Abstract: The main contents of this paper are to study the extreme values of areal rainstorm,including storm area,area average rainfall depth,total precipitation volume,etc.The maximum depth-area-duration records and other extreme rainfall values are given herein.The regional distribution and some factors influencing areal rainfall rainstorm extreme values are also investigated.
Abstract: Based on the radiosonde data observed two times a day for 125 stations in China,the total transport,eddy transport and divergence fields of water vapour are calculated and analyzed for the whole atmospheric layer over the Yangze River Valley during two typical wet/drough summers (1980/1985),when there were three currents that carried water vapour steadily from the southwest,northwest and southeast respectively,and then joined together over the Yangtze River Valley,high precipitation would appear near a convergence belt,yielding floods and water-loggings.On the other hand,during drought period,the three currents are weak and unstable,so that the condition of convergence belt formation cannot be met.Eddy transport also has similar feature.Water vapour transport due to a strong and stable current from the southwest,is a main source of precipitation.
Abstract: According to the temporal and spatial distributive concentration and the recurrence of the regional rainstorms over the Hekouzen-Shanmenxia basin,and their closing relationships with the magnitude order of flood peaks and the number of occurrences of flood at Sanmenxia (Shanxian),the regional grade index series from 1770-1989 is constructed by using the gage pile date at Wanjintan in Shanxian county,the historical information regarding stormflood disasters,and the recorded pr ecipitation data for the Hekouzen and Shanmenxia basin.From the analysis of the grade series it follows that the regional rainstorms,just like other meteorological elements,have their own variation pattterns,and that six prominent cycles of the regional rainstroms are detected for the past 200 years period.
Abstract: A mathematical model for the velocity field of vertical jet discharging into tidal flows is presented,in which the κ-ε turbulent model is adopted for turbulence and the "motion"-rigid-lid approximation of the free surface is described.According to the oscillation feature of tide,a track-while-scan line by line method for solution of the discretized equations is developed.Numerical calculations are done on the unsteady velocity fields in different periodical cases.The predicted relative height of the major recirculation region is in good agreement with the experiment date.Hence,the effect of unsteadiness is also discussed and some conclusion remarks are given.
Abstract: A new numerical simulating method for calculating open tunnel flow is established by using analytical function theory,the method for calculating the unknow discharge is put forward.The flow parameters such as discharge,free surface profile and boundary pressure distribution are simulated by numerical calculating the boundary integral equations.The calculating indicats that the method demonstrats good and fast convergence with small calculating quantity.The numerical results agree well with those meas ured.
Abstract: Some dozens of conditions of incipient motion of sediment proposed by various investigators are transformed into a unified form in terms of dimensionless critical shear stress(or tractive stress) θc=τc/(γs-γ)d.The values of θc for non-cohesive sedinvents with uniform diameters are calculated,which generally lie between 0.0231 and 0.0716.The differences of various equations can be distinguished from the results calculated.Thus,a scientific basis can be provided for selecting and using the equations.
Abstract: Basin sediment yields were simplified into the yields from slope-area regions and gullies in this paper.A conceptual modelling for slope-area soil erosion was formulated.It was developed from the physically-based conception of which sediment yield of slope-area is equal to maximum sediment-carrying capacity of flow minus resisting erosive capacity of the soil over slope-areas.A conceptual formulation for gullieswas obtained by simplifying the Bagnold's function of river sediment discharge.They were proposed for the simulation of small basin sediment yields in loess regions of the Yellow River.The testing results was satisfactory by comparison with the observed data for the simulated sediment yields in eight small basins.
Abstract: By the indices analysis of mineralization rate,hydrochemical type,ion number,hardness of water in inland rivers of the Tarim Basin,hydro chemical law in time and space is revealed.Meanwhile,combining with geographic environment the law forming reason is approached.
Abstract: The water pollution condition in the Harbin reach of the Shonghua River is very serious.Surface water may infiltrate into the aquifer and influence the groundwater quality of the Harbin-City.The purpose of this paper is to investigate the pollution characteristics of surface water and groundwater,and their purification capacities.The results show that the purification capacities of both the river reach and the aquifer are potent and can be recovered naturally.Purification mainly includes dilution,adsorption,and filtration etc.Maintaining natural purification capacities are of great importance to protecting the grouudwater quality of the Harbin City.
Abstract: Based on the water quality monitoring network density of China,the following problems are discussed:(1) the division of water quality unit region;(2) the application of cluster variety analysis in water quality monitoring network design; (3) the relationship between the network density of water quality monitoring and the developmeat of population and economics; (4) the characteristics of water quality monitoring network in China.
Abstract: In the current practice,water-quality monitoring is usually based on analysis of sampling at the instantaneous moment,without measuring water discharges.Thus,the monitoring values obtatined can only represent the instantaneous concentration of pollutant.The less the number of times of monitoring,the less adequate the representative values are.This would result in incorrect water-quality assessments,because they are based on only a few data which cannot be taken as adequate and appropriate.In this paper,the current method is discussed and a new method based on a concept of statistical concentration of water quality is proposed.Some questions on water quality assessment by the method of total quantity control of pollutant are also addresed.The new method was applied to the water quality assessment in the upper reach of Tou River,Sichuan Province.The result was found to be quite reasonable and feasible.