Abstract: It is now well established that the surface of Earth has,on average,warmed over the past 50 years. One expected consequence of this warming is that the air near the surface should be drier,which should result in an increase in the rate of evaporation from terrestrial open water bodies. However,lots of observations show that the rate of evaporation from open pans of water has been steadily decreasing all over the world over the past 50 years,and it is similar for the reference evapotranspiration. The contract between expectation and observation is called the evaporation paradox. Based on the data of 353 weather stations from 1956 to 2005,the trends in pan evaporation,air temperature and precipitation are obtained,and then the evaporation paradox and the relation between precipitation and evaporation are analyzed. The conclusions include:(1) in the past 50 years,the air temperature increased and the pan evaporation decreased,therefore the evaporation paradox actually exist in China;(2) the paradox is not consistent in space or time,for example,the pan evaporation in northeast and after 1980s increased with the increasing of air temperature;and (3) in the past 50 years,the precipitation and the pan evaporation exhibit contrary trend in rest areas.
Abstract: The particulate organic carbon content(POC)and particulate inorganic carbon content(PIC)in total suspended solid(TSS)are used to trace sediments diffusion bound in Bohai after the fourth test of water-sediment regulation of the Yellow River,the result indicates that POC and PIC in sediment are both stable with season changing,their mean content are(1.75×0.28)% and(0.51×0.08)% respectively.When TSS concentration is below 30 mg/L,PIC in TSS decrease swiftly to 0, whereas POC in TSS increase promptly.According to the analysis of chlorophyll-a and mineral in TSS,when TSS is less than 30 mg/L,phytoplankton increases,but the sediment from the Yellow River decreases in TSS.Simultaneously,ΣC20-/ΣC20+ and carbon proponderance index(CPI)of n-alkane increase and decrease obviously.TSS=30 mg/L can be regarded as the effective boundary between the allochthonous TSS and autochthonous TSS.The sediment from the fourth test of water-sediment regulation of the Yellow River diffuses to southern river-mouth at surface layer;While at bottom layer,sediments diffusion range concentrates at northern and southern river-mouth of the Yellow River.the central section of Laizhou bay is likely to be the habitation of sediment from the fourth test of water-sediment regulation of the Yellow River.
Abstract: Based on the data from the Yellow River and its tributaries in the Loess Plateau,a study of the spatial differentia tion of hyperconcentrated flows frequency is made,also the relation between hyperconcentrated flows frequency and influencing factors is analyzed The results show that the high-frequency zone of hyperconcentrated flows shows itself a shape of strip,with the northeast southwest direction There are three high-frequency centers in the strip They are at lat itude 40°N,36°N and 34° N.It seems that different factos have different effecs to cause the hyperconcentrated flows The result of the multiple-factor regression analysis shows that the efficiency of shrub,dry-land fields in hilly,woodland,loess thickness and mean annual pre cipitation to the hyperconcentrated flows are 16.6%,4.4%,6.5%,29.7% and 42.8%,respectively.
Abstract: In this paper,a three-dimension carbon cycle model,including several variables such as organic/inorganic carbon in the water,CO2 in the water,carbon in phytoplanktons,fish,and phytobenthons,and organic/inorganic carbon in sediments and the water of clearances,is constructed based on the three-dimension dynamic model.In Taihu lake,the carbon cycle simulation results show that the average difference between the simulation values and the observation values is less than 40% in 2003,so it can be conclusded that the model can simulate the carbon cycle in Taihu lake and can be used to study the carbon cycle in the lake.At the same time,the results of the model show the carbon cycle in the lake can reduce the concentration of CO2 in the air.
Abstract: Selecting Ymluoxia station's runoff data from the 1944 to 2004 and Shule river station's runoff data from the 1953 to 1999,we analyze the persistence,the periodicity and the annual variety of the flow in inland river in Hexi regions of Cansu in the past 50 years and its response to the abnormity in the surface heat intension on tibetan plateau. The result shows that water resources of the middle and the west of Cansu corridor have good persistence,especially in fall and winter. There is good correlation between water resources of the middle and the west of Cansu corridor and the surface heat intension on tibetan plateau. The early circurnfluence characteristics can forecast the runoff of late May. Xinjiang ridge is weaker,Fast Asia trough is shallower, precipitation and flow is increasing;and vice versa. Runoff forecast can be used as the Northwest drought forecasting virtually.
Abstract: The statistic downscaling models of Qinghai lake(QHSDM)are built in this paper by the output from AOGCM (Germany MPI ECHAM510)and local observed data in recent 40 years.The climate scenarios in the 30 years(2001-2030) are obtained and used to predict water-level changing of Qinghai lake in the same period.The results indicate that the water level changes of Qinghai lake would experience three phases:slowly descending,gradually ascending and steadily arising.In 2030,the lake level would rise to about 3195 14 m,about 212 m higher than present,the lake area will approach 4 500 km2 and the lake storage near 8.300 millions m3,Qinghai lake turn back to the status of 1970s in 20th century.It would alleviate the present water resources tension in the catchment of Qinghai lake,recover local vegetation and reduce the soil degenerating1 In short,it is beneficial to local ecology and social economics.
Abstract: This paper combines the hydraulic model and the physical habitat simulation model(PHABSIM)to calculate the instream ecological flow by using the Yellow River carp as target species in Lanzhou to Shizuishan reach of the Yellow River mainstream and taking water depth and velocity into consideration.By analyzing the ecological,hydrological and cross-sections data before the flood periods from 1975-1985,the ecological instream flows at Lanzhou,An'ningdu,Xiaheyan,Qingtongxia and Shizuishan station calculated by PHABSIM before flood are 195 m3/s,220 m3/s,220 m3/s,220 m3/s,175 m3/s respectively.And the result is compared with the instream ecological flow calculated by the Tennant method.The results calculated by PHABSIM are within the scope of the those calculated by Tennant.
Abstract: Along with the reclamation of Sanjiang plain mire-wetland area,the paddy field's drainage goes into the natural freshwater of the mire-wetland,which will influence the wetland's eco-systems ultimately. When paddy field drainage with certain concentrations of nitrogen and phosphorus are discharged into the Carex lasiocarpa mire-wetland water,the concentrations of TN,NH4+ N,TP and PO43- P all increase obviously. Especially in August and September the concentrations of TN and NH4+ N are 1.51-2.10 times and 1.53-3.02 times as much as those of natural mire-wetland freshwater respectively,and the concentrations of TP and PO43- P are 1.30-4.08 times and 4.33-11.33 times as much as those of natural mire-wetland freshwater respectively. The biomass of the roots and stem-leaves of Carex lasiocarpa increases in the wetland with the paddy field drainage compared with those in natural wetland. The contents of nitrogen and phosphorus in the roots and stem-leaves of Carex lasiocarpa in the wetland with the paddy field drainage are much higher than those in natural wetland,and the correlation coefficients between TN and TP concentrations in Carex lasiocarpa roots and wetland water TN and TP contents are higher in the wetland accepting the paddy field drainage,which indicates that the paddy field drainage can improve Carex lasiocarp a growth and the absorption of nitrogen and phosphorus. Therefore,Paddy field drainage should be prohibited from discharging into wetland directly because of the unbalance of N/P otherwise it will threaten the stability and bio-productivity of wetland eco-systems.
Abstract: Based on the analysis of healthy water cycle concept of wetland and its connotation,and the pressure-state-response (PSR)conceptual model for wetland healthy water cycle is proposed.The assessment indictor system for wetland healthy water cycle is established based on the model.The indictor system aims to explore relationships between the pressure and the wetland healthy water cycle change,and proposes the corresponding improvement measures.The fuzzy pattern recognition model is used to evaluate healthy water cycle of wetland,the calculating weighting method of each indicator is of analytic hierarchy process.Furthermore,the above theory and method are applied to the case study of Zhalong wetland to reveal their health grades and disadvantages.According to the choice principle of the indicator,the 9 indicators are selected.The five-grade assessment standard is adopted.The comparison shows that the evaluation result of this method is in accordance with the actual situation of Zhalong wetland.
Abstract: To simulate accurately the complicated boundary conditions and overcome the problems caused by wide gap of scale between length and width,and change of computational boundary conditions as water-level variations,a 2D river-ice numerical model based upon the body-fitted method is developed by using the principles of hydrodynamics and thermodynamics and considering the influence of the frazil ice accumulating under ice cover and the shape of freezing fringe of ice cover during the river-ice process. The model is capable of determining the velocity field,the distribution of water temperature,the concentration distribution of the frazil ice,transportation of the floating ice,the progression,stability and thaw of ice cover and the transportation,accumulation and erosion of ice under ice cover MacCormack scheme is used to solve the equations.The model is validated through the field observations in Hequ reach of the Yellow river. The results show that the 2D numerical model presented is capable of simulating the river-ice process with accuracy.
Abstract: Taking the initial condition,the flow boundary condition and the roughness as the control parameters,an adjoint model of 2D horizontal unsteady flow model is established based on the optimal control theory of partial differential equations. A variational data assimilation method is developed by the mathematical model and the field data of flow. According to the spatial density characteristic of remote sensing data,a new item of cost function is introduced in order to improve the assimilation of remote sensing water levels with the emphasis laid on the assimilation of remote sensing water level.The assimilation numerical experiment of synthetical single water level image shows that the spatially distributed information provided by the remote sensing data is available to the identification of spatially distributed parameters,and the additional item is useful for the assimilation of measurement and identification of time-dependent parameters. In the simulation of an actual river,the method is applied to the assimilation of distributed water level data from satellite remote sensing images.
Abstract: Considering the lack of the sufficient measured data of the cities' river net and unsat is factory simulation speed of the hydrodynamic model,an intelligence model for river net is presented in this paper combining the hydrodynamic model with genetic algorithm and artificial neural networks. The information is supplied by the hydrodynamic model and the original weights of artificial neural networks are optimized by the genetic algorithm. The model is used to simulate the river net of Pudong New District in Shanghai Sound agreement is obtained between the results of intelligence model and those of hydrody namic model. It shows that the accuracy of intelligence model for river net is close to that of the numerical model,and the in telligence model has an advantage of good real time performanc. It provides a good technique for forecasting water level and the similar problems.
Abstract: In order to study the energy dissipation characteristic of two jet-flow with varying discharge ratio,the unsteady in compressible flowing N-S equation,RNG k-ε turbulence model and VOF(volume of fluid)method are adopted to do the numerical simulation with reference to the Xiluodu double curvature arch dam. The impact pressure on the bottom slab of the plunge pool,the velocity and the fluid state characteristic of different flow ratio are analyzed,and the mean dynamic variation regulation in the field of flow is studied quantitatively. The research shows that,with the decreasing of the upstream jet-flow, the impact pressure on the bottom slab also decreases,and the flowing water cushion exerted by the upstream flow also lowers which makes impact pressure of the downstream flow increase gradually. There are two statuses of the plunge pool:one is the flow with the effect of flowing water cushion,the other is the flow with weakened flowing water cushion. The quantitative calculation shows that for the upstream jet-flow,the mean velocity gradient is larger,and the mean dynamic attenuation is quicker With the jet-flow lessening,the mean dynamic attenuation becomes faster than before. The discharge and dissipation ratio of the downstream are totally smaller than those of the upstream. The article gives a good reference for optimization design,the protection of plunge pool and the multi-jetting flow ratio determination.
Abstract: The comparability of disaster district recover process and water self purification process is analyzed,the concept of flood disaster "self-purification process" is presented,and the three power systems,destroy power system,self-purification power system and salvation power system,are constructed. The relations of the three power systems are established by the efficiency balance theory The problem of quantitative measure of the efficiency balance is solved by adopting disaster-after sustainable development index system. An integrated flood disaster evaluation system is constructed. The system can analyze not only the situation of disaster but also the measures of disaster reduction by local government and nation. The calculate example indicates that the system has the characteristics of the structure integrity and general evaluation,and the model of the system has the characteristics of regional and timeliness. At the same time,the system has generalization ability and can be used for other type of disaster evaluation decision.
Abstract: The automatic control of channel network is a key solution to the modern water-saving irrigation,and it is also a key technique problem of the Middle Routine of the South-to-North. Water Diversion Project.The design of controller demands a liner mathematical model,but the channel networks system is a high nonlinear system.A MIMO model of multi-channel system built in this paper is used to analyze the uncertainty introduced in the procedure of linearization;this uncertainty will be a precondition for the design of robust controller.If the liner model is taken as the standard one,the uncertainty is expressed by the largest singular value of the distance matrix of the models.And a simulation example of six-canal is given.
Abstract: It is a characterist ic that water power erosion and gravitational erosion are coinstantaneous on Loess Plateau.Most of the soil erosion models about Loess Plateau don't simulate gravitational erosion,which is one of causations that simulated re sults aren't satisfactory. Base on the characteristic of the soil erosion on Loess Plateau,in this article,the method quantifying the influence factors of the gravitational erosion is adopted,thus the grids of gully producing the gravitational erosion can be determined,and the effect of the gravitational erosion in the process of sediment yield and transport can be calculated Based on the distributed hydrological model of grid to grid conflux,this article sets up a distributed soil erosion model of grid to grid sediment transport. With the calculation method of grid to grid conflux and sediment transport adopted in this article,the soil erosion model can simulate the effects of runoff and sediment from upslope on downslope erosion process. According to the cal culated result with observed data of Xiaolihe gauge station,the simulated result of the soil erosion model is better
Abstract: The study of the distributed hydrological model is a hotspot in recent years.Because some problems in the fully distributed hydrological model cannot be settled now,an alternative conceptual distributed hydrological model is put forward. An important problem in the conceptual distributed hydrological model is how to determine the storage capacity on every grid. Considering the similarity between the maximum of grid soil moisture deficiency and the grid topographic index,a logarithmic Weibull function relation existing between them is discovered.And then a method for calculating the grid storage capacity with the grid topographic index is put forward.The method is applied to the grid distributed hydrological model with incompact structure.The results shown that,in the ungauged basin,we can get some hydrologic parameters from geographic parameters and find a new approach.
Abstract: According to the concept of Gini coefficient(GC),an index for estimating equity of the income,a method for evaluating fairness of water use is established. This method is used to assess the water use in Guangdong province in 2005,and the factors which are correlated to the allocation of water use are analyzed using the GC. The Lorenz curves of each factor are drawn,and the Gini coefficients are also calculated and analyzed. At last,the trend of the GC of each factor from 2000 to 2005 is given. The results show that the Lorenz curves and the GC of each factor can indicate the fairness of water use and also be helpful for water demand prediction and allocation.
Abstract: The cumulative impacts of the cascade power stations on water temperature are studied by using the mathematic model.The water temperatue of Jinping and Ertan in reservoir area and the outflow temperature are computed.Comparison is carried out between the joint operation and single operation of Ertan.The results show Jinping reservoir is steadily thermal-stratified in the year round.The temperature at bed keeps cold steadily at 8.6℃.The temperature on the surface near dam varies from 12.7～24.2℃ in the year round.The course of the outflow temperature is obviously delayed.Ertan reservoir is thermally stratified both at the single operation and joint operation conditions.But compared with the single operation condition,the surface temperature declines and the bed temperature rises at the joint cooperation condition.The stratification in reservoir area is weakened.The delay and evenness of the outflow temperature course is further strengthened.The cumulative impact of the cascade power station on ecology environment is obvious.
Abstract: Technique of laser induced fluorescence(LIF)remote sensing can be used in water quality monitoring for large water area.A detail water quality investigation for Taihu lake is conducted with the LIF remote sensing system.According to the principle of LIF remote sensing for water quality,the dissolved organic matter(DOM)fluorescence factor,the Rayleigh scattering factor and the chlorophyll-a fluorescence factor correspond to DOM concentration,the turbidity and the chlorophyll-a concentration respectively.The concentrations of DOM are determined by three dimension fluorescence imager,and the turbidity and the chlorophyll-a concentrations are determined by YSI multi-parameter water quality meter.The results of LIF remote sensing system,three dimension fluorescence imager and multi-parameter water quality meter are compared,which indicates that DOM fluo-rescence factors determined by LIF remote sensing system and DOM concentrations determined by three dimension fluorescence agree very well(R=0.88733).However,the Rayleigh scattering factors and the chlorophyll-a fluorescence factors determined by LIF remote sensing system do not agree with the turbidity and the chlorophyll-a concentrations determined by YSI multi-parameter water quality meter,respectively.The linear relative coefficient are -0.39185 and 0.4552,and the causes are discussed.The application potential and the probable limits of LIF remote sensing in the water quality are expatiated further.
Abstract: Surface subsurface exchange(hyporheic exchange)across the river bed plays an important role in the fate of solutes and contaminants in rivers.The main mechanisms of hyporheic exchange include pumping exchange and turnover exchange. The pumping exchange is driven by pore water flows induced by head gradients Such head gradients are typically due to interactions between currents and the streambed topography. Turnover occurs with the moving bedforms trap and the released the in terstitial fluid.The main factors of influence on hyporheic exchange are as follows:the riverine flow rate,the hydraulic conductivity,the bedform,the channel curvature,the streambed heterogeneity and the background conditions.The interplay of the reactive solutes and colloids is reviewed,and the ideas for further studies on hyporheic exchange are proposed.
Abstract: Due to the spatial variability of underlying surface information and under the influence of human activity,hydrological characteristics of irrigation area are different from those of the natural basin.The concept of irrigation hydrology is pointed out in the research on hydrological cycle at different scales in irrigation area and interaction of irrigation-drainage and hydrology.Currently,the study on the effects of water use on irrigation area hydrology and the scale effect of water saving has complemented the conten of irrigation hydrology,and the irrigation hydrology research is becoming a hot spot in the world.Based on the analysis of hydrological cycle and the influence of irrigation practice on the irrigation system,several considerations of irrigation hydrology concept are introduced.On the basis of the current situation of the study in irrigation hydrology and the relevant field,the research emphasis and the development trend of irrigation hydrology in the future are given.The paper indicates that hydrological monitoring and information acquisition in irrigation system are the research base of irrigation hydrology,the numerical simulation method and the irrigation system distributed hydrological model for at the irrigation area are the main means of the research,and the scale effect and scaling are the difficult points of the research.