Abstract: The regional distribution and the moving trajectory of the flood-causing annual maximum storm(FCAMS) in China during the 20 century are analyzed.The result shows that the whole moving trajectory is in a jumble.The FCAMS may randomly appear in any place over the country,but in the regions in the Central China and the East China the FCAMS appeared with higher frequency than other regions.The regional distribution and the moving trajectory of flood-water logging centre during the 1470-1899 period are analyzed too.The result sufficiently supports the understanding gained from the analyses of the FCAMS of the 20 century.So China has to establish Its flood prevention strategy based on the important facs mentioned above.
Abstract: In this study,the hydrological cycle especially diurnal cycle of the precipitable water vapor derived from GPS( PWV GPS) is investigated based on the ground-based the GPS observation experiment and automatic weather stations in the Chengdu Plain of southwest China during the period of J uly to September 2004.The comparison of the PWV GPS and those from radiosonde observations is given at Chengdu station,with the RMS(Root Mean Square) differences of 3.09 mm.This is surprisingly small considering the distance of up to several tens of kilometers between radiosonde station and closest GPS site.The diurnal variations of water vapor in Chengdu Plain were preliminarily investigated with the PWV GPS and the surface meteorological data.The diurnal variations of the PWV and some surface meteorological elements were composite during the warm days at Chengdu and Pixian.The PWV GPS showed a clear diurnal cycle with the amplitude of about 3 mm and changed obviously in day and little at night.A typical feature of the diurnal variation at Chengdu and Pixian is that the maximum,43.5 mm and 38.0 mm,respectively,appeared in late afternoon,and the minimum,40.5mm and 35.0mm,respectively appeared in early morning.The variation period of PWVGPS is similar to that of surface temperature,they are all controlled by the diurnal variation of solar radiation.The comparison of the PWVGPS and the rainfall shows that there is a good correlation between them in the calm warm season.The precipitating is observed frequently in the evening.The main rainfall process will occur after the PWVGPS reaches its maximum in the late afternoon,which leads to a remarkable decrease of the PWV GPS and a rapid rise of surface water vapor.When the drop of the PWV GPS is stable,the main rainfall process will stop.The accumulating and releasing processes of the PWVGPS is also well related to the rainfall,its increase or decrease continuously suggests the beginning or the end of the rainfall,respectively.
Abstract: Based on the NCEP/NCAR re-analysis climate data,the advection and convergence of atmospheric water vapor transport over the northwest China are analyzed.The results are as follow Over the most part of the northwest China,the water advection transport is of negative value,and the inflow water vapor from windward is less than that of the outflow,so it is the net water vapor loss region here.There is the large-scale negative value area of the water convergence over the miidle part of the northwest China and its local water vapor is diffused outward by the wind field only to aggravate water loss,so it is the diffuse region of water vapor.For inter-annual variation of the net water vapor transport,there is less value over the northwest China than that the north China.The advection transport shows the trend of increase while the convergence transport decreases,so the contribution of the advection increases over the northwest China For the correlation to atmosphere circulation,the water vapor advection transport over the northwest China is mainly affected by the westerly,the water vapor convergence transport has the distinct relationship with the South Asia Summer Monsoon The above variation trend suggests that effect of the westerly is increasing.
Abstract: Based on the field investigation and drilling,three kinds of original/disturbed sediments and the local surface water were sampled around the Muguandao Reservoir.Then,the temporal-spatial variation in salinity was measured carefully through the column and tank tests.At last,the salt fluxes released from the deposits were calculated.This research lays a scientific foundation for the evaluation and prediction of the water quality in the reservoir.According to the column tests,it is found that a 7.5 cm high salinity zone is formed near the interface due to molecular diffusion,and the salt concentration is relatively low and homogeneous above that level.In addition,the salt released fluxes can be expressed as the negative exponential functions, and they decrease in order of the silty clay,the medium-fine sand and pelitic silt.The tank tests show that wind may influence the salt stratification above the interface,which is favorable to salt mixture in the reservoir.
Abstract: In the previous aeration researches on the sluice structure,there are many achievements about the free-surface aeration and the sluice aeration,but there are fewer hydraulic tunnel excavation aeration researches.In order to reduce the disad-vantageous impact on the ecological environment,a set of aeration performances were conducted for the hydraulic tunnel excavation.It is found from the experiments that the oxygen transfer efficiency at the hydraulic tunnel excavation is related to Fr and ht/h.It also reveals that the oxygen-transferable efficiency of the hydraulic tunnel excavation increases with the aerator.It is expected that the results from this study will serve for the improvement of the design of the hydraulic tunnel excavation with high aeration efficiency.
Abstract: The first flush of the urban stormwater is very important to the urban non-poing pollution,it is summarized and analysed based on the definition of the first flash and the deficiency of the abroad urban storm runoff.It is suggested to adopt the difinition that is the 80% pollution volume carried by the 30% of the first runoff volume,and it can provide considerable convenience for the management of the storm runoff.The method is discussed to manage and control the runoff pollutants and protect receiving water,which can offer the scientific foundation to the treatment of the domestic urban storm runoff.
Abstract: The digital watershed model for Yellow River is the main part of the "Digital Yellow River" Project.The digital watershed model of Yellow River is developed based on the hillslope unit,under the former constructed framework,which consists of six layers:the canopy storage,the snow storage,the surface storage,the top-soil storage,the middle-soil storage and the deep-soil storage.Three kinds of runoff are considered from the ground surface to middle soil:the overland flow for fast runoff,the interflow from the top soil and that from the middle one for slow runoff.The fast runoff is the response to the current precipitation,and the slow runoff reflects the influence of former precipitation,which is very important for rain-runoff simulation in the Yellow River basin.In addition,a soil-erosion formulation is proposed for the sediment yield simulation.The suggest model is applied in three cases:the computation of the water resources in the Yellow River basin,the rain-runoff simulation in Xiaolangdi-Huayuankou area,the soil-erosion simulation in the sandy and grit area in the Loess Plateau.The wellfitted results indicate that the model would have a good prospect of application in the future.
Abstract: The water renewal is the basic aspect of water cycle and water balance.On the condition that the water inflow velocity is not equal to the water outflow velocity,a revised exchange period model for water bodies and its numerical algorithm are set up.A case study of the three reaches of the upper reach of the Yellow River is made,including Lanzhou-Xiaheyan, Xiaheyan-Shizuishan and Shizuishan-Toudaoguai,to demonstrate the water exchange period in each reach in the natural flow situation and the reservoir regulation in the past years during the flood season and non-flood season.The results are as follows: (1) In the natural flow condition,the exchange period of three reaches during the non-flood season in the past years is longer than that in the flood season in the corresponding time.But it is not same in the condition of reservoir regulation.(2) The water exchange period of each reach in the condition of the reservoir regulation is longer than that in the natural flow condition in either the flood season or the non-flood season; it means the reservoir regulation prolongs the water exchange period in the lower reaches,slows down its cycle velocity of water quantity,and restricts the water renewal quantity of the correspond reaches.
Abstract: Four different turbulence models are used to simulate the cavitating flow around a hydrofoil(NACA66),and the influence of turbulence models on the computational results is analyzed.The computed and analyzed results show that:the ASM model and the RNG k-ε model are more stable than the Realizable k-ε model and accurate than the standard k-ε model with the change of cavitation number,and the enhanced wall function is more stable and more accurate than the standard wall function and the non-equilibrium wall function.
Abstract: The presence of an ice-cover in a river will signif icantly change flow structure.The vertical two dimensional numerical model for ice-covered flow is developed by the k-ε turbulence model.Based upon the theory of dimensional analysis the factors influencing the velocity distribution patterns are proposed.The numerical experiments for various combinations of factors are conducted,and the flow characteristics such as location of the maximum velocity,mean velocities of obth ice-affected region and bed-diffected region are analyzed.The accuracy of two-point depth averaged flow measurement for ice-covered river is investigated The results reveal that the sectional velocity distribution deviates from the logarithmic law in the core flow area Meanwhile,the influence of roughness ratio of ice-cover bottom to bed,bed relative roughness and Reynold number on velocity distribution pattern is indicated.
Abstract: For the soils described by the Gardner-Russo retention function,the differences between standard estimations of interblock conductivity and the dimensionless horizontal Darcian means(k*H are symmetrical but those of k*H approaches k*V only when both △x and are small enough Therefore,it is rather essential to adopt Darcian means instead of the standard estimation of the unsaturated flow simulation.
Abstract: Mt.Jinfo,a karst dynamic system monitoring site,lies in Nanchuan city,Chongqing province.The data from the site's automatic records(CTDP300) indicates that the karst dynamic system is highly sensitive to the environment.The physico-chemical variation of the epikarst spring water is quite different under different climatic condition.In normal days without rainfall,water temperature and air temperature have the same variation,and its peak zone lags behind the top temperature for several hours.This is probably attributed to the gradient of CO2 concentration in atmosphere caused by the conversation of vegetation from photosynthesis,which is helpful to the karst process.Furthermore there is difference in the time behind the top temperature because of the vegetation cover and the geographical structure.At the beginning of a rainstorm,the physico-chemical variation of spring is mainly controlled by the dilute effect with the adjusting of vegetation and soil.It can last for the entire rainfall process,but several hours later,the hydrodynamic effect and the CO2 effect will occupy the dominant position due to the high fissure rate and permeability in epikarst zone.So it is necessary to explain the hydrochemical behavior of epikarst process in the water-rock-CO2 system.
Abstract: With regard to the motion characteristics of water-sediment between Wakouzi and Majiazui reach(the meandering and bifurcated reach) in the middle reaches of the Yangtze River,the basic principles of the 2D mathematical model for water and bedload are put forward,including the equation for the non-equilibrium bedload transport,the equation for the bed material sorting and the equation for the riverbed deformation,etc.Some key problems are treated by using the following methods: the incipient velocity and the transport law of the non-uniform bedload,the thickness of riverbed's mixed layer,etc.Some model's parameters are calibrated by mease of a plenty of flow and the riverbed deformation data.The water surface profile, the distribution of flow velocity and the riverbed deformation are verified.Based on this,the present model,according to inlet and outlet flow and sediment conditions provided by the design unit,has been applied to study a typical meandering and bifurcated reach,that is,training of navigation channel between Wakouzi and Majiazui reach in the middle reaches of the Yangtze River.The process,distribution of erosion and deposition and the change of water level and change of navigable conditions of the study reach are predicated during the initial impoundable stage of the Three Gorges Project.
Abstract: In the sediment mathematical model,three compossitions of the flow should be included in the continuity equation: the volume flow rate of a control volume,the volume flow rate in and out the control volume and the exchange flux between sediment laden flow and bed.Now,the exchange term between sediment laden flow and bed is not be considered in the flow continuity equation in most sediments mathematical models.One dimension-mathematical model is taken as an example to evaluate the importance of the exchange term with the numerical experiments.Based on the schematic model and the field data of the Weihe River,the research results show that the exchange term has obvious influence on discharge when sediment concentration is high.The phenomenon of the so-called‘change flow into bed material' or‘change bed material into flow',which often occurs in the sediment-laden river like the Yellow River,can be explained.The conclusion can be made when the sediment concentration is high.The three compositions of the equation of continuity of flow should be synthetically considered in the water and sediment mathematics model
Abstract: On the basis of the remote sensing theories,we get the spectrum and the concentration,and at the same time make sure of the correlation of the data simultaneously,then work out the remote sensing reflectance of ETM+ imagery relevant to the spectrum instrument.The photoelectricity instrument works out the suspended sediment concentration.Four kinds of the experiment models are derived from the correlation of the reflectance and the concentration.The results show that the ratio of TM4 to TM1 has the best correlation with the concentration,therefore we can make use of the model to derive suspended sediment distribution
Abstract: According to the sand conservation and the characteristics of flow and sediment transports of lake,a two-dimensional unsteady flow and nonuniform sediment model is established.The paper compares the two transformation modes of wash load and bed material load,by calculating flow and sediment transports and riverbed deformation of Dongting Lake.Based on the above,the modes of sediment deposit and moving water-and-sand boundary,especially for wash load,are put forward.The calculated results prove that the numberical mode of sediment deposit for the Dongting Lake possesses better sability and higher simulant precision.It is showed that the established deposited model for the lake has good performance and popularizing prospect.
Abstract: Based on the physical mechanism of hydrological process,a parameterization scheme for regional averaged evapotranspiration with statistical-dynamic theory is established in the moist climate region.The regional averaged evapotranspiration is supposed to be constituted of the evaporation from bare land surface and the evapotranspiration from vegetation surface.At the same time the influence of proportion of saturation and non-saturation area of surface soil humidity in the examination region on the estimation of the evaporation or the vapotranspiration is considered.A expression for estimating regional averaged evapotranspiration is educed by means of the probability density function of soil humidity over heterogeneous surface for moist climate region.The reliability and workability of the expression are proved in the Yangtze Delta region.
Abstract: This paper presents a method to subdivide and code a large river basin with the aid of GIS techniques.By overlapping the surveyed watercourses on the DEM,the elevation values of some convex cells in rivers are modified to remove the large-size falsely-closed depressions.Then a river network consistent with the surveyed river network is extracted from the modified DEM.The extracted river network is coded prior to subdivision and codification of the river basin.This paper also brings forward the improvement to the Pfafstetter coding rule because the area sizes of sub-basins at the lowest level may be quite uneven if the rule is directly adopted.The river network and the basin are coded according to the improved Pfafstetter coding rule.All tasks of codification are automatically accomplished by using a program developed in this study.The suggested method is applied to the Yellow River basin and the whole drainage basin is divided into 8255 sub-basins,of which each is assigned with a Pfafstetter code.
Abstract: In this paper,the temporal distributing characteristics of the rainstorm floods in the drainage basin of Yuecheng Reservoir are discussed in two aspects.On the one hand,the temporal distributing characterist ics are identified by counting the number of rainstorm days,the estimated frequencies of the annual maximum typical duration rainfall,the flood peak discharge,and the five-day flood volume in various ten-day according to the observed daily rainfall data and the flood events data. On the other hand,the weather factors of the rainstorm in the drainage basin described in order to validate further the temporal distributing characteristics.The starting and ending time still determined by using the relative coefficients of ten day average rainfall.The results show that there is a distinct pattern of the temporal distributing characteristics in the drainage basin of Yuecheng Reservoir The rainstorms occur frequently with more volume during one period,so there is an obvious main flood season.The flood season in the drainage basin of Yuecheng Reservoir may be partitioned three flood seasons,namely,the former flood season,the main flood season,and the latter flood season.
Abstract: In Taiwan,the streamflow in different periods reflects striking climate characteristics.Therefore,the climate characteristics should be taken into account in a streamflow model to give a more accurate simulation In this study,a climate-dependent streamflow generation model is proposed through characterizing the streamflow by the climate properties of Taiwan. Some statistical approaches are further invoked to develop the multisite streamflow generation model.The multisite streamflow generation model,unlike a single-site model which fails to account for the global basin,can reveal the correlation of flows at different sites.Excellent results are obtained by applying the proposed model to study the tributaries of Danshuei river basin in Taiwan.Accordingly,an extension of the multisite streamflow model based on the climate characteristics to water resources planning for other basins in Taiwan will be reasonably expected.
Abstract: The long-term morphodynamic model is used to simulate morphologic evolution process in a long time scale,its key is to define the model representative input condition.Based on the research purpose,the sediment transport rate is compared under the repersentative condition and the natural input to confirm reasonable representative tide.According to the compute and the analysis,three representative tides with 12.5% more than mean tide range are selected for the typical conditions in the complex paleo-Pearl River estuary bays.
Abstract: This paper analyzes and summarizes the main problems about the current integration management and its application in flood-control consultation system.The design idea of the integration management of flood-control consultation system is put forward,and its architecture is researched.It also analyzes the feasibility of the key techniques,such as Web,metadata,Java and Web GIS.Through the theoretical study,it designs and develops the templates about the integration management of flood control consultation system.In this system,the information oriented to the hotspots of flood control decision-making is effectively managed by the flood-control consultation templates.In terms of the consultation management platform,the visual thematic information can be sent to the consultation screens rapidly to support the flood control decision-making.Through a case study in Heilongjiang Province,the effects of these techniques are illustrated.
Abstract: The characteristics,the sources and the mechanism of the urban rainfall runoff pollution are introduced in this paper,and it is helpful for the studies in our country.The urban rainfall runoff pollution originates from the precipitation,the urban surface and the drainage system.The urban surface and drainage system are the main sources of the urban rainfall runoff pollution.The sediment and the associated pollutant deposits,forming in the combined sewer networks,are a major source of pollution during a storm.Several studies show that the erosion of the in-sewer pollutant stocks can provide 20-60%(depending on site and rain event characteristics) of the total SS,COD,BOD5.The initial period of the stormwater runoff,in which the concentration of pollutants is substantially higher than in the later periods,is called the fist flush phenomenon.During the first flush,an enormous quantity of pollutants are discharged into the receiving waters.The research concludes that the the first flush results in a substantial concentration peak at the beginning of storm events.However,the concentration peak may vary with the different pollutants during the same storm event,or with the same watershed during different storm events.In general, the first flush is influenced by many parameters,such as the watershed,the rainfall intensity,the impervious area,and the antecedent dry weather period.Therefore,it is difficult to establish the universal regression curves,or even the complex multiple regressional functions,which can predict the first flush loads.
Abstract: This paper analyzes the current situations of the drought management in China,and points out the existent problem.The working mode to cope with drought is being changed,which varies from the passive antidrought toward actively mitigated drought,it is the development trend of the drought management.To put forward the mode of the drought management the crisis management should be changed into the risk management.The paper mainly introduces the main contents and the ways of the drought risk management.