• 全国中文核心期刊
  • 中国科技核心期刊
  • 美国工程索引(EI)收录期刊

1993 Vol. 4, No. 4

Display Method:
Field Experiment on Solute Transport in an Unsatnrated Soil
Yang Jinzhong, Ye Zitong, Jia Weizhao, Yan Shilong
1993, 4(4): 245-252.
Abstract:
Solute concentration and water content profile at the depth to 170cm in an area of 3×6m2 during constant leaching to an unsaturated soil were measured at eight points for the determined times. Soil water movement and salute transport in the local scale were studied and the spacial variability of soil water content and concentration were discussed. As compared with the water content profile, the concentration profile shows a very great variation. The concentration profile measured at one point can not be used to represent the local scale concentration behavior. The immobile water content is about 24 to 39 percent of total water content in the experiment.
Simulation Approach of Agricultural Drought Events
Gu Ying, Zan Xia
1993, 4(4): 253-259.
Abstract:
On the basis of farmland water balance principle, this paper presents a simulation approach to simulate whole process of occurrence. expanding and mitigation of drought events. Simulated results and indices characterized drought event process are analyzed statistically. According to the experimental data about the effect of water shortage in different crop growth periods on crop production sensitivity, the drop of crop production is evaluated quantitatively and the degree of drought event is determined reasonably. It is valid that the simulation results basically fit with the actual cases.
Surface Runoff Variations Since Little Ice Age in the Daxigou-Urumqi River
Wang Zongtai
1993, 4(4): 260-267.
Abstract:
The runoff variations were analysed by a correlation method of preci-pitation runoff and precipitation and a method of ice-melt water modulus. The results show that the total runoff, ice-melt water and precipitation runoffs had reducod by about 14.8%,39.9% and 14.3% respectively, since Little Ice Age in the Daxisou-Urumqi River.It is inferred that the surface runoff in the Daaigou will continue decrease with a rise of air temperature in the future,and the surface runoff will reduce much more as compared with the precipitation.
Time-Space Distributional Characteristics of Precipitation During Rainy Season in the Changjiang-Huaihe Valleys and its Circulation Background
Li Yongkang
1993, 4(4): 268-273.
Abstract:
Inter-ekad variation of precipitation (IDVP) and its space distribution during rainy season (May to Sep.) in the Jiang-huai valleys are analysed by using correspondence analysis method. Also, the areas can be divided into four rainfall regions according IDVP. Finaly, the typical circulation background for IDVP during rainy seasons are discussed.
Application of Mass Exchanges Rates Theory in Suspended Load Transport
Cheng Niansheng, Zhu Lijun
1993, 4(4): 274-280.
Abstract:
This paper analyses and summarizes the previous methods determining the source/sink functions or bed-boundary conditions of transport equation of suspended sediment.There are some limitations in these methods due to introducing the concept of equilibrium transport and ignoring the effects of bed-load on suspendedload transport when considering the mass exchanges near the bed. The theory about mass exchange rates of sediment near the bed previously developed by writers is adopted here to make an inquiry into appropriate boundary conditions on the bed, so that the general equation of suspended sediment transport can be solved. The processes of the adjustment of sand concentrations in one-dimensional or vertical two-dimensional flows have been computed and compared respectively with the measured data, showing reasonably good agreements.
Forming Conditions and Protective Measures of Ω-collapse in the lower Yangtze River
Leng Kui
1993, 4(4): 281-287.
Abstract:
In this paper, the typical Ω-collapse in the lower Yangtze River is described and analysed, including its characteristics, forming process, geological conditions, bank slope variation, and flow-sediment movement patterns. On this basis, the cause of Ω-collapse is exposed and a mathematical formula for the critical condition of the Ω-collapse is obtained.Finally, some suggestions as to how to predict and protect the Ω-collapse are put forward.
Fuzzy Model and Method for Choosing Analogy Basins
Chen Shouyu
1993, 4(4): 288-293.
Abstract:
In this paper, the improved fuzzy model and method for choosing analogy basins in hydrological computationn is presented based on the old experiential method. The model can also be applied to other hydrological analogy problems in hydrological computation.
A Stochastic Mathematic Model for Reservoir Flood Routing
Jiang Shubai
1993, 4(4): 294-300.
Abstract:
A mathematic model of the stochastic differential equation (SDE) is applied to describe and analyze the random phenomena and their laws in the reservoir flood regulation procedures. According to the analysis of a Wiener process characteristics of the reservoir storage, an Ito Equation with a stochastic input term and a stochastic initial condition for reservoir flood routing is derived. And, by using the Fokker-Planck Equation, the probability density distributions of reservoir level hydrograph in the flood regulation procedure are solved. The calculated results show that the mathematic model of SDE in reservoir routing is favourab 1e in understanding the laws of the stochastic flood regulation procedure and developing risk analysis for flood relief.
An Integral Method for Inclined Buoyant Jets in Flowing Ambients
Huai Wenxin, Li Wei
1993, 4(4): 301-308.
Abstract:
An integral model of buoyant jets is given in this paper. The profiles for velocity density and concentration difference are assumed to be Gaussian distribution, and the relations of the entrainment rate with local densimetric Froude number and cross velocity are derived for closing the governing equations. The Finite Analytic Method is used to solve this problem. The calculated results of the inclined buoyant jets are well compared with the ezperimental data.
Calculation Formulas of Nearfield Dilution for River Multiport Diffusers
Wang Chao, Wu Dongming
1993, 4(4): 309-315.
Abstract:
The most important parameter is usually the degree of dilution in river multiport diffusers discharge. Numerical simulation and laboratory experiments are used to predict the flow characteristics of river diffusers. Continuity equation, momentum equation and Bernoulli's equation are applied to develop the calculation formulas for the degree of nearfield dilution in the recirculated flow, the non-recirculated flowand the stratified flow. The results of calculation are in good agreement with laboratory experiments.
Delphi Investigation on Some Questions in Water Science
Yang Wansu
1993, 4(4): 316-321.
Abstract:
Based on asking experts, this paper analyses the present state and the future developing tendency in water science, supplies much more useful information to help governament to make decisions of science policy, and suggests.guide for researchers in relative fields.
1993, 4(4): 322-324.
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1993, 4(4): 325-325.
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1993, 4(4): 326-326.
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1993, 4(4): 327-327.
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