Abstract:Based on analysis of the input and output of various ecological flows in a regional agricultural production system, the positive and negative effects of agricultural water utilization were evaluated through emergy analysis from a perspective of ecological economics. Then, with the emergy as a normalized basis, the method of calculating the positive and negative effects of agriculture water utilization was improved. Using Zhengzhou City as an example, the positive and negative effects of water utilization in the agricultural production system of the city in 2011 were calculated. The results show that the positive effect was 1.62 × 10²¹ J, and the negative effect was 6.82 × 10²⁰ J, which was about 42.10% of the positive effect, indicating that the city's agriculture water utilization was in a significantly negative situation. Improving the utilization efficiency of water resources and the accompanying renewable resources while minimizing the unreasonable investment and utilization of nonrenewable resources, and avoiding the harm caused by environmental pollution and overexploitation of groundwater are the keys to solving the problem of negative effects of agricultural water utilization.

Abstract:Using conventional meteorological data from 116 meteorological stations in Northeast China from 1951 to 2013, an information transfer model of daily reference evapotranspiration(ET0)between stations in Northeast China was constructed based on the information entropy theory, and the distribution of the information field was analyzed. The regional similarity structural characteristics of daily ET0 were analyzed using the cluster analysis method. Then, six representative stations were chosen based on the analysis. The rescaled range analysis method was used to analyze the time fractal characteristic of ET0 at the six stations. The results show that, in space, the information entropy of daily ET0 decreases with the increase of latitude in Northeast China, and the information transfer index of each station, with significant anisotropy, decreases with the increase of distance between the basic station and the auxiliary station. The information transfer at the site level presents a general pattern of distribution from south to north and from east to west. In time, the mean annual ET0 presents a generally decreasing trend in Northeast China, and the ET0 of the six representative stations, i. e. , the Harbin, Shenyang, Chifeng, Jagdaqi, Kiamusze, and Hailar stations, will tend to stabilize within a certain time period in the future and show strong persistence.

Abstract:In order to study the effect of different laws regarding the opening and closing of the blade on the runaway transient of a Kaplan turbine, the runaway transient of a Kaplan turbine model in five blade control modes was simulated using the three-dimensional unsteady numerical method. Changes of the rotation speed, flow rate, torques, and pressure fluctuation with time were analyzed, and the pressure distribution on the blade surface and inner flow patterns in the draft tube were examined. The results show that, compared with the maximum runaway speed under the fixed blade conditions, the variation of the maximum runaway speed ranges from -6.6% to 5.0% when the blade angle is changed from -10° to 10°. Opening blades during the runaway transient increases characteristic parameter fluctuations, causes the maximum negative pressure at the central area of the draft tube to reach 2.86 times the initial value, and produces an eccentric spiral vortex rope, which induces strongly low-frequency fluctuation and is adverse to the unit stability. Closing blades can reduce water velocity, alleviate pressure fluctuation, and improve the flow pattern in the draft tube, but reasonable closure modes should be investigated in order to avoid an excessive increase in the runaway speed.

Abstract:In order to study the influence of wave acceleration asymmetry on seabed response, a numerical model of wave-induced seabed response was developed based on the Biot theory of poroelasticity, and the model was validated against the measured data from flume experiments. A method of calculating wave pressure boundary conditions on the seabed surface, which considers wave acceleration asymmetry, is introduced. Effects of wave acceleration asymmetry on pore water pressures, effective stresses, and soil liquefaction of the seabed are discussed based on numerical simulation. Results show that wave acceleration asymmetry considerably reduces the peak value of the positive pore water pressure in the surface soil layer of the seabed, modifies the spatial distribution pattern of the pore water pressure, and eventually leads to decreases in both the depth and width of seabed liquefaction.

Abstract:In order to investigate the growth and decay processes of ice in still water and the evolution of ice cover, a prototype experiment was carried out to study the ice regime in the Nanhu Pond in Tuoketuo County, in the Inner Mongolia Autonomous Region during the period from the middle of November 2014 to the middle of March 2015. The influence of air temperature in different periods and water depth on the growth and decay processes of ice in still water, the evolution of ice cover, water temperature distribution, and temperature at the ice surface were studied. The experimental results show that the air temperature was the main factor that influences the regime of ice in still water. The ice thickness was linearly correlated with the accumulated daily mean negative temperature during the growth period of the ice cover. The slope of the increasing of ice thickness and ice cover during the unstable and late melting periods was mainly affected by the air temperature. The water depth affected the greatest ice thickness and ice melting time, while its impact on the evolution of the ice cover was not significant. The water temperature in the surface layer was significantly influenced by the variation of the air temperature, while the deep layer was less influenced. The temperature at the ice surface showed a synchronized change with the air temperature.

Abstract:Based on the theory of gas-liquid two-phase flow, the finite element method was used to simulate rainfall infiltration in loam soil with different degrees of saturation to investigate the effects of the initial degree of saturation on rainfall infiltration. Numerical results show that the pore air pressure increases gradually in the initial stage of rainfall infiltration; then, the infiltration rate decreases to a stable value because of the jacking force caused by pore air. The stable infiltration rate is mainly determined by the matrix suction and permeability characteristics of soil, varying with the initial degree of saturation. With the variation of the initial degree of saturation, the infiltration rate reaches its maximum or minimum values. The maximum infiltration rate usually appears in the stage of residual or full saturation, while the minimum infiltration rate occurs in the unsaturated stage, depending on soil unsaturated characteristics. Affected by the matrix suction of soil and the relative permeability of water and air, the infiltration rate gradually decreases with the increase of the degree of saturation at first. When the infiltration rate drops to the minimum, it starts to rise with the increase of the degree of saturation. According to the results of numerical simulation, a formula is proposed for calculation of the relatively stable infiltration rate for different initial degrees of saturation.

Abstract:In order to study the permeability characteristics and permeability evolution model of gravel soil used in core wall of earth-rock dam, a self-made seepage-stress apparatus was used to conduct permeability test for gravel soil of the Changheba Hydropower Station in complex stress state. Test results show that complex stress has significant effect on permeability evolution of gravel soil, the relationship between seepage velocity and hydraulic gradient follows Darcy’s law within the range of the design hydraulic gradient, and seepage failure of soil samples does not occur. The results also show that under the same confining pressure, permeability coefficient of gravel soil decreases gradually as the partial stress and axial stress increases. There is a stepwise relationship between the axial strain and the stress acting time in the test process. As the partial stress grows, the axial strain increases with the seepage gradient. An empirical formula for relationship between the permeability coefficient and the stress function is established, which further reveals the permeability evolution mechanism of gravel soil under complex stress theoretically.

Abstract:In order to develop a clay-based cementitious material used in hydraulic engineering, the waste clay from a waterway revetment was used as a raw material. The influence of different contents of inorganic binder, such as cement, gypsum, and slag, on the mechanical properties of the clay-based cementitious material was studied by testing the compressive strength, splitting tensile strength, and water stability of specimens. A scanning electron microscope(SEM)was used to analyze the microstructure of specimens. The results show that when the mixing proportions of the waste clay, cement, slag, gypsum, and lime are 65%, 18%, 10%, 2%, and 5%, respectively, the compressive strength, immersion strength, and splitting tensile strength of the clay-based cementitious material at 28 d reach 25.6 MPa, 24.1 MPa, and 2.5 MPa, respectively. SEM results show that cement-based cementitious materials, such as C-S-H, were observed at different hydration ages, and these products effectively improve the mechanical properties of the clay-based cementitious material. It is concluded that the clay-based cementitious material shows high strength and water stability, and it can be used in hydraulic engineering.

Abstract:In order to obtain the deformation characteristics a foamed mixture lightweight soil using river sludge(FMLSS)under a dynamic load, the effects of the confining pressure, water content, cement content, and air foam content on the dynamic deformation characteristics of the FMLSS were investigated using laboratory dynamic triaxial tests. Test results show that the fitting dynamic stress-strain curve of the FMLSS is of the hyperbolic type. The dynamic strain of the FMLSS decreases with the increase of confining pressure and cement content, and increases with the increase of water content and air foam content under a certain dynamic stress lerel. Under a constant dynamic strain, the dynamic elastic modulus of the FMLSS increases with the increase of confining pressure and cement content, and decreases with the increase of water content and air foam content. The relationship curve of the dynamic elastic modulus and dynamic strain shows a gradually decreasing trend. The water content and air foam content are the main factors influencing the dynamic deformation characteristics of a FMLSS.

Abstract:A coupled one- and two-dimensional hydrodynamic model was developed to simulate the flood wave propagation through the breaches. The Preissmann scheme was used for the one-dimensional model and the Roe scheme on unstructured meshes was used for the two-dimensional model. The special boundaries, such as roads and irrigation ditches, were generalized as broad crested weirs and were linearized. A coupled model with real terrain was established through coupling the unstructured mesh and special boundaries, and the dry and wet depth theory was used to optimize this model. The model was applied to simulation of a levee-breach flood that occurred in the West Irrigation Area of the Qingtongxia Gorge of the Yellow River. The results show that the model can truly simulate the flood wave propagation and flood inundation area in the calculation area, and can simulate the water-blocking effect of roads and irrigation ditches and water-passing effect of bridges and culverts.

Abstract:In view of the problem of inflow delay in medium-term operation of cascade hydropower stations, a concept of delayed energy is introduced, and a stored energy maximization model was constructed for the end of the operation period. A Lagrange relaxation method based on a two-stage subgradient algorithm used to update multipliers is proposed to solve the model. In the first stage, the initial multipliers are rapidly determined by increasing coefficients gradually. In the second stage, the convergence speed is increased by decreasing coefficients gradually. The proposed model and solution method were applied to medium-term optimal operation of six hydropower stations located in the middle and lower reaches of the Lancang River. The results show that the proposed method can obtain good solutions, considering delayed energy can increase stored energy of the hydropower system for the end of the operation period, and the post-effect of medium-term operation should be considered sufficiently.

Abstract:In order to effectively use available historical observation data for precipitation forecasting in the case of an uncertain cause of precipitation, a precipitation forecasting method was developed based on the naive Bayes algorithm. Using the Dongjiang Basin as an example, a rich set of features was constructed based on the basin’s precipitation data and meteorological knowledge. The forecasting accuracy of the proposed method was compared with those of the traditional time series method and the BP neural network method. The result shows that the proposed method outperformed both the traditional time series method and the BP neural network method.

Abstract:In order to explore the large-scale long-term law of river channel evolution in the Inner Mongolia reach of the Yellow River, the Pugebu-Chahekou section was selected as a study area. The lateral migrations of the river channel and the changes in river width at 129 cross-sections monitored in different years were analyzed using 3S technology and RTK data on the basis of four groups of multi-spectral remote sensing image data during the period of 1995, 1999, 2006 and 2013. The results show that the interpreted river morphology results using the 3S technology agreed with the measured results. The average width of the river showed a tendency of shrinkage, although fluctuation existed. The river width of the main stream decreased by 32. 24 m on average from 1995 to 2013, with a change rate of -9%. Curve cutoff phenomena occurred more than once. The geological conditions, inflowing water and sediment conditions, and channel morphology are important factors affecting river channel evolution. The change rates of river width in the sandy riverbed sections ranged from -12% to -33%, which were greater than those in the bedrock riverbed sections. The apparent shrinkage of the Zhaojunfen cross-section was affected by the increase of the content of sand into the Yellow River from the Kubuqi Desert in the south and ten tributaries upstream.

Abstract:Taking the middle grained sandstone in the Cretaceous as simulation object, fine sand, high strength cement, fine gypsum, iron powder and distilled water were used as raw materials to configure the quasi-sandstone similar samples. According to the orthogonal experiment method, the design scheme was determined with the water-cement ratio, the ratio of aggregate to cement and the iron powder content being controlling factors, and the influence of these factors on saturation density, acoustic wave velocity, heat conduction coefficient and uniaxial compressive strength was analyzed with the range sensitive analysis method. Experiment results show that the ratio of aggregate to cement plays a leading role in saturation density, acoustic wave velocity and uniaxial compressive strength. The saturation density and acoustic wave velocity obviously decrease with the increase of the ratio of aggregate to cement. Meanwhile, the iron powder content has a governing effect on the thermal conduction coefficient, and the thermal conductivity obviously increases with the increase of the iron powder content. Through multiple linear regression analysis, the optimal mass ratio scheme of the sandstone material was deduced, which meant the water-cement ratio was 0. 53, the ratio of aggregate to cement was 0.45 and the iron powder content was 4.2%. The physics and mechanics parameters of the quasi-sandstone using this similar material ratio are very close to that of sandstone in the Cretaceous.

Abstract:Under the effect of load and environmental factors, concrete dam materials appear different degrees of aging and the performance of dam structures degrades during the service period. With regard to this problem, studies on performance degradation mechanism under the coupling effect of multiple factors were summarized in this paper. Since the performance of the in-service dam affected by the environment and load factors is mainly driven by the evolution of material properties, the performance degradation of concrete dam system was studied from the aspect of load and structural resistance, with emphasis on research status and technical challenges of the degradation mechanism of dam structures and materials under multiple factors synergy. Finally, some key scientific problems needed to be urgently solved on the performance of in-service concrete dams are pointed out.

Abstract:Arc Hydro and Arc Hydro Groundwater hydrological data model are favored by scholars in the joint simulation of surface water and groundwater, but empirical researches on whether hydrological simulation can apply Arc Hydro and Arc Hydro Groundwater model are lack. According to this problem, the functions and advantages of these two hydrological models were analyzed, furthermore, the remaining problems and the development trend were also discussed by a review of a large number of documents. It is pointed out that although Arc Hydro has function of strong hydrological analysis and extraction, this model cannot realize hydrological simulation, data exchange is necessary to complete hydrological simulation with independent hydrological model. Arc Hydro Groundwater contains MODFLOW analysis model, however, it only can visualize process for MODFLOW model outputs and does not yet have independent groundwater simulation function. The development of integrated platform combining joint simulation model of surface water and groundwater with GIS coupling is supposed to be a hot research.