Abstract: The ions in the nature river would affect the fine sediment set ling velocity. But the sediment settling velocity formula could not reflect the influence before. So the formula could not compute the velocity of the sediment particle settling in the water with ions It is necessary to amend the formula to compute the velocity in this situation. The fundamental cause of generat ing influence on the settling velocity by ions is flocculation of fine sediment. And in this process the most importantions in river are high valency cations. Based on the analysis of sediments flocculation process,a empirical formula between the set tling velocity of the fine sediment flocculation and the ion concentrat ion is established. And the emcpirical relat ionship based on the experimentations is given. So the coefficients in the formula are confirmed by the experience of the sediment settling velocity in the distiled water and the water with different Ca2+ concentration. By taking account of the Zhang Ruijin formula and the empirical relationship formula,the sediment flocculation settling velocity formula about Ca2+ comes into being. The preliminary verification of the formula is made through the contrast between the actual measured value and computed one. The results of verification show that the results computed by the flocculation settling velocity formula are more rigorous than those done by the Zhang Ruijin formula.
Abstract: The observed facts and the researched results show that the ENSO events in the ocean have two different patterns: the Eastern patern and the Central pattern,and the variat ion of the ENSO has important relations to the Central Pattern Tounderstand the mechanism of the ENSO cycle,based on the SODA data set by the University of Maryland,the evolution characteristics of the subsurface temperature anomaly in the equatorial Pacific of the two pattern ENSO events are analyzed by the case study and the composite method. The results show that,the initial source of the subsurface temperature anomaly in the Eastern pattern ENSO events comes from the western Pacific,and that of the Central patern ENSO events occurs in the central Pacific,then the center of the subsurface temperature anomaly moves upward and eastward along the climate thermocline driven by air sea interaction,and the ENSO events happen when they reach the sea surface of the eastern Pacific.The results also show that,due to the warm and cold phase of the Eastern pattern ENSO events,one phase is the initial field of another,while one phase of ENSO events forms,another phase will follow meantime,thereby the ENSO cycle completes. But the Central pattern ENSO events develop under the weak ENSO state with long time succession,and they disturb the regularity of the ENSO cycle and may cause the break of the ENSO cycle.
Abstract: Based on the data from the map of climate,soil water and land use(1982 and 2002)in Anjiagou catchment in the loess plateau,this paper studies the change of land use,the evapotranspiration,the ecological water use for the different plant species and the catchment,and its the correlation with the change of the climate and the land use. The results indicate that (1)the the structure of land use in Anjiagou catchment had significant change from 1982 to 2002. The cropland(especially the terraces)increases while the woodland decreases significantly because of the deforestation and the expansion of the waste-land;(2)The ecological water use for all the vegetation types is controlled by the climate,and had significant variability in the study period;(3)The evapotranspiration and the ecological water use for the woodland and the shrubland was higher than those for the cropland and the natural grassland;(4)The water consumption for cropland was close to that for the natural grassland,but the water consumption for the woodland and the shrubland was significantly higher than that for the natural grassland;And(5)the ecological water use in Anjiagou catchment decreased from 1982 to 2002 due to the decrease of the woodland,which had increased the water balance of the catchment.
Abstract: Songnen Plain is an important productive base of commodities in China,but its groundwater environment is ever deteriorating due to the impacts of the global climate changes and the excessive high human activities,and it become the important factor restricting the eco-environmental construction and the socio-economic development. This paper takes the Taoer River basin as the typical study case,and the groundwater samples are analyzed scientifically and systemically,then the descriptive statistics,the correlation matrices,the ratio coefficient of the main ions and the piper diagram are used to gain the better understanding of the spatial and the temporal variation of the hydrochemistry characteristics and the evolution laws of groundwater.The following main hydro chemical processes are inferred to controll the water quality of the groundwater system: (1)the weather-dissolution,(2)the evaporative condensation,(3)the ion-exchange reactions,and(4)the mixing of the surface water with high salinity. All conclusions can offer the scientific guidance for the sustainable development and the management of water resources in Songnen Plain,Northeast China.
Abstract: Compared with commonly used deterministic methods,the stochastic hydrogeology method is a more rational resort for solving the flow and transport problems in the heterogeneous aquifers. On the assumption that the hydraulic conductivity field follows a lognormal distribution,the direct Fourier transform is introduced to generate multiple realizations of hydraulic conductivity field. Then the Monte Carlo method,based on the stochastic theory,is applied to investigate the effect of the spatial variation of hydraulic conductivity on the fate of contaminant plume. For the contaminant plume examined in this synthetic example study the spatial second moments defining the spread of the contaminant plume around its centroid increase with the enlargement of the variance of hydraulic conductivity distribution,while the first moment specifying the centroid of the plume is not influenced by the variance of hydraulic conductivity but dominated by the mean of hydraulic conductivity. Additional analysis demonstrates the sensitivity of both variance and coefficient of variation of plume concentration to the various variances of hydraulic conductivity field.
Abstract: The leakage problems of several typical sections of Gaoshuihe embankment are studied by applying the environmental isotopes method in the paper. The leakage sources of groundwater are ascertained. The result shows that the groundwater of T1# borehole at Jiangdu dockyard and T23# borehole at Xiaocaitan section is recharged by the river water,the water of Heiyu-tang around T5# borehole is recharged by the local precipitation,and the groundwater of T7# borehole at Wanshougong section is the mixing of river water and local precipitation. Because the environmental isotopes method can only qualitatively explain the problem,the paper attempts to perform quantitative analysis of fuzzy clustering by applying the fuzzy clustering method that the environmental isotope and the hydrochemistry values are taken as the index characteristic values and endued different weightings. The analysis result is according to the conclusion judged by environmental isotope and the hydrochemistry.
Abstract: According to the principle of the consumption demand of the water yield for growing field crops and its relationship with the precipitation,the dynamic variation characteristic of the regional groundwater pumpage for agriculture and the shallow groundwater level responding to the precipitation in North China Plain from 1986 to 2000,this paper suggests the regular contrary change of the regional groundwater pumpage for agriculture responding to the precipitation,the consumption demand of the water yield and the annual pumpage increases or decreases with the annual precipitation. The particular safeguard role of groundwater to the safety of the irrigation of the grain crops in North China Plain during successive low dry years is indicated from above results. A new method is suggested to evaluate the used level,the rationality and the safe potentiality of the actual regional groundwater pumpage for agriculture,and predict future pumpage,which is significance to the study of the rational use of the groundwater and the ensure safety for the supply water for the agriculture areas short of water resources.
Abstract: The experiments on open-channel flows on the rough mobile bed in the transitional region are reported in this paper. The velocity in the flume were measured by a 22D LDA,and the resistance coefficient were calculated with the Einstein's resistance division method. The experimental results show that(1)The Karman constant in the Log-law of the open channel flows in the transition region is smaller than which that of the smooth open channel flows,and the integral parameter B does not coincide well with the Nikuradse's result from the pipe flows;(2)The weak bed load in the flume may cause the drag-reducing effect;and(3)The Reynolds stress and the turbulence distribution are similar to those in the smooth open channel flows.
Abstract: Water levels in open channel fluctuate along with the change of the discharge. The change from one state of steady flow to another will take a period of time. The process of the change is affected by the characteristic of canal structure,the canal operation method,the range of discharge change and the rate of it. The hydraulic reaction of unsteady flow is also studied by means of numerical simulation of the unsteady flows in open channel in different cases.
Abstract: In this paper,the circulating flows in the sect ion is analyzed based on the characteristics of the curved channels. The forms of horizontal turbulent stress is established by the Prandtl turbulent stress.A formula for steady 2-D circulating velocity profile in curved channels is derived based on the Reynold Turbulent equation. The analysis indicates that formula has a simple and reasonable structure,and coincides with the survey data. We also study the lateral silt discharge in the curved channels and discover an available model for numerical simulation of the curved channels.
Abstract: Based the data measured before the construction of the Three Gorge Dam and using the empirical statistical approaches,this paper studies influence of variations in suspended sediment concentration and grain size on the sediment deposition of Yichang-Hankou reach of Yangtze River.And a regression equation between the annual sediment deposition in the Yichang-Hankou reach and the annual average suspended sediment concentration(Cmean,Yichang)at Yichang station is established in 1980-1997.According to this equation,a threshold of Cmean,Yichang is estimated as 0.734 kg/m3,at which this river reach is in a non-scour and fill state. A multiple regression equation is also established,which relates the annual sediment deposition in the Yichang-Hankou reach and the influencing variables including the annual suspended sediment concentration, median grain size of suspended load and annual flood at Yichang station,and the ratio of the flow diverted through the “three outfalls” to the total. The equation based on the data in 1980-1997 indicates that the sediment deposition in Yichang-Han-kou reach increased with the increases in sediment load,median grain size of suspended sediment and annual flood at Yichang station,and with the decrease in the ratio of the flow diverted through the “three outfalls” to the total.
Abstract: In order to provide some recommendation for the water management and the vegetation restoration on slope-lands, the study on the spatial variability of the soil moisture in different directions and positions on the recultivated slope-land on the Loess Plateau is carried out at the Shenmu ecological station both by the field measurements and the statistical analysis.In this paper,some key issues related to the spatial variability such as scale and time-dependence are discussed. The results show that the mean variation of the soil moisture is weak along the vertical and the N-S direction(perpendicular to slope),while it is moderate when the E-W direction,22D and 32D space are considered.Along the slope,the soil moisture decreases and then increases from its top to the bottom,and the sequence of the magnitude of the heterogeneity is the top-slope>the mid-slope >the bottom-slope;in the N-S direction,the soil moisture increases from the sunshine slope to the shadow slope,and the magnitude of the heterogeneity of the sunshine slope is larger than that of the shadow slope;in the vertical direction,the soil moisture decreases and then increases below the depth of 200cm from the soil surface,and the magnitude of the heterogeneity is significantly positive correlated to the mean moisture of the same soil layer.
Abstract: Based on the data from the tidal-gauge stations and synchronously surveyed data during Dec.9-15,2003,the present paper provides a brief analysis of the characteristics of tide,the residual currents,the suspended sediment content and salinity during the dry season at the Modaomen Estuary of the Pearl River. The preliminary research are made on the estuarine dynamic process,including the mixing of fresh water and salt water and the estuarine jet.During the dry season,the tidal current becomes dominant due to the weakened runoff.The surface residual current at each station basically goes downstream along the river course due to the effect of the runoff and wind,while the residual current near the mouth,below the middle layer,goes stably upstream. In the dry season,the suspended sediment content in the Modaomen is very small(<1 kg/m3)and the salinity changes both along the longitudinal and the vertical direction at the Modaomen Estuary. The fresh water and salt water mixes with the N parameter between 0.01 and 1 at all stations. The surveyed velocity configuration shows that the gravitational circulation exists near the mouth caused by the density difference. In light of the densimetric Froude number calculated through the actual surveyed data,the estuarine jet in the dry season in the Modaomen Estuary is buoyant.
Abstract: Climatic change is increasingly concerned. The observed and investigated rainfall and the discharge data from 20000 rainfall stations and 175 hydrologic stations on large and medium rivers in the recent 100 years(especially 50 years)of the 20th century are used to study the inter-decadal change of the extreme values of rainstorm and flood in China(mainly in exorheric basins). These studies include the decadal mean changes of rainstorms of the long series stations,contrasting the early years,mean value of the point rainstorm's extreme values with that of the recent 50 years,the decadal distribution of the maximum point rainfalls and the decadal distribution of extraordinary flood peaks. The extreme values of rainstorm and flood varying with decades are analysed from the different durations and regions;the variable facts are demonstrated;some decadal ratios are calculated;and several affecting factors are investigated.
Abstract: Water resources system is combined with natural hydrological cycle and man-made water process. The interdepen-dent relationship between these two cycles of water movement is analyzed. Based on the analysis,taking into consideration of major aspects related to water resources,the complex system can be classified as five sub-systems:natural water resources, development and use,ecosystem of water,water environment and social-economical system. The comprehensive indicator system is constructed by combining with the major factors in the sub-systems. Through the indicator system,the assessment of water resources and the status of development can be identified quantitatively with respective the indicators.Furthermore,the diagnostic indices are provided aiming at identifying the specific problems and the measures of improvement.
Abstract: China's grain issue already becomes a hot topic in the world. This paper attempts to use the concept of the virtual water as a tool to analyze the virtual water flows with grain between China and other nations,as well as between the regions within China. Based on the grain supply and demand under the different development strategies in the future,the paper identi-fies the grain trade scale and makes a prospect for the virtual water trade condensed in grain. The result shows that North China exports a virtual water flow of 18.4 billion m3 to South China in 1999,which indicates North China plays an import role in en-suring China's grain security and socio-economic development. In the future China will face with the big pressure of the rapid growth in grain demand. To ensure the national grain security China has to depend on herself to solve the grain issue. To keep the high level of the grain self-sufficiency,the inter-basin water transfer project is not only an effective way to prevent North China from suffering water crisis but also an important strategy to ensure the country's grain security,keep the social stability and promote sustainable development. In the meantime,the virtual water trade can be as a supplement to ensure water security in water scarce region.
Abstract: The 47 models used for river basin management are collected and classified into three categogies:the watershed loading model,the receiving water model and the integrated modeling system. Among them,nineteen models calculating watershed pollution load are studied. Firstly,this paper describes their input data,output,land use type,the hydrologic computing mechanics,the pollutants and sediments types,the time scale,and the software providers. Based on the modeling application and the relative literature reports,a qualitative evaluation is made from the angels of the suitability to the different land use type and the different time scale,the hydrological simulation capability,the simulation capability of the different pollutant loads,the routing methods of pollutants transportation,the output format,the input requirements,the BMP analysis supporting,and the documentation. The evaluation results are expressed by the‘High',‘Middle' and‘Low',which indicate the capability status of the model from the good to the poor.
Abstract: Considering the change of various ecological factors in lake,which effected on the whole phosphorus sediment process,a stochastic difusion model for the total Phosphorus concentration in lake is estabilished,where a standard Brownian motion perturbs the whole phosphorus sediment process. We extend the Vollenweider water quality model and obtain its analytical solution,mean,and variance According to the sediment coefficient,a method that controls the total phosphorus concentration is pointed out. The model is applied to the Chao Lake in Anhui province.
Abstract: The selection principles for regional ecosystem health index are discussed. Based on the regional rivers and the landscape,the indicators are established. According to the ecosystem hierarchy,the multi-objective and multilevel fuzzy optimization model is selected to evaluate the ecosystem health. For instance,in Guangdong province,the ecological zone are partitioned,assessed and sorted based on the synthesized attributes.
Abstract: Based on the requirement analysis of the regional water pollution control(RWPC)CAP model,the structure of CAP model is designed in the UML,and the geodatabase is selected as the developing type of the CAP model. The det ailed developing process is introduced in the case of Foshan RWPC project. The CAP model,applied in RWPC planning,can improve its planning proficiency and the corresponding data coincidence.It is proved to be a convenient CAP solution.
Abstract: The dam-break problem is important in the design and management of hydraulic engineering,which has always been studied. This paper reviews and summarizes the progress in this field as follows:the mathematical model and the difficulty of the analytical solutions is introduced;discusses the latest progress of the numerical solutions is discussed;the finite difference method,the Godunov method,the Boltzmann method,and the KFVS method of one-dimensional dam-break problem are introduced;the TVD method,the discontinuous finite element method,the finite volume method and characteristic method of two-dimensional dam-break problem are discussed;the applicability,the advantage and the disadvantage of each method are analyzed; and the progress in the numerical calculations of flow of fluid with free surface are presented.Meanwhile,According to the shortage at present and the need of the engineering field,the research direction and the developmental trend are proposed.
Abstract: In this paper,the theory of the Partial duration series(PDS)mode is presented and developed to extracting more information from observed flood data.The PDS model and its derived annual maximum series(AMS)model are reviewed and compared. The Principles for applying the PDS model,such as the independence criteria,the threshold selection and determination of the probability distribution of the number of exceedance events,are summarized.Furthermore,the latest advances in regional flood frequency analysis and on coupling of Bayesian with PDS model were described. Finally,the perspectives of the PDS model are prospected.