Abstract: Based on the observational data of 664 meteorological stations in China from 1960 to 2000 and combined with the geographic information system(GIS) of Arc GIS,the spatial and temporal distributions and their trends for pan evaporation in China are investigated in this study.The results indicate that,from 1960 to 2000,the rate of pan evaporation steadily decrease in China.Compared with the period of 1960s to 1970s,the rate of annual pan evaporation during 1980s to 1990s decreases by 99.8 mm or 5.8%.The seasonal analyses show that the decrease of pan evaporation occurs mainly in spring,summer and winter.The spatial distribution of the change rate shows that the decrease of pan evaporation mainly occurs in East and Central South of China.Further analysis shows that the decrease of pan evaporation is closely related to the reduction of the solar irradiance resulting from the sun-shine percentage decrease.
Abstract: Combined 3" digital elevate model(DEM) data with the precipitations of 102 stations in the east of Qingzang tableland from May to Nov.,based on the relation of precipitation distribution with altitude,the stations are divide into three parts,and the relatioships between the rainy season precipitations of 40 years(1961-2000) and six factors longitude,latitude,altitude,gradient,direction of slope and opening are established by using the stepwise regress method.Based on the relationships(models),the change laws of every factor's coefficiency in wet and dry years are analyzed.The result show that the relativity of the models are remarkable:the relative error is less than 20%,average value of relative error 4.4%,and the relativity passes by 0.05 test.The precipitation distribution in wet and dry years is influenced by altitude and opening in the first region with less than 1 400 m altitude; as for the second region with more than 1 400 m altitude and less than 3 600 m altitude,the precipitation is influenced by altitude,longitude and opening,as for the third region with more than 3 600 m altitude,the precipitation is influenced by opening and gradient.When the tableland monsoon becomes strong,the influence of opening and longitude on precipitation is more remarkable,and the influence of gradient and altitude is weaker,therefore,the regional character of water-vapor distribution is notable,the difference in the east and the west become more obvious,so did the precipitation.Therefore,the geographical and topographical factors influence upright motion of atmosphere,which results in difference of precipitation distribution.
Abstract: A strong decadal change of the Meiyu periods in the mid-lower Yangtze basin occurred in late 1970s since 1885:a weak Meiyu stage in 1959-1978 abruptly transformed into the strong one during 1979-1999.The average Meiyu amounts of later 21 years increased by 66% compared with the former years,accompanied with a significant increase of the occurrence of the summer waterlogging in the mid-lower Yangtze basin.The change of Meiyu periods is closely related with the frequently postponed phenomena of their ending dates and the later onsets of high summers in the mid-lower Yangtze.In a considerable degree,it reflects an abrupt change of the summer climate in eastern China.Through analysis,it is found that the preceding factors effecting the inter-annual changes of Meiyu in above 2 stages are also very different from each other.The causes of such decadal change are associated with following strengthening anthropogenic activities:China's industrialization has greatly accelerated since 1970s,accompanied with the increase of the atmospheric pollution and the reduction of the solar radiation on the ground,the sand area of northern China also expands fastly by overgrazing,and the enhanced greenhouse effect is significantly manifested in winter warming(especially in February).Meanwhile,the January precipitation of the mid-lower Yangtze tends to increase,and the El-nino events have occurred more frequently since late 1970s.The correlation-scattered diagram formed by above 5 factors clearly shows that the 2 stages with opposite anomalies of Meiyu period are grouped with the 2 totally locations and very different environmental(land-atmosphere) conditions.Now we have very possibly faced again a new stage of lesser Meiyu starting in 2000.
Abstract: Aimming at the problem of the erosion of parts of seacoast after the variation of flow and sediment in the Yellow River estuary,we research on the relationship between the epeirogenesis of seacoast and the variation of flow and sediment using the methods of f ield data analyses and theoretical study.The research results show that the flow and sediment coming from land is the foundation of the epeirogenesis of seacoast,the bigger the incoming flow and sediment is the bigger the area of the epeirogenesis.After the variation of flow and sediment,the epeirogenic area of seacoast reduces greatly because the decrease of the incoming flow and sediment The atrophy of tail channels affects greatly on epeirogenesis of seacoast,the heavier the atrophy of tail channels,the less advantageous the epeirogenesis of seacoast.By using the methods of the regress analysis,the synthetical critical mathematical relationship of the epeirogenesis of seacoast is established It provides reference usage during the process of controlling the incoming flow and sediment to defend seacoast in the Yellow River estuary.
Abstract: Based on non-uniformity,the grain shape coefficient is introduced.By analyzing influence of shape coefficient and exposure degree,the formulas for calculating equivalent grain and the incipient motion condition of non-uniform sediment are established by the relative exposure degree and shape coefficient.Verified by using the experiment data,the result shows that the experiment data are adjacent to the measured value.
Abstract: According to the transfer processes of gas,a theory is analyzed for dissolved gas supersaturation downstream of the sluicing dam.The effective saturation concentration and the effective depth where bubbles are entrapped into water are introduced to explain consideration of the gas transfer across both the water surface and the bubble interface.It is difficult to measure many parameters such as the gas transfer coefficients,the bubble size,the air void ratio and so on.So the quantitative relations between these parameters and the water turbulence parameters,such as flow velocity,turbulence kinetic energy,are developed Taking the Ice Harbor dam in U.S.for example,the dissolved gas concentrations downstream of the dam are simulated using the theoretical relations.The local measured data show the validation of the theory.
Abstract: The hydraulic conductivity between stream and adjacent aquifers is an important issue for water resource management.The hydraulic conductivity of the streambed is an essential variable in determining the hydraulic connection between a stream and adjoining aquifers.The paper applies straight and L-shaped standpipes directly to streambeds for measuring the in-situ hydraulic conductivity in the vertical(kv) and horizontal(kh) directions,as well as in other oblique directions(ks) in the middle reaches of Heihe river.Results indicate that the hydraulic conductivity of streambed has not only significant anisotropy,but also variability at the spatial scale.In the same measured spot,the hydraulic conductivity decreases with the increase of the angle between horizontal and measurea direction(θ).At the spatial scale,the hydraulic conductivity of side streambed is higher than that of the middle streambed,especially in the vertical direction This indicates that the side streambed is an important leakage region.
Abstract: Rainfalls flow along the hypsography of the earth's surface,and valley elements such as the valley lines,catchment areas and naturally.Formed watersheds the research on the digital simulation of flow paths on the earth's surface is important for the digital watershed hydrological analysis.This paper puts forward the concept of the digital flow paths model by which we can get the flow path of any raindrop on the earth's surface.The contour lines and spaces are measured by the distance transformation of map algebra,and a method of building the digital flow paths model with the contour maps is advanced in the paper.The experiment result shows that the calculation of flow directions and flow paths can avoid the effect of the DEM elevation errors since the flow direction is calculated with distance transformation instead of D8 algorithm.Compared with the existing methods of the digital hydrological analysis,the method excludes the complex step of identifying and treating the depressions or flats in DEM.The model takes contour maps as original data and it can be availably applied in the extraction of valley lines,the delineation of catchment areas and the generation of watersheds.
Abstract: The solution variables are stored at the triangular circumcenters based on unstructured meshes,which can avoid discretization errors made by all kinds of correction methods used in non-orthogonal meshes.Rhie-Chow's momentum interpolation method is adopted here to derive water level correction equation based on the SIMPLE method and a detail discretization equation is showed.The momentum equation is discretized by the power law scheme which has good numerical property.The flow phenomenon and the measured results agree with the numerical results very much,and the characteristics volumes of the eddies of the upper and down reaches around apur dike are simulated successfully.
Abstract: In order to study the entrained vortex flow and get the influence of the structure of the intake on it,the 3-D-PIV technique is used to measure this kind of flow near the horizontal intake.The image of the particles got by 3-D-PIV experiment in two media is unclear for the difference of refractivity in different media.So the refractivity-revised method is used to solve the problem.And the multi-step calibrated method is used to improve the measurement precision of the w vector.In the experiments,the distributions of the 3-D velocities of the entrained vortex are obtained.The relation between the entrained vortex and the structure of the intake is also found.Results show that the intake with 30° angle chest wall can prevent the entrained vortex effectively than that with 0° angle chest wall,so it is a good idea,through changing the angle of the chest wall,to prevent the entrained vortex near the intake.
Abstract: The reach between Three Gorges Dam and Gezhouba Dam is one of the most difficult waterways for navigation from Yichang to Chongqing.With the establishment of the numerical model for 3-D flow,the 3-D flow field in this reach is calculated and the navigable area is analyzed according to the calculated results and navigable conditions.The result shows that this reach can basically satisfy the navigable conditions of the 10-thousand-tons fleet when the discharge is no more than 25 000 m3/s; on the contrary,danger area will appear and navigable conditions will be deteriorated as the discharge increases.If the standard for navigation can be properly raised,the flux for navigation shall increase to 45 000 m3/s.
Abstract: Based on the observed data from 1991 to 2004,in north-eastern of Jiaozhou Bay,the variations of months,ten-day period and long-term in nutrient concentration and their molar ratios,and the relations between them and the chlorophyll a content are discussed in this paper.The various nutrient concentrations slowly increase in a wave in spring and summer which are closel related with the input of the outer-source nutrients.Big variations in a ten-day period in nutrient concentrations and their molar ratios mainly reflect instability of the input of the outer-source nutrients.Among various nutrients,the obvious peak value is found in August only for SiO3-Si and there are similar variations to SiO3-Si/DIN and SiO3-Si/PO4-P ratios related to rainy season which brings a lot of SiO3-Si.After autumn,the nutrient concentrations rapidly increase,particularly SiO3-Si and DIN,as high as 97.7 and 173.4μmol/L respectively,and lead to the bloom of Lauderia annulata Cleve in winter which is found first time in winter in Jiaozhou Bay.During the peak of bloom,nutrients are heavily consumed,and SiO3-Si is almost exhausted(0.49μmol/L) and SiO3-Si/DIN and SiO3-Si/PO4-P ratios rapidly drop down to 0.01and 1.04 respectively.SiO3-Si becomes the limiting factor of phytoplankton growth and the bloom is finally controlled.The study shows that there are close relations of growth and decay between the season variations of nutrients concentrations and phytoplankton.The long-term variations of nutrients and their structure show that,compared the 1999-2004 period with the 1991-1998,the average DIN and SiO3-Si concentrations increase by 1.0 and 2.2 times,respectively,and the average DIN/PO4-P and SiO3-Si/PO4-P ratios in-crease by 0.4 and 0.9 times,respectively,and the PO4-P concentration and the SiO3-Si/DIN ratio increase a little.All the molar ratios of nutrients are much different from the Redfield ratios(N/P=16,Si/P=16,Si/N=1).It is close related to the developments of a society and its economy of Qingdao city.
Abstract: As a world famous spectacular scene of tidal bore of Qiantang estuary,at present it becomes a special focused problem that the height of the tidal bore decreases or increases after the large-scale regulation and reclamation on Qiantang estuany.Based on the data of the height of tidal bore measured on the spot before and after the action on Qiantang estuary,it shows that,during the strong tide,the reach of highest tidal bore is transformed from Xinwan to Daquekou and increases by 0.4 m after the action than before that of the reaches under Yanguan,and the reach in Yanguan increases by 0.1 m,while the variation on height of the tidal bore of the reachesup Yanguan is closely related with the status of the sandbank peak rushed and silted by runoff.It also shows the height of tidal bore increases under the same other conditions.The result conforms to the fact that the standard swawall overflows take place due to the height increment of the tidal bore after the regulation and reclamation in recent years.
Abstract: The heat exchange of ocean 2 atmosphere interface acts as an important role in the climatic variation,but it has an important influenced on the further research of the air-sea interaction because the observes data over ocean are sparse.In this paper the satellite data from SSM/I(Special Sensor Microwave/Imager) and AVHRR(Advanced Very High Resolution Radiomater) are used to estimate the sensible heat flux(SHF) and latent heat flux(LHF) on the air-sea interface over South China Sea(SCS) with the advanced COARE Bulk Flux Algorithm version 3.0a.Comparing with the in-situ observations in Xisha and Wenchang stations,the estimated results are very reasonable.It means that the satellite data can be taken as an efficient alternative for sparse observations over the ocean and it has important roles in the study of the air-sea interaction in SCS,and it becomes an important basis of the climate forecast and research in China as well.Moreover,it indicates that properties of the heat fluxes in SCS has notable seasonal,interannual and decadal variation period.The period of the sensible and latent heat fluxes is 0.5a,1a and quasi-3a and 6-11a,respectively.The interannual and decadal period of the heat fluxes in SCS is consistent with that of the dry and flood in China.So,it can be thought that interannual and decadal variation of the heat fluxes in SCS will play an important role that cannot underestimated on the dry and flood distribution in China.
Abstract: A 3-D baroclinic ocean model is used to simulate the seasonal variation of temperature in Bohai Sea.Based on the difference(△T) of sea surface temperature(SST) and sea bottom temperature(SBT),it is found that △T is less than 0.5℃ throughout Bohai Sea before March,meaning that water column is mixed sufficiently; when April comes,the over 2℃ temperature difference occurs in Laizhou Bay,central basin and Bohai Sea strait,implying that the vertical stratification comes into being; the tendency that stratification area increases with heat flux through sea surface can extend to August.Thereafter,with the decreased irradiation and strengthened tidal mixing as well as wind stirring,the seasonal thermocline disappears gradually,and the water column resumes the fully mixed state.
Abstract: According to the data of water consumption from 1980 to 2000 in China,this paper analyze simply the driving factors for water demand,and construct a model for the case study on the contribution ratio of every driving factor changing water demand.The main conclusions involve:(1) The rise of industrial and residential water consumption is the direct cause of water consumption increase;(2) The top fourth positive driving factors are the increase of industrial production value,irrigation area,population,and area of forest,herd and fishing.The decrease of farm irrigation quota plays a first important role in constraining water demand while the decrease of industrial water consumption quota plays the second one;(3) Although population rise is the main contributor of residential water demand increase in North China,the increase of the average residential water consumption quota is more important in South China;(4) Industrial scale enlargement is the main driving factor for the industrial water demand,and the decline of water consumption of unitvalue is quite serious in North China; And(5) variation of the farm irrigation area has great influence on the farm water demand.
Abstract: After surveyed in situ in Nanhui east shoal several times,the rule of freshwater is described in this paper.The probability of freshwater occurred in wet season and dry season is from 76.98 to 82.94 percent and from 35.04 to 42.66 percent,respectively.And the causes of freshwater are discussed also.The runoff of Yangtze River is abundant,which is the basis of freshwater occurring in Nanhui east shoal.The Criolis's force is another important factor making the freshwater flow at the tide flat.The velocity and direction of wind in the dry season have important effect on freshwater resource.Northwest wind accelerates the probability of freshwater resource occurred in dry season,especially.
Abstract: The feature Chromophoric dissolved organic matter(CDOM) and its source in Meiliang bay and Da Taihu lake in Taihu Lake are analysed based on every 2 time's samplings in summer with algal bloom and winter.CDOM absorption coefficients and chlorophyll a concentration are significant higher in summer than winter.The DOC concentration and the CDOM absorption coefficients a(355) are in the range of 5.17-12.42 mg/L,2.57-6.77 m-1,respectively,with the maxima at the mouth of Zhihu river on Dec.15.Significant positive correlations are generally found within a(355),DOC concentration and normalized fluorescence Fn(355).The determination coefficients between a(355),DOC concentrations and Fn(355) are significantly lower in summer than winter due to the phytoplankton degradation.As the parameters representing the CDOM composition and the source,the DOC-specific absorption coefficients a*(355) are remarkably larger in summer than winter.However,M and S values are smaller in summer than winter with the seasonal variations.The spatial distribution of the CDOM absorption coefficients is similar to that of chlorophyll-a concentration in summer with algal bloom.A significant and positive correlation is found between a(355) and chlorophyll-a concentration,which shows that phytoplankton degradation is one of the potentially important sources of CDOM.By contrast,no significant correlation is found between a(355) and chlorophyll a concentration in winter.The CDOM absorption coefficient generally decreases from the mouth of river to the inlet and outlet of Meiliang bay,which shows that river terrestrial input is the potentially main source of CDOM.
Abstract: The indexes are advanced to decide the summer monsoon extent of East Asia and identify the activie region of the tropical and subtropical summer monsoon.By using the NCEP/NCAR troposphere data of wind,geopotential height,humidity,temperature,the satellite-derived OLR and TBB,the activity and variability characteristics of the monsoon circulation during ‘0506' continuous rainstorm are diagnosed from monthly,pentad and the process time scales.The results indicate that if the subtropical anticyclone is stronger,the west-point of subtropical anticyclone ridge is more farther westward and southward than the climatological average,and the cross-equatorial stream in tropical western Pacific(130-140°E) is stronger.South China is located in a region of the anomalous cyclonic depression.These characteristics are exhibited in either monthly or rainstorm process time scale.Besides the Bay of Bengal and South China sea,the water vapor of the rainstorm process is mainly from the abnormal water vapor flux over the South China sea and the tropical western Pacific.The water vapor in the tropical western Pacific transports to South China following the stream at the edge of the subtropical anticyclone via the South China sea.Consequently,plentiful water vapor is provided during the rainstorm process.The front part of tropical summer monsoon stagnates for two pentads longer than the climatological average.This characteristic is a valuable signal for forecasting South China rainstorms.The mean monsoon strength over the South China sea in J une is stronger,which is showed by the stronger meridional wind.But the rainstorm process begins in the period of inactive summer monsoon over the South China sea,which is related to the northward spread of the tropical intraseasonal oscillation.The activity and variability characteristics of monsoon mentioned above act as favorable dynamic condition and the abundant water vapor sources.
Abstract: The zone of fluctuating water level in the Three Gorges reservoir area is a vulnerable area for non point source pollution according to the special hydrological characteristics and agriculture practices.In the zone of fluctuating water level of the studied Three Gorges Watershed,ten typical soil samples with four soil types and four patterns of land use are selected.The simulative study on the risk of submerged soil phosphorus leakage to the reservoir is conducted.Under the submerged simulation with the phosphate concentration of the solution,ranging from 0.1 mg/L to 1.6 mg/L,the interactions of soil and phosphate of water are divided to three patterns:release,sorption,and combination of release and sorption The patterns are distinguished by the relationship between the equilibrium P concentration at zero sorption(EPC0) and the phosphate concentration of solution With the significantly relat ivity between EPC0 and Olsen-P,Olsen-P is used as an index which provides the thresh old of three patterns When Olsen-P of soil is lower than 14.4 mg/kg,EPC0 of the soil is lower than 0.1 mg/L,then the soil will absorb the P of native water,and this type of soil is the sink of P.When Olsen-P of soil is beyond 123 mg/kg,EPC0 of the soil is higher than 1.6 mg/L,then the soils P will be released to the native water When Olsen-P of soil is between 14.4 mg/kg and 123 mg/kg,the soil will release or retain phosphorus according to the PO43- concentration in native water.
Abstract: The dispersed type distribution of the nonpoint source pollution load is very unfavorable to the study of the relation of the nonpoint source pollution and the other social and environmental factors,therefore it very necessity to carry out the continuous space distribution handling.However,it is very important to notice the problems such as measure and information increase and decrease in the successive dispersed variable.This paper takes the pollution of the population and the livestock for example.The spatial continuous distributed model is established to calculate and simulate the quantity and the distribution of that pollution loads.And we finally verify from the result that this kind of nonpoint source pollution spatial continuously distribution processing technique is not only necessity,but also feasible.
Abstract: Some models based on(moderate resolution imaging spectrometer,MODIS) image data for estimating concentration of the suspended sediment(SS) are developed by taking Taihu lake as an experimental site in this study.SS concentration measurements,field spectra and MODIS images are obtained concurrently.An image-based atmosphere correction method is applied in preprocess of MODIS image data to reduce the atmospheric effect.Based on studying the spectral characteristic of SS,the suitable MODIS bands and band combinations are correlated with SS measurements.The field spectra data is used to confirm the result.Then,using simple regressive and multivariate regression analysis,the semi-empirical retrieval models are developed,evaluated and applied.This study demonstrates that MODIS images are useful in estimating SS concentration in large inland lakes like Taihu lake.Bands 2,4,14 with different resolutions of 250 m,500 m and 1 000 m are suitable to detect SS concentration.The combinations of r4/r3 and r4-r3 with 500 m resolution,the multivariate combination of bands 8,11,13,14 with 1 000 m resolution are chosen to develop the retrieval models(R2≥0.85).
Abstract: This paper researches the key points of TGP(Three Gorges Project) and Gezhouba's 3-D simulation system,describes exactly the database established process and the 3-D visualization project frame.The system stuies the data interface among TGP real-time database and the dispatching mathematical model,displays the dispatching methods in 3-D scene intuitively,consequently actualizes the querying and sort displaying of the shipping related data.A new platform is provided in this paper for cascade dispatching decision-making.
Abstract: Base on the idea of river management,the river restoration and the sustainable development of water resources,the hydrodynamics investigation in the veget ated open channel is brought forward.The importance of the hydrodynamic research in vegetated channel is emphasized.The studies of the flow resistance and the turbulent mechanism in the vegetated channel are introduced both at home and abroad.It is pointed out that the simulation of the shape and temper of the flexible vegetation and the quant itative rule between the flow resistance and the toughness of vegetation,and the complicated anistropic turbulence needs to be solved.The more refined numerical model of large eddy simulation must be invented to tackle the anistropic turbulence in the deep vegetated channel.
Abstract: The development in mercury biogeochemical cycle in hydroelectric reservoirs both at home and abroad is reviewed in this paper Basically,it contains four aspects,namely,the substrate mercury release behavior,the impact of mercury release on the water column,the transfer and bioaccumulation of mercury in the aquatic food chain and the reservoir's effect on the mercury distribution in the river.On these basis,the development tendency of this research is proposed since there is still some confusion and obscurity.
Abstract: Based on a large number of the papers published in journals of China from 2002 to 2005 and the important national projects and project research reports of the national natural science foundation of China in the recent years,this paper reviews the main study results and progressions in the China in the elements of hydrologic cycle such as precipitation,evapotranspiration and runoff,water balance,stream sediment,lake,swamp,wetland,glacier,frozen earth,and groundwater and subsurface water.