水科学进展

Connotation and Motie Force of Water Sciences

Chen Jiaqi

1992, 3(4): 241-245.

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Abstract:
The water sciences deal with original water that occur in the nature as object and investigate their static distribution and dynamic variation of physical, chemical and biological processes, the mode of motion and the law of variation of the water in the hydrosphere. In the water sciences study there are also involved the interrelations and interactions between hydrosphere and atmosphere, hydrosphere and lithosphere, hydrosphere and biosphere, water and other components in the environment, water and human society. The water sciences in their progress should adhere to the principle of integrating cognition with practice, cooperating their property of natural science with that of applied sciences so that the relationship between humanity and water as well as nature may be treated at more reasonable and effective level.

Experimental Research on Catchment Runoff Responses Traced by Environmental Isotopes

Gu Weizu

1992, 3(4): 246-254.

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The isotopic composition(T,180)of rainfall asd various runoff components including interflow from unsaturated zone and groundwater flow from saturated zone was monitored during the rainfall events of 1986-1989 in a special designed eaperimeatal catchment with all the runoff components are measurable. The contribution of prevenient water (old water) to surface runoff is identified and the portion of old water ranged from 0% to 50.5% is estimated. It implies that the current concept which considers surface runoff is always orginated from event rainfall is very likely a misconception. The different contributions of old water in interfiow and groundwater flow are identifled and estimated, too. The ezistance of temporal isotopic variability of runoff components during rainfall events demonstrates the temporal variations of old water composition in these components. For the four patterns of hydrograph with different combinations of runoff components, different compositions of old water are found ranged from 0% to 77%.As a comparison, several natural basins were sampled. From these results, it is shown that the current method of hydrograph separation up to now used widely in this country is, unrealistic in generally. These results also pose questions about the concepts related to rainfall-runoff relationships and to the UH analyses.

Method of Evapotranspiration Estimation in Soil-Plant-Atmosphere Continuum (SPAC)

Liu Changming, Dou Qingchen

1992, 3(4): 255-263.

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A series of processes of exchange of water and energy are contained in SPAC. This paper mainly deals with the processes and the determination of evapotranspiration, which includes mainly: a comprehensive SPAC model, description and determination of the parametric equations of evapotransipiration, and estimation of actual evapotranspiration from field. Based on the measured data obtained from Qihe County, Shandong Province, the models of evapotranspiration are developed and the fairly results in comparison with measurements are obtained.

A Method for Calculating Winter Wheat Transpiration

Kang Shaozhong, Lui Xiaomin

1992, 3(4): 264-270.

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Based on the Penman-Monteith Model(PMM), a method for calculating winter wheat transpiration in the field condition is established, and two main parameters involved in the PMM are anatysed. The emperical equations of net radiation intercepted by canopy (R_n^') and total canopy leaf resistance (r_8T) are presented, and their precision is checked. The relation between the actual transpiration in the deficient water condition and potential transpiration in the safficient water condition is analysed.

Incipient Motion Law of Cohesive Soil and the Mixture of Cohesive Sediment and Coarse Particle

Hua Jingsheng, Wan Zhaohui

1992, 3(4): 271-278.

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The incipient motion of cohesive sediment and the mixture of cohesive sediment and coarse particle are researched systematically. On the basis of turbulent flow theory, a formula for determining the critical shear stress of cohesive sediment with the Bingham stress of cohesive sedi ment is ascertained. According to a series of experiments, the conditions of incipient motion for the mixture of cohesive sediment and coarse particle in different cases are discussed and formalized. The result of all above-mentioned formulae are in agreement with experiment data. In addition, a qualitative analysis about the conditions of incipient motion of cohesive sediment and the mixture of cohesive sediment, and coarse particles above which dense flow exista are carried out.

Study on the Shoal and Trough Evolution and the Navigation Conditions of Wandering Reaches of the Hanjiang River

Xu Jinhuan, Li Anzhong

1992, 3(4): 279-287.

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This paper studies the erosion and deposition in the lower reaches of the Hanjiang River and their influences on the navigation after the building of the Danjiang-kou Reservoir. By analysing hydrological and topographic data, the characteristics of shoal and trough evolution of the wandering reaches on the Hanjiang River have been investigated. The navigator conditions have been comprehensively considered and some useful conclusions to navigation are obtained.

Heavy Metals in the Water and Sediments of Guanting Reservoir

Shen Xianchen

1992, 3(4): 288-294.

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The distribution and behavior of heavy metals (Cn,Pb,Zn,Cd) in the water and sediments of Guanting Reservoir which supplies water for Beijing city were studied. The results for the water column show that the mean percentage of metals in the solute phase is 4.2%,and that most are associated with suspended sediment. The content of metals in the bed materials is from 5000 to 10000 times higher than dissolved in the water. The exchangeable metals in the bed materials represents only 0.6% of the total. This indicates that metals in the sediments are not greatly affected by surface adsorption. The spatial distribution of metals within the reservoir reflects pollution from various sources. The spatial variation in metal concentrations provides information on temporal changes in the water quality and pollution. The trends of metals in the water show that pollution increased from 1973 to 1985, but it decreased since 1985.

Optimal Design of Main Drajnagc Projects in Reclaimed Seabeach Areas

Wu Yubai, Huang Junyou, Sun Wengao, Zhu Chengren, Chu Chenglan

1992, 3(4): 295-303.

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A method combining a mathematical programming model with an unsteady flow model is presented to determine the optimal sizes of main drainage projects in the reclaimed seabeach area, improving computional accuracy and reducing project costs. An objectiva is to minimize the cost, and constraits come from water blance, Samt-Venant equation, outflow formula of a sluice gate, the requirement of matching a sluice with a channel, and limitations to the size of a project. The optimization models are solved by dynamic programming method, in which each project is regarded as one stage, and the optimization problem is translated into a multi-stage decision process. In solving the unstead flow models, three finite difference methods, i. e., a method of characteristics, a diffusive scheme, and a two-step method are given, which automaticaly avoid nonconvergence. The results of case studies show that the above mentioned method is practicable and efficient.

Discussion on the Error of Finite Element Method due to Spatial and Temporal Discretization

Sun Yongtang, Jang Guolei

1992, 3(4): 304-309.

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Finite element method is applied more and more widespread in modeling and management of groundwater with computer development. The space and the time must be treated to be discrete, although which are continuous. So the error occurs, which is not negligible sometimes. In this paper, on the basis of dealing with superposition principle and eigenvalue finite element method, the error due to different spatial and temporal discretization is seperated and analysed through a typical example, and an approach is researched to reduce the error.

A New Direction and Developments in Computational Shallow Water Hydrodynamics

Tan Weiyan, Hu Siyi

1992, 3(4): 310-318.

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This paper provides a personal view of an overall perspective on computational shallow water hydrodynamics, divided into two parts-one dealing with algorithms and the other with applications. The former includes:some difficulties and challenges, requirements, and developments in shallow water flow computations. An emphasis is laid on discussing the underlying principles of finite-volume formulation and some current high-performance schemes. In the latter, a number of computed results are presented which reflect various applications of the finite-volume Osher scheme for Hows in open channels, over weirs, and due to dam-break, overbank and dike-corruplion.

Advances in River Mechanics

Cao Shuyoq, Fang Duo

1992, 3(4): 319-325.

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In this paper,the main contents,approaches, and status guo of river mechanics are reviewed by eight components of sediment yield from watershed, river bed form and hydraulic resistance, sediment transport, river morphology and fluvial processes, sediment problems in engineering projects, river modeling, sampling fluvial sediment, and sediment problems in environment. Some key topics that would be concerned in the near future are discussed.

1992 Vol. 3, No. 4

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