Abstract: A method for spatial spectral analysis under the constraint of spectrum power conservation and a presentation for relative terrain height(topographic perturbation with respect to mean topographic trend)are proposed,in order to analyze the effect of topographic forcing on precipitation distribution in Tibetan Plateau.The results show that below the relative maximal precipitation height,the ordinary ‘classical coherent relationship' between topographic height and the precipitation profile (i.e.,the distributing profile of precipitation is similar to the undulating profile of topography,and the ridges and peaks of precipitation correspond well to those of terrain)are very complex and the terrain-rainfall pattern in Tibetan Plateau can not correctly describe.It is further found that the so-called lock-phase relationship between terrain and precipitation to be presented in a spectral space can essentially measure the coherent degree and the profile agreement between terrains and precipitation. This paper reveals that the two different phase-locked patterns can depict well the topography-precipitation relationship in Tibetan Plateau.One is the resonance-pattern that the ridges and peaks of precipitation are well correspondent to that of terrain. Another one is the shift-pattern,in which the precipitation increases or decreases with the terrain decreases or increases,respectively.
Abstract: The biological soil crusts BSC play several important roles in many arid and semi-arid ecosystems around the world. Their effects on soil hydrology,however,are poorly understood.The experiments under 15 Bar Ceramic Plate Extractor,Star-1 soil hydrophysical characteristics determination system,and with the van Genuchten closed-form equation for predicting the hydraulic conductivity of unsaturated soils are conducted using two samplers of the BSC and the shifting dune sand.The results indicate that the water holding capacity of BSC is 3 to 9 times magnitude than that of shifting dune sand;when the matrix potential varies from -1 to -3 000 cm,the unsaturated soil hydraulic conductivity of BSC is about 12% lower than that of the dune sand,while the matrix potential varies within -3 000- -15 000 cm,the comparable value for BSC is about 9.10% and higher than that of shifting dune sand.The particular structure and particle size distribution contribute to the variation of the unsaturated soil hydraulic conductivity of the two soils,where biological crusts are formed by living organisms and their by-products,creating a crust of soil particles bound together by organic materials.It improves the micro-habitat of desert soils and increases the availability of soil moisture to shallow rooted shrubs,herbages and micro soil animals in the artificially re-vegetated ecosystems.
Abstract: On the basis of the van Genuchten Mualem constitutive relationship,a stochastic numerical model for unsaturated flow is developed.The saturated hydraulic conductivity and the pore size distribution parameter are assumed to be the random space functions with the log normal distributions. We decompose them through the Karhunen Loeve expansion and express the pressure head as polynomial chaos expansion. We derive a series of partial different ial equations in which the dependent variables are the deterministic coefficients of the head expansion and then solve these equations with the method off inite differences.The effect of perfectly correlated and uncorrelated case between two random space functions on flow quantities is studied by the proposed stochastic model.It is shown that the mean heads of the two cases are the same,but the head standard deviations of the perfectly correlated case are smaller than those of the uncorrelated case.
Abstract: Field soils contain some rock fragments,particularly,forest soil that usually has considerable amount of rock fragments.However,there is little information on the effects of the amount and the size of rock fragment on the infiltration in research paper.Based on the experiment of one-dimensional vertical infiltration in laboratory conditions,the effect of different soil-stone ratios and constitutes of rock fragments on the infiltration rate and the wetting front of the mixtures are studied.The results show that the infiltration rate and the wetting front increase with the increase of coarse-fragments for a given time.The relationship between the infiltration rate and the time can be described by the Kostiakov infiltration model;the relationship between the wetting front and time can be fitted well by one short power progressional solution of the Philip infiltration equation; and the parameters of the Kostiakov infiltration model and one short power progressional solute of the Philip infiltration equation are all fitted the power equation with the increase of soil-stone.The effect of the size and constitutions of rock fragments on the infiltration rate is expressed in the content of rock fragment after correlate analyses.In addition,rock fragments with 2-3 mm in diameter give negative correlation with the infiltration process,while rock fragments greater than 25mm in diameter are favorable to water flow in the mixture.The results of the present study may provide important data and be useful for the profound understanding of water cycle in stony soils.
Abstract: Based on the period 1956-1969 taking as a baseline period for the Wudinghe river basin,a multiple regression equation is established between the annual sediment yield and some indices of the precipitation characteristics,and used to calculate the sediment yield in the measure period(1970-1993),assuming there are no soil-water conservation measures Then the annual sediment reduction beneficials,defined as the percentage of sediment reduction of the sediment yield without soil-water conservation measures,is calculated,and its temporal variation is plot ed The curve indicates that the soil-water sonservation benef icats is a non-linear variation,which can be divided into three stages:(1)the increasing slowly;(2)increasing rapidly;and(3)remaining unchanged or even decreasing The relationships are plotted between the sediment reduction benef icials and the areas of the soil-water conservation measures such as land terracing,tree-and gras-splanting and the land created through check dams.It also shows the non-linear variations which can be fitted by the two straight lines with different slopes The turning point between the two straight lines can be regarded as a threshold of the area of the soil-water conservation measures,and the two straight lines represent a high-return area and a low-return area of the sediment reduction beneficials,respectively The curve can provide some useful information for the soil-water conservation planning in the studied area.
Abstract: The small Natong and Kuarewarma Rivers in the headwater areas of the Yellow River and the Fenhuoshan River in the headwater area of the Yangtze River,where vegetation is simple and dominated by the alpine cold meadows and the alpine grassland meadows,are selected as typical catchments to study contrastive the impacts of the alpine land cover change on the rainfal-runoff processes and the soil erosion. Based on the studies of the plots,the effects of runoff and sediment yield at the same gradient from July to August are tested in terms of three vegetation coverages of 30%,68% and over 92%.The results indicate that on the 30° slope in the alpine meadow zone and under the condition of the same precipitation,the runoff in the meadow zone that holds 30% of land cover is apparently larger than that in the meadow zone that holds 95% and 68% land cover;furthermore,the sediment yield is also larger than that of the later two,and the average sediment yield caused by one precipitation event is 2-4 times as larger as that of them.The results support the concept of vegetation as a major control upon runof and sediment production. Moreover,the simulat ive results indicate that for the moderately degraded alpine meadow land with a coverage less than 68%,the apparent ef ects of runoff and sediment yield happen when the secondary precipitation is 3.5 mm,and 1400mL runoff produce in the 5 m2 field when the precipitation reaches 7 mm and lasts 15 minutes.The sediment content,runof and its formation frequency in the seriously degraded alpine meadow land with coverage below 30% are appar ently higher than those of the alpine meadow land holding a higher land cover,on average,2-7 times as larger as that of the later than those of the alpine meadow land holding a higher land cover on the about 2-4 times as large as that of the latter. In the headwaters area of the Yangtze and the Yellow Rivers,the alpine meadow coverage,topographic gradient and precipitation characteristics(time,intensity)all influence the runof and sediment yield apparently.
Abstract: Based on the observed data in the wandering reach at the lower Yellow River,the adjustment of river regime is analyzed.The results show that the wandering position of the mainstream line in the direction of river width has a statistical rule though the river regime at the wandering reach is inconstant.The regulation between the string height and the string length of the mainstream line accords with a function relationship between the bow parameters.The bending radius reduces with increasing length of the mainstream line,and then tends to be relatively stable.The statistical relationship between the bending coefficient and the length of the mainstream line and bending radius shows that the river regime at the wandering reach of the lower Yellow River has some obvious characteristics,where steep bends are liable to take place and make the bend more wandering. There is a correlation tendency between the bending radius and river width,the wider the river,the more the increasing probability of the bending radius.
Abstract: Ecological water use safety is the primary condition for maintain river health. In this paper,according to the characters of river ecosystem,the concept of ecohydrological regime is proposed,and the multi-parameter system of the ecological water requirements(minimum and appropriated ecological water demand,ecological water requirement in flood season)are established,which are regarded as flow requirement for river health.According to the ecohydrological regime the integration of ecological water requirements can be referred to ecological with temporal characters.Based on the ecological flow regime,therefore,the warning mechanism as well as the regulation and managenent rules of ecological water use are discussed.The results of the case study in the mid-lower reaches of the Yellow River can be scientific supports to maintain security of the ecological water used in that region.
Abstract: A physically-based distributed rainfall-runoff model is developed to simulate the hydrological processes of watershed during rainfall period for considering the spatial variability of terrain,the land use,the soil type and the rainfall distribution. This model discretizes watershed into a number of square elements,and classifies them into hill-slope and channel ones based on the water flow properties.Each hill-slope grid element has model components for interception,infiltration,overland flow and soil water lateral flow,and each channel element has model components of channel flow.The infiltration and excess rainfall on each hillslope element are calculated using the Green-Ampt infiltration equation.Soil lateral flow is based on the Darcy's law and the continuity equation,the overland and channel flows are described by one dimensional kinematic wave approximation to the St Venant equations,and the implicit finite differential scheme is used to solve these equations.This model has the characteristics of simple structure,the process-based equations and the meaningful physical parameters.Most parameters of the model can be derived from the DEM,the digital soil type and the land use data,a few sensitive ones can be determined by the calibration.The model calibration and test are performed in huangtuling watershed(17.9 km2),a sub-basin of Yongjiang river in Zhejiang province,southeastern China,and applied to Jiaokou watershed(259 km2),another sub-basin of Yongjiang river,the results are promising.
Abstract: The objective of this study is to simulate the hydrologic responses to a single-storm event with a distributed hydrologic model system(HMS)in the Emei Watershed and to provide information for the study on the interactions between regional climate and hydrologic system in the upper Yangtze River. HMS was designed to study hydrologic processes and systems responding to various climatic factors. HMS utilizes spatial information on climate,soil type,land use and land cover,digital elevation,and hydrologic parameters and simulated variables have physical meaning. In this study,the SCS Curve Number and Green-Ampt methods of rainfall-runoff partitioning were used in HMS. The data sets such as DEM,soil,land use and land cover and hydrologic parameters were processed on GIS. The simulations with different time intervals in precipitation and different methods for obtaining hydraulic conductivity were conducted to examine the effects of temporal scale in precipitation and spatial variation in hydraulic conductivity on the hydrologic responses. The application of HMS was demonstrated for the hydrologic simulation in the Emei stream watershed. It was shown that simulated streamflow compares well with the observed data.
Abstract: There is much error in flood forecasting process due to the limited model and the inadequate real time information, however,it is an effective method based on the hydrograph interactive technology to reduce the forecasting error. This paper introduces the significance of the interactive correct technology applied to forecasting hydrograph,and the process fit smooth ness and the cubic interpolation technology Based on the technology above,it can be realized to correct the forecasting hydrograph interactively in the form of elastic which is applied to the flood forecasting system. The case study indicates that the technology can be used easily to improve effectively the accuracy of flood forecasting.
Abstract: A binary tree-based and dyadic indicated codification method is proposed in the digital watershed model(DWM). This method is able to locate any section of drainage network directly and operate the topological relationship effectively. This paper issues the framework and definition of the codification method in the DWM,delineates a drainage network in this special way with its own numerical character. Some detailed arithmetics of the codification method in the DWM is presented in an appendix.
Abstract: The effect of three different lower boundary conditions(free drainage,pressure head and fixed ground water table) on water drainage in irrigated field is studied using the numerical simulations based on the field data in Quzhou County on North China Plain.The water drainage in 2 m soil profile is calculated by the HYDRUS-1D model from October 1998 to September 2001 When the fixed ground water table is selected as the lower boundary condition,the soil water content at different depth in 2m soil profile is calculated by the HYDRUS-1D model,which agreeds well with the measured values,however,when taking free drainage and pressure head as the lower boundary condition,the difference exists between the measured and the simulated values. In comparison with the result of dynamic water drainage and accumulated water drainage estimated by using the Darcy law,we found that their dynamic process of water drainage by using the fixed ground water table agreed well with that of the Darcy Law.Therefore,the fixed ground water table being selected as the lower boundary condition is suit-able for the local conditions.
Abstract: The purpose of this paper is to simulate the wave profile and flow field when the wave propagates the submerged bars by using the PLIC-VOF model to trace the free surface of wave and the finite difference method to solve the 2-D N-S equations. After comparing the numerical results of two kinds of submerged bars with the experimental ones,it is believed that the PLIC-VOF model used in this study is effective and can compute wave field finely.
Abstract: The major oceanographic characteristics of the eastern Pacific warm pool(EPWP)and the relationship between the variation in the EPWP and ENSO based on the SST data from 1950 through 2002 are analyzed.The results show that the form and thermal state of the EPWP obviously exhibit the seasonal and interannual variations related to the ENSO cycle.The heat content,the area and the southern edge of the EPWP are all closely related to the ENSO.The composite analysis indicates that the heat content decreases,the area lessens and the southern edge is located at the northernmost position in the preceding year for El Nino onset,while the heat content increases,the area enlarges and the southern edge shifts to the southernmost position after El Nino onset;during the La Nina,the variation trends of the heat content,the area and the southern edge of the EPWP are contrary to those during the El Nino Besides,the meridional displacement of the EPWP may play an important part in the development of the ENSO.
Abstract: In this paper the flow properties and influence on the joint at downstream are studied.First,by analyzing on the development of boundary layer in the shallow supercritical flow and aeration properties,we find the character of energy dissipation that the resistance loss of shallow flow in the wide-steep channel is more than that of the flow in the general steep channel, and get its range value of the velocity coefficient. Then,according to the different flow and boundary condition,we analyze the flow momentum distribution in wide-steep channel,and find that when the ratio B/H<40 and the discharge is larger,the flow momentum lateral distribution in the end of steep channel shows a saddle profile which has stronger stability and anti disturbance;but when the ratio B/H >40 and the discharge is smaller,the momentum lateral distribution shows a elliptical profile which has bad stability and can't restrain the outside disturbance. Based on analyzing the we attains that the instability of shallow flow in the end of steep channel originates from lack of stronger both wings control in momentum lateral distribution, which brings about accumulation and increase progressively of minor disturbance and leads to instability of the end hydraulic jump and insufficiency of the energy dissipation. In order to improve stability of join flow at downstream,a measure adjusting of momentum lateral distribution is put forward in this paper.
Abstract: A new efficient characteristic-based numerical model for 3-D shallow water is presented and discussed in this paper. The model is based on the collocated,finite volume method with unstructured grids. One attractive feature of the model is that it has ability to handle arbitrary topology. The other is that horizontal mass and momentum flux across interface of cells is calculated by the Roe's Riemann approximation solver and the monotone,conservation scheme make a simulation results for keeping water balance in the entire computational field. The wetting-drying algorithm is also proposed to simulate flooding processes in sand shoal. To validate the model,the numerical simulation is performed for three cases:the wind driven circular flow,the dam-break wave on initial dry bed and the tidal flow in estuary of the Yangtze River. Results show that the model can accurately simulate the 3-D flow structure,and has good numerical stability.
Abstract: The Chinese sturgeon,Acipenser sinensis,is an anadromous protected species that presently only spawns in the Yangtze River. It is also the important fishery resources. Its migration pattern is blocked due to the Gezhouba projects,so the length of natural spawning site has reduced from 800 km to less than 5 km,thus,it becomes the extra-protected animal. In this article,the ecological-hydraulics models is established to simulate and analyze the 3-D flow character by using the N-S and the k-ε formulas,the method of volume of fluid is also used to simulate the two phase flow,and the finite volume method is used to disperse the calculated area,which aims to provide technical parameters for the optimizing regulation of Three Gorges reservoir.
Abstract: With use of the experimental results of water quantity and water quality of the overflow from some representative drainage systems to Suzhou Creek in rainy days and treatment the technology of the storage tanks,the integrated model of hydrodynamics and the water quality of pipe networks about the drainage systems and the river networks for Suzhou creek is set up,combined with the physical model, the influence of controlling pollution of the overflow from the initial rainwater storage tanks to Suzhou Creek and its water quality are studied in detail in 8 kinds of 1-12-h design rainfall condition.
Abstract: The water quality and its changes of the Three-Gorge reservoir(TGR)are a hotspot after it begins to store water and generate electricity.About 11.1% of water inspecting sites exceed the required quality standards at present.The pollution belts exist in some shores by the urban zones.The main sources and quantities of water pollution loads(WPLs)released into TGR are analyzed by using the problem-oriented approach used in life cycle assessment.The results show that the eutrophic pollution loads(PLs)is 27 900 t PO43- eq,in which CODCr accounts for 16.4%,the total nitrogen and phosphorus for 37.9% and 45.8%,respectively.The municipal sewages(MSs)and agriculture chemical fertilizers are the two biggest contributors,which account for 61.0% and 26.3% respectively.The freshwater aquatic ecotoxicity(FAETs)PLs is 7612.6 t 1, 4-dichlorobenzene eq,of which the contribution rates are 78.0% for volatilization hydroxybenzenes(VHs)and 21.2% for mercury.76.5% from MSs and 23.5% from main industrial enterprises(MIEs).The total eutrophic PLs,as well as the FAETs PLs of Cr6+ lead from MIEs,and VHs from MSs are increasing.
Abstract: In order to recognize the pollutant sources and build the correspondence relationships between contaminated sources and important pollutants,a set of intelligent recognizing method based on correspondence factor analysis and fuzzy C-means clustering(short for IRM-CFA&FCM)is developed IRM-CFA&FCM couples skilfully fuzzy C-means clustering,correspon dence factor analysis and clustering validity funct ion discovered by Xie,etc,and is solved by the accelerating genetic algorithm efficiently.The method is used to monitor water quality in Donghu lake,acquiring six kinds of correspondence relationships and puting forward some reasonable and valuable suggestions for decisions making of renovating Donghu's contamination comprehensively.The method is useful for recognizing pollutant sources of other city water bodies.
Abstract: Lake water is the case Ⅱ water,whose water color is influenced by three major components,namely,phytoplankton pigment,suspended sediment and yellow substance. So the optical properties,including apparent optical properties (AOPs)and the inherent optical properties(IOPs),of lake waters are more complex than ones of case Ⅰ water. One of the key solutions is under investigation and measurement. One of the ways to interpret the lake color is the empirical regression, and another is semi-analytical,i.e. bio-optical model method. The latter,concerned with the atmosphere,the water-body and the relationship between the two,is better for remote sensing of lake the water quality. It is the key technique for improving the precision of inversing the lake color to correct the atmosphere influence,and the methods are reviewed. And the water-leaving radiance is analyzed from its contents and algorithms. Then how to acquire IOPs is analyzed in detail. Subsequently, the methods and steps to implement the former model and inverse it are summarized. Finally,the key problems concerned with remote sensing of lake water color in China are put forward.
Abstract: Water depth,an important hydrological factor in shallow lake,has great influence on hydrodynamics,ecological and chemical processes. Based on the field observations from 1993 to 2002,we perform correlative analyses and establish the relation regression equations water depth to total nitrogen,total phosphorus,and chlorophyll(Chla)a in seven subareas in Taihu Lake. The changes in water depth are found to have more significant influence on the concentrations of nitrogen and phosphorus in Meiliang Bay than in other subareas,but the influence on the Chla concentration is not apparent,either in heavily polluted or better water quality subareas.The prominent effect of water depth on the concentrations of the total nitrogen and the total phosphorus in partial area of Taihu Lake suggests a feasible approach to reducing water pollution by water level regulation.
Abstract: High-resolution measurements of rainfalls,water level,pH,conductivity and temperature in Landiantang epikarst spring at Nongla,Mashan county in Guangxi Province,China were recorded by using the data logger with time interval of fifteen minutes all the year round. And,the waters from the spring represent the exit for the aquifer's conduit flow. During the rainfalls,it was found that the pH and temperature of Landiantang spring increased and the conductivity reduced. As HCO3-, Ca2+ and Mg2+ were the dominantions,we developed linear relationship between conductivity and those ions. According to the liner relationships,the calcite index(SIC),the dolomite index(SID)and CO2 partial pressure(LogPCO2)of the spring were calculated. Results indicated that the LogPCO2 of spring during rainfalls was lower than that without rain,and its SIc and SID was also lower. By studying epikarst zone,it was known that above result was caused by the dilution of precipitation because rainfall with high pH and low conductivity forming slope stream and traveling through conduit rapidly affected the hydro-chemical variations of epikarst spring.
Abstract: Environmental isotope exists extensively in various kinds of water. Every kind of water has the distinct isotope composition because of the isotopic fractionation in the transfer and the circulation among precipitation,surface water,groundwater,soil moisture and plant water. The present status of isotope hydrology is reviewed with the accent on techniques which are most frequently used or the potential perhaps,as yet,not fully utilized. The topics included within the group of environmental isotope techniques are the recharging and the dating of groundwater,the elevation of recharge area,the runoff studies,the interaction of surface water with groundwater and the leakage between aquifers. With regard to the future this paper points out the need for a more quantitative approach to the interpretation and presentation of results.
Abstract: The hydro-power developments of a river are favorable to meet the social requirements for water resources and electrical power.But simultaneously,the exploitation of water resource affets the local and regional eco-environment,especially the streamflow,the sediment transportation,the aquatic environment,and the limnobios,and so on.This paper reviews the recently studies on the river-hydro-power development and its impacts on the aforesaid aspects and discusses the significant issues in the further research.These include:(1)measures to adapt water explorations and regulations to the sustainable development theory,(2)quantifying researches on the impacts of hydraulic engineering establishment to the situation of river runoff and sediment,(3)the self-adaptation and self-restoration mechanisms of unbalanced ecosystems,(4)the threshold velocity of the flow for preventing eutrophication,and(5)the methods to deal with river-exploration threats to environment with the co-op-eration of reservoirs.
Abstract: The advances in research of the environmental flow methodolodies for rivers(EFMR)since 1980 are reviewed,including the studed status quo,and the types of methodologies and developing trends.In foreign countries,a suit of integrated method system is established from the hydrological methodologies with single hydrological elements to the holistic methodologies with the multidiscipline of learning.And in future,a comprehensive suit of methodologies,founded on best practice and sufficiently flexible to meet the needs of each situation and country,will become popular throuth an internationally collaborative research effort.In china,the research of EFMR is still in primary stage with most qualitative analysis and few quantitative analysis such as Tennant method,7Q10 etc.The emphasis will be on fundamental study and the development of EFMR adapted to the needs of our county(or basin,or regions).At the same time,study areas will shift from the arid and semiarid North to the South with abundant water resources.