Abstract: A boundary element method(BEM) for calculating groundwater flow to a multiple well system in a leaky aquifer is presented.This method treats the well walls as internal boundaries and avoids discretizing the boundaries of the well walls.At first, the boundary integral equations of the water head H and its normal derivative ∂/∂n are derived.After discretization, a system of linear algebraic.equations forsolving the integral equations is. obtained To illustrate application of the method,some type well problems are solved and the results show that the method is accurate.
Abstract: Based on systematic open Ilume flow experiments, this paper investigates the basic lows of thermal diffusion coefficients in water flow. The analysis of testing results show that the proper scale of longitudinal dispersion coefficients, related to the water surface slope and Froude number, is the nonhomogeneous compre-hensive factor of velocity distribution. A formula for calculating tt}e thermal longitudinai dispersion coefficient in water flow is proposed. Meanwhile, the authors found that the coefficient of thermal transverse diffusion has the similarities to that of chemical matter-diffusion. Finally, the formulae for estimating the uncertainties of temperature measurements and longitudinal dispersion coefficients are derived by using error theory.
Abstract: It is time-honoured to understand tire properties of the shallow-water equations and related physical phenomena by analogy of a compressible-fluia flow.However, most of previous discussions were limited to the simplest case of.prismatic channels with a rectangular cross-section. In this paper, the analogy is extended to the general case of non-prismatic channels with an arbitrary cross-section. The equivalent adiabatic exponent γ=H/hc (Where H is the hydraulic depth, and hc is a height of the centroid above bottom) is given here, with γ=2 associated with the special case of rectangular cross-sections. Then, the practical importance of the gas dynamics analogy in computational hydraulics is emphatically expounded. Two fiuxvector-splitting (FVS) difference schemes used in CFD are applied to the shallow-water flow computation by tlhis analogy. Finally, the similarities and differences of physical behavior, between the compressible-fluid flow analogy of shallow-water flows and compressible-fluid flows of a perfect gas are highlighted, and guidelines that should be followed for a correct use of this analogy are proposed.
Abstract: The previous studies on precipitation-socioeconomy relations were generally limited for different departments of socioeconomy individually. The articlf stresses the necessity to study it for the socioeconomy as a whole and makes an attempt to do so. The principles of water balance in the Nature-Man system were formulated in the preliminary Form. Several indexes were proposed for identifying different states of water balance between supply and need in the system. The results were applied to some regions of North China, showing that the proposed principles and methods are well available to these regions.
Abstract: Water resources system, which mainly deals with those problems both directly and indirectly related to utilization and protection of water resources and water emvironment, is a specialized kind of natural-social-economic complex system. In this paper, the authors concentrate upon the topic of its fundamental characteristics. First, these relationships between water and natural ecosystems, and water and social developments are discussed. Then, the role of water-work in coordinating natore and social developments is analysed. The authors point out that human water-work is a unity of numerous natural and social processes. Fnally, the general characteristics of complex water resources system as a whole are briefly outlined.
Abstract: The mathematical characteristics and physical explanation of Rouses equation for the suspended sediment concentration distribution have been discussed. Based on this, the sediments for suspended index Z< 1 and z≥1 are defined as fine and coarse grains respectively. Then, the analytical solution of Einstein total load equation for coarse grains is derived. Compared with numerical results, it shows that the derivation is correct.
Abstract: The applicability of design flood hydrograph as a basis of the design of reserviors safety withstanding flood has been examined by using statistical experiment. This examination is based on the stochastic flood model which was developed for the hydrological design of Zhi Ping Pu reservior. The results have shown that design flood hydrograph may lead the actual criterion of reservior safety withstanding flood to deviate seriously from the specified one. The main factor which may have a strong impact on such a deviation is the sample errors of certain flood volumes in a flood hydrograph. The prerequisite of the applicability of design flood hydrograph is also discussed in this paper.
Abstract: Flood routine on flood plain is a practical problem related to the utilization of flood plains. and depressions as a non-structural flood control and mitigation measures. The difficulty for solving the problem lies in the particular flood wave propagation caused by complex boundary conditions of flood plains. Based on the concept of quasi-two dimensional flow, a storage routine model, which combines hyd-rological and hydraulic methods and is characterized by considering each relatively independent area as seperate compartment, is presented to tackle the problem proposed.
Abstract: The seasonal dryness/wetness in Beijing is identified and compared. The results show that the dry/wet grades derived from the Gamma probability distribution are more effective to be representative of climate states in. that area than from other distributions. It is found that the dry climate state in the four seasons during recent 30 years occurred more frequently than ever before, and the occurrence frequency varies slightly with different season. Moreover, the dry climate state in summer occurred more frequently Than in other seasons. It follows that from the long-term variations, the dryness is prone to changing into the wetness in winter and spring; the wetness is prone to changing into the dryness in summer and autumn. From a causal analysis, it is known that, the dryness in Beijing is related to the warm/cold state of the see surface temperature in the Pacific. Also, the periodic analysis of the dry/wet grade series shows that the severity of dry state in summer would be mitigated in the next 10-30 years.
Abstract: Based on the observed data of precipitation in the 20th century, the variations of drought in Northwest. China (including Shanxi, Gansu, Ningxia, Qinghai and Xinjiang Provinces) are analyzed and compared with that occurred in the 18th and 19th centuries. The relationship between the variations of draught and air temperature in the 20th century was also studied.
Abstract: The progress of scientific research work of aquatic environmental biology in recent years in China has been summarised in this paper, which includes biomonitoring and biotreatment of water pollution, aquatic ecotoxicology and further research works.