propose a method to calculate the Skempton＇s coefficient B according to the relationship between water level and tidal strain. With this method we can get the value of B without the earthquake occurrence, which can provide the high frequency waves for research. Besides, we can also get the in-suit Skempton＇s coefficient B without the experiment of rock physics. In addition, we analyze the observed data of Changping station recorded in groundwater monitoring network （abv., GMN） before and after the Wenchuan Ms8.0 with this method, and find out there＇s a slight change of the value of B after the seismic waves passed by, which implies that the propagation of seismic waves may have brought some variations to the poroelastic medium of the well.

Effect of Sea Level Variation on Tidal Characteristic Values for the East China Sea

Tidal waves in the East China Sea are simulated numerically with POM(Princeton Ocean Model) model for normal mean sea level, 30 cm higher, 60 cm higher, and 100 cm higher, respectively, and the simulated result is compared with the harmonic analysis result of hourly sea level data from 19 tide gauges for more than 19 years. It is indicated that the long-term mean sea level variation affects notably tidal waves in this region. Generally, the tidal amplitude increases when the mean sea level rises, but this relationship may be inverse for some sea areas. The maximal variation of tidal amplitude takes place in the zones near the Fujian coast and the Zhejiang coast, rather than the shallowest Bohai Sea. The maximum increase of M2 amplitude can exceed about 15 cm corresponding to the 60 cm rise of the mean sea level along the Fujian coast. The other regions with large variations of tidal amplitude are those along the Jiangsu coast, the south-east coast of Shandong, and the south-east coast of Dalian. The propagation of tidal waves is also related to mean sea level variation, and the tidal phase-lag decreases generally when the mean sea level rises. Almost all the regions where the tidal phase-lag increases with rising mean sea level are close to amphidromic points, meanwhile the spatial area of such regions is very small. Because the influence of mean sea level variation upon tidal waves is spatially marked, such spatial effect should be considered in calculation of the tidal characteristic value and engineering water level. In the region where the amplitudes of the major tidal constituents increase, the probable maximum high water level becomes higher, the probable maximum low water level becomes lower, and both design water level andcheck water level increase obviously. For example, the design water level at Xiamen increases by 13.5 cm due to the variation of tidal waves when the mean sea level rises 60 cm, the total increase of design water level being 73.5 cm.

A New Wetting and Drying Method for Moving Boundary in Shallow Water Flow Models

To deal with the moving boundary hydrodynamic problems of the tidal flats in shallow water flow models, a new wetting and drying （WD） method is proposed. In the new method, a ＂predicted water depth＂ is evaluated explicitly based on the simplified shallow water equations and used to determine the status （wet or dry） together with the direction of flow. Compared with previous WD method, besides the water elevation, more factors, such as the flow velocity and the surface shear stress, are taken into account in the new method to determine the moving boundary. In addition, a formula is deduced to determine the threshold, as critical water depth, which needs to be preset before simulations. The new WD method is tested with five cases including three 1D ones and two 2D ones. The results show that the new WD method can simulate the wetting and drying process, in beth typical and practical cases, with smooth manner and achieves effective estimation of the retention volume at shallow water body.

HYBRID FINITE ANALYTIC SOLUTIONS OF SHALLOW WATER CIRCULATION

The hybrid finite analytic(HFA) method is a kind of numerical scheme in rectangular element. In order to simulate the shallow circulation in irregular bathymetry by HFA scheme, the model in sigma coordinate system was obtained. The model has been tested against three cases: 1) Wind induced circulation; 2) Density driven circulation and 3) Seiche oscillation. The results obtained in the present study compare well with those obtained from the corresponding analytical solutions under idealized for the above three cases. The hybrid finite analytic method and the circulation model in sigma coordinate system can be used calculate the flow and water quality in estuaries and coastal waters.

GENERALIZED WAVE EQUATION FINITE ELEMENT METHOD FOR SOLVING TWO-DIMENSIONAL TIDAL WAVES

The study of tidal circulation has a long history . The numerical simulation of tidal flow has been developed greatly with the development of computer techniques in the past two decades. The generalized wave equation finite-element method is a relatively new numerical model for studying shallow water flow . This method was used to simulate tidal waves of the Gulf of St. Lawrence in Canada . The very good agreement of the numerical results with the field data indicated that the model is an effective and promising numerical method for solving two-dimensional tidal wave problems .

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.

Research on Water-Taking Characteristics of Huanghua Power Plant Reach

In this paper the water-taking characteristics of the first,the second and the third stage of theHuanghua Power Plant are studied by numerical model and physical model.The results show that the pres-ent inlet channel only satisfies the supply need of the first stage of the power plant.If the riverbed of the in-let reach is properly dredged,the need of water supply for the third stage of the power plant could be met.

基于数值模拟的澄通感潮河段水源地预警站设置研究

针对突发性水污染事件可能严重影响水源地取水,而现有研究针对感潮河段水源地预警站的确定方法尚无系统论述的问题,基于长江澄通感潮河段水动力-水质耦合数学模型,在厘清径潮共同作用下该河段污染物扩散输运规律的基础上,初步确定了长青沙和狼山水源地的预警站位置和数量;结合影响水源地的潜在污染源分布特征和污染物累积特征对预警站进行了空间校核,利用预警响应时效性对预警站进行了时间校核,最终确定了两水源地上下游共4个预警站的位置;基于预警站位置水质与水源地位置水质的相关性确定了长青沙和狼山水源地的应急响应方案,并给出了苯酚泄漏的风险响应限值。

A method for estimating the fresh water-salt water interface with hydraulic heads in a coastal aquifer and its application

Examining the descriptions of piezometric heads at two points in both the salt water and fresh water zones reveals that when the groundwater flow system is in steady state and satisfies the Dupuit assumption, the location of the fresh water-salt water interface in a homogeneous, isotropic, and unconfined coastal aquifer can be estimated based on a piezometric head of fresh water at a point in the fresh water zone （from the water table to the interface） vertically lined up with a piezometric head of salt water at a point in the salt water zone （from the interface down）. Research shows that the new method is a general relation and that both the Hubbert relation describing the location of the interface and the Ghy- ben--Herzberg relation are special cases of this method. The method requires two piezometric wells to be close to each other and each tapping into a different zone. Measurements of piezometric heads at a well cluster consisting of piezometric wells tapping separately into fresh water and salt water zones near Beihai, China at 5-day intervals for 15 months are used to illustrate the estimation of interface location. The depth of the interface for well H5 ranges from 32 to 72 m below the sea level.

强涌潮水流条件下直立圆柱体的涌潮作用力试验研究

为厘清强涌潮河口直立式圆柱体受到的涌潮作用力与涌潮水流条件、圆柱直径的关系,通过涌潮水槽模型试验研究了三种直径直立圆柱在不同潮前水深、涌潮高度条件下的涌潮作用力。结果表明,强涌潮的涌潮作用力为直立圆柱受到冲击力叠加该时刻的水流绕流阻力、圆柱前后水位压差力。通过数据回归分析,得到了一个无量纲涌潮作用力计算公式。该公式表明,涌潮作用力分析计算除了要考虑涌潮高度、圆柱直径外,潮前水深也是关键因素,且涌潮作用力与圆柱直径之间存在显著的非线性关系。

Optimazing operation and maintenance Telang II tidal reclamation scheme in relation to agricultural development

The objective of this research is to study the hydraulic performance of the water management system of the Telang 2 tidal lowland reclamation scheme with respect to the operation and maintenance of the system. The hydraulic performance of the system should inline with the food crop water requirement and its cropping pattern. Based on the result of this research, a basic model will be set up in order to support a sustainable agricultural development in the area. The methodology of this research consists of 1) Analysing the hydraulic performance of the water management system for the existing condition as well as under the proposed scenarios;2) socio-economical approach to the related farmers in relation to the operation and maintenance of the water management system;3) Mathematical modelling of crop water requirement and an optimal water management system and its water management zoning system;4) Cost benefit analysis related to operation and maintenance of the water management system, role sharing and cost sharing. In this study, computer softwares CROPWAT, DUFLOW dan ArcGIS have been used as supporting tools in the analysis and evaluation. CROPWAT model was used for calculating the crop water requirement based on the climatological condition and proposed cropping pattern (rice-maize and rice-rice) and its calendar. Based on the result of the CROPWAT model, DUFLOW model was used in order to evaluate the capacity and hydraulic performance of the open canal system. Finally based on the field water layer condition, water management zoning can be derived by using ArcGIS in relation to the crop water requirement and required water levels in the water management system. Based on this research, it can be concluded that the cropping pattern rice-rice or rice-maize are preferable and the co sharing is 50% by the Government and 50% by the farmers is the best option and this is also inline with the hydro-topographical condition of the related area.

Environmental State of a Harbor in Terms of Waters Renewal. A Case Study for a Fishery Harbor in Thessaloniki Gulf

The waters renewal of the fishery harbor of Nea Krini is presented here. The harbor is located at the east Thessaloniki Gulf (NE Thermaikos Gulf, Greece). The main research point is focused on the environmental state of the harbor which is under construction. Under that point of view, the description of a two-dimensional, depth average, hydrodynamic model follows, in order to simulate the wind generated circulation of waters, initially on the greater area of Thermaikos Gulf and then on the coastal basin of the fishing harbor. The renewal of waters in the harbor’s basin is subsequently studied. Tidal effects on the waters’ renewal are also studied. The calculation of the concentration of Biochemically Oxygen Demand (BOD) in the fishing harbor for the average time of waters’ renewal is then examined for three different cases, concerning the existence and operation of openings on the body of the groins. Finally, the analysis of the results shows a good environmental state of the harbor. It is obvious that the use of numerical models for different scenarios of engineering and design approaches can lead to the prognosis of hydrodynamic and environmental sate of a harbor’s basin so that the best possible technical design can be adopted.