Abstract:In order to understand the development and changes of fundamental water-related challenges, the inherent relationship between river system evolution and those challenges, as well as basic characteristics, development, and variation conditions, were analyzed on the basis of previous studies. It is pointed that river system evolution and drastic changes are the source of the four water-related challenges referred to in this paper as too much water, too little water, muddy water, and dirty water, which result in significant harm to material civilization and ecological civilization construction. With social progress and environmental changes in river systems comes a large amount of development and variation of fundamental water-related challenges. The too much water challenge includes greater flood frequency, large flooding disasters even with small amounts of water in rivers, imbalanced river regulation, and flooding of cities. The too little water challenge includes increasing frequency of drought and water shortage, regional and connotation expansion, lengthening of the duration, and so on. Muddy water challenges include frequent human activities in the basin, and large decreases in river sediment discharge and its influences. Dirty water problems include significant compound pollution and non-point source pollution, and the shift from mainly industrial pollution to mainly biological pollution. Attention must be given to some new conditions and new characteristics of fundamental water-related challenges.

Abstract:Based on systematic analysis of the mechanisms of interaction between socioeconomic development and water conservancy development, as well as on the evolution and characteristics of water conservancy development, an evaluation index system for water conservancy development was designed systematically from four perspectives, including water resources utilization, water environment protection, water ecological restoration, and water disaster prevention. The integrated implementation degree of water conservancy development’s objectives in China is evaluated, and the main existing problems during the water conservancy development process are investigated comprehensively. The results show that the comprehensive implementation degree of water conservancy development’s objectives was 45％ in 2010, indicating that the natural water ecological deficit has begun shrink; that the forecasted comprehensive implementation degrees are 63％ for 2015 and 92％ for 2030, indicating that the local natural water ecological remainder will have begun to appear; and that the overall natural water ecological remainder will be realized in 2050, a human-water balance will be achieved, and water conservancy modernization will be realized.

Abstract:Using a finite volume method based on the Godunov scheme, a two-dimensional saltwater intrusion mathematical model considering the tidal bore effect was established for forecasting chlorinity at water intakes in the Qiantang River Estuary. Based on field data and computational results from the mathematical model, the effects of main factors, including runoff, tides and tidal bore, and riverbed topography, on saltwater intrusion were analyzed. Results show that the riverbed topography affects saltwater intrusion indirectly through changing tides. The larger the river volume is, the larger the tidal range and tidal prism are, leading to intensification of saltwater intrusion. The tidal bore also enhances saltwater intrusion, as chlorinity changes abruptly before and after the tidal bore. Application of the established model in chlorinity prediction shows that the computational results of the model agree with the field data, and the model has significant application value in chlorinity prediction.

Abstract:A three-dimensional mathematical model that simulates the dam-break flood routing process that occurs during local cross-section reduction has been built to investigate the effects of local cross-section reduction on dam-break flow propagation. By calculating Reynolds-averaged Navier-Stokes equations basing on pressure implicit with splitting of operators(PISO), the model is built on the basis of the RNG turbulence model. The governing equations of dam-break flow are discretized with the finite volume method, the free surface flow is dealt with using the fluid volumetric function approach. The physical variables are arranged on a staggered grid, and then the values of dam-break flow with local cross-section reduction are simulatively calculated. The simulation results are in agreement with physical model test results. The formation and propagation process of negative waves in a dam-break flood were examined with the model. The formation and propagation laws of negative waves as well as the variation characteristics of the water level were obtained.

Abstract:In order to study the influence of submerged double spur dikes on the flow characteristics between them, this study measured the horizontal flow field within the area between the spur dikes using a particle image velocimetry (PIV) system, and analyzed the flow characteristics between the spur dikes. Results show that the ratio of the gap between the double spur dikes to the dike length d／B ( B is a constant) has a significant impact on the location of the eddy’s core between the spur dikes, the recirculation flow between the spur dikes, and the vorticity distribution around the heads of the spur dikes. When the value of d／B increases, the eddy’s core is closer to the line connecting the tips of the spur dikes, and the width of the recirculation zone increases. The zero velocity line changes linearly in the streamwise direction, and its slope decreases with the increase of d／B . The velocity in the recirculation zone changes significantly with the value of d／B . The maximum negative vorticity occurs near the head of the upstream spur dike, while the maximum positive vorticity occurs near the head of the downstream spur dike.

Abstract:With regard to failure paths in concrete gravity dams, which have similar characteristics to seepage channels, the cross-section damage method for evaluating concrete gravity dams is proposed on the basis of a two-dimensional percolation transition renormalization group. First, according to the percolation transition model of square units with equal local damage probabilities, the unequal local damage probability model is determined. Then, the trapezoid and triangle primitive cell damage types are determined. The percolation transition model with triangular sections is established. Finally, taking a concrete gravity dam section as an example, the probability of cross-section damage is analyzed. The structure is divided into three parts: the upper, middle, and lower parts. The local damage probabilities of the three parts are unequal. The results of iterative calculation show that when the local damage probability is less than 0.40, the dam section is safe. When it varies from 0.40 to 0.60, the overall safety decreases, with a transition from safe to damage overall. When the probability is greater than 0.60, the overall safety is very low. Cross-section damage may occur if the external environment worsens.

Abstract:In order to improve the durability of frost resistance of hydraulic concrete under climate change conditions, a climate simulation system made by the authors was employed to study the effects of freeze-thaw temperatures on the weight loss and dynamic elastic modulus of hydraulic concrete with the three designed antifreeze levels F50, F100, and F300. During the test, the freeze-thaw processes were observed with set five center temperatures of concrete samples:-5℃, -10℃, -17℃,-30℃, and -40℃. The results show that, with decreasing center temperatures of samples in the freeze-thaw processes, the weight loss and dynamic elastic modulus loss of the three designed antifreeze levels gradually increase, while the maximum withstanding numbers of freeze-thaw cycles gradually decrease. That is to say that lowering the center temperatures of concrete samples in freeze-thaw processes will decrease the durability of frost resistance of hydraulic concrete.

Abstract:In order to understand dynamic characteristics of the new-type flexible retaining walls constructed with soilbags, small-scale shaking table model tests were conducted on retaining walls constructed with soilbags filled with natural sands. The effects of three elements of earthquakes, input accelerations, vibration frequencies, and vibration durations, as well as the size of soilbags, on the retaining walls were investigated, and change patters of horizontal displacements, dynamic earth pressures, and accelerations were analyzed. The results show that displacements of retaining walls and pressure coefficients of dynamic earth increase with the increase of input accelerations and the decrease of vibration frequencies, while the acceleration response increases with the increase of both input accelerations and vibration frequencies. However, the effects of vibration durations on dynamic characteristics are relatively small. In addition, compared with retaining walls constructed with normal-size soilbags, the seismic performance of retaining walls constructed with larger bags is slightly poorer. However, larger soilbags can be used in areas with lower seismic requirements or projects with tight schedules because of their ease of construction and high efficiency.

Abstract:With ASCE standardized reference Penman-Montieth as benchmark reference evapotranspiration equation, two commonly used ETref estimating methods, namely Priestley-Taylor and Hargreaves, were evaluated, local calibrated and validated in different climate regions in China. The results showed that Priestley-Taylor and Hargreaves performed better for grass reference crop in humid and arid regions,respectively. But the error in ETref estimating is unneglectable, and its can not be applied directly to alfalfa reference crop without local calibration. The local calibrated Priestley-Taylor and Hargreaves performed better in different climate regions, and the accuracy was significantly improved for alfalfa reference crop. Both methods performed better on grass than alfalfa reference crop. Performance of Priestley-Taylor showed no significant difference in different climate region, and Hargreaves had higher precision in arid region.

Abstract:An understanding of the optimum pre-dam water level of the Three Gorges Reservoir corresponding to flood control of the varying backwater zone is significant to reservoir regulation. Based on the water level formula obtained from a three-dimensional mathematical model with different pre-dam water levels and upstream discharges, a swell height formula for the pre-dam water level of the Three Gorges Reservoir relative to the reach of the main urban area of Chongqing (Jiulongpo to Tongluoxia) was built. The swell height formula can comprehensively reflect the relationship between the swell height of the main urban area of Chongqing and the pre-dam water level. The swell height formula also provides the maximum pre-dam water level and optimum pre-dam water level considering flood control of the main urban area of Chongqing, which can serve as a reference for pre-dam water level regulation of the Three Gorges Reservoir.

Abstract:In order to simulate urban storm water flow and analyze its influence on zonal waterlogging, a hydrological and hydrodynamic model for river networks and a hydraulic model for urban drainage networks were dynamically coupled using the OpenMI technology. Using the Dianbei zone, one of 14 water conservation zones in Shanghai, as an example, a coupled urban storm water model was established. Then, the effect of the combination of different types of rainstorms and tides on zonal waterlogging in the Dianbei zone was analyzed using the model. The results indicate that the model can precisely simulate urban zonal waterlogging in tidal river networks and provide reference for urban flood control.

Abstract:With a focus on the Gaogang second-line shiplock, under construction on the Yinjiang River in Taizhou City, as a study object, a finite element model of sheet-pile structures with underground retaining walls was established based on the ABAQUS platform. The model can be used to predict the deformation behavior of an anchor pile and underground retaining wall and the internal force state of the bar in different stages of the construction period. Based on ABAQUS user subroutines, the Duncan-Chang constitutive model was developed to simulate the stress-strain characteristics of soil in the process of soil filling and excavation. The exponential contact constitutive model was used to simulate the interaction between the underground retaining wall and the soil. Results from the finite element analysis were compared with the measured data. The results show that the established finite element model of sheet-pile structures with underground retaining walls can accurately predict the deformation of the anchor pile and underground retaining wall and the internal force of the bar in different stages of the construction period.

Abstract:In consideration of some key problems relating to the deformation of the Xiaowan Arch Dam during the first impoundment, the deformation was analyzed with qualitative and quantitative methods, including comprehensive hydrograph analysis, model analysis, numerical simulation, and mathematical statistics. The results show that the dam inclined upstream in the early stage of reservoir impoundment, mainly due to the sinking of the reservoir basin. The reservoir water level was the main factor in the dam deformation, and the time-effect component of the deformation tended to be convergent during the first impoundment. Comparisons of numerical results, modeled results, and designed warning indexes with measured data from the Xiawen Arch Dam, as well comparisons of its measured data with those of other similar projects, demonstrate that the Xiaowan Arch Dam operated normally at the normal water storage level. Although the deformation was relatively large in this case, its regularity was reasonable, demonstrating that the dam was in a safe condition during the first impoundment.

Abstract:Based on 10 years of prototype monitoring data of existing MgO concrete arch dams in China, such as the Sanjiang Arch Dam, and in combination with measured temperatures under the boundary conditions in regard to reservoir water, air, and foundation, the temperature field and temperature load of arch dams are discussed. Observed data from the Sanjiang Arch Dam using the plumb line and inverted plumb line method indicate that the deformation of the arch dam induced by adding MgO to concrete for dam construction is similar to that caused by temperature rise, verifying the expansion effect of MgO concrete. From the viewpoint of the macroscopic deformation of the arch dam, the engineering significance of MgO concrete is further discussed.

Abstract:In view of the facts that the failure simulation method adopted in elasto-plastic analysis lacks objectivity to a certain degree, and the currently used instability criteria are seriously influenced by artificial factors, a calculation method for the element bearing ratio, considering the characteristics of concrete arch dams, is put forward based on the Mohr-Coulomb yield criterion, and the adjustment of the element elastic modulus by means of the uniformity of the bearing ratio and the base bearing ratio is discussed. Then, an ultimate bearing capacity analysis method of arch dams based on the elastic compensation method and plastic limit analysis method is put forward. Analysis of an engineering case shows that this method is reasonable and effective.

Abstract:In order to study the effect of sodium sulfate solution on the shear strength of cemented soil, direct shear with unconsolidated-undrained test was carried out on sodium sulfate corrosion of cemented soil. The test results show that the shear strength of cemented soil gradually decreases with the increase of sodium sulfate solution concentration, and angle of internal friction and cohesion of the shear strength index gradually decrease. When the concentration of sodium sulfate solution is constant, the shear strength of cemented soil gradually decreases with the increase of sodium sulfate solution corrosion time, and cohesion of the shear strength index gradually decreases. The corrosion has a great impact on cohesion, while it has little effect on angle of internal friction.

Abstract:In order to investigate the effects of the dry bulk density and moisture content on the fracture toughness of compacted clay, a new method for the three-point bending test was used, in which the testing sample was rotated 90° in forward around its long side at the bottom, and the loading direction was thus turned to the horizontal direction, perpendicular to the direction of the gravity of the testing sample, so as to avoid the influence of its self-gravity on the fracture extending along the thickness and length of the soil beam. Laboratory tests on the I-type fracture toughness of high-plasticity compacted clay formed by rock weathering in the Jurassic formation in Chongqing City show that the fracture toughness of compacted clay increases with the dry bulk density, and that it increases first and then decreases with the increase of the moisture content, with an optimum moisture content existing, corresponding to the greatest fracture toughness.

Abstract:This paper reviews progress in research on the pollution accumulation in and longterm risk to ecological rainwater facilities such as grass swales, rain gardens, and stormwater ponds, which are used to control runoff pollutants such as organics, suspended solids, and heavy metals. Suggestions are given for the operation and maintenance of these three types of facilities: the service life of grass swales should be regulated according to the runoff water quality in China, and the top 5 cm soil of grass swales should be replaced when they exceed the limit of the service life; 0 to 10 cm of soil should be replaced when there are high levels of heavy metal in the media, and bark mulch is an effective way to prevent the leaching of phosphorous from the top soil due to its phosphorus adsorption ability; the dredging cycle should be determined according to where the function areas in the pond are located, and the dredging frequency of a dry pond could be discretionarily increased due to the higher concentration of PAH in its sediment.

Abstract:This paper summarizes the effects of materials commonly used for infiltration media in rainwater infiltration facilities, including natural materials (e.g., zeolite, silica sand, and wood), waste materials (e.g., coal ash and crab shell), and artificial materials (e.g., fibrous membranes, activated carbon, and zero-valent iron). The properties of different materials and the efficiency and mechanisms of the materials used as improved infiltration media to remove contaminants are analyzed and summarized. It is concluded that contaminants in the runoff, such as heavy metals and polycyclic aromatic hydrocarbons (PAHs), cannot be completely removed by ordinary infiltration materials such as soil. Improved infiltration media can not only control water pollution, but also enhance the efficiency of infiltration facilities and reduce congestion caused by infiltration media. Since each kind of material has its pros and cons, it is shown that, according to different rainwater qualities and treatment requirements, combining different materials as infiltration media or developing new materials may improve the efficiency of infiltration facilities.

Abstract:With a focus on many problems that exist in parameter sensitivity analysis, this paper first analyzes the model construction of hydrological model parameter sensitivity analysis and the main functions in the process of its application. This paper also focuses on the relationship between uncertainty analysis and parameter optimization. Three methods of classification of sensitivity analysis are summarized. Four key technological methods of analysis commonly used in hydrological models are discussed. The four key technological methods include the Morris screening method, regression-based analysis, the variance-based method, and surrogate modeling approaches. At the same time, we discuss the applicable conditions for different approaches in hydrological models, summarize the advantages and disadvantages of various methods, and review the research status of various methods used in the hydrological model. In addition, a synthesized evaluation framework for sensitivity analysis for hydrological modeling is introduced. Several future research issues are also proposed.

Abstract:The progress of research on and existing problems with polyvinyl alcohol (PVA) fibers with high tensile strength and high elastic modulus in improving crack resistance and toughness of concrete are summarized. In terms of crack resistance improvement, PVA fiber improves the resistance to plastic cracking and ultimate tensile strength of concrete. Projects in hydraulic engineering, hydropower engineering, and water transport engineering in China have begun using PVA fibers to improve crack resistance of concrete. In terms of toughness improvement, research mainly focuses on the effect of fiber content, concrete strength, the reinforcement ratio, and other factors in the flexural toughness of concrete. The theory of design of toughening materials, mechanisms of crack formation and propagation, and constitutive equations of PVA fiber-reinforced concrete should be further investigated.