Abstract: Based the total variation diminishing(TVD)finite volume method, a two-dimensional hydrodynamic model using unstructured triangularmeshes is developed formodelling dam-break flooding under actual terrain with complex geometries.Details include uses of the Roe's approximate Riemann solverwith the TVD-MUSCL (Monotone Upstream-centered Schemes for Conservation Laws) scheme as well as the procedure of predictor-corrector in time stepping, which can result in a secondrorder accurate elution for dam-break flows in both time and space.The moving boundaryproblem is resolved through the introduction of aminimum water depth concept that can efficiently treat the wetting and drying fronts during the model integration.The effectof a sing different values of the minimum water depth on the simulation of dam-break fbws in the dry river bed is exam fined.We find that the minimum water depth can significantly alter the propagation of flood waves.Model results are also compared to the analytical solution under the idealized conditions, as well as two sets of dam-break data collected from flume experiments.Lastly, the model is validated using a real dam-break case with complex geometric conditions.The model simulation compareswellwith the observations and the other studies.
Abstract: The changes n erosion-deposition pattems of downnstream riaerbed surface after the impoundnent of Three Gorges Project (TGP) are quantified by the river bed surface fractal dimension (BSD).The changing character and the physical mechanism associated with the changes are also analyzed.The study reveals a whole partre lationship between the BSD and each cross-section.The complexity of river bed surface can be well represented by BSD.After the TGP impoundment, there is a significant increase in BSD along the Huyatan and Yidu reaches While, less increase is found for the Guanzhou reach and the opposite result is obtained in the Lujiahe reach.The change in BSD of each river reach is able to characterize the deformation in the river bed surface, which is resulted from the new regime of integrated frictions after the TGP impoundment.The BSD can thus be predicted through analyzing the trend change in each reach, which provides necessary data for studying the new relationship of bed friction and water level.
Abstract: A three dimension(3-D)numerical turbulentmodel is used to study the flan characteristics of turbulent jets in crossf low which is characterized as a complex 3-D flow.The turbulent model is solved using the hybrid finiteelement analytic method, and is tested through the experimental data.The turbulent model is then applied to smiulating flow and vorticity fieldswith different diffuser forms and velocity ratios, and the formation and development of vortex structures in these flow conditions are obtained.During the initial stage of vortex formation, the crossflow detours the jet and forms the counter-rotating vortex on the lateral edges of jet.The subsequent vortex evolution depends very much upon the use of diffuser forms and the use of velocity ratios.The most complex vortex structure is found with the case of using slot diffuser.The latter has its major jet axis distributed along the streamwise.There are four separating points around the diffuser,and the separated flows gradually form four vortices.In the far zone, the jet flow is dominated by counter-rotating vortex pairs, which induce the formation of secondary vortex pairs in the near-wall region.The relation between the core position of counter-rotating vortex pairs and the velocity ratio for all types of diffuser forms is established, and so do for the rotating strength.
Abstract: Infiltration processes in typical triangular layeredpmple soils are first investigated using indoor mil infiltration devices.The devices are designed to have two distinct triangular layered soilprofiles, which are soarse-to-fine and fine-to-coarse in soil textures from surface to bottom.Experimental results show that the wetting front advance appears to be faster in the first half of the layered mil column compared to that of the second half in the coarse-to-fine soil infiltration device.The opposite result is obtainedwith the fine-to-coarse mil infiltration device.Observation from the fine-to-coarse mil infiltration device shows that the rate of advance of the wetting front increasesmore quicklywith tine in the second half of the layered soil column compared to thatof the first half in the coarse-to-fine mil infiltration device.However, there is no significant rate difference in the finer portions of layered mil columns on both devices.The inclined wetting front rate is found to be sinilaron both devices, which indicates that the mil texture has almost no influence on the rate.A mathematicmodel for simulating infiltration into triangular layered mils is developed using the power relationship and validated by the experimental data.The modeling result is in a good agreementwith the experinent The model has some physical meaning and can be transformed into the existing empirical models each other.
Abstract: Based upon the point experinents on pressure infiltration processes in an unsaturated earth-liled channel an empiricahnodel for calculating seepage losses from earth-liled irrigation channels is developed.The parameters of model are empirically correlated with thewater depth in the channel.The seepage bss is estin ated through integrating the cunulative infiltration along the channelwetted perineter.Themodel is validatedwith the experinentaldata.The result shows that themodelcan has abetterperfomanceon seepage loss estination than dlatofusing the Kostiakov infiltration modlel that is also anpirically based.The sinulated seepage bss process using themodel agrees well with the observation, which demonstrafes the feasility ofusilg the point cumulative ilfiltration approach to calculate seepage losses from earth-lined irrigation channels.
Abstract: Stable isotope compositions of hydrogen (δ2H) and oxygen (δ18O) for snow and rain were determined for a total of 443 GNIP (Global Network of Isotopes in Precipitation) samples collected from the Yangtze River basin.A correlation equation (δ2H=7.965δ18O+17.114) is obtained through linear regression between δ2H and δ18O values of snow samples.The maxmial slope and intercept values are shown in the snow equation.In contrast, correlation equations between δ2H and δ18O values for rain samples of four categories ranging from less than 10 mm to greater than 300 mm can result in prog ressively lower slope and intercept values with decreasing precipitation amount.The slope and intercept values in the four rain equations vary from 5.705 to 7.701 and -5.479‰ to 7.812‰, respectively.Analysis of the slope and intercept values of δ2H-δ18O correlation equations with amtospheric parameters such as temperature and water vapor pressure suggests that only the light rainfall events undergo secondary evaporation accompanied by isotope fractionation during raindrops descent from the cloud base to the ground.Since the light rainfall events can account for only 6.32% of the all precipitation events in the Yangtze River Basin Thus, the effect of below-cloud secondary evaporation on the stable isotopes in precipitation can only result in a slight decrease of slope and intercept values of the local meteoric water line.The study shows that the isotope analysis of individual precipitation samples can yields valuable information that cannot be obtained by the long-term weighted average samples.
Abstract: A 10-year(1999-2008) half-hour dataset of precipitable water(PTV)vapor amountwas produced from ground-based gbbalpositioning system(GPS) measurements in the Lhasa river valley of the Tibetan Plateau.The diurnal variation of GPS-PW is investigated using the dataset aswell as hourly observations from automatic weather stadons in the valley.The result reveals a pronounced diurnal variation in GPS-PW，reaching the mininum around 08:00-10:00 UTC and the maxinum around 15:00-18:00 UTC during all seams.The average diurnal variations of GPS-PW are 1.0 mm，1.7 mm，1.0 mm and 0.8 mm in spring, summer, autumn and winter, respectively.The diurnal(24 h) and semidiumal(12 h) cycles of the GPS-PW were fitted using the harmonic analysis method.The resups indicate that diurnal and semidiumal cycles are the main signal of diurnal variation of GPS-PW during all seatens.The diurnal cycle of GPS-PW is the strongest in summer and the weakest in winter.The semidiumal cycle of GPS-PW is the strongest in summer and the weakest in spring.The relationship between diurnal variations of GPS-PW and that of rain fallwas conducted in summer.It can be seen that the occurrences of the diurnal variations of GPS-PW are nearly 2 h earlier than those of mean hourly p recip nation and p recip nation frequency in summer.The diurnal variations of GPS-PW have an important impacton the diurnal variations of hourly rainfall in summer.
Abstract: The Tropical RainfallMeasuringMission(TRMM)Multi-satellite Precipitation Analysis(TMPA)3B 42 product is evaluated using the gaugeprecipitations from 650 weather stations across China at daily, monthly and annual tine steps.The TMPA-3B42 performance accuracy is also assessed using theModerate Resolution Inaging Spectroradiometer (MODIS) daily snow-cover product for the Tibetan Plateau region.Results show that TMPA-3B42 performs well at coarse temporal resolutions.However, less satisfactory result is obtained at the daily tine step.At the same temporal resolution, the humid region TMPA-3B42 performs better than the arid region ones.An exception is found for regionswith the annual precipitation excess the 2500 mm threshold.During winter, the average difference between the TMPA-3B42 product and the MODIS snow-coverproduct is only around 15% at a regional scale.However, the difference can be as high as 40% if only the region's snow covered areas are considered in the product comparison, which indicates that the TMPA-3B42 product is less skilful in winter.The MODIS snow-cover product can thus be used to improve the performance of TMPA-3B42.
Abstract: A ccordiy to the Kuo-Anthes vertical convection and Nordeng slantwise convection parameterization scheme, a vertical-slantwise convection integrated parameterization scheme is designed and introduced into the MM 5 model.Using the integrated scheme, a process of large scale strong precipitation in the Yangtze River Basin in June 1999 is smiulated and tested sensitively.Results show that the intensity and location of precipitation are improved effectively, the vertical circulation forms quickly and intensifies, and the simulated result is close to the observation when the slantwise convective param eterization is introduced into MM 5.The result illustrates the necessity of considering the slantwise convention in torrential rain smiulations for the symmetric instability weather system.
Abstract: The Penman-Monteith equation is used to estinate potential evapotranspiration in Guizhou province based on the daily meteorobgical observations from 18 stations during the period 1961-2001.The estimation of potential evapotranspiration is alms achieved by adopting simple model approaches, such as the radiation-based and the temperatore-based models.The Penman-Monteith potential evapotranspiration is comparedwith these simple model estimates.Results show that allmodels are able to well estimate the long-tern annualmean potential evapotranspiration with relafive errors less than 0.05%.However, large variations are found among simulated annual mean potential evapotranspiration series.The radiation-based models perfo}rn better than the temperature-based ones in comparison with the Penman-Monteith potential evapotranspiration, which suggests that the radiation-basedmodels are more applicable for future climate change studies in Guizhou province.
Abstract: Changes in potential evapotranspiration will affect the projection of water dan and and the detemination of irrigation quota in a region.In order to evaluate the influence of irrigation on the maintenance and development of agricultural oasis, the impacts of irrigation on annual potential evapotranspiration in Jingtai irrigation district of Gansu province are quantitatively analyzed and projected using the advection aridity complem entary relationship in regional evapotranspiration.A declined trend has been observed from both annual pan evaporation records and estmiated potential evapotranspiration since the introduction of Yellow River irrigation in 1972.The observed aerodynamic forcing has been significantly weakened in the region, and the declined trend in potential evapotranspiration is likely due to the weakening in wind speed and increasing in relative humidity that is affected by irrigation Future variations in potential evapo transpiration with different water consumptions are smiulated using the long-term mean annual precipitation and the solar radiation conditions, and the results are presented.
Abstract: In order to understand the exploitation yield formation in the North China Plain with problems of intensive over exploitation, a study is conducted using the field data collected from borehole geophysical logs with deep groundwater depression cone bcated in the Dezhou region.The data collection includes groundwater sampling and dynamic monitoring, as well as land subsidencemonibring in the region.Both elastic release ofwater from sandymaterials and water released through aquifer compression in the confined aquifer are calculated for both rate and intensity in different soil layers and partition ones, together with latter flow and aquifer recharge due to ground water exploitation.Results show both elastic release ofwater and water released through aquifer compression are inconstant due to the intensive overeaploitation effect on confined aquifers, which increase with the drop of deep groundwater levels.The longer the intensive over exploitation of groundwater and the closer to the centre of deep groundwater depression cone are, the higher the clay soil component in confined aquifers will be, as well as the greater the elastic release ofwater and the water released through aquifer compression are.The calculated composition of elastic release of water varies from 14.2% to 17.5%，and the portion of water released through aquifer compression is from 35.5% to 61.9% and closely related to the condition of land sub sidence in the region.
Abstract: A multirobjective optimization model for operating cascade hydropower stations is established.The model can maximize both firm power and annual energy production simultaneously.The model is solved using the strength Pareto differential evolution(SPDE) approach.The latter is a novel extension of the Differential Evolution (DE) algorithm to multirobjective optimization problems.SPDE adopts the fitness assign method used in the strength Pareto evolution approach 2(SPFA2)，andmodifies theDE operators according to the characteristic of multir-objective optimination.An adaptive Cauchy mutation (ACM) is also used to prevent premature convergence.The model is tested using a case of Three Gorges cascade hydropower stations.The result shows that SPDE is able to simultaneously consider the two optimization objectives and effectively dealwith complex constraints.A setof alternative non-dominated schemes with uniform coverage can be provided for decision making, which presents a viable alternative formultirobjective optimal dispatch of cascade hydropower stations.Our result could be used as a reference formaking the midbmg teffn generation scheduling schemes for Three Gorges cascade hydropower stations.
Abstract: Based on the conception of Gini coefficient and the relationship between downstream and upstream natural runoff and sediment and the regional precipitation, we establish computational models of annual distribution of runoff and sedmient transport from Lancang River, southwest China.The results from the contrast between reconstructed and measured data show that the annual runoff distribution evenness of Lancang River increases by 1.14% and varies between 7.32% and 10.81%; however, the annual sediment transport distribution evenness decreases by 0.23% and ranges from 18.98% to 26.76% since the construction of Manwan and Dacaoshan hydroelectric power plants, and during the operation period of Manwan and Dacaoshan power plants, the annual runoff distribution evenness of Lanchang River is an increase of 3.90% and the annual sedmient transport distribution evennessis down by 0.42%.After the construction of Dacaoshan hydroelectric power plant, it is shows the trend of growth continuously of the annual runoff distribution evenness of Lancang River, but the annual sediment transport distribution evenness has no sign ificant change.All of these indicate that the interaction between runoff and sediment transport has changed, whereas the change is smoothly.The research results not only can provide a way for the relevant research but also offer new evidence to scientifically evaluate the influence of hydropower development on annual runoff and sedmient transport distribution of Lancang River.
Abstract: The multi-scale dynamic change in the Bielahong River basin wetland of the Sanjiang Plain is studied using a spatial autocorrelation model and the geographic information system (GIS) technology.Results show that the wetland area was gradually decreasing and the spatial auto correlation of the entire wetland area exhibited an up-downup pattern during the period 1950s-2000.A downward trend is detected in the high-high autocorre lation type, which tends to spread toward the lower reach of the Bielahong River basin.The opposite result is obtained for the lowlow autocorrelation type.The wetland spatial autocorrelation exhibits an appreciable scale effect, as the spatial autocorrelation increases with the increase of smiulation scales.The result indicates that the dynamic change of wetland spatial autocorrelation is mainly caused by human activities.The spatial autocorrelation analysis of wetland changes can reveal the regularity of the wetland spatial cluster as well as the dynamic changes of the wetland spatial correlation pattern, which could be one of the effective approaches to study ing the spatial heterogeneity of wetlands.This study provides a scientific basis for wetland classification and decision-making management.
Abstract: The characteristic of sediment resuspension is investigated under smiulative disturbing conditions.The sedmient core samples collected from the Taihu Lake were run in the particle entrainment smiulator at smiulated bedflow shear stresses from 0.2 to 0.6 N/m2 for the period of vibration varying from 60 to 1800 seconds.Results show that the concentration of suspended particulate matter (SPM) in the overlaying water rises at a fast rate initially.The higher the smiu lated bedflow shear stress is, the faster the rising rate will be.The rising rate slows gradually and will be stabilized as tmie progressed.In addition to the divergence of sedmient resuspension, the convergence of SPM will increase over time until the two processes in the particle entrainment smiulator reach dynamic equilibrium.Our indoor expermient portrays well the characteristic of sediment resuspension observed in Taihu Lake, which demonstrates the applicability of using the particle entrainment smiulator to studying the dynamic of sediment resuspension in laboratories.
Abstract: An emergency assessment model is developed for the hazard extent of water pollution accidents in small and mediumsized rivers.The model development uses the concept of the hazard extent of water pollution accidents and the result of typical case studies.The rough set theory is applied to analyze the importance of indirect factors, eliminate the redundancy, calculate the significance of weight, and integrate the influence of both direct and indirect factors.The model is applied to a river in Chengdu city.Different water pollution scenarios are designed for the model smiulations.Results show that the model is capable of assessing the hazard extent of water pollution accidents in small and medium sized rivers.Thus, the model is able to provide the valuable information for decision-making during the emergency of water pollution accidents.
Abstract: In order to study the influence of water diversion from Yangtze River to Taihu Lake, water samples were collected from Taihu Lake subzones, and the activity of alkaline phosphatase was determ ined together with water quality parameters.The study is focuses attention on the variation of the maximum reaction rate in alkaline phosphatase activity (vmax) and the Michaelis-Menten constant (Kmm) due to the water transferring activity Results show that differences exist in the tem poral and spatial distribution of both vmax and Kmm of Taihu Lake subzones.The concentration of blue-green algae in Taihu Lake subzones is diluted as a result of water diversion, which inhibits the maxmium reaction rate in alkaline phosphatase activity.A quadratic relationship (p=0 007) bewteen Kmm and accumulated water into Taihu Lake is found for the subzones of Gonghu Bay, Western Estuary, and Taihu Lake Centre.The alkaline phosphatase (vmax/Kmm) increases with the increase of the total phosphorus concentration in the subzones of Meiliang Bay, Zhushan Bay, Gonghu Bay, and Western Estuary However, vmax/Kmm decreases with the increase of the bioavailable phosphorus concentration in the subzones of Zhushan Bay, Gonghu Bay, grass type area, Western Estuary, and Taihu Lake Centre.The vmax/Kmm is enhanced when the concentration of chlorophylla increases except for grass-type area.
Abstract: The paper reviews the main sources of nitrogen andphosphorus nutrients, as well as their transports inwatersheds, estuaries and offshore areas.The leading methods of simulating nutrient transports are introduced, and the comprehensive studies on nitrogen and phosphorus transport in an integrated system of watersheds, estuaries and offshore areas are also summarized.Finally, the main problem sand future prospects on the issues of eutmphication are discussed, the couplingofwatersheds, estuaries and offshore areas should be focused, and the advantages of distributedmodels should be taken full in the study of nutrient transports in future.
Abstract: Streamfbw reconstruction based on tree-ring data is an important direction in dendrochronology.In this study, tree-ring reconstructions of streamflow are described on the basis of the principle of dendrohydrology.The methodologies for reconstructing streamflow using tree-ring are introduced, and major advances in the subject are reviewed over the world.We will then focus on the review of nationalprogresses of tree-ring studies emphasizing on aspectsof studying regions, approaches andmethodobgies, and applications.Inadequate aspects in tree-ring researches and prospects of dendrohydrobgy studies are also proposed.It is clear that the tree-ring reconstructed long teffn streamflow series contains valuable info}rnation for better management of water resources and planning in river basins.