Water Science and Engineering - 开云电竞网

Application of spatially varying storage capacity model for runoff parameterization in semi-arid catchment

Li-liang REN, Gui-zuo WANG, Fang LU, Tian-fang FANG — 2009-06-30

Li-liang REN, Gui-zuo WANG, Fang LU, Tian-fang FANG This paper introduces the method of designation of water storage capacity for each grid cell within a catchment, which considers topography, vegetation and soil synthetically. For the purpose of hydrological process simulation in semi-arid regions, a spatially varying storage capacity (VSC) model was developed based on the spatial distribution of water storage capacity and the vertical hybrid runoff mechanism. To verify the applicability of the VSC model, both the VSC model and a hybrid runoff model were used to simulate daily runoff processes in the catchment upstream of the Dianzi hydrological station from 1973 to 1979. The results showed that the annual average Nash-Sutcliffe coefficient was 0.80 for the VSC model, and only 0.67 for the hybrid runoff model. The higher annual average Nash-Sutcliffe coefficient of the VSC model means that this hydrological model can better simulate daily runoff processes in semi-arid regions. Furthermore, as a distributed hydrological model, the VSC model can be applied in regional water resource management. Water Science and Engineering. 2009 2(2): 1-10 .

Experimental study on stable isotopic fractionation of evaporating water under varying temperature

Wei-min BAO, Tao WANG, Si-min QU — 2009-06-30

Wei-min BAO, Tao WANG, Si-min QU The variation of stable isotope ratios in natural waters provides valuable information that can be used to trace water movement. Evaporation plays a crucial role in determining the variation of stable isotopes. In this paper, several evaporation experiments were conducted in order to study the stable isotopic fractionation mechanism of water and analyze the influence of different temperatures on evaporation fractionation. Three group experiments of water evaporation under different temperatures and initial isotopic values were carried out. The results show that fractionation factors of hydrogen and oxygen may increase with temperature, and the average enrichment degree of hydrogen isotope D is 3.432 times that of oxygen isotope . The results also show that the isotopic composition of the initial water has little influence on water evaporation fractionation, which is mainly affected by the state variables in the evaporation process, such as temperature. This research provides experimental data for further understanding the evaporation fractionation mechanism. Water Science and Engineering. 2009 2(2): 11-18 .

Development of point source method and its practical significance

Bidya Sagar PANI — 2009-06-30

Bidya Sagar PANI The advantages of Reichardt’s hypothesis in dealing with single and multiple circular jets in a stagnant environment are highlighted. The stages involved in the development of the point source method, an offshoot of the new hypothesis, are presented. Previous results of experiments on multiple circular jets in a stagnant environment justify the method of superposition. As a prelude to discussion of multiple jets in a co-flowing stream, results on the excess-velocity decay, the growth of the shear layer, and the dilutions for a single jet based on Reichardt’s hypothesis are presented. The spreading hypothesis is generalized by introducing a link factor k₁to account for the co-flowing stream. The distribution of excess-momentum flux uΔu is shown to be Gaussian in nature. Based on the principle of superposition, the decay of the maximum excess velocity and the dilution are predicted for odd and even numbers of jets in an array. The predictions seem to be in good agreement with observed data Water Science and Engineering. 2009 2(2): 19-31 .

Simulation of water temperature distribution in Fenhe Reservoir

Shu-fang FAN, Min-quan FENG, Zhao LIU — 2009-06-30

Shu-fang FAN, Min-quan FENG, Zhao LIU In order to evaluate the need of controlling the temperature of water discharged from the Fenhe Reservoir, the reservoir water temperature distribution was examined. A three-dimensional mathematical model was used to simulate the in-plane and vertical distribution of water temperature. The parameters of the model were calibrated with field data of the temperature distribution in the Fenhe Reservoir. The simulated temperature of discharged water is consistent with the measured data. The difference in temperature between the discharged water and the natural river channel is less than 3℃ under the current operating conditions. This will not significantly impact the environment of downstream areas Water Science and Engineering. 2009 2(2): 32-42 .

Membrane finite element method for simulating fluid flow in porous medium

Mei-li ZHAN, Wen-jie ZHANG, Jin-chang SHENG, Jian-hui LI, Shu-yuan HE — 2009-06-30

Mei-li ZHAN, Wen-jie ZHANG, Jin-chang SHENG, Jian-hui LI, Shu-yuan HE A new membrane finite element method for modeling fluid flow in a porous medium is presented in order to quickly and accurately simulate the geo-membrane fabric used in civil engineering. It is based on discontinuous finite element theory, and can be easily coupled with the normal Galerkin finite element method. Based on the saturated seepage equation, the element coefficient matrix of the membrane element method is derived, and a geometric transform relation for the membrane element between a global coordinate system and a local coordinate system is obtained. A method for the determination of the fluid flux conductivity of the membrane element is presented. This method provides a basis for determining discontinuous parameters in discontinuous finite element theory. An anti-seepage problem regarding the foundation of a building is analyzed by coupling the membrane finite element method with the normal Galerkin finite element method. The analysis results demonstrate the utility and superiority of the membrane finite element method in fluid flow analysis of a porous medium Water Science and Engineering. 2009 2(2): 43-57 .

Seismic stability safety evaluation of gravity dam with shear strength reduction method

Da-sheng WANG, Liao-jun ZHANG, Jian-jun XU, Ming-jie HE, Wei-di ZHANG — 2009-06-30

Da-sheng WANG, Liao-jun ZHANG, Jian-jun XU, Ming-jie HE, Wei-di ZHANG A new method of numerical seismic stability safety evaluation for a rock slope is proposed based on the analysis of a gravity dam foundation subjected to earthquake loading. The shear strengths of the weak discontinuities are divided by different shear strength reduction ratios (K) and numerical seismic analysis is carried out after the static analysis is completed. With different K values, the curves of the permanent horizontal displacement of key points of the dam foundation (K-displacement curves) are studied. According to the curve change, the distribution of plastic zones in the foundation, and the slow convergence of the finite element method (FEM), the seismic stability safety factor is defined as K when the gravity dam is in the limit equilibrium state subjected to earthquake loading. These concepts were applied to the evaluation of seismic stability safety of a gravity dam for a hydropower project. The analysis of the example shows that the proposed method is feasible and is an effective method of seismic stability safety evaluation Water Science and Engineering. 2009 2(2): 52-60 .

Dynamic probability evaluation of safety levels of earth-rockfill dams using Bayesian approach

Zi-wu FAN, Shu-hai JIANG, Ming ZHANG — 2009-06-30

Zi-wu FAN, Shu-hai JIANG, Ming ZHANG In order to accurately predict and control the aging process of dams, new information should be collected continuously to renew the quantitative evaluation of dam safety levels. Owing to the complex structural characteristics of dams, it is quite difficult to predict the time-varying factors affecting their safety levels. It is not feasible to employ dynamic reliability indices to evaluate the actual safety levels of dams. Based on the relevant regulations for dam safety classification in

China

, a dynamic probability description of dam safety levels was developed. Using the Bayesian approach and effective information mining, as well as real-time information, this study achieved more rational evaluation and prediction of dam safety levels. With the Bayesian expression of discrete stochastic variables, the a priori probabilities of the dam safety levels determined by experts were combined with the likelihood probability of the real-time check information, and the probability information for the evaluation of dam safety levels was renewed. The probability index was then applied to dam rehabilitation decision-making. This method helps reduce the difficulty and uncertainty of the evaluation of dam safety levels and complies with the current safe decision-making regulations for dams in

China

. It also enhances the application of current risk analysis methods for dam safety levels Water Science and Engineering. 2009 2(2): 61-70 .

Finite element model of reinforcement corrosion in concrete

Jin-xia XU, Lin-hua JIANG, Qi WANG — 2009-06-30

Jin-xia XU, Lin-hua JIANG, Qi WANG A nonlinear finite element model (FEM) of the corrosion of steel reinforcement in concrete has been successfully developed on the basis of mathematical analysis of the electrochemical process of steel corrosion in concrete. The influences of the area ratio and the Tafel constants of the anode and cathode on the potential and corrosion current density have been examined with the model. It has been found that the finite element calculation is more suitable for assessing the corrosion condition of steel reinforcement than ordinary electrochemical techniques due to the fact that FEM can obtain the distributions of potential and corrosion current density on the steel surface. In addition, the local corrosion of steel reinforcement in concrete is strengthened with the decrease of both the area ratio and the Tafel constants. These results provide valuable information to the researchers who investigate steel corrosion Water Science and Engineering. 2009 2(2): 71-78 .

Study on soil water characteristics of tobacco fields based on canonical correlation analysis

Xiao-hou SHAO, Yu WANG, Li-dong BI, You-bo YUAN, Xian-kun SU, Jian-guo MO — 2009-06-30

Xiao-hou SHAO, Yu WANG, Li-dong BI, You-bo YUAN, Xian-kun SU, Jian-guo MO In order to identify the principal factors influencing soil water characteristics (SWC) and evaluate SWC effectively, the multivariate-statistical canonical correlation analysis (CCA) method was used to study and analyze the correlation between SWC and soil physical and chemical properties. Twenty-two soil samples were taken from 11 main tobacco-growing areas in Guizhou Province in China and the soil water characteristic curves (SWCC) and basic physical and chemical properties of the soil samples were determined. The results show that: (1) The soil bulk density, soil total porosity and soil capillary porosity have significant effects on SWC of tobacco fiels. Bulk density and total porosity are positively correlated with soil water retention characteristics (SWRC), and soil capillary porosity is positively correlated with soil water supply characteristics (SWSC). (2) Soil samples from different soil layers at the same soil sampling point show similarity or consistency in SWC. Inadequate soil water supply capability and imbalance between SWRC and SWSC are problems of tobacco soil. (3) The SWC of loamy clay are generally superior to those of silty clay loam Water Science and Engineering. 2009 2(2): 79-86 .

Factor value determination and applicability evaluation of universal soil loss equation in granite gneiss region

Wen-hai ZHANG, Xing-nan ZHANG, Zhi-dong GAO — 2009-06-30

Wen-hai ZHANG, Xing-nan ZHANG, Zhi-dong GAO Six types of runoff plots were set up and an experimental study was carried out to examine natural rate of soil and water loss in the granite gneiss region of northern Jiangsu Province in

China

. Through correlation analysis of runoff and soil loss during 364 rainfall events, a simplified and convenient mathematical formula suitable for calculating the rainfall erosivity factor (R) for the local region was established. Other factors of the universal soil loss equation (USLE model) were also determined. Relative error analysis of the soil loss of various plots calculated by the USLE model on the basis of the observed values showed that the relative error ranged from -3.5% to 9.9% and the confidence level was more than 90%. In addition, the relative error was 5.64% for the terraced field and 12.36% for the sloping field in the practical application. Thus, the confidence level was above 87.64%. These results provide a scientific basis for forecasting and monitoring soil and water loss, for comprehensive management of small watersheds, and for soil and water conservation planning in the region Water Science and Engineering. 2009 2(2): 87-97 .

Application of k-person and k-task maximal efficiency assignment algorithm to water piping repair

Su-juan ZHENG, Xiu-ming YU, Li-qing CAO — 2009-06-30

Su-juan ZHENG, Xiu-ming YU, Li-qing CAO Solving the absent assignment problem of the shortest time limit in a weighted bipartite graph with the minimal weighted k-matching algorithm is unsuitable for situations in which large numbers of problems need to be addressed by large numbers of parties. This paper simplifies the algorithm of searching for the even alternating path that contains a maximal element using the minimal weighted k-matching theorem and intercept graph. A program for solving the maximal efficiency assignment problem was compiled. As a case study, the program was used to solve the assignment problem of water piping repair in the case of a large number of companies and broken pipes, and the validity of the program was verified. Water Science and Engineering. 2009 2(2): 98-104 .

Principal-subordinate hierarchical multi-objective programming model of initial water rights allocation

Dan WU, Feng-ping WU, Yan-ping CHEN — 2009-06-30

Dan WU, Feng-ping WU, Yan-ping CHEN The principal-subordinate hierarchical multi-objective programming model of initial water rights allocation was developed based on the principle of coordinated and sustainable development of different regions and water sectors within a basin. With the precondition of strictly controlling maximum emissions rights, initial water rights were allocated between the first and the second levels of the hierarchy in order to promote fair and coordinated development across different regions of the basin and coordinated and efficient water use across different water sectors, realize the maximum comprehensive benefits to the basin, promote the unity of quantity and quality of initial water rights allocation, and eliminate water conflict across different regions and water sectors. According to interactive decision-making theory, a principal-subordinate hierarchical interactive iterative algorithm based on the satisfaction degree was developed and used to solve the initial water rights allocation model. A case study verified the validity of the model Water Science and Engineering. 2009 2(2): 105-116 .